MATHEMATICAL MODEL OF THE ASSOCIATED PROCESSES OF DENITRIFICATION AND RENEWAL OF SULFATES IN AN INNOVATIVE BIOFILTER

The problem of pollution of underground water sources with nitrates, as well as geogenic compounds (sulfates, hydrocarbonates) is of interest to researchers around the world. Nitrates represent a particular risk to the health of the population living in places without centralized water treatment. In this case, post-treatment of water at the point of use is recommended using both technologies for the removal of nitrates from treated water and their biological conversion into nitrogen. Without downplaying the role of the former, the latter technologies are seen as promising, requiring research and improvement. The purpose of the work is to study the process of nitrate biotransformation in a small submersible biofilter in the presence of basic groundwater anions (sulfates and hydrocarbonates) and their effect on the quality of treated water. The shift of sulfate-sulfide balance in aquatic environment of the biofilter and the influence of the concentrations of sulfate ions and the substrate of bacterial nutrition on the accumulation of hydrogen sulfide and its consumption in the volume of the biofilter have been studied. It is shown that the processes of denitrification and reduction of sulfates to hydrogen sulfide proceed sequentially. The reduction of sulfates to hydrogen sulfide begins after the removal of nitrates from the treated water at a dosage of the nutrient substrate that exceeds the stoichiometric requirement for denitrification. Hydrogen sulfide, which is formed in the zone of connection of inlet and outlet knees of the biofilter, is practically not detected at its outlet. The reduction of sulfates associated with the removal of nitrates can be a useful tool for additional treatment of water from impurities of heavy and polyvalent metal ions.