TECHNOLOGY FOCUS - ENVIRONMENT - Preferred Method: In increasing the specific growth rate of anaerobic, autotrophic microbes in the wastewater treatment system, the microbes are Anammox bacteria or methanogens. The optimal control value is established a mathematical equation given in the specification. The soluble CO2 concentration of the wastewater in the aeration tank is adjusted by passing the wastewater through CO2 stripping equipment, or by passing return activated sludge through CO2 stripping equipment. Alternatively, increasing the specific growth rate of anaerobic, autotrophic microbes in the wastewater treatment system comprises: optimizing soluble CO2 further comprising: establishing an optimal control value for the soluble CO2 concentration for wastewater; measuring the concentration of gaseous CO2 for the wastewater where the gaseous CO2 concentration is in equilibrium with reactor contents; comparing the measured concentration of gaseous CO2 against the optimal control value; and adjusting the measured concentration of gaseous CO2 to match the optimal soluble CO2 control value; where optimizing the soluble CO2 increases the specific growth rate of the bacteria. In treating wastewater for BOD and nitrogen removal, the step of optimizing CO2 content of the wastewater further comprises: establishing an optimal control value for soluble CO2 concentration for the wastewater effluent in the first aeration basin where the optimal control value is established by a mathematical equation given in the specification; measuring a concentration of soluble CO2 for the wastewater effluent in the first aeration basin; comparing the measured concentration of soluble CO2 in the waste water effluent in the first aeration basin against the optimal control value; and adjusting the soluble CO2 concentration in the first aeration basin to match the optimal soluble CO2 control value. The soluble CO2 concentration of the wastewater effluent in the first aeration basin is adjusted by passing the effluent through a CO2 stripping process, or adjusted by passing return activated sludge through a CO2 stripping process. The second aeration basin is an ammonium oxidizing bacteria (AOB) reactor, where the AOB reactor has a pH of at least about 8. The anaerobic reactor is an Anammox reactor, where anaerobic conditions are maintained in the Anammox reactor by internally recycling Anammox effluent to Anammox influent. The anaerobic conditions are maintained in the Anammox reactor by flowing about 1% of primary solids or raw wastewater into the Anammox reactor. Alternatively, treating wastewater for BOD, nitrogen and phosphorus removal comprises: flowing a volume of wastewater through a primary clarifier where phosphorus is removed by allowing the wastewater to occupy the primary clarifier for a sufficient hydraulic residence time (HRT); optimizing CO2 content of at least a portion of primary effluent exiting the primary clarifier; flowing effluent from steps (a) and (b) to an aerobic basin to remove BOD; adding nitrite to the effluent from step (c); flowing the effluent from step (d) into an anaerobic basin; flowing the effluent from step (e) into a secondary clarifier; and recycling at least a portion of wastewater in the secondary clarifier to provide return activated sludge to the primary clarifier. In treating sludge, the gaseous CO2 concentration in the headspace is adjusted by stripping CO2 from the biogas. The method further comprises gas-mixing the contents of the at least one anaerobic digester using the lower CO2 biogas. Preferred System: The wastewater treatment system further comprises a recycling zone where at least a portion of wastewater in the anaerobic treatment zone is recycled to re-enter the aerobic treatment zone. Alternatively, the wastewater treatment system comprises: a CO2 stripping zone; at least one anaerobic treatment zone where the anaerobic treatment zone is positioned downstream from the CO2 stripping zone; and an aerobic treatment zone where the aerobic treatment zone is positioned between the CO2 stripping zone and the at least one anaerobic treatment zone. The system further comprises a recycling zone where at least a portion of wastewater in the anaerobic treatment zone is recycled to re-enter the anaerobic treatment zone; and a recycling zone where at least a portion of wastewater in the anaerobic treatment zone is recycled to re-enter the CO2 stripping zone.