EFFECTS OF DIRECTLY SOLUBLE AND FIBROUS RAPIDLY ACIDIFYING CHEMICAL OXYGEN-DEMAND AND REACTOR LIQUID SURFACE-TENSION ON GRANULATION AND SLUDGE-BED STABILITY IN UPFLOW ANAEROBIC SLUDGE-BLANKET REACTORS

In recent years, it has become clear that the rapidly acidifying chemi cal oxygen demand (RACOD) content of the waste water and the surface t ension of the reactor liquid contribute to the phenomenon of granular growth in upflow anaerobic sludge-blanket reactors (UASB). By adding 2 0% of directly soluble RACOD, in the form of a sucrose;starch mixture, on top of the original COD load and by adjusting the reactor liquid s urface tension below 50 mN m(-1) with linear alkylbenzenesulphonate, g ranular growth and sludge-bed stability could be enhanced significantl y within 40 days, Carrot pulp, a waste product having a high short-cha in fatty acid precursor potential, was applied as an alternative fibro us RACOD source. Best results were obtained when adding the carrot pul p freshly to the laboratory-scale UASB reactor in an in-recycle liquef ying chamber. This concept of adding carrot pulp waste product as a gr anular growth supplement by means of an in-recycle liquefying chamber therefore merits testing in practice.