Electrochemical Pre-Oxidation Of Drinking Water By Electro-Generation Of Hydrogen Peroxide And Hydroxyl Radical On-Site

Pre-chlorination is the most common pre-oxidation technology which is inexpensive, but hundreds of carcinogenic disinfection by-products can be generated in disinfection process, by contrast, redox potential of H2O2 is high, and its decomposition products is only water, so it will be the ideal pre-oxidant, further more, electrogenerated H2O2 on-site can solve the problem of transportation safety and cost. However, H2O2 was electro-generated in acid or alkaline electrolyte, and usually needed membrane in most of the study. Therefore, a new electrolyzer was designed in this paper, and H2O2 was electro-generated without adding any chemical substance, and didn't need membrane any more, and raw water was cleaned after flowed through the electrolyzer, especially, the smell, the total number of bacteria, and turbidity of water were significantly improved.A new electrolyzer was designed in this paper, in which hydrogen peroxide could generated without using membrane, electrode slots was tilted 60 degrees with electrolyzer base. By meas of this design, oxygen generated from anode and blowed from aerating apparatus at the base of electrolyzer could be fully used at the cathode, because oxygen would rise along the cathode from bottom of the cell, contact time between oxygen and cathode was extended, it was benefit for generation of H2O2.Effect of cathode material, current density, flow rate and ventilation rate on electro-generation of H2O2 were studied. The performance of graphite felt was the best among five materials as the cathode for electro-generation of H2O2, concentration of H2O2 on-site was 12.3mg·L-1, and current efficiency was 36.4% under the conditions of no additional chemicals, no membrane, and current density at 2mA/cm2, ventilation at 0.4m3·h-1, flow rate at 100mL·min-1. Humic acid, the precursor of disinfection by-products was electrochemical degraded in the electrolyzer, and OH had played an important role in the degradation process. The generation of OH was proved by degradation of benzoic acid and fluorescence test, so iron silicon alloy would be used as heterogeneous catalyst in Fenton-type reaction in order to enhance the effect of pre-oxidation of raw water.It was found that electrochemical pre-oxidation technology had a great effect on remove of turbidity, sterilizing, UV254, smell and taste after the experiment of electrochemical pre-oxidation of raw water from Sanjiadian Reservoir in Beijing. Compared with pre-chlorination, the electrochemical pre-oxidation obtained better ability for turbidity removal, what's more, chloroform content in water was less after pre-oxidation. The effect of pre-oxidation would be better when iron silicon alloy filtration column was added in the whole technology in the wake of electrochemical pre-oxidation.