Characteristics of Biological Treatment of Isopropyl Alcohol Wastewater

Isopropyl alcohol (IPA) wastewater is difficult to treat using biological approaches due to its organic toxicity and high chemical oxygen demand. These negatively affect microorganism activity in biological treatment processes, with microbial activity varying depending on the degree to which the microorganisms are able to adapt to the toxicity of environment. In this study, the biological treatment characteristics of IPA wastewater in terms of the adaptation period for microorganisms to IPA wastewater were assessed. Modified Ludzack-Ettinger (MLE) and MLE type moving bed biofilm reactor (MLE-MBBR) treatment processes were used to treat the IPA wastewater and determine IPA adaptation time. After the microorganisms had adapted to IPA, IPA wastewater mixed with buffered oxide etchant wastewater containing NH4+-N was used as an influent. As a result, first, MLE-MBBR treatment processes showed higher IPA removal efficiency during the adaptation period than MLE process. Second, although the activated sludge was adapted to organic toxic wastewater, it did not exhibit higher resistance to other toxic substances such as copper, chromium, cadmium, or cyanide compared with conventional activated sludge. Third, nitrification and denitrification occurred smoothly, with nitrite and nitrate levels in the treated effluent found to be 0 mg/L. IPA was used as a hydrogen donor in the denitrification reaction, and denitrification rates of IPA adapted sludge produced by the MLE and MLE-MBBR processes were 0.062 and 0.058 mg/(g·mixed liquor volatile suspended solids·min), respectively.