The Effect of Digestion and Dewatering on Sudden Increases and Regrowth of Indicator Bacteria after Dewatering

Abstract

Several Investigators have reported higher densities of indicator bacteria after dewatering of anaerobically digested biosolids. The increases appear to occur at two points in the biosolids process: the first, referred to as "sudden increase", occurs immediately after dewatering; the second, "r'J|^wth", occurs during storage over longer periods. The objectives of digestion and dewatering fecal coliform and £, coll. and five mesophiiic digesf ilter press dewatering, Suj thermophilic processes witj in the mesophilic processj dewatering, Regrowth was processes with centrifuge dŴ ater Environ. Res., 83, 7' [is study were to examine the effect of resses on sudden increase and regrowth of i)les were collected from five thermophilic lorocesses, with either centrifuge or belt increase typically was observed in the Ktrifuge dewatering and was not observed fith either centrifuge or belt filter press feerved in both thermophilic and mesophilic latering but not belt filter press dewatering, 12011),

Effect of hygienization treatment on the recovery and/or regrowth of microbial indicators in sewage sludge

“…Some investigators have explained that this regrowth occurs during storage for long periods of time in samples from thermophilic and mesophilic‐digestion processes that use centrifuge dewatering (Chen et al . ). Others have added that coliform levels increase at 25 and 37°C, continue for up to 5 days, and then gradually decline (Qi et al .…”

“…In this respect, the suitability of certain indicator micro-organisms of faecal contamination, such as EC, is controversial because they have been shown to grow after the anaerobic digestion process and during sludge storage under certain conditions (Monteleone et al 2004;Qi et al 2007;Higgins et al 2007). Some investigators have explained that this regrowth occurs during storage for long periods of time in samples from thermophilic and mesophilic-digestion processes that use centrifuge dewatering (Chen et al 2011). Others have added that coliform levels increase at 25 and 37°C, continue for up to 5 days, and then gradually decline (Qi et al 2007).…”

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

“…However, most of the attention in the literature related to regrowth after dewatering is directed to a special microbial state that bacteria display. Since some stress conditions are known to induce pathogenic and non-pathogenic organisms to enter dormancy state, under the unfavorable conditions of anaerobic digestion the indicator bacteria are suggested to enter a viable but nonculturable (VBNC) state (Higgins et al, 2007;Chen et al, 2011b). The presence of non-culturable bacteria results in a low number of indicator bacteria determined after anaerobic digestion process by standard culturing methods, giving an impression that they are dead even though they are technically viable.…”

Do Alternate Bacterial Indicators and Pathogens Increase after Centrifuge Dewatering of Anaerobically Digested Biosolids?

“…Research during the last few years has shown that fecal coliforms and/or E. coli densities can increase after certain combinations of digestion and dewatering processes (Chen et al, 2011;Cheung et al, 2003;Erdal et al, 2003Erdal et al, , 2004Gardner and Ormeci, 2010;Hendrickson et al, 2004;Higgins et al, 2007;Iranpour and Cox, 2006;McDonald, 2008;Monteleone et al, 2004;Qi et al, 2007;Sylvester et al, 2008). E. coli have been shown to be the main fecal coliform organism in digested biosolids.…”

“…The increases in indicator organisms have been characterized to occur as two different phenomena. In some cases, the densities can increase immediately after dewatering, and this has been termed sudden increase or SI (Chen et al, 2011). Storage of dewatered cakes for longer periods (hours to days) can result in additional increases, and this increase has been termed regrowth (Higgins et al, 2007).…”