Investigation of domestic wastewater treatability by fenton and electrochemical methods

In this thesis study, the treatability performance of domestic wastewater (DWW) was investigated by using advanced treatment methods such as Fenton, electrocoagulation(EC), electrooxidation(EO) and Electro-Fenton(EF). The samples were supplied from Uskudar and Yenikapi DWW pretreatment plants of Istanbul Water and Sewage Administration. COD/H2O2/Fe(II) and Oxidant Activity Coefficient (OAC) as operational conditions was determined in Fenton process. For the treatment performance of the electrochemical methods on continuous and batch systems; effects of electrical power, conductivity, current intensity, current density, dose of H2O2 and pH were determined. The optimum efficiencies were obtained at 45th and 15th minutes for the Fenton process applied on DWW samples having COD values of 770 mg/l and 450 mg/l, respectively. While the ratio of COD/H2O2/Fe(II) were 2.2/1.7/1 and 7/3.3/1 for the samples, OAC values were measured 2.8 and 4.4, respectively.99% removal was achieved for Suspended solids(SS) and turbidity. The sludge accumulation was found as 8.5% and 3.5%, respectively. With the EC methods, discharg limits were achieved for the DWW samples having COD value of 380 mg/l at 15 min. Optimum experimental conditions were determined as 2.7 10-3 A/cm2 current intensity, 0.38 kW-h/m3-DWW energy and 0.08 kg Fe/ m3-DWW electrode consumptions. While the experimental time was 2 or 3 min. in EO system for this kind of samples, the OAC and COD/H2O2/Fe(II) values were found as 4.6 and 10/5/1, respectively. The energy consumption was maintained at 0.4 kW-h/m3-DWW. The entire SS was removed.The sludge accumulation in EO was less than 50% of that obtained in EC. The discharge limits for the samples having COD value of 610 mg/l were obtained only by using EO. During the experimental analysis, OAC and COD/H2O2/Fe(II) values were determined as 1.3 and 0.8/1.2/1, respectively. At the end of the experimental studies, it was found that, the EC method is sufficient to get attain the discharge limits with the small sized treatment plant. In addition to this, sludge quantity can be reduced by half in the EO method, and reuse of the treated wastewater according to results of organic and bacteriological parameters can be considered after the Fenton and EF treatment techniques. Keywords: Domestic Wastewater, Fenton process, electrocoagulation, electrooxidation, Electro-Fenton.