Aviani, I., Agricultural Research Organization, Institute of Soil, Water and Environmental Sciences, Newe ya'Ar Research Center, Ramat Yishay 30095, Israel, Agricultural Research Organization, Institute of Plant Sciences, Newe ya'Ar Research Center, Ramat Yishay 30095, Israel, Department of Microbiology and Plant Pathology, Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel
Raviv, M., Agricultural Research Organization, Institute of Plant Sciences, Newe ya'Ar Research Center, Ramat Yishay 30095, Israel
Hadar, Y., Department of Microbiology and Plant Pathology, Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, P.O. Box 12, Rehovot 76100, Israel
Saadi, I., Agricultural Research Organization, Institute of Soil, Water and Environmental Sciences, Newe ya'Ar Research Center, Ramat Yishay 30095, Israel
Laor, Y., Agricultural Research Organization, Institute of Soil, Water and Environmental Sciences, Newe ya'Ar Research Center, Ramat Yishay 30095, Israel

Concentrations of dissolved organic carbon (DOC) and total phenols (TP), and the phototoxicity to cress (Lepidium sativum L.) were determined for three molecular-sized fractions of olive mill wastewater (OMW), <1000, 1000-5000, and >5000 Da, before and after incubation with Pleurotus ostreatus. The <1000-Da fraction contained 82% of the total DOC and 48% of the TP, and was the most phytotoxic. Ethyl acetate separation of aqueous and solvent fractions showed that the aqueous fraction contained 93% of the total DOC, 83% of the TP, and was most phytotoxic, indicating low importance of monomeric phenols. Incubation of whole OMW and of the separate size fractions with P. ostreatus mycella reduced TP by factors of 4.3-5.3, but exerted diverse impact on phytotoxicity; overall, P. ostreatus efficacy in organic load removal and OMW detoxification was limited. Additional size fractionation of the incubated fractions revealed that most residual phytotoxicity was associated with low-molecular weight (MW) compounds originated from the <1000 Da fraction and not with low-MW byproducts from the degradation of higher-MW fractions and that polymerized metabolites were nonphytotoxic. Total phenols should not be used as sole indicators of the successful remediation of OMW. ©2009 American Chemical Society.