9 research outputs found
Effect of sludge pretreatment on the performance of anaerobic/anoxic/oxic membrane bioreactor treating domestic wastewater
In the present study, two bench-scale anaerobic/ anoxic/ oxic submerged
membrane bioreactors were used to study the effect of thermochemical
sludge disintegration system on the excess sludge production. Among the
two membrane bioreactors, one was named experimental membrane
bioreactor and another one was named as control membrane bioreactor,
where a part of the mixed liquor was treated with thermo chemical and
was returned back to membrane bioreactor. Thermo chemical digestion of
sludge was carried out at fixed pH (11) and temperature (75 °C)
for 24 % chemical oxygen demand solubilization. The other one was named
control membrane bioreactor and was used as control. The reactors were
operated at three different mixed liquor suspended solids range
starting from 7500 mg/L to 15000 mg/L. Both the membrane bioreactors
were operated at a flux of 17 LMH over a period of 240 days. The
designed flux was increased stepwise over a period of one week. During
the 240 days of reactor operation, both the membrane bioreactors
maintained relatively constant transmembrane pressure. The sludge
digestion had no impact on chemical oxygen demand removal efficiency of
the reactor. The results based on the study indicated that the proposed
process configuration has potential to reduce the excess sludge
production as well as it didn't detoriate the treated water quality
Treatment of poultry slaughterhouse wastewater in upflow anaerobic filter under low upflow velocity
The wastewater discharged by poultry slaughterhouse industries are
characterized mainly by high biochemical oxygen demand, high suspended
solids and complex mixture of fats, proteins and fibers requiring
systematic treatment prior to disposal. In this study, the performance
of an upflow anaerobic filter reactor for treating Indian poultry
slaughterhouse wastewater under low upflow velocity of 1.38 m/day at
mesophilic temperature (29-35 °C) was investigated. The reactor
was inoculated with anaerobic non-granular sludge from an anaerobic
reactor treating the poultry slaughterhouse wastewater. The reactor
took 147 days for complete start-up with removal efficiencies of total
chemical oxygen demand and soluble chemical oxygen demand of 70 and 79
% respectively. The maximum total chemical oxygen demand removal
efficiency of 78 % was achieved at an organic loading rate of 10.05
kg/m3/day and at an hydraulic retention time of 12 h. The average
methane content varied between 46 and 56 % and methane yield at maximum
removal efficiency was 0.24 m3 CH4 /kg CODremoved.day. Sludge granules
of 1-2 mm were observed in between the packing media. Scanning electron
microscope analysis revealed that sludge granules are composed of
clumps of Methanosarcina clustered with less intertwined Methanosaeta
fibre of granules. The lower velocity used in this study has achieved
better performance of the reactor by creating active microbial
formation with stable pH upto an organic loading rate of 14.3
kg/m3/day. This has proved that the poultry slaughterhouse wastewater
can be treated using anaerobic filter reactor under low upflow
velocity
Effects of sludge pretreatment on sludge reduction in a lab-scale anaerobic/anoxic/oxic system treating domestic wastewater
Excess sludge disposal is one of the serious challenges in biological
wastewater treatment. Reduction of sludge production would be an ideal
way to solve sludge-associated problems rather than the post-treatment
of the sludge produced. In this study, a new wastewater treatment
process combining anaerobic/anoxic/oxic system with thermochemical
sludge pretreatment was tested in a laboratory scale experiment. In
this study, the effects of the sludge pretreatment on the excess sludge
production in anaerobic/anoxic/oxic were investigated. The system was
operated in two Runs (1 and 2). In Run 1, the system was operated as a
reference and in Run 2, a part of the mixed liquid was pretreated
thermochemically and was returned to the bioreactor. The average
solubilization efficiency of pretreated sludge was found to be about 35
% during the study period of 220 days. Sludge production rate in Run 2
was less than that in Run 1 by about 52 %. Total phosphorous was
removed by enhanced biological phosphorous removal with the removal
efficiency of 83â87 % and 81â83 % for Run 1 and Run 2,
respectively. Total nitrogen removal in Run 2 (79â82 %) was
slightly higher than that in Run 1 (68â75 %). The mixed liquor
suspended solids/mixed liquor volatile suspended solids ratio was
identical after both runs in the range 78â83 %. The effluent
water qualities were not significantly affected when operated with
thermochemical pretreatment at pH 11 and 60 °C for 3 h during 7
months. From the present study it is concluded that thermochemical
sludge pretreatment of anaerobic/anoxic/oxic process plays an important
role in reduction of sludge production
Effect of extracellular polymeric substances on sludge reduction potential of Bacillus lichenifowrmis
The disposal of wastewater sludge generated during the treatment of the
various municipal and industrial wastewaters is a major environmental
problem. In this study the thermophilic bacterium Bacillus
lichenifowrmis , which enhances the efficiency of sludge reduction,
was isolated from waste activated sludge acclimated to 55 °C. The
resulting suspended solidsâ degradation was 12 % and chemical
oxygen demand solubilization was 18 %. To further enhance the sludge
reduction potential, extra polymeric substances, which play a major
role in the formation of flocs, were removed. A chemical extractant,
ethylenediaminetetraacetate that is also a cation binding agent, was
used to remove the extra polymeric substances. After the removal of
extra polymeric substances, the suspended solidsâ degradation
increased from 12 to 23 % and the chemical oxygen demand solubilization
increased from 18 to 25 %. These observations confirm that Bacillus
licheniformis enhanced sludge reduction in non-flocculated sludge (with
the removal of extra polymeric substances) as compared to flocculated
sludge (without the removal of extra polymeric substances)