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]���