Bioremediation of phenolic compounds in sewage water using bacterial consortia
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Date
2019
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CCSHAU
Abstract
Sewage water is a rich source of organic waste and nutrients in the form of nitrates and
phosphates, due to which it can be used in agriculture after proper treatment. Sewage water contains
various harmful compounds like phenolics which need to be treated before discharge. The direct
discharge of sewage water into natural water sources leads to the obstructive impacts on the water
sources and aquatic life, sewage water becomes an open source of harmful microbes and pollutants. To
demolish these problems the treatment of domestic waste water is must and its reuse for the domestic
as well as agriculture purpose can become an eco-friendly solution for the conservation of water.
A total of 29 bacterial isolates were retrieved from seven sewage water samples collected from
Sewage Treatment Plant, CCS HAU, Hisar. All bacterial isolates were screened for phenol degradation
in mineral salt medium supplemented with 250, 500 and 750 ppm concentration of phenol. Out of 29,
only 8 bacterial isolates were able to grow in mineral salt medium having 750 ppm concentration of
phenol. These eight bacterial isolates were further observed for growth upto 1500 ppm concentration of
phenol, out of eight, only four bacterial isolates (NI6, NI5, NR1 and JC1) were able to grow upto 1250
ppm concentration of phenol. Cultural conditions, inoculum size and aeration were optimised in culture
medium as well as sewage sludge. Fifteen percent inoculum and 2 LPM aeration rate were found to be
optimum for efficient phenol degradation. Least residual phenol in culture medium and sewage sludge
at 15% inoculum was left with bacterial isolate NI6 (265.2 ppm and 607.30 ppm respectively). Same
was observed in culture medium and sewage sludge at 15% inoculum and 2 LPM aeration in lab scale
fermenter for bacterial isolate NI6 (352.3 ppm and 761.27 ppm respectively). A consortium of four
bacterial isolates (25% each of NI6, NI5, NR1 and JC1) was found to leave least 276.93 ppm residual
phenol in sewage sludge as compared to individual isolates. Consortium was further tested for removal
of phenolic compounds, COD, BOD and Heavy metal at STP, CCS HAU, Hisar. At 9th day of
application, highest phenolic compounds degradation was observed in sewage sludge (120 ppm) and
outlet of clarifier (172.9 ppm), thereafter phenolic compounds concentration started to increase. At 9th
day COD reduced from 460 mg/L to 60 mg/L and 100 mg/L to 40 mg/L while BOD decreased from
153 mg/L to 18 mg/L and 28 mg/L to 17 mg/L in sewage sludge and outlet of clarifier respectively.
Removal of Zinc and Chromium was observed in outlet of clarifier and sewage sludge.
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