ASSESSMENT OF BIOCONVERSION PERFORMANCE AFTER ALKALINE FERMENTATION PROCESS TO RECOVER BIOGAS AND NUTRIENTS

Abstract

Alkaline fermentation of two distinct types of waste activated sludge was assessed in order to evaluate the recovery of by-products, such as nutrients, organic matter as a source of bioenergy, volatile fatty acids, and water. Also, to reduce the amount of solids to be disposed of, and the total management costs. Sludge 1 was from conventional activated sludge, and Sludge 2 was from a sequential batch reactor set for biological phosphorus removal. In the laboratory three different fermentation processes were provided in parallel, firstly treating Sludge 1, followed by Sludge 2. Treatment A was set as the control, wherein the fermentation process occurred without alkali addition, Treatment B was alkaline fermentation with a controlled pH 10 of pre-solubilized sludge; and Treatment C was alkaline fermentation at a controlled pH 10. The results indicated that alkaline fermentation significantly reduced the volatile suspended solids to 45-50 %, which was improved for both sludges when pre-solubilized, to 59-60 %. Also, comparing the biogas production test of Treatment A to the other conditions set, both increased almost 4, and 3 times, for B and C, respectively. Orthophosphate, chemical oxygen demand, carbohydrates, and proteins in soluble fractions significantly increased under alkaline fermentation in comparison with the control, and all of these parameters were boosted with pre-solubilization.