Influence of a compost layer on the attenuation of 28 selected organic micropollutants under realistic soil aquifer treatment conditions: Insights from a large scale column experiment

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Results from MAR soil-column experiments simulating soil aquifer treatments were recently published in the scientific journal, Water Reserach. The article, a collaborative effort among researchers working on the DEMEAU project, presents the results on experiments that have been used to simulate groundwater recharge and the impact of emerging pollutants in groundwater. Mario Schaffer, from the University Göttingen, is the lead author of the publication. He and a team of scientists studied 28 drugs and pesticides commonly found in treated water (in low concentrations) using soil column systems, as a continuation of the Life project ENSAT.  The experiments evaluated the efficiency of vegetable compost layers for improving the removal of the designated emerging pollutants during soil aquifer treatment. The results of the study provide valuable insights regarding the potential for effective removal of organic micropollutants under realistic soil aquifer treatment conditions.   

Soil aquifer treatment is widely applied to improve the quality of treated wastewater in its reuse as alternative source of water. To gain a deeper understanding of the fate of thereby introduced organic micropollutants, the attenuation of 28 compounds was investigated in column experiments using two large scale column systems in duplicate. The influence of increasing proportions of solid organic matter (0.04% vs. 0.17%) and decreasing redox potentials (denitrification vs. iron reduction) was studied by introducing a layer of compost. Secondary effluent from a wastewater treatment plant was used as water matrix for simulating soil aquifer treatment. For neutral and anionic compounds, sorption generally increases with the compound hydrophobicity and the solid organic matter in the column system. Organic cations showed the highest attenuation. Among them, breakthroughs were only registered for the cationic beta-blockers atenolol and metoprolol. An enhanced degradation in the columns with organic infiltration layer was observed for the majority of the compounds, suggesting an improved degradation for higher levels of biodegradable dissolved organic carbon. Solely the degradation of sulfamethoxazole could clearly be attributed to redox effects (when reaching iron reducing conditions). The study provides valuable insights into the attenuation potential for a wide spectrum of organic micropollutants under realistic soil aquifer treatment conditions. Furthermore, the introduction of the compost layer generally showed positive effects on the removal of compounds preferentially degraded under reducing conditions and also increases the residence times in the soil aquifer treatment system via sorption.

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