Centrate treatment to produce a nitrifying biomass for bioaugmentation

The City of Winnipeg is currently conducting studies to minimize expansion costs for wastewater treatment when upgrading to include nitrification. One of the methods considered is centrate treatment. This study examined treatment of centrate by nitrification in a dedicated reactor. The biomass produced was used as seed for bioaugmentation of cold reactors (10°C) treating synthetic wastewater without nitrification. As a result of seeding, nitrification was initiated in the seeded reactors. The degree to which effluent ammonia nitrogen (NH3-N) was reduced depended on the seed dose and the temperature to which the seed was acclimated. Seed acclimated to warmer temperatures experienced decreases in nitrification rates after suddenly cooling to 10°C.; Based on the results of the seeding, simulation modeling was conducted using BioWin to predict the benefits of seeding nitrifiers into treatment systems with different hydraulic and solids retention times. It was found that, when compared with conventional nitrification systems, producing seed by centrate nitrification could decrease the volume requirements by up to 20%.; Microbial analysis using fluorescence in situ hybridization (FISH) of ammonia oxidizing bacteria showed that the seed was being washed out of the seeded systems inadvertently with the effluent. This observation explained why poor NH3-N removal was achieved when seed was added to SBRs with short hydraulic retention times. The FISH signal associated with ammonia oxidizers correlated well with effluent NH3-N and nitrate-nitrogen (NO3-N) concentrations and the nitrification rate.; Centrate was found to be a suitable substrate for the production and harvest of nitrifying seed. Seed produced at the same temperature as the reactor into which it is to be added provided the greatest benefit.