Thesis (M.Sc.)--Chulalongkorn University, 2014

Lignin is the organic compound in pulp mill wastewater that can cause high level of color and toxicity pollutant to living organisms. Therefore, pulp and paper industries needed to be treated prior to discharge into the environment. Advanced oxidation processes by Fenton and modified-Fenton were investigated in order to determine the process optimization and performance of reaction. The effect of operating parameter included ratio of Fe2+ and H2O2, initial pH, chemicals dosage, step feeding operation and current density were investigated to indicate the optimum operating conditions. Results showed that the performance of the process when using step feeding of both Fe2+ and H2O2 was found to be the highest oxidation efficiency on color, lignin and COD removal because this operation could reduce the scavenging effect on the reaction process. 45% of color removal, 39% of lignin removal and 38% of COD removal in term of oxidation efficiency were achieved in 1 hour under Fe2+ to H2O2 ratio of 1:2.5, initial pH of 3 and Fe2+ concentration of 400 mg/l. Moreover, this operation also reduce the sludge production of 20.7% at the same removal efficiency as initial feeding. For electro-Fenton process, optimum operating conditions were found to be Fe2+ to H2O2 ratio of 1:1 and current density of 200 A/m2. However, removal efficiency in electro-Fenton was less than step feed operation in Fenton due to no Fe2+ regeneration. Thus, Fenton process with step feeding mode operation was effective for the treatment of pulp mill wastewater.