Microbial Communities Shaped by Treatment Processes in a Drinking Water Treatment Plant and Their Contribution and Threat to Drinking Water Safety

Abstract

Bacteria play an important role in water purification in drinking water treatment systems. On one hand, bacteria present in the untreated water may help in its purification through biodegradation of the contaminants. On the other hand, some bacteria may be human pathogens and pose a threat to consumers. The present study investigated bacterial communities using Illumina MiSeq sequencing of 16S rRNA genes and their functions were predicted using PICRUSt in a treatment system, including the biofilms on sand filters and biological activated carbon (BAC) filters, in 4 months. In addition, quantitative analyses of specific bacterial populations were performed by real-time quantitative polymerase chain reaction (qPCR). The bacterial community composition of post-ozonation effluent, BAC effluent and disinfected water varied with sampling time. However, the bacterial community structures at other treatment steps were relatively stable, despite great variations of source water quality, resulting in stable treatment performance. Illumina MiSeq sequencing illustrated that Proteobacteria was dominant bacterial phylum. Chlorine disinfection significantly influenced the microbial community structure, while other treatment processes were synergetic. Bacterial communities in water and biofilms were distinct, and distinctions of bacterial communities also existed between different biofilms. By contrast, the functional composition of biofilms on different filters were similar. Some functional genes related to pollutant degradation were found widely distributed throughout the treatment processes. The distributions of Mycobacterium spp. and Legionella spp. in water and biofilms were revealed by real-time quantitative polymerase chain reaction (qPCR). Most bacteria, including potential pathogens, could be effectively removed by chlorine disinfection. However, some bacteria presented great resistance to chlorine. qPCRs showed that Mycobacterium spp. could not be effectively removed by chlorine. These resistant bacteria and, especially potential pathogens should receive more attention. Redundancy analysis (RDA) showed that turbidity, ammonia nitrogen and total organic carbon (TOC) exerted significant effects on community profiles. Overall, this study provides insight into variations of microbial communities in the treatment processes and aids the optimization of drinking water treatment plant design and operation for public health.

Effect of Grain Size and Nutrient Feeding on the Treatment Potential of Biofilters for Treatment of   De-Icing Chemicals

“…The decrease of biofilter performance due to increase inflow was also reported by Hatt et al [10]. A higher flow may also promote microorganism wash-out due to sloughing effect of interstitial water along the pore channels of a filter [18]. This in return will decrease the viable microorganisms contributing to the biological degradation process.…”

Impacts of Hurricane Harvey on drinking water quality in two Texas cities

“…Still, changes in bacterial taxa occurred over time, including an increase in Actinobacteria from September 2017 to December 2017 and a subsequent decrease from December 2017 to May 2018, together with inverse changes in Proteobacteria (figure 3). Seasonal variation in Actinobacteria and Proteobacteria in drinking water samples has previously been reported by Li et al [27]. Due to the stability of raw water quality at the water district, the distribution system water microbiota in City A remained spatially consistent following Hurricane Harvey.…”

“…As seen in figure 3, five phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, and Proteobacteria) dominate the microbial community at all points in City A's distribution system. These phyla have been commonly reported in other drinking water distribution systems [26][27][28][29]. Still, changes in bacterial taxa occurred over time, including an increase in Actinobacteria from September 2017 to December 2017 and a subsequent decrease from December 2017 to May 2018, together with inverse changes in Proteobacteria (figure 3).…”

“…Similar to City A, the dominant phyla in treated samples in City B include Actinobacteria, Proteobacteria, and Cyanobacteria (figure 3). Firmicutes also were found in some treated samples; this phylum of Gram-positive bacteria has been found in drinking water samples due to its chlorine resistance [27,30]. Despite the presence of a few dominant phyla in samples from City B, their relative abundances fluctuate over time and with WA; specifically, increases in proportions of Proteobacteria are noted with increased WA ( figure 3).…”

Potential of Biofilters for Treatment of De-Icing Chemicals

“…The decrease of biofilter performance due to increase inflow was also reported by Hatt et al [10]. A higher flow may also promote microorganism wash-out due to sloughing effect of interstitial water along the pore channels of a filter [20]. This in turn will decrease the viable microorganisms, contributing to the biological degradation process.…”