Regrowth of Fecal Coliforms in Class A Biosolids

Abstract

Eight types of Class A biosolids were tested for fecal coliform (FC) reactivation and/or regrowth at 20, 35, and 50°C for 21 days. Growth of FC did not occur at 20 or 50°C, but it was observed in two samples incubated at 35°C after a lag period of 48 hours. In undigested biosolids, final FC concentration exceeded 10 4 MPN/g, whereas in thermophilically digested biosolids, the final FC concentration remained below 10 3 MPN/g, as FC regrowth may have been affected by the presence of the anaerobic bacterial consortium responsible for the digestion process. Fecal‐coliform reactivation and regrowth within treatment plant operations seem unlikely but can occur in land application of biosolids.

Can sludge dewatering reactivate microorganisms in mesophilically digested anaerobic sludge? Case of belt filter versus centrifuge

“…However, outcomes of several other studies support the hypothesized effect of temperature. For instance, it is reported by Jolis (2006) that storage of digested samples at 35 C led to the reactivation of indicator bacteria without implementing dewatering which is an evidence of the effect of temperature in the obtained increases. Moreover, as mentioned before, high speed centrifuges are reported to lead to greater increases of indicator bacteria compared to the low speed ones (Qi et al, 2007).…”

Gene Expression Monitoring for Detection and Quantification of Viable but Non-Culturable Pathogens in Biosolids

“…The increase was over 2 logs in mesophilically digested biosolids and over 5 logs in biosolids digested in a temperature-phased anaerobic process (Higgins et al, 2007). Similarly, Jolis (2006) investigated eight types of Class A biosolids that passed through different types of treatment and observed growth of FC after 48 hours of incubation at 35 o C. In a similar work, Iranpour and Cox (2006) observed growth of FC after various incubation periods at different temperatures in the Class A biosolids from two of the three full-scale wastewater treatment plants investigated in Southern California. Interestingly, both of the treatment plants employed thermophilic anaerobic digestion for stabilization of biosolids to a Class A level while the third treatment plant, where no increase in FC counts was observed, operated a mesophilic digester.…”

“…The viable but non-culturable (VNC) state of pathogens has been proposed within the last few decades as a survival mechanism for certain prokaryotic microorganisms, including pathogens, when they encounter unfavorable environmental conditions (Koch, A, 1971;Oliver, J.D., 1993). Several of the recent studies attributed the regrowth of indicator organisms in biosolids to the possible VNC state that microorganisms assume under unfavorable conditions during stabilization or exposure to chemical disinfectants (Higgins et al, 2007;Iranpour and Cox, 2006;Jolis, 2006;Manios, et al, 2006;Qi et al, 2007). The objective of this research is to review the current literature on pathogen regrowth in biosolids and to investigate the relationship between the expression of stress-related genes in Salmonella and cell viability.…”

Use of RNA-based genotypic approaches for quantification of viable but non-culturable Salmonella sp. in biosolids

“…Despite the favourable properties of biosolids such as high nutrient content, which can be advantageous for beneficial use such as land applications, the potential health risk from pathogen presence, residual volatile solids levels and odor problems limit the beneficial use option of biosolids Recent evidence on regrowth of pathogenic microorganisms in treated biosolids indicates that biological safety of biosolids intended for beneficial use is still a significant treat for the environment and public health (Qi et al 2004;Zaleski et al 2005;Iranpour & Cox 2006;Jolis 2006). Viable but non-culturable (VNC) state phenomenon is proposed to be one of the possible mechanisms for the regrowth of fecal coliforms.…”

“…FC growth after stabilization has been the subject of several studies and many of them observed the indicator organism regrowth in biosolids (Cheung et al 2003;Erdal et al 2003;Iranpour et al 2003;Monteleone et al 2004;Qi et al 2004). For example in a study by Jolis (2006) biosolids samples classified as Class A investigated for FC reactivation and regrowth was observed in biosolids samples when incubated at 35 degrees 8C for 48 hours after stabilization. Manios et al (2006) investigated the change in number of total coliforms (TC) on soil and grass after irrigation with secondary level wastewater and chlorinated effluent.…”