Internal Porosity of Mineral Coating Supports Microbial Activity in Rapid Sand Filters for Groundwater Treatment

Abstract

A mineral coating develops on the filter grain surface when groundwater is treated via rapid sand filtration in drinking water production. The coating changes the physical and chemical properties of the filter material, but little is known about its effect on the activity, colonization, diversity, and abundance of microbiota. This study reveals that a mineral coating can positively affect the colonization and activity of microbial communities in rapid sand filters. To understand this effect, we investigated the abundance, spatial distribution, colonization, and diversity of all and of nitrifying prokaryotes in filter material with various degrees of mineral coating. We also examined the physical and chemical characteristics of the mineral coating. The amount of mineral coating correlated positively with the internal porosity, the packed bulk density, and the biologically available surface area of the filter material. The volumetric NH 4 ؉ removal rate also increased with the degree of mineral coating. Consistently, bacterial 16S rRNA and amoA abundances positively correlated with increased mineral coating levels. Microbial colonization could be visualized mainly within the outer periphery (60.6 ؎ 35.6 m) of the mineral coating, which had a thickness of up to 600 ؎ 51 m. Environmental scanning electron microscopic (E-SEM) observations suggested an extracellular polymeric substance-rich matrix and submicron-sized bacterial cells. Nitrifier diversity profiles were similar irrespective of the degree of mineral coating, as indicated by pyrosequencing analysis. Overall, our results demonstrate that mineral coating positively affects microbial colonization and activity in rapid sand filters, most likely due to increased volumetric cell abundances facilitated by the large surface area of internal mineral porosity accessible for microbial colonization.

Microbial community composition of a household sand filter used for arsenic, iron, and manganese removal from groundwater in Vietnam

“…The mineral coating of sand particles has been shown to play an important role for sand filter colonization and microbial activity (Gülay et al, 2014). Fe and As concentrations are highest in the top sand layer (0-2 cm) and decrease with filter depth (Fig.…”

The pH dependency of N‐converting enzymatic processes, pathways and microbes: effect on net N2O production

“…Ammonia oxidizing archaea (AOA) perform autotrophic ammonia oxidation similar, but not identical to AOB (Kozlowski et al ., ); no HAO or NOR genes have been identified in pure or enrichment cultures of AOA, indicating that they might be unable to produce N 2 O enzymatically through side reactions of ammonia oxidation or nitrifier denitrification (Walker et al ., ; Tourna et al ., ; Spang et al ., ; Stieglmeier et al ., ). AOA are widespread in nitrifying bioreactors in WWTPs or biofilters for drinking water production and are also found in soil and sediments (Park et al ., ; Zhang et al ., ; Gülay et al ., ). Optimal growth of AOA has been reported in the range of pH 7–7.5 (French et al ., ; Spang et al ., ).…”

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

“…Furthermore, this genome contained mtrAB genes with homology (amino-acid sequence identity from 29% to 55%) to those found in lithotrophic ironoxidizing bacteria (Jiao and Newman, 2007;Beckwith et al, 2015). Thus, CG13 could be involved in the oxidation of ferrous iron, although the presence of mtrABC (periplasmic and outer membrane cytochromes) could also indicate electron transfer to minerals (Weber et al, 2006;Gülay et al, 2014). The CG13 bin also contained multicopper oxidases homologous (60-75% at the protein level) to those found in the known manganese oxidizers Leptothrix cholodnii str.…”

“…Most of these compounds are oxidatively transformed by microbes in the RSFs (Lee et al, 2014). Hence, microorganisms colonize the filter material and its mineral coatings (Gülay et al, 2014). In contrast to other engineered microbial systems, such as wastewater treatment plants and anaerobic digesters, RSFs treating groundwater can be considered oligotrophic (with influent concentrations of individual constituents below mM) and receive predominantly inorganic electron donors, supporting chemolithotrophic metabolisms (Gülay et al, 2016).…”

“…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).…”