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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.

    2

    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

  • 3

    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.

    4

    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.

  • 5

    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).

  • 6

    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.

  • 7

    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 So Paulo "Jlio de Mesquita Filho" (UNESP) Campus Bauru - So Paulo -Brazil.

    8

    Bauru is located in the state ofSo Paulo (southeastern Brazil)

  • 9

    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

  • 10

    Aerial picture-Research area

    Health club -Unespsservers

    WWTP

    Physical Education Dept.Students House

  • 11

    Bar ScreensBar Screens

    Equalization and settling tanksEqualization and settling tanks

    WWTP Area

  • 12

    Figure 1. AABRs profile

  • 13

    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 chambers distribution and sampling points of the AABR

  • 14

    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

  • 15

    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

    AABRs performance

    Collection - Once a week500 ml/hour - 4hours

    Sampling points: A,C1,C2,C3, AC and ST

  • 16

    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

  • 17

    AABR monitorationTemperature:

    The effluent temperature remained between 24C and29C

    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

  • 18

    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

  • 19

    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

  • 20

    CODThe average values and SD during the monitoration period were:

    C3= 8947 mg.L-1 CA= 6426 mg.L-1 E= 4728 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=22091 mg.L-1 C1=13565 mg.L-1 C2= 10642 mg.L-1

    Figure . COD values for the AABR during the monitoration period

  • 21

    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).

  • 22

    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 32 222 52 303 61 31

    Table. Average values andSD for DO during the 22

    weeks of monitorametion

  • 23

    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

  • 24

    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

  • 25

    AABR

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