Metagenomics Unravels Differential Microbiome Composition and Metabolic Potential in Rapid Sand Filters Purifying Surface Water Versus Groundwater

Abstract

Designed for retaining suspended particles, rapid sand filters (RSFs) are widely used in drinking water treatment. There is increasing evidence that microbial processes within RSFs contribute to the transformation and removal of organic carbon, nitrogen, and metal pollutants. Here, we linked microbial composition and functional profiles with the treatment performance of 12 different RSFs that significantly removed influent ammonium and manganese (Mn). Metagenomic analyses showed that chemoautotrophic or methanotrophic bacteria were prevalent in the groundwater filters, and chemoheterotrophic bacteria encoding more carbohydrate-and xenobiotic-metabolizing genes were more abundant in the surface water filters. Approximately 92% of ammonium was transformed into nitrate, with a critical contribution from comammox Nitrospira. The composition of comammox amoA differed between groundwater and surface water filters, with clade A dominating groundwater filters (78.0 ± 12.0%) and clade B dominating surface water filters (91.9 ± 8.9%). Further, we identified six bacterial genera encoding known Mn(II)-oxidizing genes in the RSFs, with Pseudomonas accounting for 71.1%. These Mn(II)-oxidizing bacteria might promote Mn(II) oxidation and thus increase the removal of influent Mn. Overall, our study gave a comprehensive investigation of microbiome in RSFs and highlighted the roles of comammox and Mn(II)-oxidizing bacteria in water purification.

Evolutionary Ecology of Natural Comammox Nitrospira Populations

“…Rapid sand filters (RSF), widely used to produce drinking water from groundwater, are useful model systems. They are characterized by stable conditions, including active growth, primarily driven by the oxidation of ammonia, methane, and other inorganic compounds present at low concentrations in the influent water, large populations (10 9 to 10 10 cells/g), significant mixing (due to backwashing), continuous but limited immigration from prokaryotes in the influent water, and no dispersal between separate sand filters (resulting in allopatric populations) ( 5 – 8 ). In addition, the microbial communities inhabiting these systems, which are usually stable across time ( 9 ), have been broadly described, showing a general dominance of complete ammonia oxidizers (comammox) ( 6 , 10 , 11 ).…”

Evolutionary ecology of natural comammoxNitrospirapopulations

“…Rapid sand filters (RSF), widely used to produce drinking water from surface-or groundwater, can be a useful model system as they are characterized by stable conditions and active growth primarily driven by the oxidation of ammonia, methane, and other inorganic compounds present at low concentration in the influent water, large populations (~ 10 9 cells/g), significant mixing, continuous but limited immigration from prokaryotes in the influent water, no dispersal between separate sand filters (resulting in allopatric populations), and relatively well defined coupling between chemical and biological processes [5][6][7] . In addition, microbial communities inhabiting these systems have been described and show the dominance of complete ammonia oxidizers (comammox) 8,9 , which are expected to have a relatively simple basic ecology (due to their chemolithoautotrophic metabolism) 10 , yet are poorly studied in terms of what drives their diversity, distribution and evolution.…”

Harnessing biodegradation potential of rapid sand filtration for organic micropollutant removal from drinking water: A review

“…Several manganese oxidizing bacteria (MnOB) have been identified on filter materials and in the water phase, including Pseudomonas sp., Streptomyces sp., and Leptothrix sp. (Bruins et al, 2014;Hu et al, 2020). The Mn and Fe oxides (MnOx and FeOx) formed and retained in RSF are able to remove OMPs by adsorption (Forrez et al, 2011) or by catalyzing chemical oxidation (Jian et al, 2019;Manoli et al, 2017) (Figure 2).…”

“…In raw groundwater, the concentrations of ammonium and methane are at hundreds mg/L, even several mg/L (Papadopoulou et al, 2019;Tatari et al, 2013). These compounds are typically removed by a combination of aeration and removal by autotrophic nitrifying and methane oxidizing bacteria (Hu et al, 2020;Papadopoulou et al, 2019). In addition to ammonium and methane removal, these autotrophic organisms also show OMPs biotransformation capacity (Batt et al, 2006;Papadopoulou et al, 2019).…”