城市污泥厌氧消化和脱水工艺对肠道病原菌的杀灭效应

Inactivation of enteric bacterial pathogens in sewage sludge by anaerobic digestion and dewatering treatment

运用最大或然数(MPN)培养法和定量PCR(qPCR)技术对不同城市污水处理厂污泥厌氧消化处理和脱水处理前后,污泥中埃希氏大肠杆菌(E.coli)、沙门氏菌(Salmonellaspp.)和志贺氏菌(Shigellaspp.)含量的变化进行了研究.MPN检测结果表明,污泥中大肠杆菌、沙门氏菌和志贺氏菌数量经厌氧消化处理后明显下降,平均下降2～5个数量级,但qPCR检测结果显示,种病原菌平均下降1～2个数量级.脱水处理3后,污泥中的肠道病原菌含量基本没有变化,没有发生脱水后再生长现象.大肠杆菌、沙门氏菌和志贺氏菌含量分别在104～107、104～105和103～105MPN·g-1(以污泥干重计)之间.MPN和qPCR检测结果之间的差异性显示厌氧消化会造成肠道病原菌的有活性但不可培养状态(VBNC),同时也提示应用传统的培养检测方法检测病原菌含量和评定污泥排放的生物安全性时需慎重.

This study investigated the quantities of three enteric bacterial pathogens, E. coli, Salmonella spp. and Shigella spp. through anaerobic digestion and dewatering treatment by using the most probable number （MPN） culture and quantitative real-time PCR （qPCR） methods. MPN results showed that the quantities of E. coli, Salmonella spp. and Shigella spp. decreased significantly after anaerobic digestion, and the average log reduction values were 2 ~ 5. However, the qPCR results showed the average log reduction values were 1 -2. After dewatering treatment, the quantities of three pathogens in the sludge changed slightly and no phenomenon of regrowth after dewatering was observed. The concentrations of E. coil, Salmonella spp. and Shlgella spp. were between 104～107、104～105 , and 103 - 105 MPN.g-I （dry weight） , respectively. The detection difference between the MPN and qPCR results indicated the existence of viable but non-culturable （VBNC） pathogens which resulted from anaerobic digestion treatment. This phenomenon suggested that the application of traditional culture methods should be careful for the bacterial pathogens detection and the biological safety assessment in sewage sludge discharge