Impact of upstream chlorination on filter performance and microbial community structure of GAC and anthracite biofilters

Abstract

a Drinking water filters may be operated to promote or deter biological activity through upstream oxidant addition. While there are several water quality benefits from biofiltration, microbial growth in biofilters warrants further investigation. In this study, routine monitoring detected target DNA sequences for Naegleria fowleri in source water and Acanthamoeba spp. in source water and biofilter effluent, triggering further microbial community characterization. Full-scale anthracite and granular activated carbon (GAC) filters receiving chlorinated waters were compared in terms of effluent water quality (i.e., turbidity and particle counts), biological activity (i.e., adenosine triphosphate (ATP)), and the composition of the microbial community (i.e., 16S/18S rRNA gene sequencing, free-living amoeba). Because of rapid chlorine quenching by GAC, greater biomass development was observed in the GAC biofilter (ATP = 5 × 10 3 -5 × 10 4 pg cm −3 media) than the anthracite filter (ATP = 4 × 10 2 -1 × 10 3 pg cm −3 media). Due to possible sloughed biomass, GAC effluent also had consistently greater turbidity, particle counts, and cellular ATP than the anthracite filter. 16S rRNA gene sequencing revealed distinct taxonomic differences between the anthracite and GAC filters, and GAC also hosted a more diverse population (Shannon index: GAC = 3.7-5.0 and anthracite = 2.4-2.9). At the genus level, the anthracite filter contained mostly Undibacterium-like taxon (45-68%), while the GAC biofilter was dominated by Massilia (8-36%), Herbaspirillum (2-44%), and unknown Comamonadaceae (9-18%), among others. The presence of viable free-living amoebas was also detected in the GAC biofilter media. Further characterization of the eukaryotic 18S rRNA gene showed that anthracite predominantly harbored copepod Leptodiaptomus (67%), while a majority of the sequences in GAC are unknown.

Microbiomes in drinking water treatment and distribution: a meta-analysis from source to tap

“…Biofilters can be extremely microbially diverse with different operational conditions causing changes to relative taxa abundances 39,43,46 . The upstream process also significantly affects filter biomass 16,17 . Various treatment and disinfectant types have variable effects on the abundance of different phyla, with no-one treatment type effectively removing all pathogens 18,19 .…”

“…Most 16S rRNA studies are discrete, across a single or few DWDS within a geographical area. They also tend to focus on one part of a system, e.g., source waters; efficacy of treatment processes; variations of biofilm communities in space, time, or operating conditions within a pipe distribution network; influences of domestic plumbing arrangements, or differences between the bulk water and biofilm communities (Ahmed et al, 2015;Chan et al, 2019;De Vera et al, 2018;Douterelo et al, 2019Douterelo et al, , 2017Fish and Boxall, 2018;Gerrity et al, 2018;Ghaju Shrestha et al, 2017;Gülay et al, 2016;Han et al, 2020;Hou et al, 2018;Lautenschlager et al, 2014;Liu et al, 2017b;Lührig et al, 2015;McCoy and VanBriesen, 2012;Potgieter et al, 2018;Potgieter and Pinto, 2019;Prest et al, 2014;Shaw et al, 2015;Uyaguari-Diaz et al, 2019;Vierheilig et al, 2015;Vignola et al, 2018;Wan et al, 2019;Wang et al, 2014Wang et al, , 2013Wolf-Baca and Piekarska, 2020;Wu et al, 2014;Zhu et al, 2019). While several of these studies have provided new insight into drinking water microbiomes, they tend to be descriptive and not predictive.…”

Drinking water biofiltration: Behaviour of antibiotic resistance genes and the association with bacterial community

“…The understanding of microbial composition in the filter media is essential in the context of microbial risk as it could dictate the microbiological quality of the effluent and shape the bacterial community structure in the drinking water microbiome (de Vera et al, 2018;Pinto et al, 2012). Variation in antibiotic resistome during drinking water treatment processes is generally associated with the bacterial community.…”

Genomic Analysis and Stability Evaluation of the Phenol-Degrading Bacterium Acinetobacter sp. DW-1 During Water Treatment

“…Previous studies have shown that Proteobacteria are generally dominant in drinking water sources ( Hou et al, 2018b ; Han et al, 2020 ), and some members of Proteobacteria are competitive at low-nutrient concentrations ( Liao et al, 2013 ; Lautenschlager et al, 2014 ). This phylum has been regarded as highly stable and is not affected by water treatment processes or seasonal changes; thus, they can exist in drinking water biofilters for an extended period and are abundant ( de Vera et al, 2018 ). This might indicate why Proteobacteria were dominant in both the CK and T groups.…”