BIOMETHANIZATION

Vegetation water in the olive constitutes 45-50% of the fruit, with a total content of 170 kg m(-3), of which 150 kg m(-3) are organic compo unds (80% of these can be directly converted to methane). Anaerobic di gestion of this waste yields methane with an average content of 37 m(3 ) m(-3) of vegetation water and an energetic yield of 325 KwH, of whic h 30% can be converted into electrical energy and 63% into calorific e nergy by the use of cogeneration processes. This is sufficient to cove r the energy needs of both an olive oil production plant and an anaero bic reactor for the integral purification of wastewater. From an econo mic point of view, and taking into account the costs of electric (15 p ts KwH(-1)) and calorific energy (3.2 pts therm(-1)), the intrinsic va lue of olive vegetation water would be 2148 pts m(-3). For the optimiz ation of this process, the following lines of research were investigat ed: (i) development of a biological process for the biodegradation of the phenolic compounds responsible for the inhibition of the biomethan ization process; (ii) selection of the nature and the characteristics of an appropriate support for the immobilization of anaerobic bacteria ; and (iii) development of a system and high density cellular reactor to obtain optimum conditions-hydraulic residence time, methane yield a nd efficiency for the purification process. (C) 1997 Elsevier Science Limited.