Impacts of Accumulated Particulate Organic Matter on Oxygen Consumption and Organic Micro-Pollutant Elimination in Bank Filtration and Soil Aquifer Treatment

Josefine Filter,Martin Jekel,Aki Ruhl

doi:10.3390/w9050349

Abstract

Bank filtration (BF) and soil aquifer treatment (SAT) are efficient natural technologies in potable water reuse systems. The removal of many organic micro-pollutants (OMPs) depends on redox-conditions in the subsoil, especially on the availability of molecular oxygen. Due to microbial transformation of particulate and dissolved organic constituents, oxygen can be consumed within short flow distances and induce anoxic and anaerobic conditions. The effect of accumulated particulate organic carbon (POC) on the fate of OMPs in BF and SAT systems is not fully understood. Long-term column experiments with natural sediment cores from the bank of Lake Tegel and from a SAT basin were conducted to investigate the impact of accumulated POC on dissolved organic carbon (DOC) release, on oxygen consumption, on mobilization of iron and manganese, and on the elimination of the organic indicator OMPs. The cores were fed with aerated tap water spiked with OMPs to exclude external POC inputs. Complete oxygen consumption within the first infiltration decimeter in lake sediments caused mobilization of iron, manganese, and DOC. Redox-sensitive OMPs like diclofenac, sulfamethoxazole, formylaminoantipyrine, and gabapentin were eliminated by more than 50% in all sediment cores, but slightly higher residual concentrations were measured in effluents from lake sediments, indicating a negative impact of a high oxygen consumption on OMP removal.

Highlights

Bank filtration (BF) is an established, sustainable, and relatively inexpensive treatment for the production of high quality water from rivers and lakes [1]
OMPs like diclofenac, sulfamethoxazole, formylaminoantipyrine, and gabapentin were eliminated by more than 50% in all sediment cores, but slightly higher residual concentrations were measured in effluents from lake sediments, indicating a negative impact of a high oxygen consumption on Keywords: bank filtration; soil aquifer treatment; sediments; organic micro-pollutants; particulate organic matter; oxygen consumption
The sediment probes from the residuals of the colmation layer incorporated in C3 and C4 revealed a loss on ignition of 0.63% by weight and a carbon concentration of 0.29% by mass, and had significantly more accumulated organic carbon compared to the subjacent sand layer

Summary

Introduction

Bank filtration (BF) is an established, sustainable, and relatively inexpensive treatment for the production of high quality water from rivers and lakes [1]. For soil aquifer treatment (SAT), an artificial infiltration basin (or an injection well) is typically used instead of natural surface waters. Both BF and SAT provide passive exposure to various processes such as adsorption, physico-chemical filtration, and biodegradation that eliminate pathogens and many organic micro-pollutants (OMPs) including pharmaceuticals, biocides, and industrial chemicals, among others [2,3,4,5]. OMPs are not fully retained by conventional wastewater treatment and persist in the water cycle in μg/L or ng/L concentrations. Scheurer et al [8] reported that the artificial sweeteners acesulfame and sucralose were persistent in monitored SAT basins

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Conclusion