EFFECT OF BIOAUGMENTATION IN STRESSED WASTEWATER TREATMENT SYSTEMS

Achieving efficient and reliable nitrification has become increasingly important to the wastewater industry. Excessive biomass losses due to washouts have adverse effects on nitrification and can slower the already slow growth rates of nitrifiers. In such situation, bioaugmentation with nitrifying bacteria can be used to help recovery and maintenance of nitrification. Bioaugmentation is the process of adding selected strains of microorganisms with known capabilities to wastewater treatment units in order to improve removal efficiencies of organic pollutants. In this study, laboratory scale CSTRs were operated to assess the bioaugmentation with nitrifying bacteria. High stress condition for the nitrifiers was created by increasing the hydraulic loading rate. A bioaugmented CSTR was compared to an uninoculated control. To predict the key trends and to illustrate the effect of addition of biomass on process performance, mathematical modeling was used. Intensive sampling was carried out during the transition period. Both experimental and modeling trends indicated that the maximum effects of a single bioaugmentation was dependent on the dose and the performance decreased as bioaugmented nitrifiers washout confirming the need for maintenance doses. The results suggests a lag period before the bioaugmentation product became completely effective.