以超声波破解剩余污泥为碳源强化污水脱氮

ULTRASOUND TREATMENT OF EXCESS SLUDGE AS CARBON SOURCE TO STRENGTHEN DENITRIFICATION OF WASTEWATER

针对污水厂生物脱氮碳源不足和剩余污泥难以处置的问题,探讨了利用超声波处理后的剩余污泥作为生物脱氮外加碳源的可行性。研究采用三因素三水平的响应曲面分析法,考察了超声波声能密度、时间和pH对剩余污泥可生化性(BOD_5)的影响,确定了超声波破解剩余污泥的最佳工艺条件。结果表明:在超声波声能密度为2. 0 W/m L,超声波时间为40 min和pH=7. 0的条件下,剩余污泥ρ(BOD_5)为2195 mg/L,增加为原来(88 mg/L)的24. 9倍,大大增强了其可生化性。超声波破解前后剩余污泥的大肠菌群检测结果证明,超声波破解也可将致病菌灭活,使剩余污泥无害化。在以3种剩余污泥产物为外加碳源的反硝化实验中,利用最佳参数条件下处理的剩余污泥为碳源时反硝化效果最好,反应仅进行14 h,ρ(NO_3^--N)从108 mg/L迅速降至3 mg/L,去除率达到95%以上,NH_4^+-N几乎无积累,整个反硝化过程完成仅需24 h,表明采用优化后的超声波预处理条件可以有效提升以剩余污泥为碳源的反硝化效果。

The insufficient carbon source for biological denitrification and difficult disposal of excess sludge are two common problems in wastewater plants. This study explored the feasibility of using excess sludge treated under optimized ultrasonic condition as additional carbon source for biological denitrification. The response surface methodology of three factors and three levels was used to investigate the effects of ultrasound energy density,ultrasonic time and pH on BOD5. The optimum conditions of ultrasonic treatment for excess sludge were confirmed. The optimum BOD5 concentration achieved 2195 mg/L at the ultrasonic sound energy density of 2. 0 W/m L,ultrasonic time of 40 minutes and pH of 7. 0,which was 24. 9 times as much as the BOD5 concentration of untreated sludge. The biodegradability was greatly improved. The detection of the coliforms including E.coli before and after ultrasonic crack showed that these pathogenic bacteria in sludge could be killed by ultrasonic crack,which made the remaining sludge harmless. In the denitrification experiments using three product of the sludge as additional carbon source,denitrification was the best for excess sludge treated under the best parameters.ρ( NO3^--N) was reduced from 108 to 3 mg/L in only 14 hours. It took only 14 hours to complete the entire denitrification process,and the removal efficiency exceeded 95%. And there was little accumulation of NH4^+-N. In summary,the optimized ultrasonic pretreatment conditions can effectively enhance the denitrification efficiency of excess sludge as carbon source.