Combining ultrafiltration and non-thermal plasma for low energy degradation of pharmaceuticals from conventionally treated wastewater

Abstract

Treatment with non-thermal plasma (NTP) is a promisingmethod to remove potentially harmful pharmaceuticals from wastewater treatment plant (WWTP) effluent. An application-oriented pilot-scale study was conducted to investigate the performance of an innovative process combining ultrafiltration (UF) and an NTP unit alternative to previously investigated thin-film designs. The studied NTP generator produces the plasma air separately and a specially designed turbine distributes the oxidizing species in the wastewater to be treated. The process was used for the treatment of effluents from a conventional activated sludge WWTP in Bad Reichenhall, Germany. Different set-ups in terms of hydraulic retention time and NTP composition (overall number of ions and ozone concentration) were tested to examine the removal efficiency of the target pharmaceuticals Diclofenac (DCF), Carbamazepine (CBM) and Sulfamethoxazole (SMX), as well as chemical and physical wastewater parameters. The reduction of DCF, CBM and SMX with optimal set-up was found to exceed 90% with initial concentrations in the WWTP effluent in the microgram per litre-range (0.80–15.15 μg L−1). Traces of ozone in the range of 120/200 ppm within the NTP increased the overall performance of the process. Pre-treatment with UF removed fractions of pharmaceuticals and other oxidable substances, which led to a decrease in ozone demand and an enhancement of the overall removal efficiency of the process during varying influent loadings. Treatment via UF or NTP alone removed the pharmaceuticals by 46–67% and 54–71%, respectively, but did exceed the 90%-threshold. The studied NTP technology in combination with UF could be a viable as fourth treatment step, as it is highly energy-efficient, according to energy yield calculations, and larger amounts of wastewater can be treated.