UV/O3 Aided Advanced Oxidation Process in Wastewater Treatment Technology

Wastewater treatment for industrial effluent can be carried out by various physical, chemical and biological treatment methods. For removal of various organic and inorganic pollutants various advanced methods are used with good effect. The general strategy of this study was based on applying Advanced Oxidation Process (AOP) of (UV/O3) for reduction of COD of effluent wastewater. Various parameters affect the oxidation process such as pH, Ozone dose and exposure time of UV. The optimized conditions were found to be pH: 7, the ozone dose of 4gm/hr and 60 min UV exposure. Finally, chemical oxygen demands (COD), before and after oxidation process was measured to ensure the entire destruction of organic load. Krishna D. Ladwani, Kiran D. Ladwani 1* , Dilip S. Ramteke 1 , Farhin Inam 2 1 Environmental Impact and Risk Assessment Division, National Environmental Engineering Research Institute (NEERI), Nagpur 440-020 2 Department of Chemistry, Institute of Science, Nagpur 440-008, India. Submission: 2 March 2016 Accepted: 7 March 2016 Published: 25 March 2016 www.ijsrm. humanjournals.com Citation: Kiran D. Ladwani et al. Ijsrm.Human, 2016; Vol. 3 (1): 11-20. 12 INTRODUCTION One of the basic requirements for all living organism including human beings is clean and nonpolluted water. Nowadays its availability is major problem [1]. Advances in technology have resulted in greater water demands for industry [2-4]. Generation of wastewaters in industrial processes is sometimes unavoidable and in most cases a process to reduce the organic load and other contaminants must be employed before water discharge. [5] This wastewater contains a variety of suspended solids, oils, metals, and organics. The successful cleaning of these new wastewaters prior to discharge, using existing treatments, has yet to be improved comparatively [2-4]. In some cases, however, due to the high organic load, toxicity or presence of biorecalcitrant compounds, biological processes cannot be used, since no chemical oxygen demand (COD) removal is achieved biologically. Among chemical processes, the advanced oxidation process (AOP) has been used to reduce the organic load or toxicity of different waters and wastewaters [5-7]. AOPs are based on the generation of hydroxyl free radicals, which have a high electrochemical oxidant potential. The generation of hydroxyl radicals involves the combination of classical oxidants, such as hydrogen peroxide (H2O2) or ozone (O3) with UV radiation or a catalyst. The formed radicals react with organic materials breaking them down gradually in a stepwise process. The generation of hydroxyl radicals can be achieved by a variety of reactions, such as ozone/UV [8], hydrogen peroxide/UV [9], Fenton oxidation [10], photoFenton [9, 11] or titanium dioxide/hydrogen peroxide/solar radiation [12]. The advantage of AOPs is that they effectively destroy the organic compounds, converting them mainly to carbon dioxide and water. Advanced oxidation processes (AOPs) are technologies based on the intermediary of hydroxyl and other radicals to oxidize recalcitrant, toxic and non-biodegradable compounds to various byproducts and eventually to inert end-products [13,14]. In view of above, this work aims at studying the effect of select UV/O3 AOP process for waste water treatment containing high organic content so as to achieve reduction in total organic load measured in terms of chemical oxygen demand (COD). In this study, O3 was used in combination with UV under varying conditions for the treatment of wastewater. www.ijsrm. humanjournals.com Citation: Kiran D. Ladwani et al. Ijsrm.Human, 2016; Vol. 3 (1): 11-20. 13 MATERIALS AND METHODS Effluent water used in this study was obtained from the effluent treatment plant of Ankleshwar, Gujarat, India. Effluent water was analyzed for its characteristics. Various physicochemical parameters were estimated as per the Standard Methods for examination of water and wastewater [15]. For the COD estimation; sample (20 ml) was refluxed on Gerhardt assembly with a known volume (10ml) of potassium dichromate (0.25N) for 2 hrs, after digestion it was titrated against Standard Ferrous Ammonium Sulphate (0.1N). Chemicals used in the study were supplied by Fisher Scientific (Qualigence fine chemicals), Mumbai, India. All the reagents were of analytical grade and the solutions were prepared with deionized water. The reactor used in the study is detailed as given in Fig. 1 and its experimental conditions are depicted in Table 1. All the experiments were performed in the completely cylindrical photo-reactor made of the glass with a total volume of 2L and water column height of 30cm. The UV irradiation source was 15W (TUV 15W/G15 model Phillips) low-pressure mercury vapor lamp (maximum emission 254nm) placed in quartz tube. A novel air cooling system was introduced instead of commercially available water cooling jacket; which is very parsimonious compared to available treatment system. The reactor was covered with an aluminum foil to avoid the light leakage to the outside. The effluent sample (1.5 liters) was uniformly mixed by an aerated pump of 10.5 liters/min capacity. Sample was then exposed to the UV lamp of 15W for a specified period of time. The experiments were started by turning the UV lamp on after the addition of reagents. After the completion of the experiment, the sample was withdrawn from its outlet pipe and stirred well on magnetic stirrer. The sample was then analyzed for COD. Samples were removed from the reactor at predetermined time intervals for the immediate analysis of COD. ELTECH Ozone Generator was used to generate ozone. Varying doses of ozone (1 – 10 gm/hrs) were introduced individually and COD reduction was found out. A bench scale pH meter (Orion plus) was used for pH measurement. COD analysis was carried out on Gerhardt assembly. The COD analysis was followed [15]. Similar procedure was performed with varying exposure time of UV light (15-280 min), O3 dose (1-10gm/hrs) and pH (4-10) so as to optimize these parameters. The removal efficiency of each set of samples was estimated by applying following formula: www.ijsrm. humanjournals.com Citation: Kiran D. Ladwani et al. Ijsrm.Human, 2016; Vol. 3 (1): 11-20. 14 RESULTS AND DISCUSSION Wastewater effluent from Ankleshwar, Gujarat is highly organic in nature with high COD, total organic carbon (TOC) and phenol content. The conventional treatment methods cannot be completely degrade or remove the pollutants from the wastewater released from treatment plants. In the present study, the optimum experimental parameters for photocatalytic treatment of wastewater effluent are determined for effective degradation of organic pollutants in the effluents. Table 2 depicts the physicochemical parameters of the effluent wastewater. pH was found to be in the range of 7.1-8.3, COD was found in the range of 848-1380mg/lit and phenol concentration was 0.59-1.89mg/lit. Optimization of UV exposure A set of experiments were carried out to optimize exposure time of UV radiation for wastewater (1.5 L) in the reactor. The intensity of 15W UV lamp was in the range of 200-280nm which remained constant for all the experiment. In this experiment, radiations time was varied and samples were collected and analyzed. The result in COD reduction in raw wastewater samples with variable time exposure of UV radiation is shown in Table 3. It was observed in Fig. 3 that there was increase in COD reduction found up to 60 min whereas further exposure with time did not show considerable reduction irrespective of original COD concentration. UV exposure to wastewater samples with an initial COD of 600mg/lit showed a reduction of 21% at 15 minutes exposure time and increased to 40% COD reduction with increase in UV exposure time to 60 min.