Bioaugmentation for nitrification at cold temperatures

Bioaugmentation of nitrifying bacteria for short solids retention time (short-SRT) nitrification is an attractive alternative for wastewater treatment plants in cold climates or for those in the process of upgrading to include nitrification. One possible source of ammonia for the production of nitrifying bacteria is the liquor generated during the dewatering of anaerobically digested sludges. The objectives of this study was to determine the impact of sudden decrease in temperature on nitrification rates and to determine if nitrification could be accomplished in sequencing batch reactors (SBRs) at 10°C by seeding nitrifying bacteria acclimated to 20°C. In this research, biomass produced during warm nitrification of dewatering liquor was seeded into cold SBRs at various hydraulic retention times from 43.3 to 96 h. The average decreases in nitrification rates were 58%, 71% and 82% for biomass cooled to 10°C when the biomass was acclimated to 20°C, 25°C and 30°C, respectively. The seeded SRTs of the cold SBRs were raised above the minimum solids retention time (SRTmin) required for nitrification. Full ammonia nitrogen removal was achieved in cold SBRs that were operated at an apparent SRT less than SRTmin.