Acidogenic fermentation of source separated mixtures of vegetables and fruits wasted from supermarkets

A pilot scale mesophilic anaerobic acidogenic fermenter was fed with mixtur es of vegetables and fruits shredded by a hammer mill and mixed in a stock tank, in order to produce a liquid phase suitable as RBCOD source in denitr ification and EBPR processes. Different operative conditions were studied w orking with a HRT in the range 1-12 days. The effluent coming from the ferm enter was screw pressed, and the solid phase was recycled adopting differen t ratios to the fermenter, in order to define its effect on the final liqui d phase composition. The variations of the VFA, lactate, methyl and ethyl a lcohol concentrations, TCOD, SCOD and pH during more than one year were ana lysed and discussed both with reference to the fresh feed, and to the conte nt of the fermenter. It was found that almost all the organic matter in the liquid phase inside the fermenter was represented by VFA (mainly acetate), lactate (in particular) and methyl and ethyl alcohols when HRT was longer than 6 days.