Anaerobic codigestion of agricultural industries' wastewaters

Abstract

Wastewaters generated from agricultural industries are usually hard to treat due to a high organic content. The basic treatment process to be used can only be anaerobic digestion, a process with the additional advantages of (i) limited production of stabilized sludge and (ii) utilization of the produced biogas. The cotreatment of such seasonally produced wastewaters is proposed in order to secure the economically favorable and stable year-round operation of a treatment plant, with the additional benefits of smaller capital costs (due to the use of centrally located rather than distributed treatment facilities) and the exploitation of complementarity in waste characteristics (e.g. avoidance of nutrients (N,P) addition when a codigested wastewater contains nutrients in excess). A mathematical model for codigesting piggery, olive-mill and dairy wastewaters was developed based on batch kinetic experiments. An organic loading rate of 3.84 g COD/l·d was found to be safe for a digester operating on a year-round basis, fed sequentially with piggery, piggery-olive-mill and piggery-dairy wastewaters.