Patent ID: 7544299

Claim:
A method for the biological treatment of a liquid in a single reactor basin containing an activated sludge material, said method comprising the steps of: a. subjecting said liquid to an oxic phase by creating in said reactor basin an oxygen-rich environment and maintaining said oxygen-rich environment until a oxic phase ending criteria has been achieved; b. after said oxic phase endpoint has been achieved, subjecting said liquid to an anoxic phase by creating in said reactor basin a limited oxygen environment and maintaining said limited oxygen environment until an anoxic phase ending criteria has been achieved; c. after said anoxic phase endpoint has been achieved, subjecting said liquid to an anaerobic phase by creating in said reactor basin an oxygen-starved environment and maintaining said oxygen-starved environment until an anaerobic phase ending criteria has been achieved, said anaerobic phase ending criteria selected from the group consisting of: (i) the expiration of the minimum time period for the anaerobic phase and a rate of change of phosphate concentration falling below a pre-set value; and (ii) the occurrence of an anaerobic phase preemptive end criteria, where said anaerobic phase preemptive end criteria is an ammonia concentration of about 5 mg/L or greater or a phosphate concentration of about 3 mg/L or greater; d. And repeating steps a)-c) until a desired level of treatment of said liquid is achieved.