Biofilters, similar to those already used for, e.g., removing particles from stormwater and combined sewer overflow can remove organic micropollutants from polluted waters. This study investigated the effects on removal of pharmaceuticals with pulse loadings of increased amounts of pre-settled raw wastewater to four individual biofilters containing different materials (sand, filtralite, stonewool, and sand amended with 1% peat). The effect of increasing BOD concentration to the removal rate constants could be divided into two groups; 1) compounds influenced by increasing loading of BOD: atenolol, propranolol, venlafaxine, citalopram, metoprolol, iohexol, and diclofenac 2) compounds only little or not influenced by increasing concentration of BOD: sulfamethoxazole, sulfamethizole, trimethoprim, iomeprol, and carbamazepine. Though BOD clearly had effects on the degradation, no indications towards a complete stop of the degradation were observed under any circumstances. The different biofilter materials influenced (indirectly) the removal of micropollutants: While the overall best performance was seen in the filtralite biofilter, the stonewool biofilter generally had the lowest removal rate constants. Furthermore, we observed different metabolic pathways of metoprolol in the four different biofilters under formation (and removal) of metoprolol acid, α-hydroxymetoprolol, and O-desmethylmetoprolol.
Keywords: Biofilm reactor; Combined sewer overflow; Micropollutants; Stormwater; Transformation products; Wastewater; β-Blockers.
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