Sludge bulking impact on relevant bacterial populations in a full-scale municipal wastewater treatment plant

Abstract

a b s t r a c tWe have investigated the changes of microbial community structures and the concomitant performance in two biological wastewater treatment systems (conventional and inverted A 2 /O processes) over a whole cycle of sludge bulking. A low level of filament abundance was observed during non-bulking period, with types 0092 and 0041 as the dominant filamentous bacteria. With the increase of the sludge volume index values from 76 (73) to 275 (300) mg/L, the filament abundance estimated by microscopic examination increased from 1 (few) to 5 (abundant), with Microthrix parvicella becoming the dominant filament bacteria. Sludge bulking resulted in a significant shift in bacterial compositions from Proteobacteria to Actinobacteria dominance, characterized by the significant presence of filamentous M. parvicella (from not detected to higher than 60% of clones) and decrease of the dominant Betaproteobacterial population (from higher than 40% to less than 1%). Important relevant bacterial populations including polyphosphateaccumulating organism (PAO, Candidatus Accumulibacter phosphatis), ammonia-oxidizing bacteria (AOB, Nitrosomonas), nitrite-oxidizing bacteria (NOB, Nitrospira) and denitrifying bacteria (Thauera) were absent under the serious bulking condition. Accumulation of nitrite and ammonia was observed during serious bulking, while the phosphorus removal performance was not decreased because M. parvicella could behave as a PAO.

Detailed comparison of bacterial communities during seasonal sludge bulking in a municipal wastewater treatment plant

“…Proteobacteria, Actinobacteria, Chloroflexi, Firmicutes, and Bacteroidetes were found in the 3 types of typical AS samples, and their abundances changed considerably with the occurrence of sludge bulking. Similar to a previous study on the bacterial community structure of AS samples from a bulking municipal WWTP in northern China using a cloning method (Wang et al, 2014), our present study showed that sludge bulking resulted in a significant shift in bacterial compositions from a dominance of Proteobacteria to a dominance of Actinobacteria. Yet another study on seasonal microbial variations of AS from a full-scale WWTP over 4 years using metagenomic analysis showed Proteobacteria to be the predominant phylum in winter and summer samples and Actinobacteria to be usually higher in winter than in summer (Ju et al, 2014).…”

“…When sludge bulking occurs, the overgrowth of filamentous bacteria could result in a decrease in non-filamentous bacteria, making these non-filamentous bacteria susceptible to being washed out from WWTPs (Wang et al, 2014). Similar to the report of Wang et al (2014), our 454 pyrosequencing results indicated that sludge bulking resulted in a significant shift in Proteobacteria compositions from a dominance of Betaproteobacteria to that of Alphaproteobacteria. A detailed analysis showed that the abundance of Alphaproteobacteria increased considerably with the occurrence of sludge bulking because of the increase in some functional bacteria such as Rhodobacter (Kong et al, 2007), whereas the abundance of Betaproteobacteria decreased markedly with the occurrence of sludge bulking due to the decrease in certain functional bacteria such as Thauera, Dechloromonas, Zoogloea, and Nitrosomonas (Wang et al, 2014).…”

“…Many studies have shown that many Proteobacteria members are always present and play a key role in the functioning of municipal WWTPs (Oehmen et al, 2007;Nielsen et al, 2010). When sludge bulking occurs, the overgrowth of filamentous bacteria could result in a decrease in non-filamentous bacteria, making these non-filamentous bacteria susceptible to being washed out from WWTPs (Wang et al, 2014). Similar to the report of Wang et al (2014), our 454 pyrosequencing results indicated that sludge bulking resulted in a significant shift in Proteobacteria compositions from a dominance of Betaproteobacteria to that of Alphaproteobacteria.…”

“…For example, in northern China, the problem occurs in over 50% activated sludge (AS) WWTPs every year (Wang et al, 2014). In general, sludge bulking includes two types: filamentous bulking and nonfilamentous bulking caused by substantial accumulation of high viscosity polysaccharide substances secreted by Zoogloea (Eikelboom, 2000).…”

“…Bacterial communities in AS from bulking WWTPs have been intensively studied by traditional molecular methods such as denaturing gradient gel electrophoresis (DGGE) (El-Latif Hesham et al, 2011) and clone library analysis (Wang et al, 2014;Jin et al, 2011). However, changes in bacterial communities in AS from different stages of sludge bulking remain largely unstudied, which can be attributed to the lack of robust techniques needed to explore complex microbial communities.…”