Removal of Pharmaceuticals in Conventional Wastewater Treatment Plants

Abstract

Over the latest years, the occurrence of pharmaceutical residues in the environment has attracted great interest, in particular in regard to the possible harmful effects of many of these pollutants to living organisms. One of the main sources of pharmaceuticals in the environment is the discharge of effluents from wastewater treatment plants (WWTPs), where their removal is often incomplete. The widespread use of pharmaceuticals and their generally inefficient removal by most WWTPs are the main reasons for their frequent detection in many water quality monitoring studies. In fact, most WWTPs are inefficient for the removal of micropollutants in general (especially hardly biodegradable organic xenobiotics) as these conventional systems were mainly designed for removing bulk pollutants. It would therefore be valuable to determine if WWTPs could be cost-effectively modified/expanded to reduce pharmaceutical discharges. Recent research has been dedicated to evaluate the application of several advanced treatment technologies, such as advanced oxidation processes, adsorption processes and membrane processes, either for the removal of organic micropollutants in general or specifically for the removal of pharmaceutical residues. However, despite the sometimes high removal efficiencies attained, these technologies are in most cases too expensive to be considered as viable solutions on a large scale. Moreover, some of these treatments may originate some transformation products that are potentially more persistent or toxic than the parent compounds. Therefore, this field of research remains very active as the search for cost-effective treatment processes continues to be pursued. In this work we intend to present a review on the fate and the removal efficiencies of pharmaceuticals in conventional WWTPs, describe the main mechanisms involved in pharmaceuticals removal in WWTPs processes, as well as a discussion of the major factors influencing that removal. In addition, we present some of the research work that has been carried out over the latest years in attempting to improve the removals of these pollutants in WWTPs. Thereafter, we describe some of the main alternative processes that are suggested by that research that can be used to complement conventional WWTPs and attain more efficient treatment of wastewaters in regard to contamination with pharmaceuticals.