Effect of combined physico-chemical processes on the phytotoxicity of olive mill wastewaters

• Published in: Water research (Oxford) 2008-03, Vol.42 (6), p.1684-1692
• Main Authors: Andreozzi, Roberto, Canterino, Marisa, Di Somma, Ilaria, Lo Giudice, Roberto, Marotta, Raffaele, Pinto, Gabriele, Pollio, Antonino
• Format: Article
• Language: English
• Subjects: aeration; Applied sciences; Bioassay; centrifugation; chemical oxygen demand; cucumbers; Cucumis sativus; culture media; Exact sciences and technology; food processing wastes; Industrial Waste; Iron - chemistry; Lactuca sativa; lettuce; Modified photoFenton; Olea; Olive mill wastewater; Olive Oil; Other industrial wastes. Sewage sludge; Ozonation; Ozone - chemistry; photolysis; Phytotoxicity; Plant Oils; Plants - drug effects; Pollution; Pseudokirchneriella subcapitata; radishes; Raphanus sativus; root growth; seed germination; Selenastrum capricornutum; solar radiation; Solar treatment; Sunlight; Wastes; wastewater; wastewater treatment; Water Pollutants - toxicity; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2007.10.018

A pool of laboratory experiments is planned with the aim of evaluating the possibility to reduce the phytotoxicity of olive mill wastewater (OMW) with combined physico-chemical processes (centrifugation–ozonation, centrifugation–solar photolysis, centrifugation–solar modified photoFenton, centrifugation–solar modified photoFenton–ozonation). A moderate COD removal of an OMW is reached by using ozonation or solar modified photoFenton separately or solar modified photoFenton/O 3 combined process even for prolonged treatment times. The O 3-treated OMWs are still toxic towards algal growth ( Pseudokirchneriella subcapitata) and only for dilutions equal to or higher than 1:160 a stimulation of algal growth is observed. The sole ozonation does not reduce significantly the phytotoxicity of tested OMW measured through the GI calculation of Raphanus sativus L., Cucumis sativus L. and Lactuca sativa L. A marked reduction of OMW inhibition, higher than 50%, is evidenced for 1:8 dilution OMW samples ozonated for 2 h. The long-term storage of OMW associated with solar irradiation without or with Fe(III) ions under continuous aeration is less efficient than ozonation, and the combined action of the two former treatments does not significantly contribute to enhance both COD removal and germination index. Better results are obtained on seed germination and root elongation of plantlets of the three selected species, which germinated on OMW-free solidified medium and were then transferred on a solidified culture medium containing O 3-treated OMW diluted 1:2 and 1:4. The operating costs are estimated for the solar modified photoFenton–ozonation process.