CHARACTERIZATION OF SPHAEROTILUS NATANS GROWTH IN A MODEL WASTEWATER SYSTEM OF A POTATO PROCESSING PLANT

CONTRERAS E.; GIANNUZZI L.; ZARITZKY N.

Veldhoven, Holanda

Congreso; Seventeenth International Conference of the International Committee on Food Microbiology and Hygiene; 1999

Food processing industries usually discharge large volumes of wastewater characterised by high chemical oxygen demand or biological oxygen demand, large amounts of total suspended solids and various inorganic constituents including nitrogen and phosphorous. The high organic load in the processing wastewater creates a serious pollution problem. The activated sludge process is a widely used method for treating industrial and domestic wastewater. One of the most common and serious problems in the operation of activated sludge plants is the inability to separate solids from treated effluents in the clarifiers. One particular solid separation problem, known as bulking, is caused by excessive growth of filamentous microorganisms. Sphaerotilus natans has long been associated with activated sludge bulking and has been studied extensively. Bulking by S. natans has been attributed to several factors such as low dissolved oxygen in the aeration basin, treatment of wastes with high carbon to nitrogen (C:N) ratios and phosphorus limitation (Jenkins, 1992; Jenkins et al., 1993; Wanner, 1994). It is better to prevent filamentous organisms in activated sludge than to eliminate them after they have become established. To prevent bulking in activated sludges, the growth kinetics of the causative organisms should be known. In case of S. natans, available data are limited to systems containing glucose as carbon source (Richard et al., 1985). However, composition of many food industry wastewaters are quite different from this. In a previous work, a model system of a typical potato processing  plant wastewater was analysed showing that citric acid was the main carbon source  (Contreras et al., 1999). The objective of the present work was to study the effect of pH on the maximum specific growth rate  (mmax), biomass yield (Yx/s) and substrate oxidation coefficient (YO/S) of Sphaerotilus natans in a culture medium with citric acid as sole carbon source.