Microbiome-Triggered Transformations of Trace Organic Chemicals in the Presence of Effluent Organic Matter in Managed Aquifer Recharge (MAR) Systems.

It is widely assumed that biodegradation of trace organic chemicals (TOrCs) in managed aquifer recharge (MAR) systems occurs via a cometabolic transformation with dissolved organic carbon serving as primary substrate. Hence, the composition facilitating bioavailability of the organic matter seems to have a great impact on TOrCs transformation in MAR systems. The aim of this study was to elucidate the character of effluent organic matter present in the feedwater of a simulated sequential MAR system throughout the infiltration by use of FT-ICR-MS analyses as well as spectroscopic methods. Furthermore, compositional changes were correlated with TOrCs targeted throughout the system as well as the abundance of different microbial phyla. On the basis of their behavior throughout the infiltration system in which different redox and substrate conditions prevailed, TOrCs were classified in four groups: easily degradable, redox insensitive, redox sensitive, and persistent. Masses correlating with persistent TOrCs were mainly comprised of CHNO-containing molecules but also of CHO which are known as carboxyl-rich alicyclic molecules, while CHOS and CHNOS can be neglected. Easily degradable TOrCs could be associated with CHNO-, CHO-, and CHOS-containing compounds. However, a shift of molecular compounds to mostly CHOS was observed for redox-insensitive TOrCs. Three hundred thirty eight masses correlated with removal of redox-sensitive TOrCs, but no distinct clustering was identified.

Inferring trophic conditions in managed aquifer recharge systems from metagenomic data.

Humans are increasingly dependent on engineered landscapes to minimize negative health impacts of water consumption. Managed aquifer recharge (MAR) systems, such as river and lake bank filtration, surface spreading or direct injection into the aquifer have been used for decades for water treatment and storage. Microbial and sorptive processes in these systems are effective for the attenuation of many emerging contaminants including trace organic chemicals such as pharmaceuticals and personal care products. Recent studies showed a superior efficiency of trace organic chemical biotransformation by incumbent communities of microorganisms under oxic and carbon-limited (oligotrophic) conditions. This study sought to identify features of bacterial genomes that are predictive of trophic strategy in this water management context. Samples from a pilot scale managed aquifer recharge system with regions of high and low carbon concentration, were used to generate a culture collection from which oligotrophic and copiotrophic bacteria were categorized. Genomic markers linked to either trophic strategy were used to develop a Bayesian network model that can infer prevailing carbon conditions in MAR systems from metagenomic data.

Biotransformation of trace organic chemicals in the presence of highly refractory dissolved organic carbon.

Previous studies demonstrated that the transformation of trace organic chemicals (TOrCs) in managed aquifer recharge (MAR) systems is favored under carbon-limited and oxic redox conditions especially, if the dissolved organic carbon (DOC) serving as primary substrate has a refractory character. Since co-metabolism is suggested to be the dominant removal mechanism, it is hypothesized that TOrCs transformation is controlled by the concentration of the refractory carbon under oxic redox conditions. A laboratory-scale soil column experiment mimicking MAR was established to investigate the influence of two different concentrations of highly refractory carbon sources on TOrCs transformation, namely drinking water (DW) and drinking water augmented with humic acid (DW + HA). Oxic redox conditions and carbon-limitation were present in both systems (ΔDOCDW+HA ≈ 0.6-0.7 mg/L; ΔDOCDW ≈ 0.1 mg/L). Of the 12 TOrCs investigated seven exhibited moderate to efficient transformation in both systems with only one compound (diclofenac) showing significantly enhanced (co-metabolic) biotransformation by adding humic acids as primary growth substrate. It is postulated that transformation of some TOrCs is characterized by metabolic degradation under starving conditions (ΔDOC ≤ 0.1 mg/L). By comparing the transformation efficiency of selected TOrCs with previous studies operated under carbon-limited and oxic conditions, an inconsistent behavior of some compounds was observed. These results demonstrate that key factors triggering the transformation of TOrCs are still poorly understood and thus, further investigations regarding the biodegradation pathways of TOrCs, upregulation of key enzymes by the microbial community but also more detailed analysis of the composition of the biodegradable DOC are needed.

Validation of Arxula Yeast Estrogen Screen assay for detection of estrogenic activity in water samples: Results of an international interlaboratory study.

Endocrine-active substances can adversely impact the aquatic ecosystems. A special emphasis is laid, among others, on the effects of estrogens and estrogen mimicking compounds. Effect-based screening methods like in vitro bioassays are suitable tools to detect and quantify endocrine activities of known and unknown mixtures. This study describes the validation of the Arxula-Yeast Estrogen Screen (A-YES®) assay, an effect-based method for the detection of the estrogenic potential of water and waste water. This reporter gene assay, provided in ready to use format, is based on the activation of the human estrogen receptor alpha. The user-friendly A-YES® enables inexperienced operators to rapidly become competent with the assay. Fourteen laboratories from four countries with different training levels analyzed 17ß-estradiol equivalent concentrations (EEQ) in spiked and unspiked waste water effluent and surface water samples, in waste water influent and spiked salt water samples and in a mixture of three bisphenols. The limit of detection (LOD) for untreated samples was 1.8ng/L 17ß-estradiol (E2). Relative repeatability and reproducibility standard deviation for samples with EEQ above the LOD (mean EEQ values between 6.3 and 20.4ng/L) ranged from 7.5 to 21.4% and 16.6 to 28.0%, respectively. Precision results are comparable to other frequently used analytical methods for estrogens. The A-YES® has been demonstrated to be an accurate, precise and robust bioassay. The results have been included in the ISO draft standard. The assay was shown to be applicable for testing of typical waste water influent, effluent and saline water. Other studies have shown that the assay can be used with enriched samples, which lower the LOD to the pg/L range. The validation of the A-YES® and the development of a corresponding international standard constitute a step further towards harmonized and reliable bioassays for the effect-based analysis of estrogens and estrogen-like compounds in water samples.