Abstract
Developing solution for photography is a mixed solution that contains some organic substances and about 10% of sodium sulfite, an antioxidant of the organic substances. Therefore, the waste developer solution displays a high COD and the treatment is difficult because the contained organic substances, p-methylaminophenol sulfate and hydroquinone (p-dihydroxy-benzene), are also hardly decomposed. In order to reduce the COD in the solution, a combined method of oxidation with ozone and coagulative precipitation with iron (III) chloride was examined.
By ozone oxidation, about 85% of the COD in the developer solution was reduced. In detail, the sulfite ions were thoroughly oxidized and most of the organic substances were also oxidized. Furthermore, the oxidized organic substances were decomposed to carboxylic acids and a part of the carboxylic acids were estimated to be decomposed to carbon dioxide. However, the conversion rate of the carboxylic acids to carbon dioxide was so slow that the acids could not be decomposed completely during that a short period. The coagulative precipitation with iron (III) after the partial decomposition by ozone oxidation enabled the concentration of COD to be reduced about 90-96%.
