Studies on the Degradation of Industrial Waste Water Using Heterogeneous Photocatalysis

Abstract

The release of wastewater into the receiving water bodies is deleterious, not only because of their color, but also because they are not easily degraded by aerobic bacteria and forms toxic compounds under the action of anaerobic bacteria. Therefore, it becomes imperative to completely degrade these organic compounds before their discharge. Such pollutants cannot be completely degraded by well established techniques like coagulation, flocculation, precipitation, adsorption, membrane separation, aerobic biological treatment. The incapability of conventional wastewater treatment methods to effectively remove such pollutants leads to explore the new, efficient and cost effective treatment systems. In order to meet stringent environmental regulations, the latest development is the oxidation of these biorecalcitrant organic compounds. These radicals have high oxidizing power superior to other usual oxidants and results in complete degradation. The methods are called advanced oxidation processes (AOP’s). AOP’s include homogenous and heterogeneous photocatalytic processes, however the latter being more promising technique for the degradation of industrial effluent. Photocatalytic process relies on the activation of semiconductor resulting in the generation of electrons and holes which results in series of redox reaction to destroy the pollutants. TiO2 In the case of Chemical and Pharmaceutical effluent, TiO has been demonstrated to be excellent catalyst and its behavior is well documented in the literature. Although the strong potential of photocatalytic process for wastewater treatment is widely recognized but its technical development at industrial scale is not met with much success due to its high operating cost. Taking all these facts into consideration, in the present study, effluent was collected from Chemical & Pharmaceutical industry from Punjab region. Photo degradation of effluent was performed in specially designed reaction vessel in the photoreactor equipped with UV tubes and constant stirring of solution was ensured at constant temperature. Experiments were performed in slurry mode in both UV and solar light at optimized condition. The degradation of effluent has been investigated in terms of change in reduction in COD and solid content. Various process parameters like catalyst dose, pH, concentration of oxidant, initially pollutant concentration were varied and their effects have been analyzed. 2 dose was optimized to be 3.0mg/l, at operating pH of 4.0 along with oxidant concentration of 250ml/l at UV intensity of 25 W/m2. So, heterogeneous photocatalytsis can be used as efficient and environmental friendly technique for the complete degradation of recalcitrant compound present in effluent which will increase the chances for the reuse of wastewater. The investigations demonstrate the importance of selecting the optimal degradation parameters for practical applications of this operation. The treatment of chemical pharmaceutical effluent result in the COD reduction from 8000 mg/l to 80 mg/l & 350 mg/l in UV and Solar light respectively after 7 hrs of treatment under optimized condition. The result shows degradation of effluent of the order of 99% and 95% in UV & Solar light respectively. The tests on solid analysis depicts reduction of TDS from 1270 mg/l to 350 mg/l & 390 mg/l in UV & Solar light respectively. Hence it is evident that the result in solar light are comparable with the result obtained in UV light, hence solar light can be suitable and effectively used as a light source for photodegradation.