Anaerobic purification of brewery wastewater in biofilm reactors with and without a methanation cascade

Abstract

A laboratory scale anaerobic treatment process for brewery wastewater has been investigated. It utilised a continuously stirred tank (CST) acidification reactor (11.3 1) plus an anaerobic treatment system which consisted of either a downflow stationary fixed film (DSFF) reactor (20.7 1) or a DSFF reactor in series with a floc (FLOC) or sludge blanket reactor (20.8 1). At the same residence time the combination of DSFF and FLOC reactor performed better than a single methane digester. Using low and high strength wastewater, degradation yields of 80-90% were obtained at total loading rates BR,COD up to 10 kg COD m−3 × d and a residence time t less than one day. Mean values of methane yield were 0.31 m3STP kg-1 COD or 2.91 m3STP m−3 × d. Inert support media investigated consisted of inorganic materials such as porous Kerapor 1000 and glass sponge (Siran) with macro- and micropores or polyurethane foam (Filtren TR 30) with an open net structure. In all cases SEM showed appropriate surface characteristics for microbial attachment. After 4 months of operation biofilm thickness on inorganic support media was 0.4-0.9 mm at a superficial linear velocity (SLV) of 10-5 mm min−1. Under these conditions biofilm on Filtren TR 30 was noticeably thicker (up to 2 mm). Concerning metal contamination of biofilm on Filtren TR 30, Al, Fe and Zn showed elevated levels above 2000 ppm.