Effect of fenton and fenton like reactions on the biological treatability of textile industry wastewaters

The carpet production has a great importance in terms of Turkey's foreign trade. During the carpet production, chemical substances containing various dyes are used to provide suitable colors. Because of toxic effects of these chemicals on microorganisms, high removal efficiencies cannot be obtained in the removal of textile wastewaters by biological processes. Therefore, it is generally preferred to implement a combination of biological processes and chemical or physico-chemical methods for increasing the removal efficiency. The fenton process which is applied with the use of iron (II) salts together with hydrogen peroxide, is suggested as a suitable process for the oxidation of inhibitory or toxic wastewaters. The efficiency of combined process depends a great extent on the operating conditions applied during the fenton stage. In this context, the aim of this study is to investigate the fenton process operating conditions which can be applied to increase the biological treatability of carpet production wastewaters. The experiments were carried out with two different processes: fenton process using divalent iron (Fe+2) and fenton-like process using trivalent iron (Fe+3). Reaction time, H2O2/COD molar ratio and amount of Fe were selected as process operating conditions. The optimum operating conditions for the Fenton process were determined as 0.06 mol H2O2/mol COD, 3,44 mmol Fe+2 and reaction time of 30 min. COD removal efficiency was obtained as 81% in the fenton process. For fenton like process, the optimum operating conditions were determined as 0.29 mol H2O2/mol COD and 3,85 mmol Fe+3 with the 30 min of reaction time. 56% of COD removal efficiency was obtained at these operating conditions. The active sludge inhibition tests carried out using the same amount of raw carpet production wastewater and wastewater treated with fenton and fenton like processes. The % 40 of inhibition was observed for the raw carpet production wastewater at the end of 180th min of inhibition test. The inhibition ratio of raw carpet production wastewater was decreased 67.8% by fenton process and 75.8% by of fenton-like process.