Improving the efficiency of wastewater treatment by the method
of activated sludge enrichment with nitrifying bacteria

Summary

Ammonium concentration in effluent is one of the most important indicators of biological wastewater treatment efficiency. Ammonium oxidation to nitrates (nitrification) is executed by nitrifying bacteria characterized by low growth rate and high sensitivity to some adverse technologic factors (e.g. low oxygen concentration, toxicants). To provide for stabilizing the number of nitrifying bacteria, increasing their activity in bioreactors with activated sludge and improving the efficiency of removing nitrogen compounds from wastewater different processing technologies are used. One of them is bioaugmentation (inoculation of essential microorganisms or arrangement of conditions for their evolution with the purpose of improving the specific activity of biosystem, e.g. activated sludge). The specialists of R&D Centre of «Mosvodokanal» JSC studied the efficiency of nitrification process in an installation working after the process flow scheme developed in the University of Cape Town in combination with an additional bioaugmented reactor. In the reactor activated sludge is being enriched with nitrifying bacteria. At increased ammonium load simulated by adding liquid phase of digested sludge the main process line did not provide for reducing ammonium to the maximum permissible concentration of pollutants in fishery water bodies. The use of bioaugmented reactor allowed reducing ammonium concentration (N–NH4) from 40–50 to 0.4 mg/l. With that the resistance of nitrifying bacteria of activated sludge to toxicants (thiourea) showed no increase. However with the availability of a bioaugmented reactor the inhibiting effect was somewhat abated.

Key words

wastewater , biological treatment , nitrification , bioaugmentation , scheme of the University of Cape Town , bioaugmented reactor