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The anaerobic and aerobic combined biosystem is assumed to consume less energy for the treatment of high strength industrial wastewater. In this study, the pollutant removal performance and microbial diversity were revealed in a long run (over 300 days) bench scale sequential anaerobic-aerobic biosystem treating coking wastewater. Anaerobic treatment could remove one third of COD and more than half of phenols at a hydraulic retention time of 42 hours, while the combined system with a total HRT of 114 hours removed COD, TOC, total phenols, thiocyanate and cyanide by 81.6±3.3%, 85.2±4.2%, 99.9±0.02%, 98.2±0.3, 87.2±3.9% respectively. Comprehensive two dimensional gas chromatography with time-of-flight mass spectrometric analysis revealed almost complete removal of phenol derivatives and nitrogenous heterocyclic compounds (NHCs) by the combination in which anaerobic process alone contributed in average 58.4% and 59.1% removal, respectively. In order to appraise microbial activity in bioreactors, the bacterial, archaeal and fungal communities were analyzed by 454 pyrosequencing. Proteobacteria (relative abundance 61.2 - 93.4%), particularly Betaproteobacteria (34.4-70.1%) were the most predominant bacterial group. Phenol degrading and hydrolytic bacteria like Ottowia (14.1-46.7%), Soehngenia (3.0-8.2%) and Corynebacterium (0.9-12.0%) were most abundant genera in anaerobic sludge, whereas in aerobic sludge Thiobacillus (6.6- 43.6%), Diaphorobacter (5.1-13.1%) and Comamonas (0.2-11.1%)were speculated as major degraders of phenol, thiocyanate and NHCs, respectively. Despite of low density of fungi, oleaginous yeast Trichosporon which degrades phenolic compounds was found abundant in aerobic sludge. The results revealed that the removal of pollutants was related with phylogenetic abundance of microbial diversity. This study revealed the feasibility of less energy intensive optimization for the removal of organic pollutants from coking wastewater, and the potential association between some important bacterial groups and key pollutants. |