Study On Three-dimensional Electrode Reactor Disposing The Secondary Effluent From Municipal Sewage Plant

Based on the resource of municipal wastewater, the electrolysis of secondary effluent from municipal wastewater plant is investigated with three-dimensional electrode. This paper mainly explore that process parameters of three-dimensional electrode influenced on removal efficiency of permanganate index, ammonia nitrogen, total nitrogen and total phosphorus of secondary effluent. It is to explore new ways for reusing secondary effluent.Three-dimensional electrode reactors were composed of packing particle electrodes which were mixed with activated carbon and manganese sands according to the proportion into traditional plate electrode reactors. Orthogonal experiment analysis showed that the proportion of particle electrode and electrical current density were significant factors which influenced the removal effects. Optimum operation parameters were that the proportion of particle electrode was 9:1, electrical current density wae 4.4 mA/cm2~6.6 mA/cm2, electrode span was 9.0cm, electrolytic time was 20~40min. The influence trends of electrical current density were similar on the removal rates of permanganate index and nitrogen compounds. With increasing electrical current density, the removal rates of permanganate index and nitrogen compounds increased at the initial reaction stage. When electrical current density was 4.4mA/cm2 and 6.6mA/cm2, the removal percent of permanganate index and nitrogen compounds appeared higher values, and they were 72%,84%in turn. Then the removal percent did not continuously elevate with electrical current density increasing. The law of total phosphorus removal rate was not obvious. Analysis suggested that total phosphorus removal mainly depended on retention of particle electrode and adsorption of activated carbon, rather than electrochemical reaction. The influence of electrolytic time on removal rate was still great. Removal efficiency of permanganate index was 70% when the reaction time was 20min. Removal efficiency of ammonia nitrogen, nitrate nitrogen and total nitrogen respectively reached 84%, 70% and 40%. Removal efficiency of total phosphorus was 28.5%, when the reaction time was 40min. Then with extending to the electrical current density, the removal rates of all indexes tended to be stable. The influence of electrode span on the removal rates was relatively small which was mainly because the distance between cathode and anode of every particle electrode was small owing to packing particle electrode to three-dimensional electrode reactor.In a word, three-dimensional electrode method can remove the concentrations of permanganate index, ammonia nitrogen, total nitrogen effectively. And a part of total phosphorus also can be removed. Based on the removal efficiency to ammonia nitrogen in secondary effluent, it is recommended that adopted three-dimensional electrode reactor to pretreatment of circulating cooling water in power plant, and it can decrease steam tube serious corrosion effectively which is caused by the high concentration of ammonia nitrogen in water.