The Interaction Between Organic Pollutants In Coking Wastewater Biodegradation And Its Enhancement Technology

Biological treatment of coking wastewater has long been challenging due to its complex composition,high toxicity and low biodegradability.In this study,focusing on the biodegradation of real coking wastewater using aerobic activated sludge,the biodegradability of coking wastewater was first characterized by investigating(1)the inhibitory effects between major components(phenol,pyridine and quinoline)in coking wastewater and(2)the impacts of high concentration on biodegradation efficiency.Then ultrasonic treatment and bioaugmentation techniques were applied in aerobic activated sludge based coking wastewater treatment to optimize its biodegradation efficiency.Major results and conclusions obtained in this study include:(1)Based on average degradation rate analysis and fractional reaction kinetics fitting,the inhibitory effects between three major components in simulated coking wastewater acclimated aerobic activated sludge(SCWAAS)were investigated.It was revealed that the biodegradation efficiency of phenol was hardly affected by pyridine and quinoline.However,the biodegradation efficiencies of pyridine and quinoline decreased more than 50% in the presence of phenol,which was consistent with the variation trend of loss coefficient k obtained by fractional reaction kinetics fitting.(2)The impacts of elevated concentration fluctuation on biodegradation efficiency of SCWAAS system was systematically investigated,and three approaches to relieve such impacts were developed.It was revealed that the COD removal rate of SCWAAS system decreased 40.3% against elevated phenol concentration due to its strong consumption capability toward dissolved oxygen(DO),which was higher than that caused by elevated pyridine or quinoline(less than 20%).The impacts of elevated concentration fluctuation can be relieved by DO supplement,UV pretreatment and external electron donors addition,which was verified by real coking wastewater.(3)Ultrasonic pretreatment was innovatively applied to enhance the biodegradability of real coking wastewater.The biodegradation efficiencies of real coking wastewater acclimated aerobic activated sludge(RCWAAS)system increased 8.1-33.0% using the developed ultrasonic method,achieving high-performance biodegradation of real coking wastewater.(4)For the first time,bioaugmentation was adopted to reduce the accumulation of intermediate product(2-hydroxypyridine).During the biodegradation process of pyridine using pyridine acclimated aerobic activated sludge(PAAS),2-hydroxypyridine exhibited lower affinity toward intracellular electron donors and were accumulated in PAAS system.The accumulation problem of 2-hydroxypyridine can be solved by adding proportionate 2-hydroxypyridine aerobic activated sludge(HPAAS)into PAAS system,saving more than 4 h of hydraulic retention time(HRT).(5)Based on high-throughput sequencing technique,microbial community characteristics of RCWAAS,PAAS and HPAAS samples were analyzed and compared with glucose acclimated aerobic activated sludge(control group).The sequencing results indicated that after the acclimation using real coking wastewater,pyridine or 2-hydroxypyridine,the microbial diversities of activated sludge increased,showing more stable ecological structures with higher resistance to environmental changes.Besides,many specialized degrading microorganisms were observed in RCWAAS,PAAS and HPAAS samples.