The Bacterial Communities of Full-Scale Biologically Active, Granular Activated Carbon Filters Are Stable and Diverse and Potentially Contain Novel Ammonia-Oxidizing Microorganisms

Abstract

The bacterial community composition of the full-scale biologically active, granular activated carbon (BAC) filters operated at the St. Paul Regional Water Services (SPRWS) was investigated using Illumina MiSeq analysis of PCR-amplified 16S rRNA gene fragments. These bacterial communities were consistently diverse (Shannon index, >4.4; richness estimates, >1,500 unique operational taxonomic units [OTUs]) throughout the duration of the 12-month study period. In addition, only modest shifts in the quantities of individual bacterial populations were observed; of the 15 most prominent OTUs, the most highly variable population (a Variovorax sp.) modulated less than 13-fold over time and less than 8-fold from filter to filter. The most prominent population in the profiles was a Nitrospira sp., representing 13 to 21% of the community. Interestingly, very few of the known ammonia-oxidizing bacteria (AOB; <0.07%) and no ammonia-oxidizing Archaea were detected in the profiles. Quantitative PCR of amoA genes, however, suggested that AOB were prominent in the bacterial communities (amoA/16S rRNA gene ratio, 1 to 10%). We conclude, therefore, that the BAC filters at the SPRWS potentially contained significant numbers of unidentified and novel ammonia-oxidizing microorganisms that possess amoA genes similar to those of previously described AOB. P ublic water utilities use surface water to produce high-quality, potable drinking water for almost 70% of the people residing in the United States (1). The conventional process for treating surface water involves a series of unit operations that include coagulation, flocculation, sedimentation, filtration, and disinfection (2). The application of these technologies has generally proven effective for protecting public health (2), although numerous exceptions have been reported (3). Given the presumptive safety of public water supplies, water consumers are increasingly concerned about the taste and odor of public water supplies as well as other esthetic concerns (4).Public water utilities, therefore, have begun to augment their treatment processes to specifically remove taste-and odor-causing compounds, such as geosmin and 2-methylisoborneol (5-7). Although a few alternative technologies can be used, filtration using biologically active, granular activated carbon (BAC) has proven successful because of its simplicity (i.e., it is easily retrofitted into preexisting operations) and effectiveness (8, 9). Filtration with BAC differs from filtration with conventional granular media (e.g., sand and anthracite) because of its high sorptive capacity (6, 8) as well as the active biofilm that grows on its surface (10-13). The biofilm on the BAC filter medium provides direct biodegradation of dissolved geosmin as well as biological regeneration of the filter medium by metabolizing the initially sorbed geosmin as it desorbs from the carbon (8,14).In this study, we investigated the bacterial community dynamics of the full-scale BAC filters at the Saint Paul Regional Water Surfaces (SPRWS) in St. Pau...

Metagenomic analysis of rapid gravity sand filter microbial communities suggests novel physiology ofNitrospiraspp.

“…At the phylum level, Proteobacteria and Nitrospirae dominate bulk sample communities with a relative abundance of 18.93% ± 1.31% and 9.22% ± 4.72%, respectively; in the top of the filter these phyla were also dominant, with Nitrospirae most abundant (26.08% ± 0.94%), followed by Proteobacteria (14.47% ± 1.07%; Figure 1). These results are inline with other observations of very high Nitrospira abundances (13% to 50% of all community 16S rRNA amplicons or clones) in similar oligotrophic water treatment and distribution systems (Martiny et al, 2005;White et al, 2012;LaPara et al, 2015;Gülay et al, 2016).…”

“…2015; Cai et al, 2015;LaPara et al, 2015). Whereas Nitrospira may be the primary ammonium oxidizer, the high abundance of heterotrophic amoA sequences, especially in the bulk samples, suggests that heterotrophic ammonium oxidation may also occur in the RSFs.…”

“…Central metabolic functions in RSFs have previously been assigned to taxa based on their activity in other environments-Nitrosomonas, Nitrospira, Gallionella and Bacillus clades have been proposed as important ammonium (van der Wielen et al, 2009;Lautenschlager et al, 2014), nitrite (Gülay et al, 2014;Albers et al, 2015;LaPara et al, 2015), iron (Søgaard, 2001;de Vet et al, 2012;Li et al, 2013) and manganese oxidizers (Mouchet, 1992;Cerrato et al, 2010), respectively. Ammonia-oxidizing archaea (AOA) have been detected in RSFs at low abundance (van der Wielen et al, 2009;Albers et al, 2015), although in a few examples they outnumbered ammonia-oxidizing bacteria (AOB; Wang et al, 2014;Nitzsche et al, 2015).…”

Metagenomic Evidence for the Presence of Comammox Nitrospira -Like Bacteria in a Drinking Water System

“…The recently published discovery of a comammox Nitrospira organism ( 5 , 6 ) in combination with our finding strongly suggests that microbial contributions to the nitrogen cycle in engineered and natural environments will need to be reevaluated. The presence of a comammox is also congruent with previous observations of abundances of Nitrospira -like bacteria that were significantly higher than those of AOB/AOA based on 16S rRNA gene assays ( 21 – 23 ), indicating that comammox activity likely contributed substantially to nitrate formation in these environments. While direct evidence of the conversion of ammonia to nitrate by a Nitrospira organism was provided ( 5 , 6 ), it will be critical to build on this initial work to understand the extent to which comammox organisms contribute to ammonia and nitrite oxidation in the wide range of environments where nitrogen cycling is important.…”

Activated Carbon, Carbon Nanotubes and Graphene: Materials and Composites for Advanced Water Purification

“…Biologically activated carbon filters are produced when specific bacteria are introduced and become entrapped within the AC porous matrix [94]. Under optimal conditions and with the appropriate organic nutrients, the bacteria can then multiply and populate the surface of the AC.…”