Removal of pharmaceuticals in biologically treated wastewater by chlorine dioxide or peracetic acid

Removal of six active pharmaceutical ingredients in wastewater was investigated using chlorine dioxide (ClO2) and peracetic acid (PAA) as chemical oxidants. Four non-steroidal anti -inflammatory drugs (ibuprofen, naproxen, diclofenac, and mefenamic acid) and two l ipid regulating agents (gemfibrozi l and clofibric acid, a metabol i te of clofibrate) were used as target substances at 40 (g/L ini tial concentration.

Three di fferent wastewaters types originating from two WWTPs were used. One wastewater was col lected after extended ni trogen removal in activated sludge, one after treatment wi th high loaded activated sludge wi thout ni tri fication and one from the final effluent from the same plant where ni trogen removal was made in trickl ing fi l ters for ni tri fication and moving bed biofi lm reactors for deni tri fication fol lowing the high loaded plant.

Of the six investigated compounds, only clofibric acid and ibuprofen were not removed when treated wi th ClO2 up to 20 mg/L. Wi th increasing PAA dose up to 50 mg/L, signi ficant removal of most of the pharmaceutical s was observed except for the wastewater wi th the highest COD. Thi s indicates that chemical oxidation wi th ClO2 could be used for tertiary treatment at WWTPs for active pharmaceutical ingredients whi le PAA was not sufficiently efficient.