Abstract
Biofiltration processes help to remove trace organic chemicals (TOrCs) both in wastewater and drinking water treatment systems. However, the detailed TOrCs biotransformation mechanisms as well as the underlying drivers behind the variability of site specific transformation processes remain elusive. In this study, we used laboratory batch incubations to investigate the biotransformation of 51 TOrCs in eight bioactive filter materials of different origins treating a range of waters, from wastewater effluents to drinking water. Microscopy, 16S rRNA amplicon and whole metagenome sequencing for assessing associations between the biotransformation rate constants, microbial composition and genetic potential complemented chemical analysis. We observed strong differences in the mean global removal of TOrCs between the individual sand filters (−1.4–58%), which were mirrored in overall biomass, microbial community composition, and enzyme encoding genes. From the six investigated biomass markers, ATP turned out to be a major predictor of the mean global biotransformation rate, while compound specific biotransformations were correlated with the microbial community composition. High biomass ecosystems were indicated in our systems by a dominance of Nitrospirae, but individual TOrC biotransformation showed a correlation with rare taxa (<2%) such as Hydrogenophaga, or individual functions such as the enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase encoding genes. In general, this study provides new insights into so far rarely addressed variability of TOrCs biotransformation. We propose potential novel biological indicators for the removal performance of TOrCs in biofiltration systems, highlighting the role of living biomass in predicting and normalizing the global transformation, and the role of the microbial community for the individual transformation of TOrCs in engineered and natural systems.
Highlights
Trace organic chemicals (TOrCs) such as pharmaceuticals, personal care products and pesticides, have raised emerging concerns regarding their effects on the aquatic environment
Biomass and organic matter content was high in Friedrichshafen, Eriskirchen and Wangen (>25 pmol/g ATP, >40 mg/g Loss on ignition), whereas the remaining five biofilters were low in biomass and organic matter, with the lowest measurements in the filter materials from drinking water systems (BWA and IFW;
We investigated the biotransformation of diverging trace organic chemicals (TOrCs) by eight biological active sand filter materials from wastewater and drinking water treatment plants, for which the metagenomic analysis of the microbial communities provided novel insights into the biological potential of TOrC transformations
Summary
Trace organic chemicals (TOrCs) such as pharmaceuticals, personal care products and pesticides, have raised emerging concerns regarding their effects on the aquatic environment. These anthropogenic compounds usually enter the wastewater system, and may end up in the receiving water bodies, leading to their frequent detection in surface water, ground water and even drinking water at the concentration ranging from few ng·L−1 to several μg·L−1 (Yang et al, 2017; Montiel-León et al, 2018; Tröger et al, 2018). Conventional activated sludge (CAS) reduces the overall load of micropollutants by both sorption and biodegradation processes but many compounds are only partially removed or persistent (Fischer and Majewsky, 2014). The removal efficiencies of diclofenac by activated sludge treatment are often below 30% (Zhang et al, 2008), while in slow sand filtration systems the removal rate was 40 to almost 80% (Matamoros et al, 2007; Casas et al, 2015)
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