Insights into biodegradation of antibiotics during the biofilm-based wastewater treatment processes

The microorganisms in biofilms live in a self-produced matrix of hydrated extracellular polymeric substances (EPS) that form their immediate environment. EPS are mainly polysaccharides, proteins, nucleic acids and lipids; they provide the mechanical stability of biofilms, mediate their adhesion to surfaces and form a cohesive, three-dimensional polymer network that interconnects and transiently immobilizes biofilm cells. In addition, the biofilm matrix acts as an external digestive system by keeping extracellular enzymes close to the cells, enabling them to metabolize dissolved, colloidal and solid biopolymers. Here we describe the functions, properties and constituents of the EPS matrix that make biofilms the most successful forms of life on earth.

This review focuses on 118 pharmaceuticals, belonging to seventeen different therapeutic classes, detected in raw urban wastewater and effluent from an activated sludge system, a usual treatment adopted for urban wastewaters worldwide prior to final discharge into surface water bodies. Data pertaining to 244 conventional activated sludge systems and 20 membrane biological reactors are analysed and the observed ranges of variability of each selected compound in their influent and effluent reported, with particular reference to the substances detected most frequently and in higher concentrations. A snapshot of the ability of these systems to remove such compounds is provided by comparing their global removal efficiencies for each substance. Where possible, the study then evaluates the average daily mass load of the majority of detected pharmaceuticals exiting the secondary treatment step. The final part of the review provides an assessment of the environmental risk posed by their presence in the secondary effluent by means of the risk quotient that is the ratio between the average pharmaceutical concentration measured in the secondary effluent and the predicted no-effect concentration. Finally, mass load rankings of the compounds under review are compared with those based on their risk level. This analysis shows that the highest amounts discharged through secondary effluent pertain to one antihypertensive, and several beta-blockers and analgesics/anti-inflammatories, while the highest risk is posed by antibiotics and several psychiatric drugs and analgesics/anti-inflammatories. These results are reported with a view to aiding scientists and administrators in planning measures aiming to reduce the impact of treated urban wastewater discharge into surface water bodies. Copyright © 2012 Elsevier B.V. All rights reserved.

The pharmaceutical and personal care products (PPCPs) are emerging pollutants which might pose potential hazards to environment and health. These pollutants are becoming ubiquitous in the environments because they cannot be effectively removed by the conventional wastewater treatment plants due to their toxic and recalcitrant performance. The presence of PPCPs has received increasing attention in recent years, resulting in great concern on their occurrence, transformation, fate and risk in the environments. A variety of technologies, including physical, biological and chemical processes have been extensively investigated for the removal of PPCPs from wastewater. In this paper, the classes, functions and the representatives of the frequently detected PPCPs in aquatic environments were summarized. The analytic methods for PPCPs were briefly introduced. The removal efficiency of PPCPs by wastewater treatment plants was analyzed and discussed. The removal of PPCPs from wastewater by physical, chemical and biological processes was analyzed, compared and summarized. Finally, suggestions are made for future study of PPCPs. This review can provide an overview for the removal of PPCPs from wastewater.