固体電解質を用いた２槽型オゾン電解併用処理による排水中難分解性有機物および窒素の除去

Abstract

The applicability of ozonation combined with electrolysis to removal of persistent organic matter and nitrogen from wastewater was experimentally investigated. Treated night soil was selected as wastewater containing ammonia and organic matter. A cation exchange membrane was used as a solid electrolyte. As a result, 1,4-dioxane as a persistent organic matter and other types of organic matter were rapidly decomposed by hydroxyl radicals generated via cathodic reduction of ozone. Organic matter in treated night soil did not interfere with 1,4-dioxane decomposition. At the anode, free chlorine was electrochemically generated and ammonia nitrogen was finally removed through break point chlorination. Ammonia nitrogen produced via decomposition of organic nitrogen was also removed. The electrolytic current required for ammonia removal was 6.5kC · mmol-NH3-1. However, a portion of ammonia and chloramines transformed into nitrate nitrogen by reaction with ozone and hydroxyl radical at the cathodic compartment. Although ammonium ion passed through the cation exchange membrane from the anodic compartment to the cathodic compartment, the ratios of the amount of nitrogen removed to that of ammonia nitrogen reacted were in the range from 0.71 to 0.76. The terminal voltage for electrolysis was successfully decreased using a solid electrolyte.