Abstract: Treatment systems are described which uncouple the solids retention time (SRT) of the recycling bacteria from the wasting bacteria. Elevated recycling bacteria SRTs increase concentrations of nitrifying bacteria in the aeration basin and Anammox bacteria in the anoxic basin, improving nitrification and anaerobic ammonium oxidation. Fluorescence in situ hybridizations were used to identify and determine the abundance of nitrifying bacteria and Anammox bacteria (recycling bacteria) in freshly settled sludge of biological nutrient removal (BNR) secondary clarifiers. An uneven distribution was observed for recycling bacteria in two BNR systems. Settling patterns suggest microcolony formation processes are sensitive to the internal recycle rate, which allow for rapid recycling bacteria microcolony growth by increasing circulation of flocs through the aeration and anoxic basins. Uncoupling the SRT enhances aeration and/or anoxic basin utilization and reduces the overall hydraulic residence time.

Abstract: Treatment systems are described which uncouple the solids retention time (SRT) of the recycling bacteria from the wasting bacteria. Elevated recycling bacteria SRTs increase concentrations of nitrifying bacteria in the aeration basin and Anammox bacteria in the anoxic basin, improving nitrification and anaerobic ammonium oxidation. Fluorescence in situ hybridizations were used to identify and determine the abundance of nitrifying bacteria and Anammox bacteria (recycling bacteria) in freshly settled sludge of biological nutrient removal (BNR) secondary clarifiers. An uneven distribution was observed for recycling bacteria in two BNR systems. Settling patterns suggest microcolony formation processes are sensitive to the internal recycle rate, which allow for rapid recycling bacteria microcolony growth by increasing circulation of flocs through the aeration and anoxic basins. Uncoupling the SRT enhances aeration and/or anoxic basin utilization and reduces the overall hydraulic residence time.

Abstract: Fluorescence in situ hybridizations were used to identify and determine the abundance of nitrifying bacteria and Anammox bacteria (recycling bacteria) in freshly settled sludge of biological nutrient removal (BNR) secondary clarifiers. An uneven distribution was observed for recycling bacteria in two BNR systems. Settling patterns suggest microcolony formation processes are sensitive to the internal recycle rate, which allow for rapid recycling bacteria microcolony growth by increasing circulation of flocs through the aeration and anoxic basins. Sludge containing high levels of recycling bacteria are selectively collected and separated from the remaining sludge, uncoupling the solids retention time (SRT) of the recycling bacteria from the wasting bacteria. Elevated recycling bacteria SRTs increase concentrations of nitrifying bacteria in the aeration basin and Anammox bacteria in the anoxic basin, improving nitrification and anaerobic ammonium oxidation.

Abstract: Fluorescence in situ hybridizations were used to identify and determine the abundance of nitrifying bacteria and Anammox bacteria (recycling bacteria) in freshly settled sludge of biological nutrient removal (BNR) secondary clarifiers. An uneven distribution was observed for recycling bacteria in two BNR systems. Settling patterns suggest microcolony formation processes are sensitive to the internal recycle rate, which allow for rapid recycling bacteria microcolony growth by increasing circulation of flocs through the aeration and anoxic basins. Sludge containing high levels of recycling bacteria are selectively collected and separated from the remaining sludge, uncoupling the solids retention time (SRT) of the recycling bacteria from the wasting bacteria. Elevated recycling bacteria SRTs increase concentrations of nitrifying bacteria in the aeration basin and Anammox bacteria in the anoxic basin, improving nitrification and anaerobic ammonium oxidation.

Abstract: A method of stimulating nitrification at low SRT by elevating pCO2 during aeration is disclosed. The improvement on solids settling performance when elevated pCO2 was supplied after 2 hours within the React cycle is consistent with the previous results that identified inorganic carbon as a potential remedy to poor settling and bulking sludge problems in activated sludge systems. Elevated pCO2 increases the concentration of carbon dioxide and lowers the pH, which improve nitrification. The specific growth rate of nitrifying bacteria is sensitive to pCO2, pH, and dissolved oxygen (DO). The DO is a function of the aeration rate. Elevating the pCO2 and lowering the aeration rate provides conditions for nitrification rates that are comparable to conventional systems. However, the lower aeration rate yields significant energy cost savings.

Abstract: A method of stimulating nitrification at low SRT by elevating pCO2 during aeration is disclosed. The improvement on solids settling performance when elevated pCO2 was supplied after 2 hours within the React cycle is consistent with the previous results that identified inorganic carbon as a potential remedy to poor settling and bulking sludge problems in activated sludge systems. Elevated pCO2 increases the concentration of carbon dioxide and lowers the pH, which improve nitrification. The specific growth rate of nitrifying bacteria is sensitive to pCO2, pH, and dissolved oxygen (DO). The DO is a function of the aeration rate. Elevating the pCO2 and lowering the aeration rate provides conditions for nitrification rates that are comparable to conventional systems. However, the lower aeration rate yields significant energy cost savings.