Bioremediation of hydrocarbon-rich wastewater by aerobic granules of oil degrading bacterial strains in salinity influence


Sayanti Ghosh
Centre for the Environment, Indian Institute of Technology Guwahati, Assam
Saswati Chakraborty
Department of Civil Engineering, Indian Institute of Technology Guwahati, Assam


Granulation of sewage and brewery sludge isolated oil degrader Brevibacterium and Staphylococcus were investigated in hydrocarbon-rich wastewater with 280 mg/L of hydrocarbon at 10-25 g/L NaCl salinity influence. Brevibacterium and Staphylococcus cultures were inoculated in aerobic granular reactors (AGRs) R1 and R2 which were operated with 24 h cycle time and 2 L/min air flow rate. Yellowish matured granules appeared within 15 days. R1 granules achieved stability till 15 g/L NaCl concentration but faced disintegration between 15-20 mg/L NaCl exposure which reduced granule size and hydrocarbon removal from 2.15-1.7 mm and 78-73%. R2 granules were more salt tolerant providing 2.5±0.5 mm granule size with 4±1 g/L volatile suspended solids (VSS) and 201±1 mg/g VSS extracellular polymeric substances (EPS) content achieving 81±0.7% hydrocarbon removal in 30 days. High granule stability and biomass concentration ensured less biomass washout from reactors. Granule settling velocity (GSV) in R1 and R2 reached 20±1 and 32±0.8 m/h which corresponded with granule size profiles. Kinetics analysis showed that at steady state, R1 and R2 were capable of 72 and 91% phenol removals in 30 and 24 h, respectively. Hence, the study provided salt tolerant oil degrading granules for refinery wastewater treatment.

April 11, 2021
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