III Symposium on Agricultural and Agroindustrial Waste Management
March 12-14, 2013-Sao Pedro, SP, Brazil
ANAEROBIC, AEROBIC AND ANOXIC TREATMENT SYSTEM FOR
SWINE WASTEWATER: ORGANIC MATTER, NUTRIENTS AND
COLIFORMS REMOVALS
1*
ROBERTO A. DE OLIVEIRA , SAMANTHA C. SANTOS
1 and 2
2
Departament of Rural Engineering, University of São Paulo State / UNESP, Jaboticabal. Via de acesso Prof.
Paulo Donato Castelane s/n., Brasil. E-mail: *[email protected]
ABSTRACT: In this study it was evaluated the performance of the anaerobic-aerobic-anoxic
process composed of an anaerobic baffled reactor (ABR), with two chambers, a submerged
aerated filter (SAF), filled with bamboo as support material, and an anoxic upflow sludge blanket
reactor (USB), installed in series, to treat swine wastewater in order to remove organic matter,
nutrients and pathogens. The ABR, SAF and anoxic USB volumes were 360, 160 and 120 L,
respectively. The hydraulic detention times (HDT) were 24 and 12 h in the ABR reactor. At SAF
and USB reactor the HDT were 8 and 4 h. The mean of totalCOD removal efficiency were from 95
to 99% in the anaerobic-aerobic-anoxic treatment system under organic loading rate (OLR) of
38.8 to 77.7 g total COD (L d)-1 in the ABR reactor, 6.7 to 10.9 g total COD (L d)-1 in the SAF and
2.5 to 8.4 g total COD (L d)-1 in the anoxic USB reactor. The N2 percentage in the anoxic USB
reactor biogas reached 74% with OLR of 6.1 g total COD (L d) -1 and HDT of 4 h. Applying the
HDT of 24 h, the mean removal efficiencies were of 99,96; 85 and 88% for thermotolerant
coliforms, TKN and total-P, respectively, in the anaerobic, aerobic and anoxic treatment system.
Key words: anaerobic reactor, post-treatment, nitrification, denitrification, metals removal.
INTRODUCTION
Swine global production increased 3.5 times over the past 40 years and its meat remains
as the most consumed. The swine meat is the most consumed in the world, representing 39% of
total worldwide population meat consumption. This fact is mainly related to the high per capita
consumption in China and Europe for cultural reasons (SONG et al. 2010). There is a research’s
need to find the appropriate management program and effluent treatment systems which ensure
and promote benefits in reducing the pollutant and in the reuse of these waters.
A high rate reactor developed to implement the technology of anaerobic digestion is the
anaerobic baffled reactor (ABR) (KUSCU e SPONZA, 2006). The most significant advantage of
ABR is its ability to phase separation (hydrolytic, acidogenic and methanogenic) along the
reactor. This may allow selection of different bacteria in each compartment. The separation
causes an increase in protection from toxics compounds and resistance to changes in
environmental conditions such as temperature and Ph. The ABR is able to maintain the biomass
retained for a longer period of time and is resistant to shock organic and hydraulic load (KUSÇU
e SONZA, 2006).
Due to the high concentration of nutrients in wastewater effluent from agribusiness,
research and studies have been established to investigate biological processes to remove
nitrogen and phosphorus forms. High levels of ammoniacal nitrogen are generated in the process
of anaerobic digestion of swine wastewater. Therefore, the post-treatment is required to achieve
effluent discharge standards, avoiding deleterious effects on the environment The most common
and efficient method used to remove nitrogen from swine wastewater is the biological process of
nitrification and denitrification, widely used in process of intermittent aeration. In biofilms, the
nitrification process is less temperature dependent than in activated sludge systems (BODIK et
al., 2003).
Therefore, this study aimed to evaluate the removals of COD (total and dissolved), solids
(total and volatile suspended solids), nutrients and coliforms (total and thermotolerant) in an
anaerobic reactor (ABR), followed by submerged aerated filter (SAF) for the treatment of swine
wastewater with concentrations of TSS of 8,491 to 18,722 mg L-1, by applying different hydraulic
retention times and organic loading rates. An anoxic upflow sludge blanket reactor (USB) was
also added, which was intended to obtain anoxic conditions to complement the removal of
organic matter and nitrogen via denitrification.
III Symposium on Agricultural and Agroindustrial Waste Management
March 12-14, 2013-Sao Pedro, SP, Brazil
MATERIAL AND METHODS
The treatment system consisted of an affluent storage tank equipped with a mixer, a
helical pump, an anaerobic baffled reactor with two chambers (C1 and C2 - ABR), a submerged
aerated filter (SAF) and an upflow sludge blanket reactor (USB) anoxic, at pilot-scale, installed in
series. The first chamber of the anaerobic baffled reactor, C1, had a volume of 200 L and the
second, C2, with a volume of 160 L. The submerged aerated filter (SAF) presented a diameter of
300 mm. The material used to support biomass adherence was composed of clean and dry
bamboo rings, without treatment, occupying the entire column of SAF bed, with 1800 mm height.
The rings had 46 mm medium length, 20 mm internal and 25 mm external diameter, specific
surface area of 92.5 m2 m-3 and 75% empty index. The aeration system used was composed of
air compressor with 3 m3 h-1 medium air flow, and a porous thin membrane capsule, which was
attached to the bottom of the reactor for bubble aeration. For the last step of the anaerobic,
aerobic and anoxic treatment system, an anoxic upflow sludge blanket reactor (USB) had a total
volume of 120 L.
Table 1 shows the operating conditions of the experiment with the anaerobic, aerobic,
anoxic combined treatment system divided into two tests for different hydraulic detention times
(HDT) used, and then divided into five phases for the different organic loading rates (OLR)
applied and conditions of intermittent and continuous aeration in the SAF.
For experimental phases with intermittent aeration (phases 2 with 12 hours of aeration
and 12 hours without aeration, phases 3 and 4 with 1 hour with aeration and 1 hour without
aeration) samples were collected from the effluent of SAF and anoxic USB during periods with
and without aeration.
The chemical analyses and physical and microbiological examinations performed on
samples of influent and effluent, of sludge and biogas, as well as the sampling frequencies and
the sources of the methodologies utilized are described in Table 2.
RESULTS AND DISCUSSION
The pH values in the effluent of the chamber 1 and 2 of the anaerobic baffled reactor
increased relative to the affluent in all tests of the treatment system operation, indicating
adequate buffer conditions. Most anaerobic treatment systems are operated at pH range
between 6.5 and 7.5, it is recommended to maintain the pH above 6.2 (Henze et al., 1997). Low
pH values are generally related to high concentrations of total volatile acids and consequently the
breakdown process.
The average values of pH of the influent ranged of 6.21 to 7.10 and increased to 7.04 to
7.64 in the effluent of ABR. For the output of the FAS, the range was 6.67 to 7.88 and 7.15 to
8.04 in the effluent of anoxic USB reactor as a consequence of volatile fatty acids (VFA) removal
and increased total alkalinity (TA).
Nitrification is a process that occurs at the expense of the consumption of alkalinity and
dissolved oxygen present in the system. If the alkalinity supplied to the system is not sufficient to
maintain the pH within the optimum value (between 6.5 and 8.0) for the metabolism of nitrifying
bacteria was inhibited. The alkalinity required to oxidize 1 g of ammoniacal nitrogen to nitrite is
7.07 g CaCO3. The pH of the FAS was within the optimum range for nitrification. The operation of
the favorable denitrification reactors, as in the anoxic USB reactor, is to be held in high values of
pH, between 7 and 9, because at pH below 7, there may be accentuated production of nitrogen
oxides, which is highly toxic to microorganisms (HENZE et al., 1997).
Average values of total COD of the influent in both tests ranged of 21.9 g L1 to 40.0 g L-1,
decreasing over the ABR, the FAS and anoxic USB reactor (Table 3). Although with application
of higher OLR during test 2, with the HDT decrease of 24 h to 12 h, the treatment system was
able to maintain the effluent quality regarding the removal of organic matter, evidenced by the
high removal efficiencies during all phases, of 95 to 99% (Figure 1). It is possible to emphasize
the importance of treatment composed by ABR reactor, which showed the highest values of
organic matter and suspended solids removal efficiencies, demonstrating that union positive
aspects of the anaerobic, anoxic and aerobic series stages promoted benefits to swine
wastewater treatment.
III Symposium on Agricultural and Agroindustrial Waste Management
March 12-14, 2013-Sao Pedro, SP, Brazil
At the anaerobic baffled reactor, operated with OLR values of 38.8 to 77.7 g total COD (L
d) -1, it was observed removal efficiencies of total COD predominantly above 80% (Table 1 and
Table 3). In the submerged aerated filter, with OLR from 6.7 to 10.9 g total COD (L d) -1, the
average removal efficiencies of total COD ranged of 11 to 70%. In the anoxic USB reactor, with
OLR applied from 2.5 to 8.4 g total COD (L d) -1, were obtained removal efficiencies of total COD
of 44 to 85%. The results demonstrates that, despite the lower values of removal efficiency of
FAS, there was a significant contribution of the aerobic step and anoxic USB reactor for the
anaerobic, aerobic and anoxic treatment system to reach up 99% of total COD removal efficiency
(Figure 1), stabilization of the sludge, nitrification and denitrification, and also attenuation of
organic shock conditions.
The volumetric methane production in ABR ranged of 0.064 to 0.293 m3 CH4 (m3 reactor
-1
d) and in anoxic USB reactor of 0.016 to 0.199 m3 CH4 (m3 reactor d) -1. Although with higher
OLR of 76.9 and 77.7 g total COD (L d) -1, applied in ABR in test 2, the highest volumetric
production of methane into the system of ABR+SAF+ anoxicUSB was 0.314 m3 CH4 (m3 reactor
d) -1.
Regarding the volumetric methane production obtained in other anaerobic reactors
(UASB, batch and filter) treating swine wastewater, the values were lower than for similar
conditions of OLR, due to the absence of a device phase separation (biogas, sludge and effluent)
in ABR. The percentage of methane in the biogas ranged from 73 to 83% in ABR, and 19 to 60%
in the anoxic USB reactor.
In the biogas produced at the anoxic USB reactor it was observed up to 74% of nitrogen.
The mean values of nitrite and nitrate in the anoxic USB reactor effluent decreased, compared to
values observed in SAF, showing the final step in biological nitrogen removal, the denitrification.
Mean values of ammoniacal-N ranged of 83 to 215 mg L-1, 146 to 254 mg L-1, 42 to 151 mg
-1
L and 59 to 94 mg L-1 in the affluent of ABR, FAS and anoxic USB reactor, respectively. The
consumption of alkalinity in the SAF (Table 2) occurred due to the oxidation of ammonia-N. It
would take the average values from 296 to 1067 mg CaCO3 L-1 to oxidize the ammonia-N (mean
values of ammonia-N in FAS ranging from 42 to 151 mg L-1). The values found show that TA
available in the effluent (727 to 1160 mg CaCO3 L-1) of the ABR was sufficient to oxidize the
ammonia-N to nitrite.
It was possible to obtain mean values of removal efficiency of total nitrogen up to 91% in
the anaerobic, aerobic and anoxic treatment system, with OLR applied of 6.6 to 20.5 g total COD
(L d)-1 and 2.1 to 18.3 g total COD (L d)-1 in submerged aerated filter and anoxic USB reactor,
respectively, and with variations at SAF aeration, resulting average values of dissolved oxygen of
3.72 to 4.38 mg L-1
Taking as a basis the limits for thermotolerant coliform by Brazilian legislation (BRASIL,
2005), the effluent from the anoxic USB reactor, during phase 3, reached mean values of 1,9 x
103 MNP 100 mL-1. This results are below the limit established of 4,000 MPN 100 mL-1 to
freshwater bodies, which can be used for irrigation of tree crops, cereals and forage crops.
CONCLUSIONS
Most of the organic matter removal, suspended solids, macro and micronutrients occurred
in ABR, especially in the first chamber. The use of submerged aerated filter was essential to the
occurrence of nitrification, removal of total and thermotolerant coliforms. The anoxic USB reactor,
installed in series, was important to maintain the removal efficiencies of the treatment system
stable in response to changes in aeration, for denitrification, to promote further stabilization of the
sludge and to reduce the adverse effects of organic shock loads.
The post-treatment inclusion allowed obtaining high values of removal efficiency for the
anaerobic, aerobic, anoxic treatment system, up to 91% for total nitrogen and 99.96% for
thermotolerant coliform. For effluents with high organic load, the combination of the anaerobic
process, aerobic and anoxic was effective, showing ability to withstand high influent
concentrations as observed during the operation of the treatment system.
ACKNOWLEDGEMENTS
FAPESP and CAPES for financial support
REFERENCES
III Symposium on Agricultural and Agroindustrial Waste Management
March 12-14, 2013-Sao Pedro, SP, Brazil
Apha/Awwa/Wef (2005) Standard methods for the examination of water and wastewater.
21th, Washington, 1569 p.
Bodik, I., Kratochvil, K.,Gasparikova, E.,Hutman, M. (2003) Nitrogen removal in an anaerobic
baffled filter reactor with aerobic post-treatment. Bioresource Technology, 86, 79-84.
Henze, M., Harremoës, P., Arvin, E., Jansen, J. la C. (1997). Wastewater treatment: biological
and chemical processes. 2.ed. Berlim: Springer Verlag.
Jenkins, S.R.; Morgan, J M.; Sawyer, C.L. (1983). Measuring anaerobic sludge digestion and
growth by a simple alkalimetric titration . J. Water Poll. Control Fed. 55, 448-453.
Kuscu, O.S, Sponza, D.T. (2006). Treatment efficiencies of a sequential anaerobic baffled
reactor (ABR)/completely stirred tank reactor (CSTR) system at increasing p-nitrophenol and
COD loading rates. Process Biochem. 41, 1484-1489.
Song, M.; Shin, S.G.; Hwang, S. (2010). Methanogenic population dynamics assessed by realtime quantitative PCR in sludge granule in upflow anaerobic sludge blanket treating swine
wastewater. Bioresource Techonoogy, 101, 523-528.
Table 1. Operating conditions (HDT, OLR, aeration conditions and operation time) of the
anaerobic, aerobic and anoxic treatment system for swine wastewater.
Tests
HDT (h)
Phase Operation OLR
SAF’s aeration
time
condition
ABR
SAF USB
(days)
C1
C2
1
13.6 10.5
7.9
7.8
2
6.8
3.9
3.9
5.2
1
2
3
4
5
85
34
53
44
45
-1
52.2
70.6
38.8
77.7
76.9
continuous
Intermittent of 12 h
Intermittent of 1 h
Intermittent of 1 h
continuous
HDT - hydraulic detention time; OLR - organic loading rate (g COD (L d) ); COD - chemical oxygen demand; C1 e C2
chambers of anaerobic baffled reactor (ABR); SAF- submerged aerated filter
Table 2. Examinations and determinations, frequencies and sources of methodologies
Examinations and
determinations
Frequency
Sources of methodologies
Influent and effluent
Total alkalinity
COD (total COD)
N-NO2 e N-NO3
1
Nutrients
Dissolved oxygen (DO)
2
Coliforms
Biogas
Composition
Production
1
2 x per week
2 x per week
2 x per week
3 x per week
2 x per phase
Apha, Awwa, Wpcf (2005), Jenkins et al.
(2003)
Apha, Awwa, Wpcf (2005)
Apha, Awwa, Wpcf (2005)
Apha, Awwa, Wpcf (2005)
Apha, Awwa, Wpcf (2005)
Apha, Awwa, Wpcf (2005)
1 x per week
Daily
Apha, Awwa, Wpcf (2005)
Fernandes and Oliveira (1997)
2 x per week
2
(Kjeldahl N, total-P); (total and thermotolerant)
System removal efficiency (%)
100
98
96
94
92
90
88
86
84
82
80
Phase 1
Phase 2 (a) Phase 2 (a'
) Phase 3 (a)
totalCOD
dissCOD
Phase 3 (a'
) Phase 4 (a) Phase 4 (a'
)
TSS
Phase (5)
VSS
Figure 1. Mean removal efficiency of total COD, dissolved COD, total and volatile suspended
solids (TSS and VSS) in the anaerobic-aerobic-anoxic treatment system
(ABR+SAF+anoxicUSB), during phases 1, 2, 3 (Test 1); 4 and 5 (Test 2).