Dissipation of Micropollutants in a Rewetted Fen Peatland: A Field Study Using Treated Wastewater

Sebastian Maassen,Bruno Guimarães,Dagmar Balla,Elisabeth Richter,Anja Coors

doi:10.3390/w9060449

Abstract

In the present study, a mixture of treated wastewater and surface water was used to rewet a degraded fen peatland site during a three-year rewetting experiment. We studied the behavior and effects of micropollutants by means of hydrological, physico-chemical, microbiological and ecotoxicological monitoring. The highest concentrations of micropollutants in the treated wastewater were found for the pharmaceuticals carbamazepine and diclofenac, some metabolites, the sweetener acesulfame, tolyl- and benzotriazole and diatrizoate. In the underlying, shallow groundwater where treated wastewater application for rewetting had been expected to have the greatest impact due to seeping and evapotranspiration processes, only a sporadic occurrence of micropollutants was found. The influence of dilution by groundwater movements was examined by applying a geohydrological model. The sorption of micropollutants onto the peaty soil also played a role, as found for carbamazepine. Further processes such as photolysis, microbial decay under low redox conditions and plant uptake can be assumed to be relevant for the removal of many substances. Ecotoxicity tests with the soil before and after rewetting did not indicate any negative impact on the soil habitat quality by wastewater application, but clearly pointed at ecotoxicologically relevant geogenic arsenic concentrations at the study site. Although a positive effect on receiving surface water systems is expected if wastewater is applied on land instead of discharged to water bodies, the rewetted soil may turn into a sink for micropollutants in the long term. Hence, the findings of the present field study encourage further investigations in order to identify the governing processes in the elimination of micropollutants in rewetted peatlands flooded with treated wastewater.

Highlights

In Europe, improving water quality and counteracting water scarcity has become an increasingly important issue as reflected in the Blueprint to Safeguard Europe’s Water Resources released by the European Commission in 2012 [1]
A positive effect on receiving surface water systems is expected if wastewater is applied on land instead of discharged to water bodies, the rewetted soil may turn into a sink for micropollutants in the long term
The findings of the present field study encourage further investigations in order to identify the governing processes in the elimination of micropollutants in rewetted peatlands flooded with treated wastewater

Summary

Introduction

In Europe, improving water quality and counteracting water scarcity has become an increasingly important issue as reflected in the Blueprint to Safeguard Europe’s Water Resources released by the European Commission in 2012 [1]. One of the key topics addressed in this communication is the evaluation of the reuse of treated wastewater for irrigation or industrial purposes, which is supposed to increase about 35–60% worldwide by the year 2025 in order to meet increasing water demand and to reuse nutrients within the watershed. Another key topic of the European Commission Blueprint is the establishment of buffer strips that prevent or reduce pollution of water bodies by agrochemicals and nutrients applied to agricultural land. Lowland peatlands can be considered as buffer zones because they link terrestrial and aquatic growing, preserve carbon in their organic matter and store water within their organic layers

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