2015
Water Environment School
Clackamas Community College
Lessons Learned:
35 Years Optimizing A Combined
Treatment Process
Dan Hanthorn
Corvallis, Oregon
Optimization - op·ti·mi·za·tion
The process of making a treatment system as fully
perfect, functional, or effective as possible.
Adjusting parameters without violating some constraint.
The most common goals are minimizing cost (labor,
resource inputs, capital), maximizing throughput, and/or
treatment efficiency.
Optimization is restricted by the lack of full information,
and the lack of time to evaluate available information.
Optimization - op·ti·mi·za·tion
Fundamentally, there are four parameters that can be
adjusted to affect optimal performance:
• Equipment - examining operating data to identify
equipment bottlenecks.
• Operating procedures – consistently applied;
appropriate to operating regime.
• Control optimization – effective use of
lab/sensor/observer data to manage process
control; accurate and timely.
• Performance supervision – frequency of process
monitoring updates and control adjustments.
About Corvallis, Oregon WWTP
Relevant Features:
• Population 55,000
• Oregon State University
• Combined sewers
• 7 operators
• One shift -10 hrs/day
• Less than 1,000 kW per MGD w/Influent pumping
• Landfill leachate
Process Flow Diagram
Process Flow Diagram – STF/SAS
Corvallis Unit Processes
Trickling Filters X 2
160’ X 8
161,000 cu. ft. each
Speed controlled
distributors
TF Circulation Pumps X 2
11.5 MGD each
40 hp each
Snail Sumps X 2
Aeration Basins X 2
75’ X 40’ X 15’ each
Process Blower
35 hp
Secondary Clarifiers X 2
115’ X 18’
Inboard Weirs
Trickling Filters - 1964
Trickling Filter Rock
Trickling Filters - Characteristics
 Low energy requirements
 Low maintenance
 Snails, over-grazing & snail control
 Limited process control
 Partial nitrification & high Cl2 demand
 Periodic sloughing
 Filter flies
 Seasonal energy savings
Trickling Filter
Cross Pumping Manifold - 1989
Trickling Filter
Cross Pumping Manifold - 1990
Trickling Filter
Snail Sumps - 1994
Trickling Filter
Snail Sumps - 1997
Filter Snails
Snail Sump
Trickling Filter
Speed Control - 2005
Trickling Filter
Speed Control - 2005
Old style: fixed
rotation @ 1 RPM
New style: variable RPM
23 hrs/day @ 0.25 RPM
1 hr/day @ 1 RPHr
Trickling Filter
Speed Control - 2005
WesTech HydroDoc Rotary Distributors
Trickling Filter
Selector Mode - 2008
Trickling Filter
Enhanced Selector Mode - 2008
Trickling Filters - Accomplishments
 Lower energy requirements
 Lower maintenance
 Effective snail control
 Enhanced process control
 Nitrification control & lower Cl2 demand
 Controlled sloughing – consistent TSS & BOD
loading
 Eliminated filter fly episodes
 Improved “SRT” or biofilm persistence
Trickling Filter/Solids Contact - 1978
Trickling Filter/Solids Contact
Characteristics
 No additional energy requirement
 Improved TSS & BOD performance
 Impacted by snails
 Limited nitrification control
 RAS return failures
 Periodic sloughing
 Filter flies
Trickling Filter/Solids Contact
Max RAS Q - 1988
Trickling Filter/Activated Sludge - 1994
Trickling Filter/Activated Sludge - 1994
Trickling Filter/Activated Sludge
Characteristics
 Easy to operate - change wasting rates seasonally
 MLSS range 900 to 3300 mg/L
 Early/late season nitrification control
 Limited nitrification control
 Carbon deficient
 Filamentous organisms
 Low pH
Trickling Filter/Activated Sludge
Anoxic Selector – mid- 90’s to 2001
Trickling Filter/Activated Sludge
Anoxic Selector
Anoxic Cell
Partition
Submersible
Mixers - 2001
Trickling Filter/Activated Sludge
Parallel Selector Treatment - 2006
Eff Ammonia <0.01
Eff pH <6.0
Trickling Filter/Activated Sludge
Max Anoxic Selector Mode - 2007
Improved de-nitrification
Eff pH >6.0
Trickling Filter/Activated Sludge
Selector with Carbon Source - 2010
Trickling Filter/Activated Sludge
Max Selector, Carbon & MLSS Recycle
Future Trial
Mode
Recap……
Corvallis Selector TF/Selector AS
Advantages
Disadvantages
Low power
Nitrification management
Low solids
TF O2 residual
Nutrient capability
De-nitrification
Good for hi/low flows
Effluent pH
Good for hi/low loads
Gravity thickening of WAS
Challenge & Opportunities
• Optimal nitrification mode
• Partial nitrification Cl2 demand
• Partial de-nitrification
• Filaments
• Carbon source control
• Infrequent TF odors
Challenge & Opportunities
(continued)
• Optimize alkalinity recovery
• Diurnal impacts
• Seasonal variations
• Automated process control opportunities
• Wastewater Master Planning projects
• Data restricted – end of the road?
Continuous Process Information
ZAPS Technologies
LiquID Station
What is it?
 Zero Angle Photon Spectroscopy (ZAPS)
 Optical based, solid state
 Broad multi-spectrum
• Deep UV
• Visible
• Infrared
 400 individual tests per optical pairing
 4 to 7 optical pairings per parameter
New Information - Diurnal Loading
• Influent monitoring has led to the identification and
tracking down of two significant source control
problems - both were food processors with illicit
discharges
• Diurnal BOD range is significantly greater than
diurnal flow
• Very low BOD values at night
New Information - Diurnal Loading
New Information - Diurnal Loading
• BOD removal rates in the primaries of up to 90%
before 6:30 a.m.
• Between 6:30 a.m. and 7:00 a.m. the removal
efficiency drops to 10%.
• Limited testing of chemically enhanced primary
settling has demonstrated that night time removal is
not complete - without the chemical addition.
• Material is settling just enough to keep most BOD,
TSS & E.coli inside the tanks at low flow
• Material is carried over the launders in the morning
with the slightest increase in plant flow.
New Information - Diurnal Loading
• The carryover results in a sudden and very high
increase in loading to the biological processes
• At 7:00 a.m. the highest loading rate of the day is
experienced
• Peak loading occurs 3 hours ahead of peak diurnal
flow rates
• The sudden change in loading ripples through the
plant in a cascade of consequences…including
increased E.coli and an increased demand for
sodium hypochlorite
New Information - Diurnal Loading
New Information - Diurnal Loading
Effluent Ammonia vs. Nitrite+Nitrate
New Information - Trickling Filter
Loading & Ventilation
• TFs operated in series optimize and stabilize BOD
and NH3 removal.
• Compartmentalizing the process enhances the
removal of both constituents and reduces the
incidence of partial nitrification
• Transient dips in TF BOD & NH3 removal were linked
to insufficient TF ventilation from two separate
cause/effect relationships.
• The most common is a sharp reduction in natural
draft when the ambient air temperature is less than
+/-2 degrees F from the process water temperature
New Information - Trickling Filter
Loading & Ventilation
• Insufficient temperature differential to generate a
draft - either up or down.
• Most commonly this occurs as air temperature
swings past the water temperature in the morning
and evening and usually lasts less than an hour
•
May persist more than a day during times of "just
right" atmospheric temperature stability.
New Information - Trickling Filter
Ventilation
• The other occurrence of insufficient ventilation is
during a combination very warm weather with near
100% nitrification across the TFs.
• Demand will outstrip O2 provided by a strong natural
draft
• To the extent that anoxic conditions and denitrification are evident across the filters.
New Information - Trickling Filter
De-nitrification
New Information - Activated Sludge
Loading
• Soluble BOD is only about 1-2 mg/L following the TFs
• Methanol and crude glycerol have been used as a
supplemental carbon source in the past
• Using primary clarifier effluent, bypassed around the
TFs
• 15% bypass rate during the day; at night the bypass
rate could be doubled due to the low BOD in the PE
at low flow conditions.
• A LiquID Station data may control the optimal dose
rate of PE VFAs
New Information - Activated Sludge
DO Control
• Nitrification can be successfully sustained in the A/Bs
during the night with much lower D.O. residuals than
needed during the day
• Within a reasonable D.O. range, maintaining a similar
"oxidation pressure" (intensity X duration) at low
flows does not inhibit the conversion of NH3.
• A LiquID Station monitors the secondary effluent as
well, used as a sentinel for BOD & TSS anomalies.
LiquID Station - Other New Information
• Monitors final effluent E.coli
• Cut hypo dose based on E.coli rather than Cl2
residual
• Cut hypo and NaBs consumption by more than half
• Use to provide continuous BOD & TSS data for
modeling the existing secondary clarifiers
• The MLSS Station and SE Station were used to
document clarifier stress testing alongside the
customary grab samples
• Event monitoring and Pretreatment Program Source
Control
Oregon State University
Football Event
kickoff
tailgating
half-time
Food Processor Discharge
Cheese Whey Discharge
Effluent BOD is Strongly Tied
to TSS
Nitrification Affected by Flow
and Temperature
Effluent TSS Tied to Limited
De-nitrification
Effluent pH Tied to
Nitrification/De-nitrification
Future Process Enhancement Projects
• Use primary sludge fermentation to generate VFAs
• Mixed liquor recycle at 3-4X
• Trickling filter forced ventilation
Combined Process Optimization
Lessons Learned
• Very low energy requirement for full nitrification
• Capable of very low sludge yield
• High dynamic range for flows and loads
• Combined systems may have complex interactions
• Keep the big picture in mind
• Design in operational flexibility
• Consider the insults
• Adjustments may be low cost
• If you are non measuring it, you can’t fix it
Questions?
Dan Hanthorn
Operations Supervisor, Retired
City of Corvallis, Oregon
[email protected]
Define:
Wastewater Professional
 Enthusiastic explorer
 Thirst for knowledge
 Formulates calculated risks
 Processes each experience
 Pushes the envelope
 Repeat