Evaluation of the Activation Procedure on Oxone Efficiency for Synthetic Olive Mill Wastewater Treatment

Abstract

Wastewater from the olive oil industry is an environmental problem which is growing in the Mediterranean region. Presence of phenolic compounds and high organic matter load are characteristics of this effluent that make it difficult to treat. In this study, the applicability of sulfate radical based advanced oxidation processes (SRbAOPs), using peroxymonosulfate (PMS) as oxidant, was evaluated in the treatment of synthetic olive mill wastewater (OMW). Different procedures for PMS activation were studied such as activation by Fe(II), radiation (visible and UV-A) and ultrasounds. The operation conditions were optimized by testing pH values, Fe(II) and PMS loads. At optimal conditions ([PMS] = 1600 mg/L, [Fe2+] = 700 mg/L and pH = 5) 60 2% COD removal was achieved. This process shows to be selective since complete degradation of 3,4,5-trimetoxybenzoic acid was obtained after 3 min of reaction. The addition of light, PMS/LED/Fe(II) and PMS/UVA/ Fe(II), did not increase the efficiency of organic matter removal, with 56 2% and 58 1% of COD removal, respectively, comparatively to PMS/Fe(II) (60 2%). PMS activated by ultrasounds led to 52 3% and 23 2% removal of phenolic compounds and COD, respectively, after 60 min. Toxicity tests using Lepidium sativum showed that treatment with PMS/UV-A led to a treated sample with mild inhibition of plant growth.