Pretreatment of biocide containing wastewaters by advanced oxidation processes

Abstract

Biocide is an antimicrobial agent used in various industrial applications to control the bacterial growth that leads to environmental, ecological and toxicological problems in water. The discharge effluents from manufacturing, production and industrial applications contain complex and diverse groups of chemicals. These effluents are hard to treat by conventional treatment methods because of the inhibitive effect of biocides on bacterial growth in biological treatment process. Advanced Oxidation Processes (AOPs) have the ability to generate short-lived, powerful hydroxyl radicals (•OH) that readily attack and destroy contaminants in wastewaters. The purpose of the study was to investigate the most suitable process (or processes) and its optimal operating conditions for the pre- or post-treatment of hexahydrotriazine (HHT) containing wastewaters (in an ultrasonic bath operated individually, sequentially (before an ultrasonic probe) or simultaneously with an advanced oxidation process (AOP)). It was found that a low power ultrasonic bath alone was an ineffective method for sufficient degradation of HHT to render biodegradability or organic matter destruction, but its sequential operation with an ultrasonic probe, or simultaneous operation with photo-Fenton process were very effective, particularly for enhancing the biodegradability of the solution. The synergy was the result of increased mass transfer rates and OH radical formation under ultrasonic irradiation.|Keywords: biocide, hexahydrotriazine, advanced oxidation, ultrasound