Abstract:The inactivation and viable but non culturable (VBNC) occurrence of Salmonella sp. in sewage sludge by anaerobic digestion and subsequent treatment was investigated by Most probable number (MPN) and Reverse transcription quantitative PCR (RT-qPCR) method. Four anaerobic digestion processes had different effects on the inactivation of Salmonella spp. The reductions of Salmonella spp. in sewage sludge after mesophilic anaerobic digestion (MAD) and high temperature (65℃) pretreatment anaerobic digestion (65℃+MAD) were 2.8 and 5.6 orders of magnitude. Thermophilic anaerobic digestion (TAD) and temperature-phased anaerobic digestion (TPAD) exhibited excellent efficiencies on the inactivation of Salmonella spp. with the final content below the detection limit. The inactivation rate coefficients decreased in the following order: 65℃+MAD (39.64 d-1), TAD (3.75 d-1), TPAD (2.96 d-1) and MAD (0.21 d-1), indicating the high temperature accelerated the inactivation of Salmonella spp.. The logarithmic densities of VBNC Salmonella spp. in sewage sludge after TAD and TPAD are 2 orders of magnitude higher than that after MAD, 65℃+MAD, indicating the high temperature led to more pathogens entering into the VBNC state. Salmonella spp. densities in digested sludge increased after centrifuge dewatering with the logarithmic increase of 1.1, 2.4, 3.7 and 2.5 for MAD, 65℃+MAD, TAD and TPAD, respectively, but the densities of VBNC Salmonella spp. significantly decreased after dewatering with the values of 1~3 orders of magnitude, which indicated that several VBNC Salmonella spp. in digested sludge reactivated after centrifuge dewatering, resulting the increase in the number of culturable Salmonella spp. by MPN. The results revealed that the regrowth of Salmonella in digested sludge was attributed to the reactivation of Salmonella in VBNC state. The Salmonella content gradually decreased in the subsequent storage at room temperature.
符波, 王燕, 姜谦, 陈燕, 刘和. 污泥厌氧消化和后续处理中沙门氏菌杀灭及VBNC发生[J]. 中国环境科学, 2013, 33(1): 103-110.
FU Bo, WANG Yan, JIANG Qian, CHEN Yan, LIU He. Inactivation and VBNC occurrence of Salmonella spp. in sewage sludge by anaerobic digestion and subsequent treatment. CHINA ENVIRONMENTAL SCIENCECE, 2013, 33(1): 103-110.