SEASONAL IN-SITU AERATION IN CONSTRUCTED WETLANDS TO
FACILITATE NITRIFICATION
By
Omar Al-Shafie
A Project Presented to
The Faculty of Humboldt State University
In Partial Fulfillment of the Requirements for the Degree
Master of Science
In Environmental Systems; Environmental Resources Engineering
Committee Membership
Dr. Brad Finney, Committee Chair
Dr. Margaret Lang, Committee member
Dr. Robert Gearheart, Committee member
Dr. Christopher Dugaw, Graduate Coordinator
December 2014
ABSTRACT
SEASONAL IN-SITU AERATION IN CONSTRUCTED WETLANDS TO
FACILITATE NITRIFICATION
Omar Al-Shafie
Throughout most of the year, Arcata California is home to approximately 18,000
residents who are served by an innovative wastewater treatment plant that utilizes
constructed wetlands to treat a range of flows from 1.0 MGD to 13 MGD. The City of
Arcata is required to renew its National Pollutant Discharge Elimination System
(NPDES) permit through the North Coast Regional Water Quality Control Board
(NCRWQCB), which will dictate the need to reduce nitrogen levels compared to current
effluent values. This project explores facilitating the nitrification and denitrification
process with an in-situ aeration system, which has the potential to reduce nitrogen levels
to assumed requirements on the next NPDES permit issued by the NCRWQCB. The City
of Arcata is required to comply with the renewed NPDES permit standards by January
27, 2017.
The primary objective of this study is to determine the nitrogen removal efficiency of a
small-scale in-situ aeration system for the Arcata Wastewater Treatment Facility
(AWTF). The aquaphyte, a scaled down treatment marsh was built, planted, and aerated
to observe the nitrification and denitrification process, which converts ammonia nitrogen
ii
in the wastewater to di-nitrogen in the atmosphere. Design parameters were altered to
determine which variables have the greatest influence on the conversion of ammonia to
nitrate (nitrification) and nitrate to di-nitrogen (denitrification). Aerating the aquaphyte
proved to be an effective method to reduce ammonia concentrations. This experiment
was scaled up to a larger system in Treatment Wetland - 4 (TW- 4) to determine if the
98% reduction of ammonia concentrations seen in the aquaphyte could be replicated.
There were many variables that created a divergence of similitude between the
Aquaphyte and TW–4, and the results observed in the aquaphyte did not translate to the
aeration system installed in TW-4. Operating conditions in the aeration system and
inflows into TW-4 were altered to find similar operating parameters as the aquaphyte.
TW-4 has been operating as a treatment marsh for approximately 35 years and has
developed a substantial volume of nitrogen in the form of biomass from plant growth and
senescence cycles, accreted ammonia that has precipitated into the wetland soil, and
settled algal solids. The accumulation of biomass was the primary difference between the
aquaphyte and TW-4. Influent loading into both systems was pumped from the same
source (Oxidation pond 2). Nonetheless, the oxygen that was transferred into TW-4 to
facilitate nitrification appeared to be consumed by the carbonaceous oxygen demand that
was created from the accumulation of biomass throughout its operation. Therefore, the
larger scale TW-4 nitrification system experiment resulted in little to no ammonia
reduction.
iii
NOMENCLATURE
AWTF
Arcata Wastewater Treatment Facility
BOD
Biological Oxygen Demand
CBOD
Carbonaceous Biological Oxygen Demand
DO
Dissolved Oxygen
EPA
Environmental Protection Agency
gpm
Gallons per minute
HRT
Hydraulic Retention Time
MGD
Million Gallons per Day
mg/L
Milligrams per liter
NBOD
Nitrogenous Biological Oxygen Demand
NCRWQCB North Coast Regional Water Quality Control Board
NPDES
National Pollution Discharge Elimination System
SCFH
Standard Cubic Feet per Hour
SCFM
Standard Cubic Feet per Minute
TSS
Total Suspended Solids
TW- 4
Treatment Wetland – 4
iv
ACKNOWLEDGEMENTS
I want to thank Dr. Brad Finney, Dr. Bob Gearheart, Dr. Margaret Lang, Dr. Eileen
Cashman, Dr. Stewart Oakley, Dr. Peter Rohloff, Britany MacFarlane, Mary Burke,
Charles Swanson, Heidi Halverson, Lauren Adabie, William Karis, Cody Bowers,
Meagan Butler, Nicole, Mama J, Mama Hen, Pachamama, Mama Aya, Machute, Sitee,
Abuelito, Tata, Pops, Papa J, Brendo, Jaymes, Kriz, Bo Beau, Deepah, Shani, the family
of river otters that live at the Marsh, and all my plant allies for your support and
guidance.
v
TABLE OF CONTENTS
ABSTRACT........................................................................................................................ ii
NOMENCLATURE .......................................................................................................... iv
ACKNOWLEDGEMENTS ................................................................................................ v
TABLE OF CONTENTS ................................................................................................... vi
LIST OF TABLES ........................................................................................................... viii
LIST OF FIGURES ........................................................................................................... ix
INTRODUCTION .............................................................................................................. 1
REVIEW OF LITERATURE ............................................................................................. 3
Global Nitrogen Cycle .................................................................................................... 3
Conventional Wastewater Treatment.............................................................................. 5
Oxygen Transfer ............................................................................................................. 7
Submerged Diffused Bubble Systems ............................................................................ 9
Wetlands for Wastewater Treatment ............................................................................ 10
Wetland Nitrogen Cycle ............................................................................................... 12
Ammonification ............................................................................................................ 14
Nitrification and Denitrification ................................................................................... 15
Vegetation Effects......................................................................................................... 17
Temperature Effects ...................................................................................................... 21
Artificial Aeration ......................................................................................................... 22
METHODology ................................................................................................................ 24
Aquaphyte ..................................................................................................................... 24
vi
Treatment Wetland Four ............................................................................................... 30
Monitoring and Laboratory Analysis ............................................................................ 38
RESULTS and Discussion ................................................................................................ 39
Aquaphyte ..................................................................................................................... 39
Effects of temperature on the rate of nitrification. .................................................... 39
Effects of aeration on nitrification. ........................................................................... 49
Media and contact time. ............................................................................................ 58
Scale Up: Treatment Wetland 4 .................................................................................... 62
Water quality analysis. .............................................................................................. 62
DO and BOD. ............................................................................................................ 64
Nitrogen dynamics. ................................................................................................... 72
Media and fouling. .................................................................................................... 76
Quantifying internal load contribution...................................................................... 77
COMPARISON ............................................................................................................ 80
Conclusion ........................................................................................................................ 82
Recommendation .......................................................................................................... 83
REFERENCES ................................................................................................................. 86
Appendix A ....................................................................................................................... 91
Operational parameters ................................................................................................. 91
Aquaphyte water quality data ....................................................................................... 95
Treatment Marsh 4 water quality data ........................................................................ 101
Normalized calculations tables ................................................................................... 106
vii
LIST OF TABLES
Table 1: Devices for aeration systems (adapted from Metcalf and Eddy, 2003) ................ 9
Table 2: Primary nitrogen pathways in constructed wetlands (adapted from Vymazal,
2007) ................................................................................................................................. 14
Table 3: Nutrient removal potential of common treatment wetland plant species (adapted
from Kadlec and Knight, 1996) ........................................................................................ 19
Table 4: aquaphyte dimensions and hydraulic retention time .......................................... 24
Table 5: Water flow and typical loading into aquaphyte .................................................. 25
Table 6: Estimated available surface area for a submerged depth of 0.6 m, bolded
numbers were used in calculations (adapted from Lagace, 2000). ................................... 29
Table 7: Estimated surface area of submerged plant biomass in aquaphyte within the
volume of water containing DO concentrations above 1.0mg/l (using data from Lagace,
2000). ................................................................................................................................ 29
Table 8: Dimensions and HRT of one channel in Treatment Wetland 4. ......................... 30
Table 9: Water flow rate, typical ammonia loading, typical BOD loading, airflow, and
HRT into experimental cell of Treatment Wetland – 4 .................................................... 32
Table 10: Estimation of available surface area on the additional plastic media; it is
assumed that 70% of area is available. ............................................................................. 37
Table 11: Percent removal of ammonia, NBOD, CBOD with average temperatures above
and below 10oC (based on 21 samples) ............................................................................ 46
Table 12: Aquaphyte performance winter of 2010; average temp 10.5oC, average influent
concentration 32.5mg/l, with aeration .............................................................................. 49
Table 13: Reaction of water quality parameters throughout the period of aeration ......... 50
Table 14: Residence time within media, mass of oxygen within contact volume, and mass
of oxygen per square foot of surface area on 3/20/14 ....................................................... 61
Table 15: Comparison of results; normalized values between the two systems; a transfer
efficiency of 20% was assumed; 20.95% oxygen concentration in air was assumed....... 81
viii
LIST OF FIGURES
Figure 1: Overhead view of Arcata Wastewater Treatment facility (AWTF) indicating
component locations. .......................................................................................................... 1
Figure 2: Oxidation/reduction pathways available for Nitrogen (image from: Reddy,
2008) 1. Ammonification 2. Immobilization 3. Nitrification 4. Denitrification 5.
Dissimilator nitrate reduction to ammonia, 6. Di-nitrogen fixation, 7. Ammonia
volatilization. ...................................................................................................................... 5
Figure 3: Nitrogen pathways within Wetland system (adapted from Kadlec, 2008)........ 12
Figure 4: Photo of aquaphyte adjacent to oxidation pond 2 ............................................. 26
Figure 5: Diagram of aquaphyte with sample ports and equipment. ................................ 27
Figure 6: Existing plant growth within aquaphyte water column. .................................... 28
Figure 7: Aeration system installed in Treatment Wetland 4. .......................................... 33
Figure 8: Diagram of Treatment Wetland 4 aeration system, sample ports, and pier. Water
flows in from the bottom right corner of the diagram and past the sample ports indicated
in red with distance from aeration system. ....................................................................... 34
Figure 9: Left photo indicates the wooden frame containment and media. Right photo was
the chicken wire “bags” that contained large honey comb media and strapping material.
Both were installed into Treatment Marsh 4 to facilitate nitrification.............................. 35
Figure 10: Operation of the aeration system installed in Treatment Marsh 4 downstream
of the constructed pier. ...................................................................................................... 36
Figure 11: Aquaphyte performance with no aeration and cold temperatures 1/4/13;
average temperature 7.4oC. Sample ports are equally spaced along the length of the
aquaphyte .......................................................................................................................... 41
Figure 12: Total BOD characterized as NBOD and CBOD, average temp 7.4oC
(01/04/13).......................................................................................................................... 42
Figure 13: Total BOD average temp 6.9oC 1/11/13 ......................................................... 43
ix
Figure 14: Ammonia reduction in the aquaphyte on 4/12/14; average temp 12.6oC ........ 45
Figure 15: Temperature vs. Ammonia removal over time; large increase in removal
efficiency is a result of operating the aeration system. ..................................................... 47
Figure 16: Constant head flow regulation; average temp 8.1oC; 34% ammonia reduction
(2/08/13)............................................................................................................................ 51
Figure 17: Total BOD concentrations during period of aeration; average temp. 12.3oC
(2/17/13)............................................................................................................................ 52
Figure 18: One week after install of peristaltic pump flow regulation; average temp
7.9oC; (2/22/13), 28 days after aeration began ................................................................. 55
Figure 19: (3.10.13); 100% reduction in NBOD, 50% reduction in CBOD ..................... 56
Figure 20: 4.05.13; 70 days of aeration operation; average temperature 13.3oC; 50 scfh 57
Figure 21: Garrison, average temp 12.5oC, with plastic media, influent concentration of
27.21ppm, air flow 70 scfh ............................................................................................... 59
Figure 22: Nitrogen dynamics on 3.20.14; average temperature 12.2oC, no installed
plastic media ..................................................................................................................... 60
Figure 23: The initial pilot project, Treatment Marsh 4, on September 3, 1980. The
system was designed and operated in series with 10 separate treatment cells (W= 20' x L
= 200' x D = 2') Initially, the treatment cells alternated plantings from Bulrush to Cattail.
Plant biomass was still sparse and developing. ................................................................ 63
Figure 24: TW-4 in the Summer 2013 after 35 years of loading with municipal
wastewater. Biomass development is extensive when compared to Figure 23. It now
operates in parallel with a sinusoidal flow pattern. Cattail has emerged as the dominant
macrophyte. ....................................................................................................................... 64
Figure 25: Total BOD reduction of 30% on 5/22/13 indicating that the DO was being
consumed .......................................................................................................................... 65
Figure 26: Total BOD reduction with DO consumption on 6/6/13 .................................. 66
Figure 27: Total Biological Oxygen Demand (BOD) reduction (6.26.13); with wooden
frames and two weeks after installation of wire bags ....................................................... 68
Figure 28: 7/17/13; 68% reduction in NBOD, 74% reduction CBOD ............................. 69
Figure 29: Dissolved oxygen concentration TW 4 after removal of wire bags (7.25.13). 70
x
Figure 30: 50% reduction of total BOD 9.17.13, final media configuration, installed
downstream of aeration system. ........................................................................................ 71
Figure 31: 5/30/13 ammonia reduction of 32% (2.8mg/l), peak DO concentration 2.5mg/l,
slight increase in nitrate (1.6mg/l) within the zone of elevated DO ................................. 72
Figure 32: Performance two weeks after installation of wire bags (6/26/13). .................. 74
Figure 33: Nitrogen dynamics of system 22 days after final configuration of media (wire
bags) downstream of aeration system; 9.09.13 ................................................................. 75
Figure 34: Microbial growth on membrane diffusers; half brushed off to observe extent of
fouling ............................................................................................................................... 77
Figure 35: Ammonia concentrations throughout the year for all treatment marshes and
pond 2................................................................................................................................ 78
Figure 36: Ammonia effluent concentrations throughout 2012 ........................................ 79
xi
1
INTRODUCTION
Arcata California is located on the coast in the Pacific Northwest approximately 100
miles south of the Oregon border. To treat the City’s wastewater, the Arcata Wastewater
Treatment Facility (AWTF) utilizes conventional headworks technology, which consists
of a bar screen, grit chamber, and primary clarifier to mitigate the loading of solids to
secondary treatment processes. The total footprint of AWTF is approximately 90 acres.
Two oxidation ponds, totaling 40 acres, have been in operation since the 1950s, and for
about the past 30 years, AWTF has been using treatment marshes for their secondary and
tertiary treatment. The existing area of treatment marshes is approximately 10 acres, and
the enhancement marshes have an area of 30 acres (Figure 1).
Headworks
Previous Hatchery Ponds
Figure 1: Overhead view of Arcata Wastewater Treatment facility (AWTF) indicating
component locations.
2
Humboldt State University is within the city limits of Arcata and effectively doubles the
population to approximately 18,000 residents while school is in session. The flow rates
into the treatment plant have large fluctuations, seasonally from a 1.0 MGD summer time
low to a 13 MGD winter high.
The city of Arcata needs to renew its NPDES permit, which will require them to reduce
effluent ammonia nitrogen levels compared to current discharge concentrations during
cold weather months. The standards set by the NCRWQCB will likely target effluent
limits on ammonia concentrations; however, the limits and timeline for Arcata to comply
are uncertain. The purpose of this project is to investigate a system Arcata can
implement, which will reduce ammonia concentrations through nitrification and
denitrification during cold weather months when the natural processes of the oxidation
ponds and treatment marshes are inhibited.
3
REVIEW OF LITERATURE
Global Nitrogen Cycle
Nitrogen is one of the most abundant elements on this planet and is a critical nutrient for
all life. The nitrogen cycle is intimately linked to the carbon cycle to effectively regulate
primary biomass production of aquatic and terrestrial ecosystems (Thamdrup, 2012).
Both cycles have been drastically altered with the increase of human population,
development of infrastructure, and industrialization. Agriculture is the greatest
contributor of nitrogen to the environment. The discovery and invention of providing
ammonia from atmospheric nitrogen has created an on going source for use as a fertilizer.
This has allowed humans to dramatically increase food production, bypassing cover crops
and microbial communities (Vymazal, 1995). The consequence of this method of food
production creates an imbalance in the nitrogen cycle. Accordingly, human influenced
alterations to the global nitrogen cycle have generated results such as; increased nitrogen
input into the land based nitrogen cycle, increased emissions of nitrous oxide (N2O),
reduction of soil nutrients (calcium and potassium), significant changes to aquatic and
terrestrial ecosystems, and alterations to the carbon cycle (Vitousek, 1997). Excess
nitrogen leaches from agriculture runoff into surface waters resulting in a modification of
nutrient ratios and ultimately eutrophication. Blooms of particular phytoplankton will
dramatically affect the water chemistry and can be detrimental to aquatic life, due to
changes in pH, fluctuations in dissolved oxygen concentrations, and increased
4
accumulation of organic material (Eilers, 2008). Additionally, civil infrastructure
contributes to these alterations through nitrogen loading of surface waters. High-density
developments and industry production generate concentrated point source waste streams
and emissions. Consequently, municipal wastewater contains pollutants and nutrient
concentrations that are toxic to aquatic life if directly discharged to surface waters.
Vitousek (1997) suggests that human influence on the nitrogen cycle has environmental
consequences related to soil health, aquatic ecosystem health, and alterations to
atmospheric composition. As the understanding of the nitrogen cycle increases, it
becomes more evident that it is necessary to reduce loading to aquatic ecosystems.
Fortunately, nitrogen speciation has become better understood and technology has
advanced to facilitate nitrogen removal of infrastructural waste streams. Municipal
wastewater treatment plants typically utilize two methods for removal, biological or
physical treatment. Biological treatment and removal of nutrients relies on microbial
communities to convert nitrogen into its many different forms (Davis, 2011). These
different forms of nitrogen are dependent upon microbial metabolisms that influence the
nitrogen cycling, which are dictated by the oxidation-reduction potential of the
wastewater (Figure 2) (Reddy, 2008).
5
Figure 2: Oxidation/reduction pathways available for Nitrogen (image from: Reddy,
2008) 1. Ammonification 2. Immobilization 3. Nitrification 4. Denitrification 5.
Dissimilator nitrate reduction to ammonia, 6. Di-nitrogen fixation, 7. Ammonia
volatilization.
Conventional Wastewater Treatment
Environmental engineers and wastewater treatment plant operators design and control
reaction chambers that remove nitrogen from municipal wastewater. This can be
accomplished by creating ideal conditions for the microbial communities existing within
wastewater to remove nitrogen. Autotrophic bacteria utilize carbon dioxide for cell
creation and are much slower growing than the heterotrophs that use organic carbon for
6
cell development; both of which can be further classified as chemo-autotroph or chemoheterotrophs that derive their energy from the oxidation of inorganic and organic
compounds, respectively (Metcalf and Eddy, 2003). Typically, suspended growth or
attached growth systems are utilized when reducing nutrient loads of municipal
wastewater in conventional wastewater treatment facilities. Activated sludge systems are
a very common application of suspended growth design in the treatment of wastewater
for nutrient reduction. Suspended growth systems retain and feed microorganisms
through energy intensive aeration systems creating active microbial cultures that are
recycled to break down nutrient inflows (Davis, 2011). Effluent from the reaction
chamber flows into a clarifier where the solids (microbial biomass) settle and condense
into what is known as activated sludge due to the high concentrations of micro-organisms
and diverse microbial ecology (Davis, 2008). This culture is recycled back to the reaction
chamber as Return Activated Sludge (RAS) where it meets influent flows with high
concentrations of nutrients and is supplied with sufficient oxygen to facilitate the process
of converting ammonia to nitrate (nitrification) (Metcalf and Eddy, 2003). Although
effective, this process is typically the highest consumer of energy in wastewater treatment
plant operations due to the mixing and aeration requirements.
Alternatively, attached growth systems do not require as much energy to operate. These
designs utilize the same microorganisms as suspended growth systems; yet provide
physical substrate for the formation of microbial biomass or biofilm (polysaccharides
concentrated microbial communities) (Metcalf and Eddy, 2003). The higher the surface
7
area of substrate, the more available sites for attachment. Conventional technologies like
Trickling filters or Bio-towers are the most common method for treatment plants to
utilize the attached growth process (Nourmohammadi, 2012). Influent flows are directed
through a distribution mechanism that sprays the wastewater over the packing material
(plastic media) and as the water moves down through the media it is passively aerated.
Through the consumption of ammonia ions and the presence of oxygen, biofilm is created
and accumulates, eventually detaching and flowing out with the effluent (Davis, 2008).
Due to the volume of biofilm that is generated, clarifiers are constructed downstream of
the trickling filter to settle out the accumulated solids. Energy requirements for trickling
filters are generally lower than that of suspended growth designs such as activated
sludge; however, they require a longer period of time to develop biofilm in order to meet
effluent quality standards. If maintenance issues occur and loading ceases, the biofilm
will die. This can cause operational problems, a period of decreased effluent quality, and
potential regulatory violations. To effectively facilitate nitrification, both suspended
growth and attached growth systems rely on the transfer of oxygen into the water column,
either passively or actively.
Oxygen Transfer
Transferring oxygen into wastewater requires a substantial and continuous energy
investment or a large area of land to utilize solar radiation. An aerobic environment will
initiate the metabolism of microorganisms that breakdown organic material (EPA, 1999).
8
Oxidation ponds are very effective in transferring oxygen through algal photosynthesis,
and this method is typically used in alternative treatment systems, such as AWTF.
Oxygen transfer will vary depending upon the characteristics of the wastewater, method
of aeration, and parameters of the reaction chamber (Metcalf and Eddy, 2003). The latter
two dependencies can be controlled by design and operation of the wastewater treatment
facility. Conventional treatment utilizes active aeration to transfer oxygen, which is
typically the most energy intensive activity in wastewater treatment plant operations. In
order to reduce costs, dissolved oxygen concentrations are measured at the water surface
of the reaction chamber and operations are adjusted to keep those concentrations below
or approximately1.0 mg/l. There are generally two types of aeration systems: submerged
and surface (EPA, 1999). Submerged aeration systems are installed below the water
surface where air is pumped through diffusers. Surface aeration systems generally rely on
mixing at the water surface to facilitate oxygen transfer. Some commonly used aeration
devices are presented in Table 1.
9
Table 1: Devices for aeration systems (adapted from Metcalf and Eddy, 2003)
Classification
Diffused fine bubble
system
Description
Submerged
Ceramic, plastic, and
flexible membranes
Diffused course
bubble system
Orifices, injectors, nozzles,
or shear plates
Sparger turbine
low speed turbine and
compressed air injection
Tubes with internal baffles,
air injected and retained at
the bottom of tube
Surface
Large diameter turbine
which exposes liquid to
atmosphere
propeller expose liquid to
atmosphere
Inclined propeller assembly
Water flows over steps
Static tube mixer
Low speed turbine
aerator
High speed floating
aerator
Aspirating
Cascade
Application
Activated sludge process
Activated sludge, channel or grit
chamber aeration, and anaerobic
digestion
Activated sludge and aerobic
digestion
Aerated lagoons and activated
sludge
Activated sludge, aerated lagoons,
and aerobic digestion
Aerated lagoon and aerobic
digestion
Aerated lagoons
Post-aeration
Submerged Diffused Bubble Systems
There are many systems available for oxygen transfer in wastewater treatment, yet
submerged diffused bubble systems will be used in this investigation. Submerged
diffused bubble systems can be categorized into fine or coarse bubble diffusion, usually
depending upon bubble size and therefore transfer efficiency; however, the exact
definitions between the two systems are still ambiguous (Metcalf and Eddy, 2003).
10
Porous diffusion systems are generally characterized as using a disk, dome, membrane, or
panel to transfer oxygen into liquid (Davis, 2011). These can come in many
configurations and are generally designed for conventional activated sludge chambers
that are typically 12-15 ft in depth. The materials used to manufacture these diffusors
range from: rigid ceramic/plastic, flexible plastic, rubber or cloth (Metcalf and Eddy,
2003).
Membrane diffusers are fine bubble diffusers that are designed to transfer oxygen into the
water column in addition to mixing and circulating air at the surface of the open water to
promote the transfer of oxygen into solution (Metcalf and Eddy, 2003). These oxygen
transfer systems are typically used in conventional wastewater treatment systems that
have limited space and available capital for operation. Small communities, with limited
capital, often have access to available land for alternative systems that utilize solar
radiation to generate necessary oxygen requirements.
Wetlands for Wastewater Treatment
Treatment wetlands have been used for water quality improvements throughout the world
since the 1950’s and usage in the United States has increased in the past 35 years
(Verhoeven, 1999; Kadlec, 2009). These natural systems provide an alternative passive
option to energy intensive conventional methods for small municipalities to treat their
11
wastewater, which also provides community resilience to large climate and energy
market fluctuations. Oxidation ponds are typically used in alternative wastewater
treatment systems to fulfill the oxygen demand of municipal wastewater. When combined
with treatment wetlands, the two can produce enhanced effluent quality. The algae
produced within oxidation ponds flow into treatment wetlands planted with emergent
macrophytes. Solar radiation is reduced and the algae die and settle to form a layer of
decomposing algal biomass.
Constructed wetlands have proven to be an effective method to improve municipal
wastewater quality when combined with primary treatment mechanisms (EPA, 1999).
Engineers and scientists are still attempting to understand and determine what parameters
of design are needed to facilitate an increase in effluent water quality. Two general
configurations that have been studied, Free Water Surface (FWS) wetlands and
Subsurface Flow Wetlands (SFW); both types have proven to be effective mechanisms to
improve water quality (Kadlec, 2008). Conventional biological treatment can control the
types of dominant microorganisms through slight variation in design parameters and
inputs. Constructed wetlands utilize natural ecosystems that perform relative to the
climate, temperature, and concentration of dissolved oxygen. In order to meet discharge
requirements, constructed wetland systems in cold climates require operational schedules
that differ according to seasonal changes in effluent quality. There is opportunity for
innovation in the design and operation of constructed wetlands and their capacity for
nitrogen speciation and reduction.
12
Wetland Nitrogen Cycle
Innovation in treatment wetland design has been spurred by the need for nitrogen
reduction (Austin, 2002). The nitrogen cycle in wetlands is very complex and is not fully
understood (Figure 3).
Figure 3: Nitrogen pathways within Wetland system (adapted from Kadlec, 2008)
Nitrogen has many pathways within a constructed wetland system. Typical nitrogen
sources of input into an engineered wetland system are atmospheric nitrogen fixation by
algal microorganisms, agriculture/urban (stormwater) runoff, and human waste (Reddy,
13
2008). Physical transportation of nitrogen within wetland systems can be broken down
into the following seven pathways: particulate settling and re-suspension, diffusion of
dissolved forms, plant uptake and translocation, litter fall, ammonia volatilization,
adsorption of soluble nitrogen on substrates, and organism migration (Kadlec, 2008).
Treatment wetlands receive the majority of nitrogen from nutrient enriched municipal
wastewater. Organic forms of nitrogen enter the system within municipal wastewater
predominately in the form of Urea, a by-product of human waste, which can be
hydrolyzed and changed into different valence states (Vymazal, 1995). There are five
primary processes of nitrogen speciation: ammonification (mineralization), nitrification,
denitrification, nitrogen fixation, and nitrogen assimilation (Kadlec and Knight, 1996).
Primary nitrogen pathways within constructed wetlands are summarized in Table 2.
14
Table 2: Primary nitrogen pathways in constructed wetlands (adapted from Vymazal,
2007)
Process
Transformation
Ammonification
Organic-N (urea) -> ammonia-N
Nitrification
Ammonia-N -> nitrite-N -> nitrate-N
Nitrate-ammonification
Nitrate-N -> ammonia-N
Nitrate-N -> nitrite -> gaseous N2,
N20
Ammonia-N (aqueous) -> ammonia-N
(gas)
Ammonia, nitrite, nitrate-N -> organicN
Denitrification
Volatilization
Plant/microbial uptake (assimilation)
ANAMMOX (anaerobic ammonia
oxidation)
Ammonia-N -> gaseous N2
Ammonification
Organic nitrogen enters and cycles within the system as a byproduct of human waste
(Urea) or plant and animal biomass (Vymazal, 1995). The majority of organic nitrogen
entering a wetland system is converted to ammonium (inorganic nitrogen). This process
is called ammonification, which is dependent on the rate that existing organic material is
being degraded (Kadlec, 2008; Reddy, 2008). The chemical process of Urea
transformation is presented in equation 1 (Kadlec, 2008):
𝑁𝑁𝐻𝐻2 𝐶𝐶𝑂𝑂𝑂𝑂𝑂𝑂 + 𝐻𝐻2 0  2𝑁𝑁𝑁𝑁4 + 𝐶𝐶𝐶𝐶2
(1)
15
Ammonium is the initial conversion of nitrogen within municipal wastewater treatment.
However, during laboratory analysis ammonium is converted to ammonia with a buffer
solution that dramatically increases pH and converts all ammonium in the wastewater
sample to ammonia. This report will now refer to ammonium concentrations as ammonia
(NH4).
Nitrification and Denitrification
To effectively remove nitrogen from the system it is necessary to promote the processes
of nitrification and denitrification. Parameters that influence the nitrification process
include temperature, hydraulic retention time, type and density of plant species, existing
microbial communities, climate, and wastewater characteristics (Chang-gyun, 1990).
Nitrifying bacteria (Nitrosococcus, Nitrospira, Nitobacter, Nitrosomonas) are
characterized as autotrophic that utilize ammonia ions for energy and require an aerobic
environment to convert ammonia to nitrite (Reddy, 2008; Nogueira et al., 2000). The
conversion of ammonia to nitrate is primarily generated by chemolithotrophic bacteria
that are only capable of respiring under aerobic conditions (Vymazal, 2007).
Additionally, heterotrophic bacteria are facultative and also have the ability to nitrify
(Chang-gyun, 1990; Vymazal, 1995). Nitrite (NO2-) is the interim product of the
nitrification process, however it is typically short lived and a variety of bacteria can
convert the nitrite to nitrate. Many microbial communities, and some fungi, have the
16
capability to denitrify in facultative conditions (Wallace, 2006). Stoichiometries in
equations 2-4 show the transformation of nitrogen in the nitrification and denitrification
processes (Medcalf and Eddy, 2008).
Nitrification:
Ammonia to nitrite (Nitrosonomonas)
3
𝑁𝑁𝑁𝑁3 + �2� 𝑂𝑂2  𝐻𝐻𝐻𝐻𝐻𝐻2 + 𝐻𝐻2 𝑂𝑂
(2)
Nitrite to nitrate (Nitrobacter)
3
𝑁𝑁𝑁𝑁3 + �2� 𝑂𝑂2  𝐻𝐻𝐻𝐻𝐻𝐻2 + 𝐻𝐻2 𝑂𝑂
(3)
Denitrification:
Nitrate to di-nitrogen
1
3
2
1
�3� 𝑁𝑁𝑁𝑁2− + �2� 𝐻𝐻 + + 𝑒𝑒 −  �3� 𝐻𝐻2 𝑂𝑂 + �6� 𝑁𝑁2
(4)
Heterotrophic bacteria are facultative and can function with anaerobic or aerobic
respiration depending upon the environmental conditions. These bacteria exist in the
microbial communities of wastewater and they are the initial consumers of existing
oxygen if excessive organic carbon is present (Gearheart, 1965). Due to the higher energy
content of oxidized organic carbon, the heterotrophs are stimulated to reduce the
17
carbonaceous load (CBOD). In addition to dissolved oxygen concentrations and
temperature, nitrification of ammonia is dependent upon the amount of available organic
carbon (Wallace, 2006). Heterotrophic bacteria require carbon to facilitate the
denitrification process, yet if excessive carbon is present they will dominate the microbial
consumption of available oxygen. If sufficient oxygen is not supplied to the system then
the heterotrophic bacteria inhibit the process of the autotrophs necessary to initiate the
reduction of the nitrogenous load (NBOD), and ultimately ammonia conversion
(Nogueira et al., 2000). These processes naturally occur within the rhizome region of
plant growth where there is potential for an oxygenated environment (Kadlec, 2008).
Accordingly, wetland vegetation plays a role in the influence on nitrification in wetland
systems.
Vegetation Effects
Wetland ecologies have an assortment of different flora. Treatment mechanisms utilize
vegetation for physical, ecological, and biological functions. Constructed wetland
ecosystems have a multitude of ancillary benefits that are primarily associated with the
abundant vegetation: wildlife habitat creation, recreational use, and beneficial economic
externalities. The primary benefit of the wetland biota is its innate ability to improve
degraded water quality (Maltais-landry, 2009). Accordingly, orientation of planting
regimes and types of plants used can have an effect on the effluent quality of constructed
wetlands. Nitrogen can be stored and essentially remain in the system through the
18
process of plant uptake and senescence where it becomes a part of nutrient cycling, peat
formation and burial, and settled algae biomass (Kadlec, 2008). Harvesting the plants is
required to fully remove nitrogen that is locked in the plant nutrient cycling. As in nature,
plants in constructed wetlands can also act as surface area for the attachment of nitrifying
bacteria to better facilitate the nitrification process. This surface area would reduce the
need for additional plastic media when considering design for nitrogen removal.
Table 3 indicates biomass development and nitrogen uptake of common plants found in a
treatment wetland. In temperate climates, such as those in Arcata, the typical successional
species of plants that eventually dominate the wetland ecosystem are Typha spp. and
Scirpus spp. (Verhoeven, 1999). Burke (2011) found that Typha latifolia and Scirpus
acutus at AWTF together accumulated a combined 996 kg/ha of nitrogen and 159 kg/ha
of phosphorous.
19
Table 3: Nutrient removal potential of common treatment wetland plant species (adapted
from Kadlec and Knight, 1996)
Species
Nitrogen
Phosphorus
Stock
Growth
Stock
Growth
(kg/ha)
(kg/ha/year)
(kg/ha)
(kg/ha/year)
Typha
250-1,560
600-2,630
45-375
75-403
Juncus
200-300
800
40
110
Scirpus
175-530
125
40-110
18
Phragmites
140-430
225
14-53
35
Eichhornia craspies
300-900
1,950-5,850
60-180
350-1,125
pistia stratiotes
90-250
1,350-5,110
20-57
300-1,100
90-300
540-3,200
23-75
130-770
240-425
1,400-4,500
30-53
175-570
Lemna minor
4-50
350-1,200
1-16
116-400
Salvinia
15-90
10.4-213
4-24
92-450
Hydrocotlye
Alternanthera
Philoxeroids
In northern climates the rate of nutrient uptake by macrophytes within a constructed
wetland system varies with seasonal growth and senescence. As indicated in Table 3
20
plant species can have large differences in nutrient accumulations. Harvest of the
dominant emergent macrophytes is an effective method to remove nitrogen from the
system, although this would increase operation and maintenance costs. Orientation of
planting regimes can also have an influence on total nitrogen concentration within the
wastewater effluent. Garcia-Lledo (2011) found that macrophyte coverage at the inlet
achieved higher removal efficiencies of nitrate and ammonia when compared to
vegetation coverage at the outlet.
Through photosynthesis, plants and algae transfer oxygen into the water column, the
concentration of dissolved oxygen is subject to diurnal and seasonal changes, especially
in cold climates. During the warmer months, higher temperatures and increased solar
radiation stimulate algal blooms in oxidation ponds or any exposed water surface in
treatment marshes. Algal blooms super saturate the wastewater with DO to reduce the
ammonia concentration through nitrification for a part of the year. Constructed wetlands
in cold climates cannot sustain high dissolved oxygen concentrations throughout the year
and may require mechanical aeration units to ensure total nitrogen removal. In addition to
oxygen limitations and vegetation effects, temperatures regulate the nitrification process
due to the reduced microbial activity during winter months (Wallace, 2006).
21
Temperature Effects
Temperature may have the greatest effect on the nitrification process. Microorganisms
that facilitate nitrification have varying sensitivities to temperature, and each metabolism
is affected differently. Ideal temperature ranges that energize biological processes depend
upon the characteristics of the wastewater, operation of the treatment facility, and the
wetland ecosystem (soil, vegetation, and climate) (Kadlec, 2001). Compared to most
places on this planet, Arcata, CA experiences small fluctuations in ambient temperature,
which lowers water temperatures below 10oC. Kadlec (2001) suggests that nitrification is
seriously inhibited at temperatures below 10oC; however, it is difficult to project if
wastewater at the AWTF will generate the same temperature thresholds. Werker (2002)
found that the rate of nitrification quickly declines to zero as water temperatures drop
below 6oC, which can also be sporadically experienced at AWTF. Accordingly, to
generate appropriate levels of nitrification in constructed wetlands during cold periods
and slow biological reaction rates of microbial processes, it is necessary to design
treatment wetland cells with a higher capacity for nutrient and BOD removal. However,
many municipalities like Arcata have limited land area available to increase treatment
capacity. In-situ aeration could be a viable option if temperature doesn’t substantially
inhibit nitrification during operation of the aeration system.
22
Artificial Aeration
The ammonia removal capacity in a constructed wetland system can be directly
facilitated through artificial aeration and the nitrification and denitrification speciation
pathway. Seasonal variations in climate and solar radiation in colder regions reduces the
rate of algal and macrophyte photosynthesis, thereby reducing oxygen production. Input
of oxygen through an aeration system can provide sufficient transfer to initiate the
metabolism of nitrifying bacteria.
Aeration systems may be useful within many regions of the world where temperature
fluctuations inhibit the nitrification process. Cottingham (1998) indicates that an aeration
unit can increase ammonia transformation from 18% to 68% with dissolved oxygen
concentrations ranging from 2.8 to 4.6 mg/l. This experiment was tested in a horizontal
subsurface flow treatment cell that had 3 years of plant growth and was 30m long, 5m
wide, and 0.6m deep. There were low rates of denitrification in this treatment cell
because of the lack of existing organic carbon (Cottingham, 1998). Due to the age of the
system the results indicated might not transfer to wetland cells that have substantially
more internal load associated with the time of operation. Since the treatment cell was
designed with a 7mm gravel bed matrix, Cottingham (1998) did not introduce any
additional media.
23
Alternative designs were studied in order to determine the performance of ammonia
removal. Jamieson (2003) found that laboratory scale containers with 1 year of plant
growth and length to width ratio of 4:1 achieved substantial removal of ammonia
concentrations. This system treated dairy waste and removal efficiencies increased from
50% before aeration to 93% approximately 16 days after the start of aeration (Jamieson,
2003). Performance of this system is desirable for ammonia removal rates; however, it
was studied in a greenhouse under a controlled environment, which is unlike typical
wetland conditions. Innovative wetland designs have been altered and tested with the
intention of nitrogen removal. Performance of these innovative systems has generated
similar removal efficiencies as seen by Jamieson (2003). Xianqiang (2007) showed that
vertical subsurface flow wetlands generated 77.8%, 92.2%, and 67.1% ammonia removal
depending on the flow regime. These systems show that in-situ aeration has the potential
to reduce ammonia concentration, although no studies have shown that this level of
performance can be achieved in a wetland cell that has been in operation for an extended
period of time.
24
METHODOLOGY
Aquaphyte
Initial aeration studies were conducted in the aquaphyte at the AWTF. The aquaphyte is
an elevated transparent Plexiglas flume that attempts to represent a scaled down treatment
wetland. The sidewalls were lined with black covering to obstruct exposure to solar
radiation and inhibit algal blooms. Dimensions and hydraulic retention time of the
aquaphyte are presented in Table 4. Filling and draining the aquaphyte measured
porosity, and plant biomass occupied approximately 55% of subsurface volume.
Table 4: aquaphyte dimensions and hydraulic retention time
Dimension
Cross section (ft2)
3.375
Height (ft)
1.5
Width (ft)
2.25
Length (ft)
32
Volume (ft3)
108
Volume (gal)
808
Porosity
55%
Theoretical HRT (days)
2.33
25
The aquaphyte received influent from a sump pump triggered by a float switch that
intermittently pulled water from Oxidation Pond 2 where it collected in a 50 gallon
barrel. A peristaltic pump was installed to regulate and ensure consistent water flow into
the aquaphyte. Typical water flow rates, ammonia loading, and BOD loading rates that
the aquaphyte received are represented in Table 5.
Table 5: Water flow and typical loading into aquaphyte
Water Flow
(Gal/day)
190.5
(L/min)
0.5
Typical loading
Ammonia loading (lbs N/day)
0.03
BOD loading (lbs BOD/day)
0.19
Plant species in the aquaphyte predominately consist of bulrush (Scirpus acutus), water
celery (Vallisneria americana), and morning glory (Cressa truxillensis) (Figure 4). Plants
were taken from the edges of the oxidation ponds and transplanted in the summer of
2010. There has been 3 years of plant growth and senescence, which created an
observable layer of accreted peat combined with settled algal biomass.
26
Figure 4: photo of aquaphyte adjacent to oxidation pond 2
Prior to any inputs, performance of the aquaphyte was analyzed to determine if any
nitrification occurred with low dissolved oxygen content, low water temperature, or
during the seasonal period of plant senescence. Oxygen was then introduced by an
aeration system installed approximately 10 feet downstream of the influent to observe
how an increase in DO would affect ammonia removal. The 10-psi, 1/10 horsepower
compressor pushed air into the system through a pumice stone aquarium diffuser.
Manufacturer specifications for the air diffusor were unavailable so, 20% transfer
efficiency was assumed.
27
The air stone diffuser was housed in a wooden frame constructed of 2in x 4in lumber.
Airflow was measured and regulated using a traditional rotameter with an operating range
from 0 to 100 SCFH. The components of the aquaphyte are represented in Figure 5.
Samples ports are equally space along the length of the system at approximately 4 ft.
increments.
Stabilization
Tank - from
Oxidation
Pond 2
Sample port
(Influent)
(Effluent)
Peristaltic
pump
Aeration
Air Pump
Rotometer
Figure 5: Diagram of aquaphyte with sample ports and equipment.
Before this experiment, the aquaphyte was previously tested with plastic media to house
nitrifying bacteria. However, the introduction of plastic media on a large scale may have
issues with operation and maintenance or potentially harmful effects on the existing bird
populations. Birds and mammals within the wastewater ecosystem may mistake the
plastic media for food, which would have detrimental effects if ingested. To avoid this
28
potential issue, it was assumed that there would be sufficient surface area on existing
plant biomass to harbor microbial communities and no additional plastic media was
necessary. As the aquaphyte aged, the macrophyte plant species (bulrush) occupied the
entire water column (Figure 6).
Figure 6: Existing plant growth within aquaphyte water column.
Lagace (2000) determined the submerged surface area of bulrush in different planted
densities (Table 6). Available surface area to harbor nitrifying microbial communities in
the aquaphyte was estimated from existing plant density (Table 6) within the reach of DO
concentrations > 1.0mg/l (Table 7).
29
Table 6: Estimated available surface area for a submerged depth of 0.6 m, bolded
numbers were used in calculations (adapted from Lagace, 2000).
Submerged plant biomass Area
Units
m2/m2
Low density
Medium density
3.79
High density
7.58
11.37
Extremely compact
15.16
Submerged plant biomass volume
m3/m2
0.021
0.042
0.063
0.084
ft3/ft2
0.066
0.131
0.197
0.263
Table 7: Estimated surface area of submerged plant biomass in aquaphyte within the
volume of water containing DO concentrations above 1.0mg/l (using data from Lagace,
2000).
Surface area
13.49
m2
136.44
ft2
Volume of submerged biomass
0.075
m3
2.41
ft3
56.74
ft2/ft3
30
Treatment Wetland Four
Treatment wetland four (TW-4) was the original pilot project at the AWTF and was used
to demonstrate that wastewater “enhancement” could be achieved with constructed
wetlands. TW-4 has been in operation for approximately 35 years and the vegetation has
never been harvested, which has generated a substantial internal load of nitrogen,
phosphorous, and carbon associated with the time of operation and plant life cycles. TW4 consists of ten adjacent cells with a trapezoidal cross section operated in series. Each
treatment cell has a width of 20 ft, and length of 200 ft for a total system length of 2000 ft
(Table 8). Testing was conducted on one cell during the summer of 2013 to determine if
the results seen in the aquaphyte can be repeated in a larger scale system.
Table 8: Dimensions and HRT of one channel in Treatment Wetland 4.
Treatment Wetland 4
Cross Sectional Area ft2
Height (ft)
42.75
2.25
Top width (ft)
20
Bottom width (ft)
18
Length (ft)
200
Volume ft3
8550
Volume (gal)
63958
31
TW-4 was initially planted with Bulrush and Cattail (Typha latifolia) in alternating
channels to determine if the dominant vegetation would influence treatment. Although
bulrush still exists in the system, cattail has established itself as the dominant species in
all channels. Operating water depth is higher than the original value in all of the treatment
wetlands and has generated enough buoyant force on the root system to dislodge the
rooted plants and create a floating mat of detritus and plant vegetation. Macrophytes
created a layer of degrading biomass at the water surface that provides sufficient
substrate for the existing rhizome systems, which has essentially enabled them to survive
without soil substrate.
Wastewater is pumped from Oxidation Pond 2 (ox-pond 2) into a stilling tower and then
loaded into TW-4. Flow rates into TW- 4 started at approximately 0.2 MGD, which is the
flow under normal operation. These flows were reduced after initial testing in an attempt
to converge towards greater similitude between the aquaphyte and TW-4 (Table 9).
32
Table 9: Water flow rate, typical ammonia loading, typical BOD loading, airflow, and
HRT into experimental cell of Treatment Wetland – 4
Water flow
Air flow
Reduced water flow (gal/day)
22300.0
CFM
8.00
Normal water flow (gal/day)
200,000
O2 transfer efficiency
0.2
Typical Loading
HRT
Nitrogen loading (lbs N/day)
3.72
HRT (days) reduced flow
2.87
BOD loading (lbs BOD/day)
27.88
HRT (days) normal flow
0.32
The aeration system was installed at approximately half the length of the entire treatment
wetland or 11.5 days into the HRT (with the reduced flow rate), where one of the 200 ft
channels was analyzed for nitrification and denitrification. The aeration system consisted
of a 0.75 hp compressor, PVC piping, rubber hose, and eight 9 inch diameter membrane
diffusers. Fine bubble membrane diffusers were chosen instead of stone diffusers to
reduce required maintenance and inhibit flooding of the conveyance system if the
compressor was shut down. Piers and platforms were constructed to access the aeration
system for maintenance and to gather samples (Figure 7).
33
Figure 7: Aeration system installed in Treatment Wetland 4.
Sample ports were installed in order to observe the transformation of ammonia as it
advects along the length of the treatment cell (Figure 8).
34
Figure 8: Diagram of Treatment Wetland 4 aeration system, sample ports, and pier. Water
flows in from the bottom right corner of the diagram and past the sample ports indicated
in red with distance from aeration system.
Samples were analyzed from TW-4 with no plastic media installed to test the hypothesis
that there would be sufficient surface area within the existing plant biomass; however,
there is a substantial difference in the configuration of the emergent macrophytes
between the aquaphyte and TW-4. Consequently, plastic media was installed to
determine if surface area for microbial attachment was a parameter that would increase
ammonia reduction. Wooden frames with plastic mesh (Figure 9 left) were constructed
35
and installed to contain the plastic media. Additionally, laundry bags and chicken wire
“bags” were filled with Bio-Pac honey comb media and plastic strapping (Figure 9 right).
Figure 9: Left photo indicates the wooden frame containment and media. Right photo was
the chicken wire “bags” that contained large honey comb media and strapping material.
Both were installed into Treatment Marsh 4 to facilitate nitrification.
Eight wooden frames were installed adjacent, on the downstream (left) side, of the
aeration system (indicated by the multiple PVC pipes sticking out of the water in Figure
10).
36
Figure 10: Operation of the aeration system installed in Treatment Marsh 4 downstream
of the constructed pier.
Additional media, in laundry bags, was installed directly above the aeration unit and the
system was tested. These bags were replaced with chicken wire “bags” in an attempt to
allow for more mixing to occur on the water surface and the system was retested.
An estimation of the available surface area in TW-4 is presented in Table 10. These
values approximate the media surface area that was added to the system and does not
consider any other available surface area in the form of chicken wire, plastic mesh on
wooden frames, or plant biomass.
37
Table 10: Estimation of available surface area on the additional plastic media; it is
assumed that 70% of area is available.
Surface area TM 4
Strapping (ft2)
Strapping volume (ft3)
540
3
Strapping (ft2/ft3)
Strapping (ft2) * 70%
180
378
Biopac (ft3)
Biopac (ft2)
Biopac (ft2/ft3)
Biopac (ft2)* 70%
47.04
1411.2
30
987.84
Poly Pall rings ft2/ft3
Volume of poly pall rings ft3
Surface area (ft2)
Total media volume (ft3)
45.59
10
456
60.04
Total media surface area (ft2)
1822
Performance of the aeration system installed in TW-4 was analyzed during the summer
months by observing the internal load being released from the wetland. The turbulence
created by the aeration system stirred accreted ammonia that has accumulated over the
past 35 years of operation. This was evident by observing excessive organic content in
the samples taken directly above the aeration system, which did not exist in samples
taken further downstream.
38
Monitoring and Laboratory Analysis
Samples from each of the installed sample ports monitored performance of both the
aquaphyte and TW-4 on a weekly or bi-weekly schedule. The aquaphyte had ten sample
ports with the additional samples from the influent and effluent. Samples in the
aquaphyte were extracted using a PVC pipe with a connected container, which was rinsed
three times with surface water in each associated port before each sample was bottled –
the bottles were also rinsed three times. A hand pump was used to extract the samples
from TW-4 to get a representative sample at the same depth in each sample port.
Water quality conditions were determined from laboratory testing that included:
ammonia, nitrate, NBOD, CBOD, and TSS. Additionally, in-situ field tests of DO, pH,
and temperature were taken while samples were being extracted. Laboratory analysis of
BOD, ammonia, nitrate, and TSS were conducted according to procedures presented in
AWWA (2005).
39
RESULTS AND DISCUSSION
The aquaphyte has proven to have an effective design that facilitates nitrification. This
chapter will discuss the variables and observations relative to temperature, aeration,
media and contact time that appeared to affect the rate of nitrification in the aquaphyte.
Additionally, relevant data recorded for TW- 4 will also be presented and discussed in
this chapter.
Aquaphyte
Effects of temperature on the rate of nitrification.
Located in the Pacific Northwest, Arcata experiences coastal climate effects of mild
temperature fluctuations and high rates of precipitation. Ambient temperatures can reach
below freezing, which lowers water temperatures down to approximately 4oC at the
wastewater treatment facility. These low temperatures occur during periods when
ammonia concentrations are high, and the natural treatment capability of wetland
ecologies cannot reduce the effluent ammonia to acceptable values. Reduction in
performance of constructed wetland systems during the winter months is attributed to
water temperature, plant dormancy, and reduced oxygen transport (Werker, 2001). Water
temperature is an important variable when designing an in-situ aeration system.
Understanding how water temperature affects nitrification at AWTF will help avoid an
40
unnecessary economic burden during periods when lower water temperatures inhibit
microbial metabolisms.
Throughout the year, and especially during the winter months, sections of the AWTF
operate as an oxygen deficient system with DO concentrations below 1.0mg/l. However,
some nitrification occurs under these conditions throughout cold periods of the year.
Laboratory analysis was performed during the cold winter months to determine how
temperature affects the capacity of the aquaphyte to nitrify without any inputs. The
aquaphyte reduced ammonia levels by 44% without any mechanical input during cold
weather months (Figure 11). Nitrate concentration increased by about half compared to
the ammonia reduction. It is possible that some of the ammonia volatilized, however this
would require an increase in pH that wasn’t observed. Additionally, although short lived,
some of the difference between the reduction in ammonia and the increase in nitrate
could be accounted for by an increase in nitrite, which wasn’t measured in the laboratory
analysis. Ultimately, it is likely that denitrification is occurring at about half the rate of
nitrification.
41
20
NH3-N Conc. (ppm)
NO3-N Conc. (ppm)
18
Observed Value (mg/L)
DO (ppm)
16
Temp (Celcius)
14
pH
12
10
8
6
4
2
0
Sample Ports
Figure 11: Aquaphyte performance with no aeration and cold temperatures 1/4/13;
average temperature 7.4oC. Sample ports are equally spaced along the length of the
aquaphyte (4 ft increments).
There is evidence that microbial metabolism is still active at some of the lowest
temperatures (7.4oC) of the season (Figure 11). During the same week of testing, NBOD
was reduced by 25% of the initial load, while CBOD was reduced by 27% (Figure 12).
Heterotrophic bacteria, typically dominating the microbial populous, are capable of
facilitating nitrification under anoxic conditions, which may indicate that ammonia ions
42
are utilized as a source of energy when oxidized organic carbon is not available.
Autotrophic bacteria are more dormant and far slower growing, which leads to the
conclusion that heterotrophic bacteria are degrading the NBOD during cold winter
months.
Observed value (mg/L)
20.00
CBOD
NBOD
18.00
16.00
14.00
12.00
10.00
8.00
6.00
4.00
2.00
0.00
SP 1 SP 2
(INF)
SP 3
SP 4
SP 5
SP 6
SP 7
Sample Location
SP 8
SP 9
(EFF)
Figure 12: Total BOD characterized as NBOD and CBOD, average temp 7.4oC
(01/04/13)
Similar reductions were seen when average temperatures reached 6.9oC, generating a
52% decrease in ammonia, most converting to nitrate, some of which was then converted
to di-nitrogen. This indicates that nitrification does occur at colder temperatures without
any assistance. However, the BOD trend in Figure 12 doesn’t continue as cold
temperatures prevailed. With an average temperature of 6.9oC, NBOD increases by 75%
43
while the CBOD was reduced by 69% (Figure 13). It is uncertain why such an increase in
NBOD was observed.
Observed Value (mg/L)
25.00
20.00
15.00
10.00
NBOD
5.00
CBOD
0.00
SP 1
(INF)
SP 2
SP 3
SP 4
SP 5
SP 6
SP 7
Sample Location
SP 8
SP 9
(EFF)
Figure 13: Total BOD average temp 6.9oC 1/11/13
The increase of NBOD and reduction of CBOD continued as water temperatures
remained below 10oC. This trend approximates the dynamics of oxygen demand during
the cold-water temperatures and low rates of solar radiation throughout the testing period.
Typically an increase in NBOD can be attributed to the breakdown of organic material,
which is unlikely due to the low temperatures and inhibited microbial processes. It is
difficult to determine why NBOD increases so dramatically.
44
Seasonal changes, dictated by higher levels of solar radiation, gradually increase water
temperatures as the calendar moves into the spring months. By the middle April, the
average water temperature was approaching 13oC, which is near the threshold where a
significant increase in the rate of nitrification occurs (Kadlec and Reddy, 2001). The
nitrogen dynamics of the system in the middle of April, with an average temperature of
12.6oC, showed a 45% reduction in ammonia concentrations (similar to that seen with
temperatures of 6.9oC). However, there is not a corresponding increase in nitrate
concentrations suggesting that nitrification may not be occurring. An alternative nitrogen
pathway may be reducing the ammonia concentrations. For instance, the reduction of
ammonia could be attributed to plant uptake. Solar radiation and plant growth were
observed during this period of the year, which could explain why nitrate concentrations
did not increase. Otherwise, anoxic zones may exist within the aquaphyte where
denitrification can occur, which is not detected by the existing sample port orientation.
45
Observed value (mg/L)
25.00
DO
Ammonia
Nitrate
20.00
15.00
10.00
5.00
0.00
SP 1
(INF)
SP 2
SP 3
SP 4
SP 5
SP 6
Sample Location
SP 7
SP 8
SP 9
(EFF)
Figure 14: Ammonia reduction in the aquaphyte on 4/12/14; average temp 12.6oC
The average removal of ammonia, NBOD, and CBOD relative to temperatures above and
below 10oC is presented in Table 11. There are slightly higher rates of ammonia removal
when water temperatures are greater than 10oC. However, the rate of ammonia removal is
not dramatically different so temperature may only have a slight effect on the rate of
nitrification with loading rates near 20 mg/l at the AWTF.
46
Table 11: Percent removal of ammonia, NBOD, CBOD with average temperatures above
and below 10oC (based on 21 samples)
Constituent
Ammonia
Average cold temp removal (<10oC)
Average warm temp removal (>10oC)
Percent Removal
56%
68%
NBOD
Average cold temp removal (<10oC)
Average warm temp removal (>10oC)
564% (increase)
72%
CBOD
Average cold temp removal (<10oC)
Average warm temp removal (>10oC)
56%
68%
Throughout the testing period, NBOD shows a dramatic change as temperatures increase.
Below 10oC, the aquaphyte contributes nitrogen from the internal load of previous
ammonia accretion, but as the temperature increases NBOD is removed from the system.
Coincidentally, the removal rates for CBOD and ammonia are the same, supporting the
theory that heterotrophic bacteria dominate microbial populous under cold water
conditions. Other environmental variables confound the interpretation of the removal
presented in Table 11. For instance, 70% of the data was measured under conditions of
aeration, making the direct effect of temperature more difficult to isolate.
Low temperature is known to inhibit microbial processes and reaction kinetics. However,
Figure 15 indicates that high rates of nitrification occur at temperatures below ideal
ranges for nitrifying bacteria reported in the literature. Ammonia removal rate reaches
47
approximately 100% nearly two months before average water temperatures are in the
ideal ranges. Removal of ammonia approaches 100% while the temperature average is
still only 9oC. The average influent ammonia concentration was 23.3 mg/l during this
winter season. Such high removal rates at low temperatures suggest that low water
temperatures with average ammonia influent concentrations of 23.3 mg/l do not seriously
influence rates of nitrification. However, AWTF has seen ammonia concentrations three
times higher than observed during this study. If loading rates approach those levels and
water temperatures are below 10oC the system may have difficulty achieving desired
removal.
16.0
100%
14.0
80%
10.0
60%
8.0
6.0
40%
4.0
20%
2.0
0.0
12/17/12
temp
1/6/13
1/26/13
ammonia removal %
2/15/13
3/7/13
3/27/13
0%
4/16/13
date
Figure 15: Temperature vs. Ammonia removal over time; large increase in removal
efficiency is a result of operating the aeration system.
percent removal
Temperature oC
12.0
48
Garrison (2011) observed a period of influent concentrations that averaged approximately
32 mg/l with an average water temperature of 10.5oC. The aquaphyte performed very
well with influent concentrations 50% higher than observed during this study. However,
there seemed to be an initial adjustment period for the system to adapt to the increased
loading (Table 12). Temperatures during Garrison’s study were slightly higher than
observed during this study, but still below the temperature threshold of 13oC. Between
11/27/10 and 12/03/10 water temperatures averaged approximately 7.7oC (lowest
temperatures of the season) and ammonia removal efficiencies of 99%. The influent
concentrations during these two weeks averaged approximately 20 mg/l, which were very
similar to the conditions and results observed during this study (winter 2012/2013). The
50% increase of ammonia loading with a corresponding 4.3oC increase in temperature on
12/10/10 reduced ammonia removal from 99% to 53%. It appears that the low
temperatures inhibit the rate of nitrification and biofilm development, but don’t eliminate
it completely. Due to the low water temperatures the system potentially required more
time for the microbial ecology to adjust to the new loading conditions.
49
Table 12: Aquaphyte performance winter of 2010; average temp 10.5oC, average influent
concentration 32.5mg/l, with aeration
Date
Influent ammonia
concentration (mg/L)
11/27/10
12/3/10
12/10/10
12/17/10
1/19/11
1/22/10
1/26/10
2/11/10
3/1/10
18.5
22.3
31.9
34.5
28.9
29.4
32.2
30.9
32.5
Ammonia
removal (%)
99%
100%
53%
92%
99%
98%
94%
94%
79%
Average temp
(C)
6.6
8.8
12.0
8.9
12.5
11.3
10.3
9.4
11.9
With the loading rates seen during this study, low water temperatures don’t appear to
drastically effect the rate of nitrification as observed by Garrison (2011). However, for
the performance of the system to reach above 90% removal with cold-water
temperatures, artificial aeration is necessary.
Effects of aeration on nitrification.
The aeration system was installed in the aquaphyte and the system performance was
analyzed. One week after the aeration system started operating, the nitrogen speciation
dynamics resulted in a sharp increase in nitrate (ammonia probe malfunctioned this
week), indicating that the start up time for removal of ammonia may be fairly short.
However, high rates of nitrification don’t become consistent until approximately 28 days
of aeration (Table 13). Additionally, NBOD wasn’t reduced until 35 days of aeration and
50
a full reduction did not occur until 45 days of aeration. Correspondingly, temperature was
gradually increasing during this period, which might account for some of the delay.
Table 13: Reaction of water quality parameters throughout the period of aeration
Date
1.25.13
2.01.13
2.08.13
2.15.13
2.22.13
3.01.13
3.10.13
3.20.13
3.29.13
4.05.13
Days of
aeration
0
7
14
21
28
35
45
55
64
71
Ammonia
reduction (%)
40%
NA
34%
38%
98%
NA
NA
99%
99%
98%
NBOD
reduction
830% (increase)
362% (increase)
8% (increase)
319% (increase)
NA
52%
100%
94%
94%
93%
CBOD
reduction
42%
NA
41%
78%
NA
71%
96%
73%
81%
87%
Ammonia reduction in the aquaphyte increased during the period of aeration. The system
responded to aeration with a sharp decrease in ammonia concentrations and a
corresponding increase in nitrate concentrations as the flow approaches the plume of DO
saturated water (Figure 16). With these rapid changes in concentration, it is evident that
the system quickly responded to the influx of oxygen and nitrification is occurring.
51
Observed value (mg/L)
30.00
DO
Ammonia
Nitrate
25.00
20.00
15.00
10.00
5.00
0.00
SP 1
(INF)
SP 2
SP 3
SP 4
SP 5
Sample Location
SP 6
SP 7
SP 8
SP 9
(EFF)
Figure 16: Constant head flow regulation; average temp 8.1oC; 34% ammonia reduction
(2/08/13)
Denitrification is also seen in the oxygen deficient zones of the aquaphyte downstream of
sample port 5 as nitrate concentrations decrease. During this period (2/08/14, Figure 16)
there is a slight 8% increase of NBOD, CBOD was reduced by 40%, and the DO
concentrations remain at near saturated levels within the region of sample port 3.
Additionally, the spatial zone between sample port 5 and 9 allow observation of the
ammonia internal load contributions.
The following week of aeration (2/17/13) was unusually warm with an average
temperature in the system of 12.3oC. The first significant drop in DO concentration in the
52
aeration zone occurred during this period, from 9.5 ppm (the first week of operation) to
6.0 mg/l, which resulted in an 80% reduction in CBOD concentrations (Figure 17).
However, due to the increase in NBOD from the internal load of the system, the
reduction of total BOD was only 20%.
35.00
CBOD
NBOD
Observed value (mg/L)
30.00
25.00
20.00
15.00
10.00
5.00
0.00
SP 1
(INF)
SP 2
SP 3
SP 4
SP 5
SP 6
Sample Location
SP 7
SP 8
SP 9
(EFF)
Figure 17: Total BOD concentrations during period of aeration; average temp. 12.3oC
(2/17/13)
Some ammonia conversion by nitrification was offset by the aeration unit, which stirred
up ammonia-laden peat and decomposing algal biomass that has settled to the bottom of
the aquaphyte over the past three years of operation. The stirring of peat and algal
biomass became apparent when observing the samples extracted directly above the
53
aeration system. These samples contained visible organic matter that wasn’t observed in
samples downstream of the aeration unit.
Soil is where the highest concentrations of ammonia are stored within wetland
ecosystems (Bowden, 1987). This can be a significant contribution of ammonia as
wetland cells age and store nutrients, which would increase demand for oxygen and
operational energy requirements. To avoid this economic burden, it may be necessary to
harvest live and decomposing biomass every 3-5 years of operation. This frequency can
change depending upon the loading received during that operational period.
Soon after aeration began, the peristaltic pump that regulated influent flow required
maintenance and the system reverted to constant head flow regulation for the first three
weeks. The constant head flow regulation is easily clogged with debris and showed
consistent diurnal fluctuations of flow through the system. The first 21 days of aeration
generated an average ammonia reduction of 36%. The peristaltic pump was reinstalled
on 2/16/13, which once again supplied a constant influent flow rate. After 21 days of
aeration, during the seven-day period following the reinstallation of the peristaltic pump,
and a 4.6oC decrease in water temperature, ammonia reduction increased from 37%
(2/15/2014) to 98% (2/22/13).
The high rates of nitrification with the corresponding drop in temperature also helps
justify the conclusion that in-situ aeration to facilitate nitrification is insensitive to low
54
water temperature with the loading rates seen during this study. In addition, lower water
temperatures potentially inhibit biofilm development at the AWTF enough that
approximately 28 days of growth within an aerobic environment is required to achieve
desired rates of removal.
After 28 days of aeration, the aquaphyte facilitated a 98% reduction of ammonia
concentrations together with an 80% increase in nitrate concentrations (Figure 18). The
remaining 18% could have taken multiple pathways within the system. Findings from
Shammas (1986) indicate that some of the ammonia could remain in the form of nitrite,
because the biological processes of Nitrobacter, bacteria that convert nitrite to nitrate, is
slightly more sensitive to cold than Nitrosomonas (bacteria that convert ammonia to
nitrate). Considering what the low temperature was that week, some of the ammonia
could be in the form of nitrite. The 98% reduction in ammonia concentration (Figure 18)
continued until 4/05/13 when the aeration system shut down, 70 days after start up.
55
Ovserved value (mg/L)
30.00
DO
Ammonia
Nitrate
25.00
20.00
15.00
10.00
5.00
0.00
SP 1
(INF)
SP 2
SP 3
SP 4
SP 5
SP 6
Sample Location
SP 7
SP 8
SP 9
(EFF)
Figure 18: One week after install of peristaltic pump flow regulation; average temp
7.9oC; (2/22/13), 28 days after aeration began
Performance of the system for the first and nearly coldest month of aeration (between
1/12/13 – 2/22/13) showed that NBOD increased from the internal load resulting in a
higher concentration in the effluent than that of the influent with concurrent reductions
seen in CBOD concentrations. Forty-five days after the installation of the aeration unit, a
100% reduction in the NBOD concentration in the aquaphyte is observed, in addition to
50% reduction in CBOD (Figure 19) indicating that the microbial population appeared to
be dominated by nitrifying bacteria.
56
Observed value (mg/L)
40.0
CBOD
NBOD
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
SP 1
(INF)
SP 2
SP 3
SP 4
SP 5
SP 6
Sample Location
SP 7
SP 8
SP 9
(EFF)
Figure 19: (3.10.13); 100% reduction in NBOD, 50% reduction in CBOD
Concentrations of BOD drastically increase in the spring as the water starts to warm.
Figure 20 shows how the system handles high BOD loading, which increased
approximately fivefold. The NBOD was reduced by 96% and CBOD was reduced by
92% with an airflow rate of 50 SCFH and an average temperature of 13.3oC. This shows
that the system can sufficiently reduce high loading rates of BOD.
57
250.00
Observed Value (mg/L)
CBOD
NBOD
200.00
150.00
100.00
50.00
0.00
SP 1
(INF)
SP 2
SP 3
SP 4
SP 5
SP 6
Sample Location
SP 7
SP 8
SP 9
(EFF)
Figure 20: 4.05.13; 70 days of aeration operation; average temperature 13.3oC; 50 scfh
Ultimately, the effective performance of the aquaphyte appears to be attributed to the
operation time of the aeration unit, but may also be dependent upon temperature, and the
total age of the system. Due to the slow growth of nitrifying bacteria, it may take up to 28
days to achieve reductions in NBOD. Additionally, the CBOD may need to be degraded
sufficiently for the microbial population dynamics to be dominated by nitrifying bacteria.
58
Ammonia removal efficiencies continue at these rates throughout the cold weather
months and remain consistent as temperature increases.
Media and contact time.
Basviken (2003) suggests that media plays an important role in nitrification by providing
a substrate for biofilm to develop in attached growth reactions. Increasing the density of
biofilm will produce high rates of nitrification, assuming that surface area is a limiting
factor. Surface area of the substrate can come in many forms. Plastic media has been used
in conventional wastewater treatment systems to provide substrate for nitrifying bacteria
to attach. Garrison (2011) performed a previous analysis on the aquaphyte from 20102011. During Garrison’s study, the aquaphyte was approximately one year old, and the
plant density was comparably sparse. With the addition of media, Garrison observed that
the aquaphyte removed 99% of the ammonia and there was an approximately 82%
increase in nitrate (Figure 21). Garrison (2011) did not analyze the system without media
so it is difficult to determine if the system would have achieved the same levels of
removal without the installation of plastic media.
59
35
DO
Observed value (mg/L)
30
Ammonia
Nitrate
25
20
15
10
5
0
Pt 1 (in)
Pt 2
Pt 3
Pt 4 (air)
Sample Location
Pt 5
Pt 6
Pt 7
pt 8 (out)
Figure 21: Garrison, average temp 12.5oC, with plastic media, influent concentration of
27.21ppm, air flow 70 scfh
This study of the aquaphyte has shown that nitrification (ammonia reduction and
conversion to nitrate) occurs without the addition of plastic media (Figure 22). Arcata
operates a natural treatment system that is constantly changing and adapting to variations
in climate and time of operation. It was determined that the aquaphyte, after three years
of growth, contained sufficient submerged plant surface area for microbial attachment
and no additional media was installed. Approximately 99% conversion of ammonia to
nitrate was observed without the use of plastic media (Figure 22).
60
30.00
DO
Ammonia
Nitrate
Observed value (mg/l)
25.00
20.00
15.00
10.00
5.00
0.00
SP 1
(INF)
SP 2
SP 3
SP 4
SP 5
SP 6
Sample Location
SP 7
SP 8
SP 9
(EFF)
Figure 22: Nitrogen dynamics on 3.20.14; average temperature 12.2oC, no installed
plastic media
This study measured a porosity of approximately 55% that provided sufficient surface
area of microbial attachment; however, it appears that the amount of surface area may not
be as important as the location of this surface area within the system. Figure 21 and
Figure 22 illustrate how the nitrogen dynamics change as the flow approaches the
aeration zone of the aquaphyte where dissolved oxygen concentration is above 1.0mg/L.
Newly constructed systems with sparse plant density may require the use of plastic
media. If necessary, plastic media needs to be installed within the reach of DO
concentrations > 1.0 mg/l to achieve appropriate ammonia removal efficiencies. After
61
three years of operation, the aquaphyte has extremely dense bulrush growth within the
zone of aeration, so additional surface area added by plastic media was unnecessary.
Residence time and plant growth within elevated levels of DO could also be of some
significance when designing in-situ aeration systems for constructed wetlands (Table 14).
Table 14: Residence time within media, mass of oxygen within contact volume, and mass
of oxygen per square foot of surface area on 3/20/14
Contact time within media (Hrs)
12.72
Mass of oxygen available within contact volume (g)
2.02
mg O2 / ft2 surface area
1.32
Contact time in the emergent plant substrate within the region of DO concentrations
above 1 mg/l is approximately 1/4 of theoretical HRT. Design of in-situ aeration systems
should incorporate the type of media appropriate for constructed wetland waste treatment
systems. It is recommended to use plant surface area as a substrate due to the
complications that could arise when using plastic media in an in-situ design. However, if
plants are utilized for substrate, specific operational parameters need to be strictly
followed. For instance, periodic harvesting of biomass is necessary to avoid accumulation
of organic carbon in addition to accreted ammonia, reducing the effect of the seasonally
compounding internal load. Ultimately, periodic harvesting is a necessary parameter of
62
operation in any constructed wetland system or the system will eventually reduce its own
capacity to improve water quality as it fills with decomposing plant and algal biomass
(Kadlec, 2008).
Scale Up: Treatment Wetland 4
Water quality analysis.
The rate of ammonia conversion observed in the aquaphyte was desired in a full-scale
system. Aeration equipment was installed into TW-4 and operated during the summer
months when ammonia concentrations at the treatment plant are typically low, but the
internal loading of ammonia from decomposing plant and algal biomass made it feasible
to test the scaled up aeration system.
There are some major observable differences between TW-4 and the aquaphyte. TW-4
has been loaded with municipal wastewater for approximately 35 years and has had a
tremendous amount of biomass accumulation and ammonia accretion throughout that
period of operation (Figure 23 and Figure 24). Additionally, the emergent macrophytes
established in TW-4 have become dominated by cattail, which have uprooted and float on
a one-foot thick mat of peat on the water surface. These differences were considered
when establishing the aeration system. The aquaphyte water column is dense with
bulrush and additional media for nitrifying bacteria attachment was unnecessary. Due to
the floating vegetation mat in TW-4, media was added to the system in an attempt to
63
generate uniform loading of media through the entire cross section of the treatment cell
and aeration system.
Figure 23: The initial pilot project, Treatment Marsh 4, on September 3, 1980. The
system was designed and operated in series with 10 separate treatment cells (W= 20' x L
= 200' x D = 2') Initially, the treatment cells alternated plantings from Bulrush to Cattail.
Plant biomass was still sparse and developing.
64
Figure 24: TW-4 in the Summer 2013 after 35 years of loading with municipal
wastewater. Biomass development is extensive when compared to Figure 23. It now
operates in parallel with a sinusoidal flow pattern. Cattail has emerged as the dominant
macrophyte.
DO and BOD.
The installed aeration system produced a peak DO concentration of 5.2 mg/l directly
above the aeration system, which is well below the near saturation levels (9.5 mg/l) that
were recorded in the aquaphyte. Peak DO concentrations, near 5 mg/l, remained for
approximately 22 days after the installation of the aeration system with no visible
response in the concentration of ammonia. Following this 22 day period, while the air
65
flow rate stayed constant, DO concentration decreased by 15% (from 5.2 mg/l to 4.4
mg/l) that reduced total BOD in TM – 4 by approximately 30%, which could be due to
the break down of the extensive carbonaceous load (Figure 25).
Observed value total BOD (mg/L)
140
120
100
80
60
40
20
0
P2
Pre-Air
Air
5 ft
10 ft
15 ft
20 ft
25 ft
30 ft
35 ft
40 ft
Sample Location
Figure 25: Total BOD reduction of 30% on 5/22/13 indicating that the DO was being
consumed
DO concentrations continued to decline as the oxygen demand was reduced. The system
generated a 25% reduction in total BOD, which may indicate that the performance is
oxygen limited (Figure 26). Potentially, if the DO concentrations were near saturated
levels, the necessary reductions in CBOD would occur and degradation of the
nitrogenous load would begin. However, due to the design of the membrane diffusers and
the depth of water in the treatment cell, it is difficult to artificially achieve high rates of
66
oxygen transfer. Membrane diffusers are typically installed in activated sludge reaction
chambers, which are designed with depths of approximately 12-15ft. Oxygen transfer is
reduced when the depth of the water column is reduced, as is the case when installing
diffusors in a treatment wetland.
DO (mg/L)
130.0
1.6
120.0
1.4
1.2
110.0
1
100.0
0.8
90.0
0.6
80.0
0.4
70.0
0.2
0
60.0
-5
5
15
25
35
Distance from aerator (ft)
Figure 26: Total BOD reduction with DO consumption on 6/6/13
In an attempt to increase performance of the aeration system to reduce ammonia and
BOD, different orientations and volumes of media were added and the system was
Dissolved Oxygen (mg/L)
Observed BOD value (mg/L)
Biological Oxygen Demand
67
retested. Chicken wire “bags” filled with plastic media were installed to replace the
laundry bags to promote more mixing at the water surface with the intention of increasing
oxygen transfer. Laundry bags had mesh walls that appeared to clog with biofilm
accumulation and reduce the aeration through the media, thereby inhibiting oxygen
interaction on the media surface area. Replacing laundry bags with wire “bags” did not
generate elevated DO concentrations as no change was seen after their installation.
Although, three days prior to the installation of the chicken wire bags NBOD and CBOD
were reduced by 30% and 25%, respectively. Interestingly, three days following
(6/13/13) the replacement of laundry bags with wire, CBOD reduction essentially
doubled to 54%, while NBOD remained at a 30% reduction, totaling 41%. The most
significant reduction in total BOD occurred two weeks after the installation of the wire
bags with a reduction of 68% (Figure 27). It is assumed that the reduction of BOD could
be attributed to the work of the heterotrophic bacteria and the decrease of the
carbonaceous demand (CBOD), as there was no reduction in ammonia.
68
140
Total BOD Observed value (mg/L)
120
100
80
60
40
20
0
P2
Pre-Air
Air
5 ft
10 ft 15 ft 20 ft
Sample Location
25 ft
30 ft
35 ft
40 ft
Figure 27: Total Biological Oxygen Demand (BOD) reduction (6.26.13); with wooden
frames and two weeks after installation of wire bags
Additionally, water flow rate was reduced from 200,000 gal/day to 22,300 gal/day in an
attempt to generate a greater similitude between TW-4 and the aquaphyte. Changing the
flow rate generated no observable difference in the nitrogen dynamics, yet reduction in
BOD concentrations continued (Figure 28). Under those circumstances, HRT within the
aeration zone increased, which helped contribute to reductions in BOD.
69
120
CBOD
NBOD
100
Observed value (mg/l)
80
60
40
20
0
P2
-15 ft -5 ft
Air
5 ft
10 ft 15 ft 20 ft 25 ft 30 ft 35 ft 40 ft 200 ft
Sample Location
Figure 28: 7/17/13; 68% reduction in NBOD, 74% reduction CBOD
The sample port at 10ft consistently had high levels of visible organic material, which
was obviously stirred up by the aeration system. The organic material may have
eventually settled, giving the appearance that the aeration system generated the high rates
of reduction. If the effluent is compared to Oxidation Pond 2 concentrations and not
sample port 10ft, there is approximately a 12% increase in NBOD. On the contrary,
effluent CBOD samples compared to ox-pond 2 concentrations were reduced by
approximately 74%.
Concern about the low oxygen concentrations dictated the removal of the wire bags that
were installed directly above the aeration system. It was observed that the wire bags
70
allowed biofilm growth during the period of operation when installed above the air
diffusers; although, the growth of biofilm was sparse. DO levels were recorded after the
wire bags were removed and the highest concentrations of DO seen in this system were
observed (Figure 29).
7.0
6.0
4.0
3.0
2.0
Disolved Oxygen (mg/L)
5.0
1.0
0.0
-15
-5
0
5
10
15
20
25
30
35
40
Distance from Aerators (ft)
Figure 29: Dissolved oxygen concentration TW 4 after removal of wire bags (7.25.13).
DO concentrations observed in TW-4 after the removal of media prompted a new
configuration of the aeration system and media. The media was re-installed just
downstream from the aeration system with the assumption that higher DO concentrations
would advect through the media bags. Peak DO concentration seen on 7/25/13 (Figure
71
29) and gradually decreased as the system remained in operation, eventually dropping
back down to previous levels, 1.5-2.5 mg/l. The final configuration of the aeration system
in the TW-4 experimental cell generated no new trend in ammonia reduction; reduction
in DO concentrations appears to be a result of CBOD degradation. TW-4 generated a
50% reduction of BOD on 9/17/13 (Figure 30).
Observed Total BOD value (mg/L)
80
BOD
70
60
50
40
30
20
10
0
-15 ft -5 ft
Air
5 ft
10 ft 15 ft 20 ft 25 ft 30 ft 35 ft 40 ft
Sample Location
Figure 30: 50% reduction of total BOD 9.17.13, final media configuration, installed
downstream of aeration system.
It is evident that the microbial communities in TW-4 are utilizing the DO to reduce BOD.
However, it appears that the DO is primarily being consumed to reduce existing organic
carbon sources available for biological degradation.
72
Nitrogen dynamics.
Laboratory analysis has indicated that the in-situ aeration system installed in TW-4 did
not facilitate rates of nitrification seen in the aquaphyte. Of the 30 data points collected,
within the five months of aeration, there were only two days where ammonia
concentration was reduced and nitrate concentrations increased (Figure 31 and Figure
32).
Ammonia (NH3-N)
Nitrate (NO3-N)
DO (O2)
8.0
3.0
2.5
7.0
6.0
2.0
5.0
1.5
4.0
3.0
1.0
2.0
0.5
1.0
0.0
0.0
P2 -15 -5
0
5
10
15
20
25
30
35
40
Observed Nitrate-N & DO values
(mg/L)
Observed Ammonia-N value (mg/L)
9.0
Distance From Aerators (ft)
Figure 31: 5/30/13 ammonia reduction of 32% (2.8mg/l), peak DO concentration 2.5mg/l,
slight increase in nitrate (1.6mg/l) within the zone of elevated DO
Ammonia concentrations showed very little response to the influx of oxygen through the
aeration system. Following the installation of the chicken wire bags, there was a 2-mg/l
drop in ammonia levels, which may indicate that nitrification occurred (Figure 32). This
73
reduction is insignificant when considering that ammonia concentrations during recent
winter months typically averaged approximately 20-30mg/l. As previously stated, the
aeration system appeared to be oxygen limited with an extensive internal load of organic
carbon that was consuming the available DO. Nutrient rich peat and decomposing algal
biomass that had settled throughout the operation of TW-4 was stirred up by the aeration
system and increased oxygen demand as well as reduced the potential for nitrification of
the influent loads.
A decrease of ammonia concentrations within the reach of DO concentrations > 0.2 mg/l
(Figure 32) resembles the nitrogen dynamics seen in the aquaphyte. However, nitrate
concentrations don’t reflect the 2 mg/l decrease in ammonia, which could be due to an
insufficient number of samples ports.
74
Ammonia (NH3-N)
12.0
Nitrate (NO3-N)
DO (O2)
1.2
10.0
1.0
8.0
0.8
6.0
0.6
4.0
Nitrate-N & DO (mg/L)
Ammonia-N (mg/L)
1.4
0.4
2.0
0.2
0.0
0.0
-5
0
5
10
15
20
25
30
35
40
Distance From Aerators (ft)
Figure 32: Performance two weeks after installation of wire bags (6/26/13).
Placing the media just downstream (Figure 33) of the aeration system proved to have no
apparent influence on ammonia concentration relative to the previous configuration of
media directly above (Figure 32) the aeration system. Ammonia concentrations decreased
by 32% within the volume of water that contained DO concentrations above 1 mg/l
(Figure 33). The aeration system appeared to be reducing a fraction of the ammonia that
was added from the internal load. However, the influent and effluent concentrations are
approximately equal.
75
16.0
Ammonia (NH3-N)
Nitrate (NO3-N)
DO (O2)
2.5
2.0
12.0
10.0
1.5
8.0
1.0
6.0
4.0
0.5
2.0
0.0
Observed Nitrate-N & DO (mg/L)
Observed Ammonia-N (mg/L)
14.0
0.0
-15
-5
0
5
10
15
20
25
30
35
40
100 TW 4
Eff
Distance From Aerators (ft)
Figure 33: Nitrogen dynamics of system 22 days after final configuration of media (wire
bags) downstream of aeration system; 9.09.13
Nitrate concentrations decreased through the plume of DO so it is difficult to determine if
nitrification occurred. Further research may benefit from an increased number of sample
ports to better characterize the nitrogen dynamics. The TW-4 aeration system proved to
be an ineffective method to facilitate nitrification. However to fully realize the potential
of in-situ aeration design, it would be advantageous to install the system within a younger
treatment cell with less accumulation of decomposing biomass.
76
Media and fouling.
Reorientation of the wire bag media, moving the media from above the aerator to just
downstream of the aerators, proved to have no consistent affect on ammonia
concentrations. Upon further observation, the media downstream of the aeration system
appeared to generate less biofilm than when installed directly above the diffusors. There
was a strip of biofilm that had accumulated in the areas where the media was in direct
contact with the turbulent zone of aeration. Biofilm accumulation was solely based on
observation of the media, no volume or weight measurements were collected.
The aeration system was raised out of the water column and a significant amount of
microbial growth was observed on the membrane diffusers, although the fouling did not
appear to reduce the flow of air into the system but could have changed the bubble size
and therefore aeration efficiency. Accumulation of biofilm on the membrane diffusers
could be a result of operating the diffusers at the lower threshold of the manufacturers
recommended airflow range. A compressor with higher capacity or less diffusers may
provide enough agitation to prevent microbial growth accumulation. This could also
generate a more uniform DO concentration throughout the cross section of the treatment
cell, which would prevent potential short circuiting through areas of low DO
concentrations. When examining the aeration system and media containers, the majority
of biofilm growth was generated on the wooden frames holding media in addition to the
membrane diffusers (Figure 34), which is not ideal.
77
Figure 34: Microbial growth on membrane diffusers; half brushed off to observe extent of
fouling
After the reorientation of the wire bags, further examination of the installed media
revealed that the strapping material and Bio Pac Honey Comb had little to no biofilm
accumulation.
Quantifying internal load contribution.
The internal load within TW-4 was subsequently increased throughout the period during
aeration. The system was shut down at the end of September where the effluent ammonia
78
concentration recorded in TW- 4 was reduced to levels comparable to the other treatment
marshes (Figure 35).
35.0
Pond 2
TM1
TM2
TM3
TM4
TM5
TM6
Observed Amonia Value (mg/l)
30.0
25.0
20.0
15.0
10.0
5.0
0.0
12/7/12
1/26/13
3/17/13
5/6/13
6/25/13
8/14/13
10/3/13
11/22/13
Date of sample
Figure 35: Ammonia concentrations throughout the year for all treatment marshes and
pond 2
In-situ aeration in a marsh system that has been in operation for approximately 35 years
contributes ammonia to the water column at a higher rate due to the stirring of
decomposing algae and plant detritus. This is evident when observing ammonia effluent
concentrations from the previous year (Figure 36). TW-4 follows similar performance
79
trends as the other treatment marshes, although there is a slightly higher internal load
observed. Ammonia from decomposing plant and algal biomass leaches from the system
and is easily observable in the summer months when ammonia concentrations in
oxidation pond 2 (TW-4) are nearly zero. TW-4 has the highest average internal load
likely due to the age of the system and time of operation.
90.0
Pond 2
TM1
TM2
TM3
TM4
80.0
Observed Ammonia Values(mg/l)
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
11/3
-10.0
12/23
2/11
4/1
5/21
7/10
8/29
Date of Sample
Figure 36: Ammonia effluent concentrations throughout 2012
10/18
12/7
1/26
80
Comparison
Normalized values were calculated for both systems to elucidate why the results seen in
the aquaphyte did not translate to TW- 4. Oxygen transfer efficiency was assumed to be
20% due to lack of information on diffuser specifications, and the depth of the treatment
marsh relative to conventional activated sludge chambers. Calculated values provide
some insight into the divergence of results that were observed between the aquaphyte and
TW - 4 (Table 15). In particular, contact time within the water containing levels of DO >
1.0 mg/l is substantially higher in the aquaphyte than that of TW-4. This difference could
indicate that the system in TW-4 is oxygen limiting and may require increased
compressor capacity to generate a plume of DO large enough to reach a volume that is
approximately 25% of its HRT. However, increased oxygen input doesn’t necessarily
facilitate high rates of nitrification if excessive organic carbon is available. Furthermore,
the volume of media for microbial attachment within the DO plume in the aquaphyte was
about 50% of available volume, compared to the 10% in TW-4, indicating that volume of
media may need to occupy at least half the volume within the oxygenated zone.
81
Table 15: Comparison of results; normalized values between the two systems; a transfer
efficiency of 20% was assumed; 20.95% oxygen concentration in air was assumed.
Comparison values
Contact time within reach of oxygen volume (hrs)
Contact time within media (HRT)
Media surface area/ volume of DO water
Volume of media/volume of DO water
aquaphyte
12.72
25%
8.1
48%
TW-4
3.9
6%
2.0
9%
The plant biomass in the aquaphyte exists within the entire reach of dissolved oxygen.
Additionally, TW-4 has lower concentrations of dissolved oxygen as well as lower
volume (by percentage) of available media within the oxygen advection zone. Ultimately,
the long operational history of TW-4 contributes to the divergence in performance
between the two systems. Plant cycles and high ammonia loading over the past 35 years
have negatively impacted performance of the wetland cells and the capacity to increase
water quality.
82
CONCLUSION
The aquaphyte pilot project has shown that in-situ seasonal aeration to facilitate
nitrification can be a potentially viable option for AWTF to reduce ammonia
concentrations, despite full-scale designs proving to be ineffective. Water temperature did
not fully inhibit rates of nitrification in the aquaphyte with the loading seen over the
winter of 2011 and 2013. Additionally, no media was necessary due to the density of
plants that existed within the water column. Ultimately, the aquaphyte required
approximately 28 days to generate consistent ammonia reduction and BOD removal. This
operational startup period may depend on the water temperature and loading rates.
In conclusion, with the loading rates and water temperatures observed, in-situ aeration
can facilitate nitrification in young wetland cells. Effectiveness was lost in scale up due
to the extensive accumulation of accreted ammonia and organic carbon over the past 35
years of operation. Both constituents are stirred up during operation of the large scale
aeration system, which consumes much of the available oxygen reducing the potential for
influent ammonia conversion. As a result of deferred maintenance throughout the lifetime
of the AWTF treatment wetlands, the capacity to improve water quality will continue to
degrade if maintenance and harvest of accumulated biomass continues to be avoided.
Consequently, inhibited performance coupled with future increases to water quality
standards could result in a preventable economic burden for the City of Arcata. Full-scale
in-situ aeration to facilitate nitrification is a plausible solution for increases to ammonia
83
limits, dictated by the NCRWQCB. Nevertheless, an increase in treatment capacity in
addition to algal and plant detritus harvesting will be necessary to generate appropriate
ammonia removal efficiencies in a full scale system for AWTF.
Recommendation
The City of Arcata can utilize conventional treatment technologies like a bio-tower,
trickling filter, or an aeration channel to reduce ammonia and nitrate concentrations.
These are proven technologies that effectively reduce nitrogen levels, although they
would require substantial infrastructure development and operational training. Space is
limited at the AWTF and it would be advantageous to avoid additional infrastructure
development. Conventional technologies exist to sufficiently reduce nutrient loads,
although there is still potential to utilize an in-situ aeration design when considering
alternative treatment methods. The aquaphyte experiment has proven that artificial
aeration in wetland cells has the potential to be an effective method to facilitate
nitrification, but further research is required to determine necessary operational and
design parameters of a full-scale system. Installing an aeration system into a full-scale
newly established wetland cell (2-3 years old) would help quantify how much the internal
load affects the treatability of influent loading. Additionally, it could be beneficial to
construct a new wetland treatment cell, perhaps where previous hatchery ponds existed,
with the particular objective of reducing ammonia concentrations. This step in research
and scale would help AWTF further understand the feasibility of in-situ aeration. AWTF
84
is an aging system and its capacity to improve water quality will continue to become
inhibited as it stores nutrients and organic carbon. A new treatment wetland would be
beneficial to the city, as it will be required to temporarily shut down existing treatment
wetlands to eventually manage the deferred maintenance of biomass and peat removal.
Consequently, in order for in-situ aeration systems to become a viable option to
sustainably treat nitrogen loading, AWTF should adhere to a strict peat and plantharvesting operational schedule. This will prolong the effectiveness of treatment wetlands
to improve water quality, although the nutrient dense biomass will also require
mitigation. Capacity for composting or bio-digestion of the wetland plant biomass and
nutrient laden peat should be incorporated within any new wetland design. Alternatively,
Bioconversion through black soldier fly (Hermetia illuscens) production may be a viable
option for the city of Arcata to reduce the biomass that has accumulated over the past 35
years of operation. Pilot scale black soldier fly systems have proven to reduce dairy
waste, swine manure, chicken manure, municipal organic waste dry matter weight by
58%, 56%, 50%, and 68%, respectively (Sheppard, 2006 and Myers, 2008 and Diener,
2011). This process converts highly concentrated nutrient laden waste into high value
pupae biomass that is approximately 35% lipid and 45% proteins that can create potential
revenue for the City of Arcata (Diener, 2009).
It is recommended that the City of Arcata take steps in mitigating the accumulation of
biomass and peat. In addition, supplementary research with a full-scale in-situ aeration
85
system is necessary to accurately determine its feasibility at AWTF. Land area for further
study is available in the previously used hatchery ponds.
86
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91
APPENDIX A
Operational parameters
Date
Notes
time
(min)
sec/500mL
Volume
(gal)
Flowrate
(gpm)
HRT
(days)
Rotameter
(SCFH)
12/31/12
60
1.00
0.13
0.13
2.7
0
1/1/13
60
1.00
0.13
0.13
2.7
0
1/2/13
60
1.00
0.13
0.13
2.7
0
1/3/13
59
0.98
0.13
0.13
2.6
0
1/4/13
58
0.97
0.13
0.14
2.6
0
1/5/13
60
1.00
0.13
0.13
2.7
0
1/6/13
59
0.98
0.13
0.13
2.6
0
1/7/13
58
0.97
0.13
0.14
2.6
0
1/8/13
60
1.00
0.13
0.13
2.7
0
1/9/13
60
1.00
0.13
0.13
2.7
0
1/10/13
61
1.02
0.13
0.13
2.7
0
1/11/13
59
0.98
0.13
0.13
2.6
0
1/12/13
60
1.00
0.13
0.13
2.7
0
1/13/13
61
1.02
0.13
0.13
2.7
0
1/14/13
60
1.00
0.13
0.13
2.7
0
1/15/13
61
1.02
0.13
0.13
2.7
0
1/16/13
63
1.05
0.13
0.13
2.8
0
1/17/13
NA
0
1/18/13
NA
0
1/19/13
59
0.98
0.13
0.13
2.6
0
1/20/13
65
1.08
0.13
0.12
2.9
0
1/21/13
58
0.97
0.13
0.14
2.6
0
1/22/13
58
0.97
0.13
0.14
2.6
0
1/23/13
59
0.98
0.13
0.13
2.6
0
1/25/13
59
0.98
0.13
0.13
2.6
0
1/27/13
58
0.97
0.13
0.14
2.6
0
59
0.98
0.13
0.13
2.6
30
61
1.02
0.13
0.13
2.7
0
1/28/13
1/29/13
Air started
air off electrical issue
92
Date
Notes
1/30/13
air off
Ball-valve
system:
parastalitic
pump off-line
needing repair,
Flowrate taken
as average of
instantaneous
and adjusted
Flowrate taken
as average of
instantaneous
and adjusted
Flowrate taken
as average of
instantaneous
and adjusted
Flowrate taken
as average of
instantaneous
and adjusted
New air stone:
~60 SCFM
above water
Flowrate taken
as average of
instantaneous
and adjusted
Flowrate taken
as average of
instantaneous
and adjusted
1/31/13
2/1/13
2/2/13
2/3/13
2/4/13
2/6/13
2/7/13
2/8/13
2/10/13
2/11/13
Flowrate taken
as average of
instantaneous
and adjusted
Flowrate taken
as average of
instantaneous
and adjusted
2/13/13
2/15/13
Parastaltic back
online,
Flowrate taken
time
(min)
sec/500mL
Volume
(gal)
Flowrate
(gpm)
HRT
(days)
Rotameter
(SCFH)
62
1.03
0.13
0.13
2.8
0
53
0.88
0.13
0.15
2.3
35
49
0.81
0.13
0.16
2.2
36
36
0.60
0.13
0.22
1.6
36
39
0.64
0.13
0.21
1.7
37
59
0.98
0.13
0.13
2.6
42
42
0.69
0.13
0.19
1.9
51
33
0.55
0.13
0.24
1.5
53
73
1.22
0.13
0.11
3.3
53
41
0.68
0.13
0.20
1.8
48
54
0.89
0.13
0.15
2.4
50
59
0.98
0.13
0.13
2.6
52
36
0.60
0.13
0.22
1.6
93
Date
Notes
as average of
instantaneous
and adjusted
time
(min)
sec/500mL
Volume
(gal)
Flowrate
(gpm)
HRT
(days)
Rotameter
(SCFH)
2/17/13
56
0.93
0.13
0.14
2.5
51
2/18/13
56
0.93
0.13
0.14
2.5
52
2/19/13
68
1.13
0.13
0.12
3.0
2/21/13
65
1.08
0.13
0.12
2.9
52
63
1.05
0.13
0.13
2.8
52
65
1.08
0.13
0.12
2.9
52
60
1.00
0.13
0.13
2.7
52
2/25/13
59
0.98
0.13
0.13
2.6
53
3/1/13
59
0.98
0.13
0.13
2.6
52
3/3/13
59
0.98
0.13
0.13
2.6
52
3/4/13
59
0.98
0.13
0.13
2.6
52
59
0.98
0.13
0.13
2.6
52
2/22/13
2/24/13
2/24/13
Rinsed
stabilization
tank - minimal
sediment
Installed new
float switch
anchor
3/8/13
3/10/13
Ammonia probe
on order
60
1.00
0.13
0.13
2.7
53
3/13/13
60
1.00
0.13
0.13
2.7
53
3/20/13
61
1.02
0.13
0.13
2.7
53
3/24/13
60
1.00
0.13
0.13
2.7
53
60
1.00
0.13
0.13
2.7
52
60
1.00
0.13
0.13
2.7
51
60
1.00
0.13
0.13
2.7
52
60
1.00
0.13
0.13
2.7
50
60
1.00
0.13
0.13
2.7
50
60
1.00
0.13
0.13
2.7
51
60
1.00
0.13
0.13
2.7
0
60
1.00
0.13
0.13
2.7
0
62
1.03
0.13
0.13
2.8
0
56
0.93
0.13
0.14
2.5
0
3/25/13
3/29/13
Slight drop in
air: diffuser
fouling?
3/31/13
4/5/13
4/6/13
4/7/13
Out: 68s/0.5L
Out: 61s/0.5L,
Air turned off at
4 pm
4/12/13
4/14/13
pump sounds
funny
4/15/13
4/19/13
Pump
malfunction -
94
Date
5/10/13
Notes
switched to
constant head
system
pump back
online, air stone
broke; installed
new air stone
time
(min)
sec/500mL
Volume
(gal)
Flowrate
(gpm)
HRT
(days)
Rotameter
(SCFH)
61
1.02
0.13
0.13
2.7
38
60
1.00
0.13
0.13
2.7
41
56
0.93
0.13
0.14
2.5
40
60
1.00
0.13
0.13
2.7
40
60
1.00
0.13
0.13
2.7
40
63
1.05
0.13
0.13
2.8
40
70
1.16
0.13
0.11
3.1
40
94
1.57
0.13
0.08
4.2
38
6/7/13
55
0.92
0.13
0.14
2.5
38
6/12/13
60
1.00
0.13
0.13
2.7
38
5/17/13
5/20/13
lots of new
vegetation
(bullrush,
celery)
5/22/13
5/23/13
lots of red small
organisms in
pond
5/27/13
5/30/13
6/5/13
pump sounds
funny
replaced tubing,
pump sounds
less funny
6/13/13
windy
60
1.00
0.13
0.13
2.7
38
8/20/13
plant harvest
60
1.00
0.13
0.13
2.7
0
59
0.98
0.13
0.13
2.6
0
59
0.98
0.13
0.13
2.6
0
61
1.02
0.13
0.13
2.7
40
11/24/13
0.00
0.13
12/13/13
0.00
0.13
12/14/13
0.00
0.13
12/16/13
0.00
0.13
12/19/13
0.00
0.13
12/30/13
0.00
0.13
12/31/13
0.00
0.13
59
0.98
0.13
0.13
2.6
0
59
0.98
0.13
0.13
2.6
0
11/14/13
11/21/13
Turned on air
after sample for
nutrients
11/23/13
11/14/13
11/21/13
Turned on air
after sample for
95
Date
Notes
nutrients
time
(min)
sec/500mL
11/23/13
Aquaphyte water quality data
61
1.02
Volume
(gal)
0.13
Flowrate
(gpm)
0.13
HRT
(days)
Rotameter
(SCFH)
2.7
40
96
Ammonia-N (mg/L)
SP 1
Date
(INF)
1/4/13
17.3
1/12/13
17.9
1/18/13
39.7
1/25/13
26.5
2/8/13
25.5
2/15/13
23.0
2/22/13
25.4
SP 2
SP
3a
SP 3b
SP 3
(Avg)
SP 4
SP 5a
SP 5b
SP 5
(Avg)
SP 6
SP 7a
SP7
b
SP 7
(Avg)
SP 8
SP 9
(EFF)
16.7
16.4
14.3
15.4
14.3
13.7
9.1
11.4
10.7
11.8
7.1
9.5
8.5
9.3
18.4
18.2
16.6
17.4
16.4
16.0
9.7
12.8
13.9
12.4
6.9
9.7
8.6
9.0
25.3
39.8
24.0
31.9
25.6
14.3
9.6
11.9
11.7
13.6
7.8
10.7
7.4
11.9
25.7
24.3
24.5
24.4
24.3
22.8
13.6
18.2
16.9
16.4
12.9
9.5
15.9
25.4
19.3
15.9
17.6
15.5
14.7
13.4
14.1
15.5
16.1
14.4
16.2
16.7
22.7
22.8
18.2
20.5
17.6
17.5
15.0
16.2
16.9
16.3
9.4
12.
7
14.
6
15.4
15.0
14.3
25.9
19.6
2.0
10.8
1.4
0.8
0.3
0.5
0.5
0.7
0.1
0.4
0.4
0.4
Ammonia probe malfunction - no ammonia data
3/20/13
26.5
22.5
16.1
2.1
9.1
1.3
1.0
0.4
0.7
0.6
0.7
0.3
0.5
0.4
0.3
19.4
18.7
15.3
0.9
8.1
0.6
0.2
0.1
0.2
0.3
0.6
0.1
0.4
0.2
0.2
14.6
15.2
15.1
1.3
8.2
0.6
0.5
0.2
0.3
0.5
0.5
0.2
0.3
0.5
0.3
19.1
18.8
18.6
20.6
19.6
17.5
16.7
12.3
14.5
14.7
12.8
8.3
10.6
9.8
8.1
0.0
1.7
3.0
3.8
3.4
0.2
0.3
0.4
0.4
0.7
0.8
0.5
0.6
1.0
0.8
0.3
2.1
2.9
4.2
3.6
0.2
0.3
0.2
0.3
0.4
0.9
0.2
0.5
0.4
0.3
1.7
2.8
3.3
5.9
4.6
0.4
0.5
0.3
0.4
0.6
0.5
0.3
0.4
0.5
0.4
3/29/13
4/5/13
4/12/13
5/17/13
5/22/13
5/27/13
5/27/13
97
Nitrate-N (mg/L)
SP 1
Date
(INF
1/4/13
0.7
1/12/13
0.2
1/18/13
0.2
1/25/13
0.2
2/1/13
2/8/13
SP
2
SP 3
(Avg)
SP7b
SP 7
(Avg)
SP 8
SP 9 (EFF)
3.0
6.9
4.9
5.2
4.6
2.8
3.3
6.4
4.9
4.1
4.1
5.4
4.5
4.8
8.4
6.6
7.4
3.6
4.6
2.7
1.8
1.8
4.8
3.3
2.9
1.3
5.3
3.0
4.2
3.1
4.2
3.3
3.7
4.8
4.1
9.1
9.7
9.3
9.5
7.8
5.7
6.7
6.2
5.1
4.7
3.1
5.4
5.2
6.3
5.7
5.5
5.1
5.5
5.3
5.0
5.5
21.6
13.5
21.5
22.4
20.9
21.6
21.1
19.7
19.5
19.6
17.9
17.6
4.2
17.9
11.0
18.5
19.4
19.0
19.2
19.2
18.1
16.3
17.2
16.8
17.0
1.7
9.6
25.8
17.7
26.2
26.0
25.7
25.8
23.2
21.1
16.4
18.7
16.7
16.8
2.9
2.3
4.4
18.2
11.3
18.3
18.0
16.0
17.0
15.9
13.7
12.3
13.0
11.2
11.0
4.3
2.4
1.9
16.6
9.2
17.1
16.6
14.5
15.6
14.4
13.1
9.7
11.4
10.1
8.7
2.8
2.0
0.9
0.6
0.7
0.6
0.5
0.7
0.6
0.3
0.4
0.7
0.6
0.3
0.8
5.9
2.7
1.3
1.4
1.4
5.9
5.4
3.2
4.3
3.5
2.4
1.1
1.7
0.6
0.8
5.1
1.4
1.0
0.7
0.8
3.6
3.3
2.0
2.7
1.7
1.0
0.5
0.8
0.3
0.2
2.0
0.4
0.2
0.3
0.3
2.9
2.6
1.0
1.8
1.5
0.8
0.4
0.6
0.3
0.3
SP 3a
SP 3b
1.3
1.9
3.2
2.5
0.4
0.8
2.0
0.8
1.3
0.5
0.3
SP 4
SP 5
(Avg)
SP 5a
SP 5b
SP 6
2.4
2.3
5.9
4.1
5.2
1.4
1.7
1.8
5.3
3.5
2.1
1.7
2.3
2.5
8.4
0.8
1.0
0.9
0.6
0.8
0.6
6.7
6.0
6.3
6.0
0.3
1.2
6.5
8.9
7.7
0.3
1.2
1.2
4.9
0.4
1.7
5.5
0.3
1.0
0.8
SP
7a
2/15/13
2/22/13
3/1/13
3/20/13
3/29/13
4/5/13
4/12/13
5/17/13
5/22/13
5/27/13
98
BOD (mg/L)
Date
1/4/13
CBOD (mg/L)
SP 1
(INF)
SP 2
SP 4
SP 6
SP 8
SP 9
(EFF)
SP 1 (INF) SP 2
SP 4
SP 6
SP 8
SP 9 (EFF)
18.5
13.2
13.7
10.4
8.6
7.6
18.3
17.2
18.1
14.1
8.6
4.4
16.8
12.6
12.8
9.5
13.4
7.5
7.3
5.9
19.1
17.8
18.2
22.2
18.1
14.2
8.2
8.0
15.4
23.8
24.7
22.7
13.2
11.6
11.2
11.0
23.2
32.4
27.2
18.2
16.3
16.7
13.3
11.0
27.2
16.8 15.3
23.0
23.1
BOD probe investigation - Lauren moved BOD equipment to campus
7.5
5.6
5.4
14.1
7.6
11.7
16.1
17.8
10.9
7.5
10.1
1/11/13
1/20/13
1/27/13
2/3/13
2/10/13
2/17/13
2/24/13
3/3/13
3/10/13
3/24/13
3/31/13
4/7/13
24.5
28.5
48.5
136.8
147.6
33.8
36.3
57.2
197.7
20.9 14.7
8.3
10.9
7.3 (a)
17.7 (a)
29.5
33.8 18.8
8.3
4.9
8.0
13.5
11.4
22.3 21.5
10.6 15.2
21.0 21.3
37.1
35.3 (a)
10.5
7.6
9.3
5.6
4.0
5.7
7.2
4.6
99
BOD (mg/L)
Date
4/12/13
4/14/13
5/23/13
5/30/13
6/7/13
6/13/13
CBOD (mg/L)
SP 1
(INF)
SP 2
(a)
(a)
108.0
108.8
84.8
42.8
SP 4
SP 6
47.6
40.8
SP 8
SP 9
(EFF)
SP 1 (INF) SP 2
31.3 (a)
15.8
19.4
17.0
8.9
28.5
37.1
37.8
20.7
SP 4
14.0
SP 6
13.5
SP 8
SP 9 (EFF)
(a)
7.9
9.7
12.6
100
TSS (mg/L)
Date
1/20/13
SP 1
(INF)
SP
2
SP
3a
SP 3b
(b)
(b)
(b)
(b)
48
47
36
34
SP 3
(Avg)
SP
4
SP
5a
SP
5b
(b)
(b)
(b)
40
68
37
SP 5
(Avg)
SP
6
SP
7a
SP7b
(b)
(b)
(b)
39
22
22
SP 7
(Avg)
SP 8
SP 9
(EFF)
(b)
(b)
23
20
1/27/13
35
52
22
2/3/13
40
44
44
26
2/10/13
54
54
44
34
188
52
57
25
2/17/13
53
67
39
28
34
34
20
24
22
35
19
24
21
22
15
59
96
84
62
73
71
43
31
37
63
34
34
34
28
16
55
92
43
39
41
28
39
33
31
31
31
43
2/24/13
3/3/13
3/10/13
67
3/24/13
67
3/31/13
80
4/7/13
140
19
8
48
8
4/14/13
46
24
8
5/23/13
102
53
45
19
67
95
45
56
51
72
38
47
43
38
26
47
61
100
43
70
57
58
37
49
43
35
18
204
76
140
96
53
50
51
55
30
32
31
29
18
45
39
42
63
43
39
41
52
31
32
32
29
18
75
4/12/13
5/30/13
162
33
21
6/7/13
81
14
6/13/13
99
14
101
Treatment Marsh 4 water quality data
Date
5/22/13
5/30/13
6/6/13
6/7/13
6/13/13
6/17/13
6/26/13
Sample Location
BOD (ppm)
CBOD (ppm)
NBOD (ppm)
BOD (ppm)
CBOD (ppm)
NBOD (ppm)
BOD (ppm)
CBOD (ppm)
NBOD (ppm)
BOD (ppm)
CBOD (ppm)
NBOD (ppm)
BOD (ppm)
CBOD (ppm)
NBOD (ppm)
P2
-15
-5
109.20
5 ft
128.40
10 ft
20 ft
77.10
30 ft
40 ft
0.00
85.95
27.75
58.20
122.70
92.80
0.00
0.00
91.35
86.88
38.58
48.30
83.25
94.20
53.63
40.58
91.50
92.40
22.38
70.02
51.00
13.50
37.50
84.45
33.06
51.39
75.60
39.60
36.00
79.50
27.90
51.60
38.55
12.36
26.19
74.55
24.90
49.65
44.55
18.10
26.45
BOD (ppm)
64.05
59.25
59.25
58.80
CBOD (ppm)
23.60
40.62
24.72
23.10
NBOD (ppm)
40.45
18.63
34.53
35.70
BOD (ppm)
118.60
40.65
36.75
38.40
200 ft
CBOD (ppm)
NBOD (ppm)
7/3/13
BOD (ppm)
72.40
74.28
162.60
74.04
58.43
56.63
67.20
55.20
52.03
CBOD (ppm)
34.92
15.28
60.60
38.97
19.13
13.63
14.64
13.15
12.03
NBOD (ppm)
37.48
59.00
102.00
35.07
39.30
43.00
52.56
42.05
40.00
102
Date
Sample Location
P2
-15
-5
5 ft
10 ft
20 ft
BOD (ppm)
53.64
70.68
71.00
41.60
108.80
36.43
36.08
CBOD (ppm)
28.04
17.95
17.31
14.80
18.56
8.80
7.38
NBOD (ppm)
25.60
52.73
53.69
26.80
90.24
27.63
28.70
75.72
69.12
34.60
33.30
35.63
37.80
7/17/13
BOD (ppm)
9/3/13
30 ft
40 ft
200 ft
CBOD (ppm)
NBOD (ppm)
Ammonia
(mg/l)
Date
4/18/13
4/25/13
4/26/13
5/3/13
5/9/13
5/16/13
5/30/13
6/3/13
6/5/13
6/17/13
6/19/13
6/26/13
7/1/13
7/3/13
P2
0.2
5.4
2.0
1.7
0.1
0.0
0.4
1.4
0.2
-15 ft
8.2
3.9
5.9
0.4
11.1
8.1
-5 ft
18.9
18
13.6
14.8
4.8
7.7
3.1
0.0
11.4
3.6
0.4
7.2
9.6
Air
18.4
18
4.5
4.9
4.6
4.5
4.4
5.1
0.4
9.2
8.4
5 ft
18.8
18
19.8
16.0
15.7
7.9
5.2
4.7
5.2
4.2
7.5
0.4
9.6
10.1
10 ft
17.1
19
15 ft
20 ft
25 ft
30 ft
35 ft
40 ft
18
18
19
18
16.6
16.7
16.7
17.0
9.1
5.2
4.8
4.6
4.2
5.4
0.4
10.3
10.2
6.5
5.3
4.5
0.0
4.1
4.9
0.4
9.5
9.5
18
18.6
16.8
15.9
8.5
5.1
4.6
0.0
4.0
5.3
0.4
9.6
9.4
6.6
5.1
4.7
0.0
4.0
5.1
0.4
9.8
9.7
5.9
4.9
4.7
0.0
4.1
4.9
0.4
9.9
10.8
18
16.9
17.3
15.5
5.4
5.0
4.8
0.0
4.5
6.2
0.4
9.1
10.5
6.1
5.2
4.6
0.0
4.1
4.9
0.4
9.8
10.8
100 ft
0.0
0.4
9.6
11.6
TW-4
Eff
16.9
18.0
17.4
9.9
6.7
5.2
8.2
6.2
6.6
0.4
10.4
103
Ammonia
(mg/l)
Date
7/8/13
7/10/13
7/15/13
7/22/13
7/25/13
8/15/13
8/18/13
8/23/13
8/27/13
9/2/13
9/09/13
9/16/13
P2
0.6
0.9
0.1
0.1
-15 ft
8.7
6.8
9.3
13.2
-5 ft
8.7
6.5
9.2
13.0
Air
9.9
8.5
9.2
13.7
5 ft
10.1
6.8
9.2
13.9
10 ft
13.2
10.7
10.9
13.6
8.2
10.1
8.9
10.3
11.6
12.0
2.4
8.2
7.6
9.4
11.6
14.1
10.7
5.1
9.9
8.6
11.3
13.2
9.6
11.2
4.8
12.4
9.5
12.4
15.7
10.6
14.6
5.5
17.9
9.7
14.8
15.3
9.2
14.8
15 ft
10.8
16.7
9.9
14.7
8.8
11.0
9.6
12.9
10.4
14.2
20 ft
10.9
11.0
9.9
17.2
7.8
11.5
11.5
15.6
9.6
14.0
25 ft
11.3
30 ft
11.3
35 ft
11.2
40 ft
13.1
100 ft
12.6
9.9
15.8
9.9
13.0
8.9
12.8
9.2
12.9
9.2
13.1
TW-4
Eff
9.3
9.4
9.7
12.7
15.4
10.3
15.5
10.1
9.9
14.4
12.5
10.6
15.1
9.6
12.1
16.1
17.1
10.3
12.1
9.9
10.5
10.7
21.8
10.4
12.9
9.4
16.0
9.7
8.9
11.1
14.6
17.3
12.2
13.7
104
Nitrate (mg/L)
Date
4/18/13
4/25/13
4/26/13
5/3/13
5/9/13
5/16/13
5/30/13
6/3/13
6/5/13
6/17/13
6/19/13
6/26/13
7/1/13
7/3/13
7/8/13
7/10/13
7/15/13
7/22/13
7/25/13
8/15/13
8/18/13
8/23/13
8/27/13
9/2/13
9.09/13
9/16/13
P2
-15 ft
0.8
Air
5 ft
10 ft
15 ft
20 ft
25 ft
30 ft
35 ft
40 ft
1.0
0.5
0.9
0.8
1.1
0.6
0.35
2.8
1.7
0.5
0.6
0.5
1.3
0.4
0.4
0.4
0.3
0.3
0.6
4.0
2.3
2.6
0.3
0.8
3.1
0.7
0.4
0.5
0.4
0.9
0.5
0.3
0.4
0.5
0.6
0.4
0.5
0.3
0.9
0.4
0.3
0.3
0.4
0.4
0.3
0.7
0.3
0.9
0.4
0.3
0.3
0.4
0.3
0.3
1.1
1.1
1.0
0.7
0.6
1.0
0.2
0.9
0.8
0.8
0.6
0.5
0.7
0.2
0.8
0.7
0.7
0.4
0.4
0.6
5.1
2.2
1.5
2.1
1.2
0.9
0.3
0.3
0.6
0.4
-5 ft
0.2
2.7
2.6
1.4
1.9
0.4
0.6
0.5
0.5
0.4
0.56
2.7
1.6
0.8
0.6
0.4
0.9
0.3
0.3
0.3
0.3
0.3
0.3
0.5
0.3
0.9
0.3
0.3
0.3
0.4
0.3
0.3
0.5
0.3
0.9
0.3
0.3
0.3
0.3
0.3
0.3
0.2
0.7
0.6
0.7
0.4
0.4
0.5
0.2
0.6
0.5
0.6
0.4
0.3
0.4
0.6
0.5
0.6
0.3
0.3
0.4
100 ft
2.6
2.5
1.4
0.5
0.4
0.0
0.5
0.4
1.8
0.5
0.4
0.3
0.49
2.5
1.8
2.2
0.5
0.4
0.6
0.3
0.9
0.3
0.3
0.3
0.3
0.3
0.3
0.6
0.3
0.9
0.3
0.3
0.3
0.5
0.3
0.9
0.3
0.3
0.3
0.5
0.3
0.9
0.3
0.4
0.2
0.5
0.3
0.9
0.3
0.4
0.3
0.3
0.2
0.3
0.2
0.3
0.2
0.3
0.2
0.2
0.2
0.6
0.5
0.5
0.3
0.3
0.4
0.6
0.4
0.5
0.3
0.3
0.4
0.5
0.4
0.4
0.3
0.2
0.3
0.5
0.4
0.4
0.3
0.2
0.3
0.5
0.3
0.5
0.3
0.2
0.3
0.5
TW 4
Eff
0.23
1.3
0.2
2.3
0.3
0.3
0.9
0.3
0.4
0.7
0.2
0.9
0.3
0.3
0.2
0.2
0.4
0.3
0.4
0.3
0.2
0.3
105
DO (mg/L)
Date
4/18/13
4/25/13
4/26/13
5/3/13
5/9/13
5/16/13
5/30/13
6/17/13
6/19/13
6/26/13
7/1/13
7/3/13
7/8/13
7/10/13
7/15/13
7/22/13
7/25/13
8/15/13
8/18/13
8/23/13
8/27/13
9/2/13
9.09/13
9/16/13
-5 ft
-15ft
Air
5 ft
10 ft
15 ft
20 ft
25 ft
30 ft
35 ft
1.3
4.63
5.06
5.21
4.6
3.51
5.63
2.43
0.83
0.23
0.17
0.22
3.4
1.16
19.2
0.11
2.28
0.45
0.1
4.68
3.37
3.24
2.65
2.18
2
3.31
1.56
2.4
2.89
2.91
2.92
3.32
2.71
2.45
0.54
2.48
1.25
2.65
1.20
2.03
0.05
0.61
19.4
2.01
0.71
6.496
4.5
1.33
0.3
1.25
0.37
0.32
0.08
3.37
1.15
0.49
0.16
0.25
0.19
0.02
0.13
19.1
0.08
0.1
3.05
1.65
0.68
0.65
0.07
0.1
0.07
0.06
2.25
3.1
3.28
3.04
2.2
1.58
0.5
0.22
0.20
0.08
0.02
0.09
19.1
0.07
0.15
0.33
0.46
0.18
1.17
0.3
0.15
0.07
0.05
1.93
1.53
0.47
0.14
0.19
0.05
0.01
0.04
19.3
0.05
0.05
1.69
1.53
0.71
0.2
0.23
0.20
0.03
0.01
0.01
19.2
0.04
0.03
0.94
1.69
0.53
0.15
0.27
0.25
0.01
0.01
0.01
2.46
3.97
2.28
1.79
1.47
0.83
0.16
0.1
0.15
0.01
0.01
0.01
0.14
0.17
0.01
0.01
0.01
0.19
0.24
0.01
0.01
0.01
17.3
0.02
0.01
0.7
0.01
0.24
0.01
0.09
0.01
0.015
0.01
0.08
0.72
0.14
0.07
0.06
0.05
0.05
0.67
0.07
0.07
0.05
0.05
0.03
0.6
0
0
0
0.01
0.01
0.3
0
0.04
0
0
0.01
0.24
0
0.02
0
0
0.01
0.01
0.01
0
0
0
0
3.35
2.18
0
0.12
0.11
0.13
0.00
1.4
0.25
0.32
21.7
0.24
0.19
0.25
0.17
0.23
0.2
0.1
5.16
0.97
0.08
1.9
0.22
0.00
0.31
0.09
0.14
19
0.18
0.26
0.37
0.18
0.26
0.17
0.18
0.16
0.14
40 ft
100 ft
TW 4 Eff
0.32
0.38
1.12
0.4
0.01
0
0
0.01
0.01
106
Normalized calculations tables
Aquaphyte values
Oxygen concentration
4.43
mg/l (average sp 3)
125.3
mg/ft
6.16
mg/l (average sp 4)
174.2
mg/ft
Submerged surface area
3
mg/l (average sp 5)
50.9
mg/ft
mg/l
116.8
mg/ft
8
feet
13.5
3
ft3 water
1.6
grams
55%
porosity
272.88
ft
2
3
0.1494442
m
4.8093696
ft
3
56.74
Average between points
4.13
m
volume of submerged media
3
1.8
2
26.97
3
2
ft /ft
3
Operational parameters
Flow (gal/day)
190.5
(L/Day)
720.0
Flow (L/min)
3
0.5
ft /day
25.5
Velocity (ft/day)
15.1
contact time within reach of oxygen (Hrs)
contact time within media (HRT)
mass of oxygen available within oxygen reach (mg)/media surface
2
area ft
12.72
25%
5.77819
media surface area/ volume of oxygen reach
8.09
volume of media/volume of DO water
48%
107
Treatment Marsh 4
volume water within oxygen reach
Length (ft)
surface area on media (ft3/bag)
10
Width (ft)
18
Height (ft)
3
3
Water Volume (ft )
7.84
2
strapping (ft )
540
3
strapping volume (ft )
2
3
3
strapping (ft /ft )
180
540
3
6 bags of media (ft )
2
plan view
47.04
3
biopac (ft /ft )
2
surface area (ft )
180
30
2
biopac (ft )
1411.2
2
available surface area (ft )
media/reach volume
0.0926
70%
987.8
3
total media volume (ft )
50.04
2
total media surface area (ft )
1527.84
time through contact
volume
Oxygen concentration
2.2
mg/l
62.21
mg/ft
volume of media storage container
3
wooden boxes (ft3)
14.6
chicken wire bags
72
water flow (gal/day)
22300
(L/Day)
84294
3
ft /day
2981.084
velocity (ft/day)
69.73
contact time within reach of oxygen volume (Hrs)
3.9
contact time within media (HRT)
mass of oxygen available within oxygen reach (mg)/media surface area ft
6%
2
22.0
media surface area/ volume of oxygen reach
2.0
volume of media/volume of DO water
9%