Enhancing sewage sludge dewaterability by bioleaching approach with comparison to other physical and chemical conditioning methods  

作　　者：Fenwu Liu Jun Zhou Dianzhan Wang Lixiang Zhou 

机构地区：[1]Department of Environmental Engineering,College of Resources and Environmental Science,Nanjing Agricultural University,Nanjing 210095,China.

出　　处：《Journal of Environmental Sciences》2012年第8期1403-1410,共8页环境科学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China (No. 21177060,20977048);the National High Technology Research and Development Program (863) of China (No. 2012AA063301)

摘　　要：The sewage sludge conditioning process is critical to improve the sludge dewaterability prior to mechanical dewatering. Traditionally, sludge is conditioned by physical or chemical approaches, mostly with the addition of inorganic or organic chemicals. Here we report that bioleaching, an efficient and economical microbial method for the removal of sludge-borne heavy metals, also plays a significant role in enhancing sludge dewaterability. The effects of bioleaching and physical or chemical approaches on sludge dewaterability were compared. The conditioning result of bioleaching by Acidithiobacillus thiooxidans and Acidithiobacillusferrooxidans on sludge dewatering was investigated and compared with the effects of hydrothermal （121℃ for 2 hr）, microwave （1050 W for 50 sec）, ultrasonic （250 W for 2 min）, and chemical conditioning （24% ferric chloride and 68% calcium oxide; dry basis）. The results show that the specific resistance to filtration （SRF） or capillary suction time （CST） of sludge is decreased by 93.1% or 74.1%, respectively, after fresh sludge is conditioned by bioleaching, which is similar to chemical conditioning treatment with ferric chloride and calcium oxide but much more effective than other conditioning approaches including hydrothermal, microwave, and ultrasonic conditioning. Furthermore, after sludge dewatering, bioleached sludge filtrate contains the lowest concentrations of chroma （18 times）, COD （542 mg/L）, total N （TN, 300 mg/L）, NH4＋-N （208 mg/L）, and total P （TP, 2 mg/L） while the hydrothermal process resulted in the highest concentration of chroma （660 times）, COD （18,155 mg/L）, TN （472 mg/L）, NH4＋-N （381 mg/L）, and TP （191 mg/L） among these selected conditioning methods. Moreover, unlike chemical conditioning, sludge bioleaching does not result in a significant reduction of organic matter, TN, and TP in the resulting dewatered sludge cake. Therefore, considering sludge dewaterability and the chemical properties of sludThe sewage sludge conditioning process is critical to improve the sludge dewaterability prior to mechanical dewatering. Traditionally, sludge is conditioned by physical or chemical approaches, mostly with the addition of inorganic or organic chemicals. Here we report that bioleaching, an efficient and economical microbial method for the removal of sludge-borne heavy metals, also plays a significant role in enhancing sludge dewaterability. The effects of bioleaching and physical or chemical approaches on sludge dewaterability were compared. The conditioning result of bioleaching by Acidithiobacillus thiooxidans and Acidithiobacillusferrooxidans on sludge dewatering was investigated and compared with the effects of hydrothermal （121℃ for 2 hr）, microwave （1050 W for 50 sec）, ultrasonic （250 W for 2 min）, and chemical conditioning （24% ferric chloride and 68% calcium oxide; dry basis）. The results show that the specific resistance to filtration （SRF） or capillary suction time （CST） of sludge is decreased by 93.1% or 74.1%, respectively, after fresh sludge is conditioned by bioleaching, which is similar to chemical conditioning treatment with ferric chloride and calcium oxide but much more effective than other conditioning approaches including hydrothermal, microwave, and ultrasonic conditioning. Furthermore, after sludge dewatering, bioleached sludge filtrate contains the lowest concentrations of chroma （18 times）, COD （542 mg/L）, total N （TN, 300 mg/L）, NH4＋-N （208 mg/L）, and total P （TP, 2 mg/L） while the hydrothermal process resulted in the highest concentration of chroma （660 times）, COD （18,155 mg/L）, TN （472 mg/L）, NH4＋-N （381 mg/L）, and TP （191 mg/L） among these selected conditioning methods. Moreover, unlike chemical conditioning, sludge bioleaching does not result in a significant reduction of organic matter, TN, and TP in the resulting dewatered sludge cake. Therefore, considering sludge dewaterability and the chemical properties of slud

关 键 词：SLUDGE BIOLEACHING conditioning FILTRATE sludge cake 

分 类 号：X703[环境科学与工程—环境工程] TS939[轻工技术与工程]