Development of nitrate stimulated hydrocarbon degrading microbial consortia from refinery sludge as potent bioaugmenting agent for enhanced bioremediation of petroleum contaminated waste

Stable and efficient hydrocarbon degrading microbial consortia were developed from a refinery sludge through nitrate amendment for their application in enhanced bioremediation of petroleum contaminated waste. Nitrate induced biostimulation of refinery sludge resulted in increased abundance of hydrocarbon degrading Rhodocyclaceae, Xanthomonadaceae, Syntrophaceae and Comamonadaceae members. Repeated subculturing of nitrate stimulated communities in crude oil supplemented basal medium was done under aerobic and anaerobic conditions. Aerobically enriched consortia (composed ofPseudomonadaceae, Pseudoxanthomonadaceaeand unclassifiedComamonadaceae) showed their ability to utilize alkanes, aromatics and crude oil as growth substrates. Anaerobically enriched consortium was predominated by Bacillaceae, Pseudomonadaceae, Xanthomonadaceae, Porphyromonadaceae and Comamonadaceae members. Anaerobic consortium was found to be relatively less efficient in terms of TPH (total petroleum hydrocarbons) degradation compared to its aerobic counterpart. These enriched microbial consortia were finally tested for their biodegradation performance and stability during bioremediation of highly contaminated refinery sludge using different strategies. A 30 days microcosm based bioremediation trial showed that bioaugmentation of aerobic cultures with refinery sludge was more effective in TPH degradation (similar to 65% degradation) compared to the anaerobic consortium (only 36% TPH degradation) and a combination of bioaugmentation and nitrate amendment with sludge resulted in enhanced hydrocarbon attenuation (up to 86% TPH degradation). Subsequent community analysis at the end of bioremediation trial confirmed the stability of the added microbial populations. Thus, the strategy of bioaugmentation of specially enriched native microbial populations in combination with nitrate amendment was successfully used for the enhanced bioremediation of petroleum hydrocarbon contaminated refinery waste.