Assessment of organic carbon removal by particle size distribution analysis

Particle size distribution (PSD)-based fractionation, an alternative methodology in wastewater characterization, was employed to gather detailed information on the organic matter content of a raw olive mill wastewater (OMW) and to investigate the changes brought about in this characteristic after application of certain chemical treatment alternatives, namely, lime precipitation-coagulation, Fenton oxidation, and electrocoagulation. PSD-based analysis of the untreated OMW demonstrated that more than two-thirds of its organic carbon content, measured as chemical oxygen demand (COD) (69%), total organic carbon (TOC) (74%), as well as antioxidant activity (AOA) (74%) caused by the polyphenolic carbon fraction, was at the soluble range (2 nm). Treatability experiments, with maximum overall removal efficiencies below 50% even under optimized conditions, indicated that none of the applied chemical pretreatment methods was sufficiently effective in removing the organics from the investigated OMW. Nonetheless, PSD-based fractionation of the pretreated samples provided an insight about the treatment alternatives and the size fractions where they performed better. Electrocoagulation was capable of removing particulate and colloidal matter and provided a relatively higher overall performance with 23, 20, and 34% decreases in COD, TOC, and polyphenol contents of the OMW, respectively. Fenton process, on the other hand, showed a lower overall performance in terms of COD and TOC removal (17 and 15%, respectively), yet it was significantly effective on the soluble fraction, and thus more successful in removing the polyphenols mostly originating from the soluble range, with an overall efficiency of 42%. Based on these observations, PSD analysis was suggested as a useful tool to perform detailed wastewater characterization, as well as to differentiate between specific impacts of different pretreatment processes and help choose between alternatives, especially when a particular pollutant is targeted. Copyright 2009, Mary Ann Liebert, Inc

Effect of chemical treatment on the aromatic carbon content and particle size distribution-based organic matter profile of Olive mill wastewaters

The present experimental work was carried out to examine the physicochemical treatability of a high-strength olive oil mill wastewater (OMW). Firstly, the wastewater was subjected to environmental characterization and particle size distribution-based COD-TOC-UV254-UV280 analyses. The following treatment schemes were selected for the study: Coagulation-flocculation in the presence of anionic and commercial polymers at varying pH and coagulant/polymer dosages; Fenton treatment at different pH's and Fe(II): H2O2 concentrations as well as electrocoagulation using stainless steel electrodes at different electrolyte concentrations and current densities. Results of the study have indicated that none of the investigated physicochemical treatment methods was capable of removing the organic carbon content of the wastewater by more than 30% in terms of COD and 20% in terms of TOC that is at least partially attributable to the high, soluble organic carbon content of the wastewater. Alternative treatment processes and/or combinations have to be explored for effective treatment of OMW effluent. © by PSP