Thesis (M.Sc.)--Chulalongkorn University, 2012

This research investigated the feasibility of treating phenol-production wastewater by treatment combination among Fenton, electro-Fenton and aerobic biological processes. Wastewater used in this study was obtained from a phenol-production plant and found to be highly toxic and refractory. Major pollutant was cumene hydroperoxide within the range of 250-550 mg/l with the pH and COD of 12-13 and 3,000-6,000 mg/l, respectively. It was found that cumene hydroperoxide could rapidly react with ferrous ion to form acetophenone and was easily biodegraded. This implies that the toxicity and biological stability of this wastewater are derived from other pollutants rather than cumene hydroperoxide. As a result, this research was focused on the removal of refractory organic pollutants in term of COD. Optimum conditions for DOD removal of Fenton process were at pH 3.0 and the hydrogen peroxide to ferrous molar ratio of 1:0.2. Removal efficiency increased with increasing Fenton’s reagent concentrations; however, the COD of the Fenton-treated effluent were in between 700-1,000 mg/l which were still much higher than the industrial effluent standard of 120 mg/l. Electric current discharge to transform the process to electro-Fenton could not significantly improve the COD removal. Nonetheless, it could obviously increase the BOD to COD ratio. The BOD to COD ratios of the raw wastewater, Fenton-treated and electro-Fenton treated effluents were 0.4, 0.5, and 0.8, respectively. As a result, the effluent from electro-Fenton process had high potential to be further treated by aerobic biological process. Biodegradation study revealed that the activated sludge SBR system could reduce the COD to be lower than 40 mg/l with the hydraulic retention time of 2 days. Thus, the effective integrated treatment scheme for phenol-production wastewater is the electro-Fenton process followed by aerobic biodegradation process.