Electrochemical oxidation of leachate pretreated in an upflow anaerobic sludge blanket reactor

This study was conducted to develop a two-stage process for the treatment of Hong Kong leachate. The leachate, containing 4750 mg l(-1) of chemical oxygen demand (CCD) and 1310 mg l(-1) of ammoniacal nitrogen (NH3-N), was first treated in a UASB (upflow anaerobic sludge blanket) reactor at 37 degreesC. The process removed on average 66.1% of COD with 6.1 days of hydraulic retention time (HRT), corresponding to an organic loading rate of 0.78 g-COD (1-day)(-1). The UASB effluent. which had an average FH of 8.9, COD of 1610 mg l(-1) and NH3-N of 1480 mg l(-1), was then further treated by electrochemical oxidation in a hatch reactor with recirculation With the addition of 2000 mg l(-1) of chloride tin the form of sodium chloride) and at a current density of 32.3 mA cm(-2), 87% of COD and 100% of NH3-N were removed from the UASB effluent in six hours. The energy consumption was <55 kWh kg-COD-1. The final effluent contained no residual NH3-N and only 209 mg l(-1) of COD.