Influence of Sorption and Nitrification Processes on Pharmaceutical Attenuation During Biological Wastewater Treatment

Wastewater treatment plants (WWTPs) provide a direct route for pharmaceuticals to enter the environment. Although WWTPs are not currently designed to specifically treat pharmaceuticals, biological treatment holds potential for pharmaceutical attenuation through sorption and biodegradation. Interestingly, recent observations suggest that WWTPs operated to achieve nitrification may provide greater pharmaceutical attenuation. This idea is explored by elucidating pharmaceutical sorption and cometabolic biodegradation by nitrifying organisms. Pharmaceutical sorption during biological wastewater treatment is assessed through the development and implementation of quantitative structural property models. Results highlight the need to include both hydrophobic and hydrophilic interactions, as well as characteristics of the biosolids surface. Interestingly, the charge of the dominant species at the reactor conditions is the best single predictor of pharmaceutical sorption. Biodegradation of atenolol, metoprolol, naproxen and sotalol is examined during nitrification using results from lab scale batch experiments. Although all are degraded during biological wastewater treatment, only atenolol and naproxen are biodegraded by nitrifiers, specifically ammonia oxidizing bacteria (AOB). Importantly, atenolol competitively inhibits AOB growth at environmentally relevant concentrations. Rates of biodegradation are well described by a cometabolic process based (CPB) model developed using transformation coefficients to quantify rates of cometabolism by AOB under growth and non growth conditions. The CPB model developed herein is the first model to mechanistically integrate PhAC biodegradation with AOB process kinetics. This research demonstrates the feasibility of developing predictive models to describe pharmaceutical attenuation during biological wastewater treatment. Further research is warranted evaluating the generalizability of these models and integration into process simulators utilized for design and operation of WWTPs.