Electrochemical treatment of pulp and paper industry wastewater

Abstract

The aim of the present research is to study the possible improvement in the biodegradability of pulp bleaching effluent by electrochemical treatment and to propose an economically viable treatment strategy for its effective implementation. The work is divided into three modules. The first module establishes the technical feasibility of the biodegradability improvement of the pulp bleaching effluent through electrochemical treatment. The optimal operating condition for maximum biodegradability has been found out using response surface methodology. The specific energy consumption and current efficiency have been analyzed critically. Moreover, there is considerable reduction in the pollutant load (COD removal: 55 % and color removal: 87 %) at optimum conditions. In the second phase, various electrochemical reactors such as batch, batch recirculation, recycle and single pass reactor have been studied to select appropriate reactor geometry for effective implementation of electrochemical treatment of the bleaching effluent. Phenomenological models of the configurations are derived. In the third module, the economic feasibility of various electrochemical processes as pretreatment step for biological treatment is studied in the batch recirculation mode and the results are compared with that of the conventional chemical coagulation followed by biological treatment. A modeling methodology for integrating processes involving electrochemical and biological is proposed. Optimal combinations of operating variables giving a definite completion of pollutant removal are derived from the empirical models of each process. Though, both the electrochemical steps as electrocoagulation and electro-oxidation found performing technically better, the former was noticed more attractive based on the overall operating cost. The research reveals the technical feasibility of electrochemical steps as primer in reduction of organic load and improvement in the biodegradability of pulp bleaching effluent.