Enzymatic treatment of pharmaceuticals and personal care products (PPCPs) in municipal wastewater

Abstract

Conventional wastewater treatment plants do not effectively remove pharmaceuticals and personal care products (PPCPs). As a result, PPCPs enter the environment via treated wastewater discharge. Enzymatic treatment, using the laccasemediator system, is a novel biochemical process that has been shown to effectively treat some PPCPs. This study investigates the efficacy of the laccase-mediator system to treat PPCPs using a process that can be easily implemented at an existing wastewater treatment plant. Enzymatic treatment will be most beneficial after primary sedimentation and before conventional biological treatment, where unoxidized PPCPs and byproducts could have the opportunity for further degradation in biological treatment. In this work, two enzymatic treatment configurations were studied. A step-wise optimization process was used that alternately varied treatment conditions: pH, enzyme activity, mediator concentration, and reactor detention time. In the optimization process of each configuration, successful oxybenzone removal (~90%) was achieved in municipal primary effluent. In a direct comparison of treatment configurations, both resulted in vi similar percent removals of oxybenzone. Therefore, the configuration with the simpler operation and reactor design was chosen for further study. During the optimization process, several noteworthy conclusions were made that might have full-scale enzymatic treatment implications. Specifically, successful oxybenzone removal occurred at unadjusted pH and without aeration, but increased biological oxygen demand of the wastewater increased the required mediator concentration. While the first finding would decrease enzymatic treatment costs, the latter would increase the costs associated with the mediator. Thus, an alternative mediator source, specifically one high in phenolic compounds, is desired. The use of wine, as a surrogate of winery wastewater, was in investigated and proved ineffective. Further investigation of alternative mediator sources is required. Treatment of another PPCP, sulfamethoxazole, was less efficient (65% removal) than that of oxybenzone, but nevertheless, the substantial removal might indicate that other PPCPs can be treated with the laccase-mediator system. The most promising result of this work was the simultaneous treatment of multiple PPCPs, oxybenzone and sulfamethoxazole. Simultaneous treatment proved to be as effective as when each PPCP was treated individually.