Electrochemical oxidation of saline industrial wastewaters using boron-doped diamond anodes

Similarly to other catalytic advanced oxidation processes electro-oxidation by means of boron-doped diamond (BDD) anodes generates a very efficient oxidant media containing, among others, hydroxyl radicals. In this work BDD electro-oxidation is demonstrated to be an efficient alternative to treat a wide variety of saline industrial effluents, which main properties were as follows: TOC = 266–4479 mg/L; [N-NH3] = 61–1150 mg/L; [Cl−] = 1996–37,645 mg/L; conductivity = 5.6–64 mS/cm. Experiments were conducted at laboratory and pilot scale. Treatment efficiency was evaluated in terms of TOC and N-NH3 removal, and of formation of undesired by-products such as nitrate ions and trihalomethanes. The results showed that the high concentration of chloride ions in the wastewaters resulted in chloride oxidation taking place primarily, favouring ammonia oxidation in detriment of TOC elimination. Consequently, complete elimination of ammonia could be achieved for all the wastewaters studied while TOC removals reached values as high as 90%. Additionally, biodegradability of the effluent prior to and after treatment was also evaluated by means of the respirometry technique and the energy consumption of the process was estimated. The analysis of the energy consumption recommends the application of process integration approaches for the treatment of heavily polluted industrial effluents.