Electrochemical and biological processes for removal of pollutants from textile effluent

Textile processing industries are one of the major chemical intensive industries. Textile dyeing effluent contains dyes, defoamer, bleaches, detergents, optical brighteners, equalizers and inorganic salts like sodium chloride, sodium sulphate and carbonates. The electrochemical oxidation (EO) process recently gained attraction as a potential tool to oxidize a broad range of organic molecules. However, techniques of electrode fabrication and evolution of chlorine/hypochlorite in the EO process limit the industrial utility. On the other hand, biodegradation process is a well-established wastewater treatment method, but dyes and other several other organics are recalcitrant and resistant to biodegradation. The lack of colour removal process is the limitation in biodegradation process. In this study, EO process followed by biodegradation was strategically combined for complete degradation of textile effluent. In this approach, biodegradability of organic compounds in the textile effluent was increased by EO process and then treated by bacteria. The major limitation is that EO process followed by biodegradation cannot be done due to the toxicity of hypochlorite produced during EO process. To overcome this issue, the EO treated effluent was treated by sunlight induced photolysis process prior to biodegradation. In this study, EO process was carried-out using RuO2-TiO2/Ti anode and Ti cathode. The sunlight treatment was carried out directly under natural sunlight to enhance the biodegradation efficiency. The biodegradation of EO+Sunlight treated effluent was carried-out using Laccase positive bacterial consortium at aerobic condition (Chapter 3), P.aeroginosa at high compressed gas pressure condition (Chapter 4), and Oxic, Anoxic, and Aoxic-Anoxic bacterial consortia (Chapter 5). The COD removal, TOC removal, HPLC analysis, UV spectroscopy and Florescence spectroscopy were utilized for organic degradation quantifications. The studies observed that chlorine mediated EO treatment was efficient for color removal and sunlight treatment after EO process facilitated the removal of hypochlorite. Abstract v The pre-treatment by EO+Sunlight enhanced the biodegradability of the textile effluent. Among all the system studied, biodegradation of EO+Sunlight treated textile effluent at Oxicanoxic condition resulted in >95% TOC removal and complete COD removal in textile effluent.