Complete detoxification of olive mill wastewaters by integrated treatment using the white rot fungus Phanerochaete chrysosporium followed by anaerobic digestion and ultrafiltration

Abstract

In this study, we investigated an integrated technology for the treatment of the recalcitrant contaminants of OMW, allowing water recovery and reuse for agricultural purposes. We have developed a pilot plant based on fungal pretreatment using Phanerochaete chrysosporium followed by anaerobic digestion. P. chrysosporium DSM 6909 was cultivated on pre-stared OMW as sole carbon and energy sources in a 120 L Air Lift Reactor (ALR) in a semi-continuous feed of OMW at a Hydraulic Retention Time (HRT) of 3 to 5 days. The P. chrysosporium DSM 6909 pre-treated OMW was fed in a 3001 anaerobic filter after a decantation step. The anaerobic filter was loaded with undiluted pre-treated OMW at a starting loading rate of 2-3 g of COD per litre of reactor and per day. The COD loading was increased when no apparent toxicity was encountered This anaerobic reactor worked continuously for 6 months at loading rates reaching 7 g L -1 d-1 of COD without any apparent toxicity. The percentages of inhibition of Vibrio fisheri luminescence after exposure to OMW showed that compared to the 100% inhibition of untreated OMW, P. chrysosporium DSM 6909 decreased the relative toxicity to 74%. Consequently, the P. chrysosporium DSM 6909 pre-treated OMW was well converted into biogas by anaerobic digestion which resulted in an effluent with 38% toxicity referred to as untreated OMW. Moreover, the use of ultrafiltration (UF) as post-treatment technology completely detoxified the anaerobic effluent and removed its black color. Results showed that compared to irrigation with water, treated effluent increased the Germination Index (GI) of Lycopersicon esculentum and enhanced plant growth while diluted untreated OMW decreased the GI and caused a pronounced growth inhibition. © 2005 Asian Network for Scientific Information.