Effect of Diclofenac Concentration on Activated Sludge Conditions in a Biological Wastewater Treatment Plant

Abstract

Significant quantities of pharmaceutical substances enter biological wastewater treatment plants, where they interact with activated sludge microorganisms. An example of a pharmaceutical commonly used is the non-steroidal anti-inflammatory drug diclofenac (DCF). The presence of high concentrations of DCF in wastewater can disrupt nutrient removal processes, which are highly sensitive to external environmental factors. This paper discusses the effect of high DCF concentrations (1.04 mg/dm3–12.5 mg/dm3; 0.25 mg/gTS–3.0 mg/gTS) on the efficiency of nitrifying, denitrifying and phosphate-accumulating organisms in the wastewater treatment cycle. The condition of the activated sludge was assessed on the basis of the oxygen and nitrogen uptake rates values and the ability to biologically remove phosphorus compounds from the wastewater. The effect of DCF on the ability of methane-forming bacteria to produce biogas in the anaerobic digester was also investigated. None of the biochemical reactions of activated sludge were inhibited at applied DCF concentrations. A 33% reduction in biogas production was observed at a DCF dose of 0.0391 mg/gTS. Slight deviations from the typical course of biochemical transformation of ammonium compounds were recorded at a DCF concentration of 3 mg/gTS of sludge. However, in the concentration range studied, no negative effect of DCF, on the operation of the activated sludge, was found.