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

The removal of colour from olive mill wastewaters (OMW) using aluminium sulphate [Al2(SO4)3•18H2O], 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.