Christian W. Götz

Bromide Sources and Loads in Swiss Surface Waters and Their Relevance for Bromate Formation during Wastewater Ozonation.

Bromide measurements and mass balances in the catchments of major Swiss rivers revealed that chemical industry and municipal waste incinerators are the most important bromide sources and account for ∼50% and ∼20%, respectively, of the ∼2000 tons of bromide discharged in the Rhine river in 2014 in Switzerland. About 100 wastewater treatment plants (WWTPs) will upgrade their treatment for micropollutant abatement in the future to comply with Swiss regulations. An upgrade with ozonation may lead to unintended bromate formation in bromide-containing wastewaters. Measured bromide concentrations were <0.05 mg L(-1) in ∼75% of 69 WWTPs, while they ranged from 0.4 to ∼50 mg L(-1) in WWTPs with specific bromide sources (e.g., municipal waste incinerators, landfill leachate, and chemical industry). Wastewater ozonation formed little bromate at specific ozone doses of ≤0.4 mg O3/mg DOC, while the bromate yields were almost linearly correlated to the specific ozone dose for higher ozone doses. Molar bromate yields for typical specific ozone doses in wastewater treatment (0.4-0.6 mg O3/mg DOC) are ≤3%. In a modeled extreme scenario (in which all upgraded WWTPs release 10 μg L(-1) of bromate), bromate concentrations increased by <0.4 μg L(-1) in major Swiss rivers and by several micrograms per liter in receiving water bodies with a high fraction of municipal wastewater.

Multi-Level Approach for the Integrated Assessment of Polar Organic Micropollutants in an International Lake Catchment: The Example of Lake Constance

Polar organic micropollutants (MPs) can have ecotoxicological effects on aquatic ecosystems and their occurrence in drinking water is a threat to public health. An extensive exposure assessment of MPs in large river and lake catchments is a necessary but challenging proposition for researchers and regulators. To get a complete picture of MP exposure in a large catchment, we employed a novel integrated strategy including MP measurement in the international catchment of Lake Constance and mass-flux modeling. A comprehensive screening of 252 MPs in the lake water by high-resolution mass spectrometry was used to identify the most commonly present MPs for the study site. It was found that the wastewater borne MPs diclofenac, carbamazepine, sulfamethoxazole, acesulfame, sucralose, benzotriazole, and methylbenzotriazole accounted for the most frequent and prominent findings. The concentration pattern of these compounds in the catchment was calculated based on regionalized inputs from wastewater treatment plants (WWTPs) and substance specific elimination rates. In 52, 8, and 3 of the 112 investigated river locations the concentration exceeded the predicted no-effect levels for diclofenac, sulfamethoxazole and carbamazepine, respectively. By coupling the catchment and lake model the effect of future trends in usage as well as possible mitigation options were evaluated for the tributaries and the lake. The upgrade of the major WWTPs in the catchment with a postozonation step would lead to a load reduction between 32% and 52% for all substances except for sucralose (10%).

Assessment of micropollutants from municipal wastewater - Combination of exposure and ecotoxicological effect data for Switzerland

Micropollutants (MPs) from municipal wastewater are frequently detected in surface waters and occur in ecotoxicologically relevant concentrations. Therefore a broadly accepted method for the assessment of MPs is needed. Here we propose a procedure for the assessment of MPs from municipal wastewater. The method suggested comprises (1) an approach for the identification of potentially polluted sites, (2) a compilation of a substance list with relevant MPs, (3) (eco)toxicologically based quality criteria, (4) a sampling strategy that considers the input-dynamics of chemicals and (5) a scheme to rate water quality with respect to MP contamination. In the proposed concept the assessment focuses upon those substances found repeatedly in municipal wastewaters (continuous inputs). Additionally, we explain how the Environmental Quality Standard (EQS) proposals were derived in accordance with the Water Framework Directive (WFD), and the currently developed Technical Guidance Document for EQS (TGD for EQS). Based on the proposed EQS, we provide a Swiss-wide risk assessment for 6 selected MPs.

Response to comment of Sierra Rayne on “Targeting aquatic microcontaminants for monitoring: exposure categorization and application to the Swiss situation [Götz et al., Environ Sci Pollut Res (2010) 17:341–354]”

In the comment of S. Rayne on the article “Targeting aquatic microcontaminants for monitoring,” two concerns are raised: (1) The article lacked pKa data. The author of the comment claims that the pKa values are missing for 26 of the approximately 250 substances investigated. (2) The model that was applied for the calculation of water–organic phase partitioning is too simplistic to correctly describe sorption to solid phases. Essentially, both questions target the applicability of the presented method for assessing the aquatic fate of ionizable substances. The method presented clearly has its shortcomings with respect to these substances. However, since the method presented in our article was intended as a screening tool to select substances for monitoring, it was developed to cover the broadest range of chemicals possible, and therefore false positive and negative answers have to be accepted to a certain extent, as in every screening tool. The main objective was to develop an easily applicable method that had a lower data demand than other existing models and allowed the identification of new substances that might warrant more intense investigation. Response to query 1: “lack of pKa data”