Q
Use of a Pilot Plant Sequencing Batch Reactor for the Treatment of
Shrimp Aquaculture Wastewater
C. Lyles, Q. Fontenot, M. Kilgen, and R. Boopathy Nicholls State University, Thibodaux, LA 70310, USA.
Introduction
-III
Anaerobic
Fill
Aerobic
React
Settle
Decant
Time
-II
-I
Hydroxylamine
NH2OH
0
Nitrogen Gas
N2
+I
Nitroxyl
NOH
Nitrous Oxide N20
+II
Nitric Oxide NO
+III
Nitrite
NO-
NO-2
2
+IV
Nitrate
NO-3
Aerobic
Anaerobic
Nitrification
Denitrification
Figure 2. Illustration of the aerobic - anaerobic sequence used for a
sequencing batch reactor during the react stage
Figure 1. Illustration of the aerobic - anaerobic sequence used for a
sequencing batch reactor during the react stage
Anaerobic
Aerobic
Anaerobic
Aerobic
Settle
Aerobic
80
110
70
Control
Anaerobic
Aerobic
Cont_PreAerated
Control_NoPre
SBR_Preaerated
SBR_NoPre
Aerobic
Settle
800
SBR
600
Total Ammonia (mg/L)
50
40
30
20
Total Ammonia (mg/L)
88
60
66
44
Control
SBR
Acknowledgements
200
22
0
0
1
2
3
4
5
6
7
0
8
2
3
4
5
6
7
0
8
1
2
3
SBR
150
5
6
7
450
360
200
4
Day of Experiment
450
Nitrite (mg/L)
Nitrite Concentration (mg/L)
Control
1
Day of Experim ent
Day of Experiment
250
0
Cont_Preaerated
Cont_NoPre
SBR_Preaerated
SBR_NoPre
This work was supported by the funds from the U.S.
Department of Agriculture, Cooperative State Research
Service United States Marine Shrimp Farming Program. Heidi
Atwood (WMC) and John Ogle (GCRL) provided assistance for
this project.
360
Control
Nitrite (mg/L)
0
SBR appears to be a viable option for treating wastewater
produced by intensive recirculating shrimp culture systems.
Results of this study are not as obvious as previous studies
(Boopathy et al. 2005; Boopathy et al. 2007; Fontenot et al.
2007). Initial ammonia, nitrite, and nitrate concentrations were
lower than previous treatment studies (Boopathy et al. 2005;
Boopathy et al. 2007; Fontenot et al. 2007). Both the WMC and
GCRL has just started their culture system for the season and
the necessary microbes may not have been established.
High levels of nitrite may have been caused by partial
denitrification. Because the culture system had just been
started for the season, the microbial community responsible
for denitrification may have been limited. The most promising
results occurred when the SBR was operated anaerobic first
(Figure 6). This may have allowed the denitrifying bacteria to
become more established and reduce some of the initial nitrite
before ammonia denitrification.
More work needs to be conducted at the pilot scale. Future
studies will include work with a more mature sludge source.
Microbial isolates from an active SBR will be identified to
determine the more important species.
400
10
270
180
SBR
270
180
100
50
90
90
0
0
0
0
1
2
3
4
5
6
7
8
0
1
2
3
Day of Experiment
4
5
6
7
0
8
1
2
3
4
5
6
7
References
Day of Experiment
Day of Experiment
80
700
400
SBR
320
60
40
Cont_Preaerated
Cont_NoPre
SBR_Preaerated
SBR_NoPre
525
Nitrate (mg/L)
Control
Nitrate (mg/L)
Nitrate Concentration (mg/L)
Experiments were conducted at the Waddell Mariculture
Center (WMC), SC, and and the Gulf Coast Research
Laboratory (GCRL), MS. The WMC operates a 228,000 L
intensive recirculating shrimp culture raceway. Solids are
removed via backflushing a bead filter approximately 227 L
per backwash. Backwash was pumped into two 12,545 L
round fiberglass holding tanks (Figure 3). One tank was left
unaerated and the other was operated as a SBR. The SBR
sequence was aerobic 2 days, anaerobic 3 days, and aerobic
2 days for a 7 day cycle. Aeration was provided by forcing air
through submerged airstones.
The purpose of this
experiment was to compare SBR treatment to an unaerated
treatment. This experiment was conducted twice, however
only one replicate was obtained for days 7 and 8.
GCRL operates 12 raceways within a single greenhouse
for intensive shrimp culture and solids are removed via
individual settling cones. Solids are gravity fed to one of two
central round 500 L fiberglass collection tanks.
Each
collection tank is located within a separate greenhouse (SG1
and SG2). Within each greenhouse are 4 additional 300 L
fiberglass round tanks that can be operated as a SBR. Two
experiments involving different aeration sequences were
conducted at GCRL. For the first experiment, the wastewater
in the SG1 collection tank was continuously aerated before
transfer to SBR and control tanks. The wastewater in the SG2
greenhouse was not aerated prior to transfer to the SBR and
control tanks. This design resulted in four treatments:
SBR:Preaerated, SBR:Notpreaerated, Control:Preaerated,
Control:Notpreaerated. The SBR sequence was aerobic 2
days, anaerobic 3 days, aerobic 2 days, and settle one day for
an 8 day cycle. Each treatment was duplicated.
A third experiment involved manipulating the aerobicanaerobic sequence at GCRL.
SBR tanks were run
anaerobically the first three days and then aerobically for the
last four days of a seven day sequence. The control tank was
run anaerobiclly for the duration of the experiment. As with
the second experiment, one holding tank was pre-aerated
prior to transfer to experimental tanks and the other holding
tank was not pre-aerated. However, data from samples taken
from the pre-aerated and not pre-aerated holding tank was
pooled within the SBR (N=2) and control (N=2) treatments.
To
determine
ammonia,
nitrite,
and
nitrate
concentrations (mg/L), 30 mL of sample was taken from each
tank, centrifuged at 5,000 rpm for 10 min and the supernatant
was analyzed colorimetrically with a Hach water analysis kit
and spectrophotometer. Data were subject to analysis of
variance (alpha = 0.05) followed by Tukeys post hoc analysis
if necessary.
Idle
Ammonium
NH+4
+V
300
Methods
NITROGEN OXIDATION STATE
Aerobic
Total Ammonia (mg/L)
One of the main issues for intensive inland recirculating
culture systems is the accumulation and disposal of sludge.
Besides the cost of sludge disposal, usable water and salt is
lost through sludge disposal. Previous work has shown that
sequencing batch reactor (SBR) is effective at removing
nitrogen and carbon from sludge, so that water and salt can
be safely returned to the culture system (Boopathy et al. 2005,
Boopathy et al. 2007, Fontenot et al. 2007). Sequencing batch
reactor (SBR) incorporates alternating aerobic and anaerobic
periods to achieve nitrification and denitrification in a single
container (Figure 1). Naturally occurring microbes associated
with the sludge are responsible for the nitrification and
denitirification process (Figure 2). Time is needed at the end
of the sequence to allow the sludge to settle so that surface
water can be decanted.
The carbon and nitrogen composition of sludge from
shrimp aquaculture operations depends largely on the feed
used. Microbial degradation of any waste depends on the
amount of carbon, nitrogen, and phosphorus available for
their activity. If there is too little nitrogen present, the bacteria
will be unable to produce necessary enzymes to utilize the
carbon. If there is too much nitrogen, particularly in the form
of ammonia, it can inhibit the growth of the bacteria.
Previous work involving treatment of wastewater
consisted of multiple bench top studies (Boopathy et al. 2005,
Boopathy et al. 2007, Fontenot et al. 2007). This study
evaluated a pilot scale SBR at the Waddell Mariculture Center
(WMC), SC, and the Gulf Coast Research Laboratory (GCRL),
MS. Nitrogen removal by SBR was compare to a control tank
that remained unaerated for the study duration.
Discussion
240
160
Control
Boopathy, R., C. Bonvillain, Q. Fontenot, and M. Kilgen. 2007.
Biological Treatment Of Low-Salinity Shrimp Aquaculture
Wastewater using Sequencing Batch Reactor. International
Journal of Biodeterioration and Biodegradation 59:16-19.
SBR
350
175
20
80
0
0
0
0
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5
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7
8
0
1
3
4
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7
8
0
1
2
3
4
5
6
7
Day of Experiment
Day of Experiment
Day of Experiment
Figure 4. Total ammonia-N, Nitrite-N, and
Nitrate-N (mg/L) for SBR and control
treatments for each day of the experiment at
the Waddell Mariculture Center.
2
Figure 5. Total ammonia-N, Nitrite-N, and
Nitrate-N (mg/L) for each of four treatments
for each day of experiment one at the Gulf
Coast Research Laboratory.
Figure 6. Total ammonia-N, Nitrite-N, and
Nitrate-N (mg/L) for SBR and control
treatments for each day of experiment two
at the Gulf Coast Research Laboratory.
Results
Figure 3. SBR (left) and control (right) used at the Waddell
Mariculture Center.
Initial nitrogen levels were relatively low for the WMC
experiment. By day 6 of the WMC experiments, ammonia and
nitrate were lower in the SBR than the control tank; however,
there was no difference between the two treatments for nitrite
(Figure 4). Nitrite levels increased for the SBR and control
treatment for the duration of the experiment (Figure 4).
Aeration of the wastewater at the GCRL previous to
SBR treatment reduced ammonia and nitrite levels (Figure 5).
Although ammonia and nitrate levels were generally lower in
the SBR than the control tanks by the end of the experiment,
there was no difference between the treatments for nitrite
(Figure 5).
Ammonia, nitrite, and nitrate were lower in the SBR
than the control tanks by the end of the third experiment
(Figure 6). Variance was greater for the control tank than for
the SBR.
Fontenot, Q.C., C.P. Bonvillain, M.B. Kilgen, and R. Boopathy.
2007. Effects of Temperature, Salinity, and Carbon:Nitrogen
Ratio on Sequencing Batch Reactor Treatment of
Recirculating Intensive Aquaculture Wastewater.
Bioresource Technology 98:1700-1703.
Boopathy, R., Q. C. Fontenot, and M. B. Kilgen. 2005. Biological
Treatment of Shrimp Wastewater with Sequencing Batch
Reactor. Journal of the World Aquaculture Society 36:542545.