Fermentation of agro-food wastewaters by activated sludge

This study investigates the potential of agro-food wastewater fermentation by activated sludge. Experimental results shown that all of the agro-food wastewaters studied initially had considerable concentrations of fermentable substrates, ranging from 19% to 68% of the total COD, but not all of the substrates contained in this COD fraction were fermented after an anaerobic stage of 10 h. The percentage of fermentable substrates fermented by the activated sludge during the anaerobic stage ranged from 14% to 68%, presenting the potato processing wastewater the highest concentration of fermented substrates. A mathematical model was proposed to describe the fermentation process. By using this model, the maximum fermentation rates were obtained, ranging their values from 0.6 to 3.4 (g COD g COD−1 d−1). The fermentation potentials of the agro-food wastewaters were also determined, their values ranged from 0.17 to 0.20 (g COD g COD−1) except for the cheese and the winery wastewater which presented fermentation potentials of 0.12 and 0.14 (g COD g COD−1), respectively.