Study On Degradation And Transformation Of Polynuclear Aromatic Hydrocabons (PAHs) During Digested Sludge Compost

There are polynuclear aromatic hydrocabons (PAHs) with high concentration in digested sludge of Licunhe sewage treatment plant. If PAHs can not be treated and untilized by agriculture, soil and crops will be polluted. Considing the aforementioned question, the digested sludge in Licunhe sewage treatment plant was composted, and made it reduction, unharm and resource. Under analyzing phsico-chemical and biological characteristics, the degradation and transformation of PAHs was also investigated, and it will provide scientific basis for environmental effect evaluation of composting product in agriculture untilization.In this study, digested sludge, sawdust and reflux sludge acted as composting materials, and four groups experiment have been carried. Each group experiment arrived at high temperature from the 3th day to the 5th day. The bacteria, fungi and actinomycetes had different successional changes. The bacteria and fungi were first rise and then degrade, and actinomycetes kept the degradating tredency. The cress seed germination index (GI), used as indicator of phytotoxicity and maturation of compost , exhibited that the sludge compost was almost stabilized and mature near the 31th day of composting , and 80% of GI were obtained. In addition, E. Coli ,as a common indicator of pathogens in sludge , reduced to 102 in the final examination of the compost. The experiment results shows compost of digested sludge of Licunhe sewage treatment plant and sawdust is feasible.Degradation and transformation of PAHs in different ratio of sludge and sawdust was also studied. The Ratio of sludge, sawdust and reflux with 1, 1 and 1 had higher efficiency than the ratio of sludge, sawdust and reflux with 2, 1 and 1. The content of naphthalene was higher than other PAHs in composting products and raw sludge. Besides naphthalene, medium molecular weights with 3-, 4-benzene rings concentration has higher concentration distribution pattern, and low molecular weights with 2-benzene rings and high molecular weights with 5-benzene rings has low concentration..∑PAH has significant degradation, and the period of cooling kept stable. The∑(PAHs)carc had the same trendency with the∑PAHs in experiment III,however, degradation of∑(PAHs)carc in experiment IV is not significant.PAHs Content, distribution pattern and degradation effect is connected with characteristics of PAHs in raw sludge. The experimental results show that composting of municipal sludge and sawdust is feasible for degrading PAHs and meet the standard of agriculatre utilization.