Decolorization of olive oil mill liquid wastes by chemical and biological means

The removal of colour from olive mill wastewaters (OMW) using aluminium sulphate [Al-2(SO4)(3) . 18H(2)O], lime (CaO) and hydrogen peroxide (H2O2) was investigated, along with the decolorizing effect of sixteen strains of Pleurotus. In general terms all chemical substances exerted a clear decolorizing effect, yet the most effective was hydrogen peroxide, followed by lime and alumina. The tests with Pleurotus isolates were carried out on plates using different concentrations (25%, 50%, 75%, 100%) of sterilized OMW solidified with 1.5% agar. For all strains tested, decolorization proceeded more slowly than radial growth. Among the six Pleurotus species P. cornucopiae (ATCC 38547) and P. ostreatus (ATCC 34675) were the most efficient. (C) 1997 Elsevier Science Limited.