DECOLORIZATION OF OLIVE OIL MILL EFFLUENT BY PHYSICAL AND CHEMICAL TREATMENT PRIOR TO ANAEROBIC-DIGESTION

Chemical and physical treatment of olive oil mill effluent (OOME) was performed using iron and lime as complexing agents, Duolite XAD 761 re sin as phenolic adsorbent and hydrogen peroxide as oxidant. We have sh own that 10 g dm(-3) of ammonium iron(III) sulphate . 12H(2)O, or calc ium dihydroxide were sufficient to precipitate more than 50% of the in itial COD and remove 50% of the initial colour within a short contacti ng time. The aromatic adsorbent resin retained more than 50% of the co louring compounds (chromophores) corresponding to removal of more than 60% of the initial COD after treating three bed volumes of crude OOME . The efficiency depended on the volume treated. Hydrogen peroxide rem oved the substituents of the aromatic rings which resulted in a decrea se in length of the colouring compounds in OOME. However, they were no t completely degraded, leading to shorter wavelength absorption. This chemical treatment was efficient in colour removal but only 19% COD re moval was possible. In all cases, simple aromatics were reduced, as de termined by GPC analysis. The chemical and physical decolorization of OOME was efficient in reducing the toxic effect of recalcitrant compou nds. The resultant OOME by each of these alternative treatments was re adily degradable through anaerobic digestion. (C) 1998 Society of Chem ical Industry.