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STUDY OF DECENTRALIZED WASTEWATER
TREATMENT: ANAEROBIC/AEROBIC
BAFFLED REACTOR
Julliana A. Silva, Prof. Dr. Arnaldo Sarti, Prof. Dr. Gustavo H. R. Silva
Rapid growth in population, urbanization,industrialization, demand of energy and climatechange has drawn attention of many researcherstowards the scarcity of clean water.
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Worldwide billion people are sufferingdue to inadequate sanitation,wastewater treatment and unavailabilityof water. The situation is serious insmaller towns (or peri-urban areas )and rural communities in developingcountries
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82,7% - Estimated access to piped water supply
42,3% - Estimated access to sewer services
Only 38,7 % are treated in WWTPs
The average water consumption ofBrazilians in 2012 was 167.5 litersper capita per day (an increase of4.9% compared to 2011).
The lack of financial resources toinvest in WWTP - demand ofengineers environmentally andeconomically sustainable projects ofwastewater treatment systems.
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The consequence of this is the commonpractice of discharging large amounts ofuntreated wastewater directly into streamsand lakes in many developing countries.
Althought, among the variousdevelopments, treatment of wastewater isalways considered one of the lowestpriorities.
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There is a direct need to develop reliabletechnologies with low-cost implementationand simple operation, that does not requirelarge areas and energy demand (Gopala-Krishna et al., 2008).
Many publications have revealed the potential ofAnaerobic Baffled Reactors (ABR)(Cao et al., 2011; Qi et al., 2013, Silva et al, in press).
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However, there is a need to install furtherpolishing steps, whose option may be anAerobic Chamber.
Mainly advantage of the ABR is the separation ofacidogenesis and methanogenesis phaseslongitudinally down the reactor, allowing the differentbacterial groups to develop under favorableconditions.
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To monitor an Anaerobic/Aaerobic BaffledReactor (AABR), analyzing its behavior duringthe start-up and the hydraulic retention timechanges, in order to apply it in smallcommunities.
Wastewater source Wastewater was from the Wastewater Treatment Plant at State
University of São Paulo "Júlio de Mesquita Filho" (UNESP) –Campus Bauru - São Paulo -Brazil.
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Bauru is located in the state ofSão Paulo (southeastern Brazil)
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ParametersAffluent Average Values
Average Standard DeviationTemperature (°C) 25 3pH 7.3 0.2Alkalinity (mg.L-1) 337 93Volatile Acids (mgHac.L-1) 56 22COD (mg.L-1) 220 81BOD (mg.L-1) 85 36Ammonial Nitrogen (mg.L-1) 56 18TSS (mg.L-1) 43 28VSS (mg.L-1) 30 21
Table 1. Affluent characteristics
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Aerial picture-Research area
Health club -Unesp´sservers
WWTP
Physical Education Dept.Students House
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Bar ScreensBar Screens
Equalization and settling tanksEqualization and settling tanks
WWTP Area
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Figure 1. AABR´s profile
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Chamber High (m) Diameter(mm)
Volume (L) Treatmentprocess
C1 0.90 600 405 Anaerobic
C2 0.90 300 96 Anaerobic
C3 0.90 300 96 Anaerobic
AC 1.70 400 220 Aerobic
Table 2. Dimensions and volumes of each chamber of AABR
AC C3 C2 C1
ST
A
Figure 2. AABR chamber´s distribution and sampling points of the AABR
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Start-up: the reactor was inoculated withsludge from an UASB reactor
22 weeks of operation
3 phases, with different hydraulic retentiontime (HRT) and flow
Table 3. Phases of operation and HRTs of the Anaerobic/aerobic baffledreactor
PhaseFlow
stablished(L.h-1)
Hydraulic retention time (hours)Anaerobic chambers Aerobic chamber TotalC1 C2 C3 AC1 (8 weeks) 24 12 6 6 9 332 (7 weeks) 36 8 4 4 6 223 (7 weeks) 48 6 3 3 4.5 16.5
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Analytical methods Dissolved oxygen BOD COD Nitrate Ammonial nitrogen pH Total Suspended solidsTemperature Alkalinity: Volatile Acids:
System monitoration
Affuent flow
4 times per week
Rice et al, 2012
Ripley et al, 1986Adorno et al, 2014
AABR´s performance
Collection - Once a week500 ml/hour - 4hours
Sampling points: A,C1,C2,C3, AC and ST
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Analyses of inoculation process during start-up
Follow the methods described by Chernicharo (2007)
Supernadant (parcial volume) Supernadant (total volume)
ParametersChambers
ParametersChambers
C1 C2 C3 C1 C2 C3Volatile Acids(mgHac.L-1)
72 72 71 Volatile Acids(mgHac.L-1)
168 120 96
Alkalinity(mgCaCO3.L-1)
328 288 282 Alkalinity(mgCaCO3.L-1)
300 283 280
COD (mg.L-1) 108 38 20 COD (mg.L-1) 100 30 18pH 7.1 7.1 7.1 pH 7.3 7.3 7.4Temperature(°C)
27 28 28 Temperature(°C)
26 27 26
Table 3. Results from the supernadant analyses of the AABR ininoculation phase
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AABR monitorationTemperature:
The effluent temperature remained between 24°C and29°C
Mesophilic rangeTable 4. Average values and SD for temperature in each samplingpoints and phases of study
Temperature (°C)Sampling points Phases of study
1 – HRT1 2 – HRT2 3 – HRT3 TotalAffluent 28 ±2 26 ±2 22 ±2 26 ±3
Chamber 1 28 ±2 26 ±2 22 ±2 25 ±3Chamber 2 28 ±2 26 ±3 22 ±2 26 ±3Chamber 3 28 ±2 26 ±2 22 ±1 25 ±3
Aerobic Chamber 27 ±4 26 ±3 22 ±2 25 ±3Settling tank 27 ±2 26 ±3 23 ±2 25 ±3
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pHThe pH values in the AABR remained between 6.4 and 7.7
Optimal range for bacteria growth
6.8
6.9
7.0
7.1
7.2
7.3
A C1 C2 C3 CA ST
pH
Sampling points
Figure 3. pH values along the AABR, during the twenty two monitoring weeks
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0
100
200
300
400
A C1 C2 C3 CA ST
Tota
l Alk
alin
ity(m
gCaC
O 3.L
-1)
Sampling points
0
50
100
A C1 C2 C3 CA
Vola
tile
Acid
s(m
gHA.
L-1 )
Sampling points
Acidogenesis(production)
Volatile Acids inanaerobic digestion
Methanogenesis(comsumption)
Figure. VA average values in the AABR,during the monitoration period
Alkalinity neutralize acidsformed in the process and alsoto buffer the pH in a possibleVA accumulation. There was noVA acumulation, so theAlkalinity values remained inequlibrium in the anaerobicchambers. The CA and STcomsuption are related tonitrification activity.
Figure. Alkalinity average values in the AABR,during the monitoration period
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CODThe average values and SD during the monitoration period were:
C3= 89±47 mg.L-1
CA= 64±26 mg.L-1
E= 47±28 mg.L-1
0
100
200
300
400
500
600
0 1 2 3 4 5 6 7 8 9 10111213141516171819202122
COD
(mg.
L-1 )
Monitoration weeks
E
C1
C2
C3
CA
SD
Phase 1 Phase 2 Phase 3
A=220±91 mg.L-1
C1=135±65 mg.L-1
C2= 106±42 mg.L-1
Figure . COD values for the AABR during the monitoration period
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0102030405060708090
100
0 1 2 3 4 5 6 7 8 9 10111213141516171819202122
COD
rem
oval
(%)
Monitoration period (weeks)
CODThe AABR performance was satisfactory in all phases of monitoration(Phase 1, 2 and 3), however Phase 2 and 3 the COD removal was moreeffective, than Phase 1.
Lower removal efficiency in phase 1 Start-Up period.
Figure . Average values of COD removalduring the monitoration period
Comparing with Silva etal (in press) research,the results obtained inthe present researchshowed a higher CODremoval efficiency thanthe five steps researchedby Silva et al. (in press).
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0102030405060
A C1 C2 C3 CA STNitr
ate
–Am
mno
nia
Nitr
ogen
(mg.
L-1)
Sampling points AmmonianitrogenNitrate
Nitrate and Ammonial NitrogenNitrification was observed in AC ( which had air supply), but thedesnitrification did not happened no carbon source
Figure. Nitrate and Ammonia nitrogen average values in theAABR, during the monitoration period (22 weeks)
Dissolved oxygen(mg.L-1)
PhaseSampling
pointsAC ST
1 3±2 2±22 5±2 3±03 6±1 3±1
Table. Average values andSD for DO during the 22
weeks of monitorametion
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0
20
40
60
A C1 C2 C3 CA ST
48
13 11 8 5 3TSS
(mg.
L-1 )
Sampling points
Total Suspended Solids (TSS)High retention of TSS in the reactor.Average removal - 93%.The AABR and the settling tank wereeffective for the TSS removal, evenwith the low strength affluent
0
50
100
A C3 ST
89
46
23
BOD 5
(mg.
L-1 )
Sampling points
BOD5The higher removal efficiency was inphase 2 (HRT=22 hours), with aaverage removal of 80%,Phase 1 - 57 %Phase 3 – 79 %
Figure. Average values of TSS, during themonitoration period
Figure. Average values of BOD5,during the monitoration period
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The simple and compactconfiguration
has shown to be efficientfor a low strengthsanitary wastewater
treatment
It may be used insmall communities.
There was high CODremoval rates:
•Phase 1 (8weeks): 76 %•Phase 2 (7 weeks): 79%•Phase3 (7 weeks): 79%
The pH values remained within theoptimal range (7.1 and 7.3).
Good for microbiological activity.
The VA were inequilibrium, indicating
an appropriateoperation (separationof phases) common
for ABRs.
1 2
3
4
5 AABR
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AABR had high retention of TSS.High removal
Effluent - 3 mg.L-1There was Ammonial nitrogen
reduction(Nitrification).
The AABR is still under adaptation process.Two more phases will be studied - with lower HTRs.
It is in progress to achieve even better results.
6 7
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AABR
Pos Graduate Program in Civil andEnvironmental Engineering
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Proc. n 2011/10816-2Proc. n 2014/18343-4
email: [email protected]
