Extensive research has been carried out to figure out safe means of disposing various industrial effluents. Industrial wastewaters from the aeration industry such as heavy metals and oily substances contain a high degree of contamination. The advanced oxidation process is one of the most effective and rapid methods of removing contaminations, which can lead to a high chemical oxygen demand (COD). The aim of the present study is to reduce the COD of an aeration effluent with the initial COD of 13,004 mg/L. About 20 sets of experimental tests were conducted to identify the contribution of H2O2, O3, and UV to the treatment process. The influence of the quantities of additives and the dose of the UV irradiance were, too, among the subjects of the study. These factors were altered throughout the experiments and their mutual effects were measured. To design the experiments, Minitab software 16 was utilized. The experimental conditions were set at the standard values of 25 °C and 1 bar to minimize any uncertainty. Based on the results, a correlation was derived, which was capable of expressing the effects of the input parameters (AOPs parameters) on the response (the COD level). Finally, the optimization process was conducted to find the quantities of H2O2, O3, and UV irradiance required to decrease the CODs of the effluent to their lowest possible. Based on the findings, when the doses of H2O2, O3, and UV to the treatment process were 40 mg/L, 8 mg/L and 86 mWs/cm2, respectively, the COD percent change was 51.5%.

Excess sludge in municipal plants normally contains high amounts of organic compounds (chemical oxygen demand [COD] of about 60,000 mg/L) and is capable of producing biogas. Anaerobic digestion is one of current methods to produce biogas. Municipal treatment plants' excess sludge contains high amounts of microbial cells with robust walls which inhibit microorganisms' access to the cells' organic content. This decreases biogas production efficiency as well as prolongs the time of anaerobic digestion process. In this study, a combination of the low‐temperature pretreatment techniques was used to increase biogas production efficiency in Isfahan South treatment plant. Through the mentioned techniques, which involve chemical, alkaline, microwave, and mechanical pretreatments, the cells' external structure is decomposed, and microorganisms' access to organic content is facilitated. All the experiments were carried out in two stages. The results of the first stage show that the highest amount of biogas efficiency is 365 mL/g COD for the sample under alkaline pretreatment by NaOH at 20 °C and pH = 12. The results of the second stage demonstrate that the highest rates of biogas production efficiency are obtained in samples under chemical pretreatment by KOH on secondary sludge at an ambient temperature (22 °C), and under 2400 H2O2 oxidation, respectively. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13072, 2019