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Aerobic granulation with petrochemical wastewater in a sequencing batch reactor under different operating conditions S. Milia, E. Malloci and A. Carucci Università degli Studi di Cagliari
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  • Aerobic granulation with petrochemical wastewater in a sequencing batch reactor under different operating conditions

    S. Milia, E. Malloci and A. CarucciUniversità degli Studi di Cagliari

  • Introduction

    Petrochemicalwastewater

    Organic and inorganic pollutants

    TREATMENT:• combination of biological and physical-chemical treatments • considerable investments and operating costs

  • Granular sludge Sequencing Batch Reactor (GSBR)

    • formation of dense and compact biomass without support material• high VSS concentration inside the reactor• less sludge production• less area (-80%) and energy (-30%)• aerobic, anoxic and anaerobic conditions achieved simultaneously in the GSBR• diffusive phenomena as a barrier against toxic and inhibitory substances

    Introduction

  • Aim of the study

    Define the best operating conditions for the successful start-up of a Granular sludge Sequencing Batch Reactor (GSBR) treating petrochemical wastewater (PW)

  • Petrochemical wastewater

    Parameters U. M. Concentration

    Alcalinity ppmCaCO3 2000pH 10-10.8

    Ammonia mg/l 240-630Cyanide mg/l 10-15

    COD mg/l 340-610TOC mg/l 260-490

    Phenol mg/l 2.7Formate mg/l 1000-1500

    TSS mg/l 300-500

    Integrated Gasification Combined Cycle (IGCC) uses a gasification system to convert fuel (i.e., heavy refining liquid residues) into a synthesis gas (syngas) and produce steam. Process water is used for the purification of syngas (IGCC wastewater).The PW was supplied by SARAS SpA (Sarroch, Italy), and it is currently treated at full scale by a combination of chemical-physical and biological processes

  • GSBR• working volume: 3 L• diameter/height: 0.3• room temperature: 20 – 25°C• exchange ratio (effluent

    volume/total working volume): 0.5

    • Hydraulic Retention Time (HRT): 8 h

    • 4-h cycles▫ 5 min feeding▫ 222-215.5 min aeration▫ 8-1.5 min settling▫ 5 min effluent withdrawal

  • Start-up operating conditions

    Operating conditions Phase A Phase B

    Seed sludge Domestic WWTP Petrochemical WWTP

    pH control range 7.0±0.2 7.8±0.2

    Superficial gas velocity (cm/s) 2.3 2.8

    Additional supplies

    Acetate (COD), P, trace elements Acetate (COD), P

    vOLR(gCOD/gVSS·d) 3 3

  • Fraction of PW and influent characteristics

    Phases Day %PW Settling time(min) COD:N

    A1-67 10 8-4 100:11

    68-154 20 4-1.5 100:14 - 100:10155-220 30 1.5 100:12

    B

    1-10 10 8 100:411-62 20 8-1.5 100:763-97 30 1.5 100:11 - 100:7.4 - 100:898-133 50 2 100:11 - 100:14

  • Results and DiscussionAerobic granules formation

    0

    0,2

    0,4

    0,6

    0,8

    1

    1,2

    1,4

    30 60 90 120 150 180 210 230

    Aver

    age

    size

    of

    gran

    ules

    (m

    m)

    Time (d)

    10% PW 30% PW20% PW

    Phase A 10% PW20% PW

    30% PW

  • 0,00

    0,05

    0,10

    0,15

    0,20

    0,25

    0,30

    0,35

    0,40

    0,45

    0,50

    10 40 70 110 130

    Aver

    age

    size

    of

    gran

    ules

    (m

    m)

    Time (d)

    10% PW 30% PW20% PW 50% PW

    Results and DiscussionAerobic granules formation

    5mm

    Phase B 10% PW 20% PW and 30% PW

    50% PW

  • VSS, SVI and effluent TSS – PHASE A

    Results and Discussion

    VSS

    , TSS

    (g/

    L)

    0,5

    1,0

    1,5

    2,0

    2,5

    3,0

    Time (d)

    TSS

    (g/

    L)

    0

    1

    2

    3

    4

    SVI

    (mL

    /gT

    SS)

    0

    100

    200

    300

    400

    500

    600

    VSS (g/L) effluent TSS (g/L) SVI (mL/gTSS)

    10% PW 20% PW 30% PW

  • VSS

    (g/L

    )

    0

    2

    4

    6

    8

    10

    12

    14

    16

    18

    20

    Time (d)0 20 40 60 80 100 120 140 160

    efflu

    ent T

    SS (g

    /L)

    0,0

    0,1

    0,2

    0,3

    0,4

    0,5

    0,6

    0,7

    SVI (

    mL/

    gTSS

    )

    0

    100

    200

    300

    400

    500

    VSS (g/L) effluent TSS (mg/L) SVI (mL/gTSS)

    20% PW 30% PW 50% PW10% PW

    VSS, SVI and effluent TSS – PHASE B

    Results and Discussion

  • Conc

    entr

    atio

    n NH

    4+-N

    ( mg/

    L)

    0

    20

    40

    60

    80

    100

    120

    140

    160

    Time (d)

    20 40 60 80 100 120 140 160

    Rem

    oval

    effic

    iency

    (%)

    0

    20

    40

    60

    80

    100

    Influent (mg/L)Effluent (mg/L)Removal Efficiency (%)

    20% PW 30% PW 50% PW10% PW

    Con

    cent

    ratio

    n N

    H4+

    -N ( m

    g/L

    )

    40

    60

    80

    100

    120

    140

    160

    180

    Time (d)

    0 50 100 150 200 250

    Rem

    oval

    eff

    icie

    ncy

    (%)

    0

    20

    40

    60

    80

    100

    Influent (mg/L)Effluent (mg/L)Removal Efficiency (%)

    20% PW10% PW 30% PW

    NH4-N and TOC removalPHASE A PHASE B

    Date

    0 10 20 30 40 50 60 70 80 90 100

    110

    120

    130

    140

    150

    160

    170

    180

    Con

    cent

    ratio

    n T

    OC

    (mg/

    l)

    0

    100

    200

    300

    400

    500

    600

    Rem

    oval

    eff

    icie

    ncy

    (%)

    0

    20

    40

    60

    80

    100

    TOC in (mg/L) TOC out (mg/L) Removal Efficiency (%)

    50% PW30% PW20% PW10% PW

    Average TOC removal 93±2%

    Date

    0 50 100

    150

    200

    250

    Con

    cent

    ratio

    n TO

    C (m

    g/l)

    0

    100

    200

    300

    400

    500

    600

    700

    Rem

    oval

    effic

    ienc

    y (%

    )

    0

    20

    40

    60

    80

    100

    TOC in (mg/L) TOC out (mg/L) Removal efficiency (%)

    20% PW10% PW 30% PW

    Average TOC removal 92±6%

    Average NH4-N removal of 29%

    21±5%

    LATELY WE WERE ABLE TO RISE THE REMOVAL TO 100%, WITH THE ADDITION OF NITRIFYING BACTERIA

  • Comparison Phase A and BPhase A Phase B

    Granulation (day) 20 8

    Average diameter (mm) 0.9±0.3 0.4±0.05

    Max density (gTSS/Lgran) 15.8 48

    Max VSS (g/L) 1.9 16.8

    Max SRT (days) 7 34

    NH4-N removal (%) 28±8% 32±19%

    TOC removal (%) 92±6% 93±2%

    Results and Discussion

  • Working volume 250 mlDiameter 5 cmWorking height 12.5 cmSampling: inlet, outlet after settling (180 min) and at time 0, 15, 30, 60, 90, 240, 300, 360 min.125 ml of washed biomass from the mother reactor.

    Batch Experiments: pH and cycle lenghtinfluence on NH4-N removal

    4- and 6-hours tests were performed at pH 7.0±0.2 and 7.8±0.2

    Specific VOLR = 0.22 gCOD/gVSS·dSSV = 0.54±0.05 g/L% petrochemical wastewater: 30, 50, 75, 100 %.

  • BatchExperiments

    01234567

    0 100 200 300 400

    NH

    4+-N

    con

    cent

    rati

    on

    (mg/

    L)

    Time (min)

    100 % PW - pH 8100% PW - pH 7.230% PW - pH 830% PW - pH 7.2

    0

    1

    2

    3

    4

    5

    6

    0 100 200 300 400

    NH

    4+-N

    con

    cent

    rati

    on (

    mg/

    L)

    Time (min)

    50% PW

    75% PW

    100% PW

    4h-cycle under different pH conditions.No differences were noticed.

    6h-cycle:+ 7.7% at 50%+3.8% at 75%+1.8% at 100%

  • Acute toxicity assessmentsA titrimetricbiosensor (ANITA, Ammonium NITrificationAnalyser) was used in order to evaluate the acute inhibiting effects of -100% PW- 50% PW- GSBR effluent at 50%on unacclimatedsludge

  • Acute toxicity assessments

    0

    25

    50

    75

    100

    0 20 40 60 80

    Inhi

    biti

    on [

    %]

    Cumulated Volume [mL/gVSS]

    100% PW

    50% PW

    GSBR effluent at 50% of PW

    88 mL/gVSS

    100 % inhibition

    9.5 mL/gVSS

    17.2 mL/gVSS

    During phase B (days 98-133), when 50% PW was fed to the GSBR

  • Conclusions• Aerobic granular sludge can be cultivated in a GSBR fed

    with petrochemical wastewater:▫ in phase B, the use of acclimated sludge as inoculum and

    harsher environmental conditions (i.e., higher shear stress) allowed the formation, development and retention of compact, dense and well settling granules in the GSBR.

    • GSBR performance was good in terms of TOC removal. • NH4-N removal was low and stable during Phase A;

    while it was influenced by new stocks of PW during Phase B.

    • Batch experiments showed that pH and cycle length do not significantly affect NH4-N removal.

    • Ammonia degradation can be improved by adding nitrifying bacteria to the GSBR.

    • The GSBR fed with 50% PW was able to provide an effluent with negligible residual toxicity.

  • Next steps

    • Rising to 100% the petrochemical w.w. treated by the GSBR

    • Achievement and maintenance of optimal conditions in the GSBR in the long-term

    • Pilot scale GSBR• Treatment of different kind of industrial w.w.

  • Aerobic granulation with petrochemical wastewater in a sequencing batch reactor under different operating conditions� �IntroductionIntroductionAim of the studyPetrochemical wastewaterGSBRStart-up operating conditionsFraction of PW and influent characteristicsResults and DiscussionResults and DiscussionVSS, SVI and effluent TSS – PHASE AVSS, SVI and effluent TSS – PHASE BNH4-N and TOC removal � PHASE A PHASE BComparison Phase A and BBatch Experiments: pH and cycle lenght influence on NH4-N removalBatch ExperimentsAcute toxicity assessmentsAcute toxicity assessmentsConclusionsNext stepsGrazie,�Thank you!��Emanuela Malloci [email protected]���


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