In the wake of the ever stricter requirements concerning waste water purity, sugar factories have in recent years installed, in addition to existing aerobic facilities, anaerobic systems as the first stage in waste water treatment. To reduce the capital costs of such anaerobic systems, studies have been conducted in the last ten years on the deployment of high-performance systems which occupy only a fraction of the area and volume of conventional contact sludge systems. These studies looked particularly at aspects peculiar to sugar manufacturing, including high calcium levels in the waste water which can lead to incrustations and diffusion problems, startup times which must be brief in view of the short production period, and the rapid changes in effluent composition characteristic of sugar factory waste waters. The findings relating to these aspects are discussed. Further studies had to be carried out on scaling up, following the failure of earlier attempts to realize industrial-scale moving-bed systems because of insufficient consideration of the resulting gradients (e.g. pH value, acid concentration, gas holdup). These involved studies with reactors on a laboratory (up to 30 l) and pilot-plant (1 to 10 m3) scale. The systems and their performance are described, as is the operation of the first industrial moving-bed reactor (500 m3) which was installed in the Clauen sugar factory in 1995.
pdf download: 1996-847-854.pdf