Summary:

Biological methods have always played an important role in sludge treatment technology. Biological treatment may be conducted in various ways, in many cases as activated sludge method. Currently the processes and factors affecting efficient elimination of pollutants from municipal wastes have been relatively well identified. On the other hand the situation is different for industrial sludges. Efficiency of industrial sludge treatment plant depends mainly on physicochemical properties of sludge inflowing from individual enterprises. The work aimed at identification of sugar industry waste composition in view of its susceptibility to the processes of biological treatment, mainly removal of nitrogen compounds. The subject research was conducted in a laboratory model of bioreactor composed of an anoxic chamber where the denitrification process was conducted and aerated tank with a built-in secondary settlement tank in which nitrification process was taking place. Analyzed were sugar-mill wastes supplied from a factory and sewage treated in the analyzed model. Conditions in both chambers of the model treatment plant were monitored during the investigations. Activity of the activated sludge and the course of nitrification and denitrification processes were determined using OUR, AUR and NUR tests. The analyses have revealed that sugar wastes composition is variable in time and dependant on the production process realized in the factory. The variability may negatively affect the future treatment plant operation, particularly the course of nitrification process. It has been also demonstrated that the analyzed sewages are susceptible to biological decomposition because they contain a considerable proportion of organic substance undergoing biodegradation (92% of the total COD). A considerable content of the degradable substance in raw sewage is advantageous for the proper course of denitrification process. Problems with proper course of nitrification process, caused mainly by the composition of inflowing sewage, were observed during the experiment. Periodical presence of surface-active substances and fats in sewage caused a development of thread bacteria and accompanying activated sludge swelling. Maintaining long sludge age (on average 17days) caused the sludge stabilization as has been evidenced by low value of OUR test equaling 7.77 mgO₂ · gsm^-1·h^-1. Due to periodical maximum loading of the sludge by ammonium nitrogen, nitrification process was unstable (mean nitrification rate was 0.67 mgN-NO₃ ·gsm^-1·h^-1) whereas maintaining long sludge age and high oxygen concentration in the aerated tank might be the cause of low nitrification rate (0.52 mgN-NO₃ ·gsm^-1·h^-1) and small participation of denitrifying bacteria in the system (19% of all microorganism populations). Despite these operational problems a satisfactory reduction of ammonium nitrogen (61%) and total nitrogen (64.8%) from the sewage was obtained.