TREATMENT OF MEDIUM DENSITY FIBERBOARD WASTEWATER by Fe2+/PERSULFATE AND Fe2+/PERSULFATE ENHANCED HYDRODYNAMIC CAVITATION PROCESSES

Abstract

The present work highlights the novel approach of combination of hydrodynamic cavitation (HC) and Fe2+/persulfate (PS) processes to develop a feasible and effective process for the post treatment of biologically treated wastewater obtained from a medium density fiberboards (MDF) industry (COD = 448 mg/L; TOC = 243 mg/L; pH = 7.7). Fe2+/PS and Fe2+/PS enhanced HC treatment processes were evaluated and compared on the basis of chemical oxidant demand (COD) and total organic carbon (TOC) removals as well as PS consumption rates. In the first part of the study Fe2+/PS oxidation experiments were performed at different initial PS concentrations (5, 10, 20 and 30 mM) in the presence of 0.5 mM Fe2+ catalyst at pH = 3. Fe2+/PS process was rather inefficient, resulting in 12% and 10% COD removals and 12% and 9% in TOC abatements after 75 min treatment for 5 mM and 10 mM initial PS concentrations, respectively. Increasing the PS concentration did not significantly enhance the organic carbon removal efficiencies, therefore, HC process was applied in order to enhance the treatment efficiency for selected initial PS concentrations (5 and 10 mM). Under the investigated reaction conditions, after 75 min Fe2+/PS enhanced HC treatment, approximately 60% COD and 40% TOC removals were achieved for 5 mM initial PS concentration. The calculated average oxidation state (AOS) values suggested that more oxidized organic intermediates were formed during Fe2+/PS enhanced HC treatment of biologically treated MDF wastewater.