An investigation of temperature effects on denitrifying bacterial populations in a biological nutrient removal (BNR) system

The goal of this research was to characterize the effects of temperature changes on the denitrification process in a biological nutrient removal (BNR) system. Specifically, there were three objectives. First, the effects of temperature changes on denitrification rates by a bacterial population from a BNR system were investigated. Next, the role which PHAs (poly-beta-hydroxyalkanoates) played in the denitrification process were examined. Finally, the effect of temperature changes on the production and consumption rates of PHAs was determined.

Sacrificial batch experiments were performed to assess the kinetic and chemical trends present in the denitrification process. Mixed liquor from the last anaerobic zone of a pilot scale BNR system was injected into vials. These vials were pre-purged with nitrogen gas in order to prevent dimolecular oxygen (02) from being entrained in the mixed liquor. Next, the vials were placed on a shaker table for 30 minutes in order to allow all external COD to be consumed. Following this, each vial was injected with nitrates and various macronutrients. This process was repeated for three different sets of batch tests; each set was identical except for the added substrate. One set received no added substrate while the other two received either acetate or glucose. Vials were sacrificed over a period of three hours and analyzed for nitrate, phosphate, PHB (polybeta-hydroxybutyrate), PHV (poly-beta-hydroxyvalerate), glucose and acetate.