Simultaneous removal of arsenic and fluoride from synthetic solution through continuous electrocoagulation: Operating cost and sludge utilization

The present study deals with simultaneous removal of arsenic and fluoride by continuous electrocoagulation (EC) process using aluminum electrodes. Effects of flow rates: 0.48-1.40 L/h and residence time (tau): 60-173 min have been studied on the removal of arsenic and fluoride. The percentage removals of arsenic and fluoride are found greater than 98.83% and 87.5% respectively. The concentrations of arsenic and fluoride in treated water are also found below the permissible limits as per World Health Organization (WHO) guidelines (As: 10 mu g/ L, F: 1.5 mg/ L). The optimum cost of continuous EC is found to be 0.358 USD/m(3) at a flow rate of 0.88 L/h with 95 min residence time. Produced sludge has been analyzed by FESEM, XRD and FTIR. Sludge characterization confirms that arsenic and fluoride are linked with aluminum hydroxide complexes. Solidification technique has been used for the management of the produced sludge by its immobilization in the form of clay brick. Leaching test results show that leaching of arsenic and fluoride from the brick is much below the permissible limits assigned according to the US Environmental Protection Agency (USEPA) norms. The brick quality parameters are found above the respective permissible limits as per Indian standard indicating it suitability for use in construction purposes.