Polluting characteristics and lime precipitation of olive mill wastewater

Abstract Olive mill wastewaters originating from olive extraction units are the most polluted wastewaters of the food industry which present a toxicity towards plants as well as certain impacts to the hydro‐flora. Pollution abatement for olive mill wastewater is difficult, because they are seasonal, highly concentrated, very polluting, and the processing units are small, and can not withstand the cost of a depollution. This paper mainly concentrates on the polluting characteristics and lime precipitation as a minimal pre‐treatment procedure for the removal of organic matter content. The sludge produced of the addition of 0.5–3% CaO reduces the concentration of suspended solids in the “vegetation waters”; by 27.6% whereas 77.1% of the oil and grease are distributed in the precipitate fraction. The COD as well as the toxic load in terms of phenolic compounds are not strongly affected by the addition of CaO.