Abstract: A method and apparatus (1) for the control of biological treatment of waste water in which waste water is fed to a substantially air tight supported growth biological filter unit (2) that includes an exhaust gas vent (5). Dissolved oxygen is supplied to the filter unit and the oxygen consumption rate across the filter is measured by comparing the flow rate of oxygen into the filter (2) to the flow rate of oxygen exiting the filter through the gas vent (5). The feed rate of waste water is adjusted to maintain a predetermined oxygen consumption, thereby controlling the effluent quality.

Abstract: A method for efficiently treating wastewater by aerobic digestion whereby on-site oxygen generating equipment continually provides a predetermined quantity of dissolved oxygen to the wastewater, the dissolved oxygen content being maintained at a predetermined level during peak flows by air being dissolved into the wastewater. The method being used for upgrading the capacity of an existing plant to treat wastewater; increasing the scope of an existing plant to allow removal of biological nitrogen and/or phosphorus; and designing new wastewater treatment plants. Further efficiency is introduced by using methane produced, during subsequent anaerobic digestion of the wastewater, to fuel compressors or the like which provide the air to the wastewater.