Parameter evaluation on the selectivity of ozonation towards the dechlorination of refractory components in complex-matrix industrial wastewaters
Due to industrial, agricultural, medical and domestic activities, significant amounts of toxic and hazardous pollutants are emitted to the environment. Most of such pollutants are xenobiotic and recalcitrant in nature, and are characterized by a high persistence and bioaccumulation in the environment. In particular, halogenated organics pose a serious threat because of their widespread occurrence in soils, sediments, surface and ground waters. As a representative for these components, chlorophenols are frequently used as model components because of both their widespread use and chemical properties. Because of their antimicrobial properties, chlorophenolic chemicals are primarily used in pulp and paper, textile, leather tanning and wood bleaching industries. Their presence is also observed in landfill leachates. The toxicity of chlorophenols depends on the degree of chlorination and the substitution away from the ortho position. In this context, the dechlorination of these components is beneficial to reduce their toxicity and improve their biodegradability, so further treatment in a typical aerobic treatment becomes feasible. Advanced Oxidation Processes (AOPs) and membrane filtration methods are widely acknowledged for the treatment of industrial wastewaters containing refractory organic components. For AOPs, while complete mineralisation is in most cases not feasible from an economic point of view, these technologies present an interesting method for partially degrading the molecules. And membrane processes are suitable to remove organic matter of different sizes, from small solutes to macromolecules. So integration of AOPs and membrane separation could be used to increase their biodegradability, creating the possibility for further biological treatment. The current doctoral project responds to the necessity to study the overall applicability of Advanced Oxidation Processes as a pre-treatment technology and membrane filtration as a post-treatment for complex wastewaters containing chlorinated toxic organics. Main focus will be laid on determining the selectivity towards dechlorination in multiple substrate solutions and evaluating the decrease in toxicity for aerobic biological wastewater treatment. Based on the results, long-term effects on the activity treatment plant in suspended growth and immobilized biofilm systems will be studied by using a pilot-scale continuous treatment system.