Abstract
The feasibility of using the photo-Fenton reaction to improve the biodegradability of non-biodegradable compounds that originated from sewage was examined. Non-biodegradable compounds are degraded by hydroxyl (OH) radicals generated by the photo-Fenton reaction. During the degradation of non-biodegradable compounds, biodegradable intermediates such as organic acids are produced, resulting in improved biodegradability. The results of an experiment, in which a filtered supernatant solution of activated sludge from a sewage treatment plant was used, confirmed that the 5-day biochemical oxygen demand (BOD5) increased with decreasing total organic carbon (TOC) concentration as a result of the photo-Fenton reaction. This increased the ratio of BOD5 to TOC, which indicated that the biodegradability was improved. Although many non-biodegradable compounds have electron-dense structures, many biodegradable compounds have electron-lucent structures. Hydroxyl radicals, which are an oxidant in the photo-Fenton reaction, act as an electrophilic agent. In the degradation experiments using a mixture of biodegradable and non-biodegradable compounds, OH radicals preferentially attacked non-biodegradable compounds, and biodegradable compounds accumulated in the solution. As a result, the biodegradability was improved.
