STUDY OF DECENTRALIZED WASTEWATER … OF DECENTRALIZED WASTEWATER TREATMENT: ANAEROBIC/AEROBIC...

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.

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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: gustavoribeiro@feb.unesp.br