(641a) Electrochemical and Photochemical Wastewater Treatment

Photochemical and electrochemical Advanced Oxidation Processes (AOP/EAOP) are efficient oxidation operations for degradation of persistent pollutants such as pharmaceuticals, pesticides, substituted aromatic hydrocarbons, dyes and complexing agents. The UV/H2O2 -, UV/O3- processes and the Photo-Fenton process are representative photochemical AOPs. Anodic oxidation is an electrochemical AOP. Both technologies generate reactive hydroxyl radicals which mineralize contaminants or at least convert pollutants into less toxic or biodegradable products.

The aim of the project is the comparison and documentation of approved photochemical and electrochemical processes for different substance classes. This catalogue should help to evaluate a proper technology for specific application. Criterion for comparison is the potential of degradation and mineralization, as well as the specific energy consumption.

Several substances, the selection was mainly based on the properties of substituents, were investigated. The experiments were carried out with a start concentration of 500 ppm of the investigated substances. Photochemical degradation was carried out in a Heareus Noblelight UV-reactor system (UV-RS-2), equipped with a 15 W mercury low-pressure lamp. Electrochemical degradation was performed in open cell electrolysis with diamond coated electrodes and 0.05 M Na2SO4 for conductivity reasons. The results demonstrate different rate of mineralization and degradation related to the substituent of the model substance and the absorption properties in the UV Range. In general electrochemical experiments show a simultaneous degradation and mineralization whereas photochemical experiments show degradation of substances in a first step followed by mineralization.