Simultaneous Anoxic Biological Phosphorus and Nitrogen Removal with Energy Recovery

A method for treating a wastewater stream while recovering energy, the method comprising:

• providing the wastewater stream in a pretreatment tank that comprises anaerobic microorganisms that react with the wastewater stream removing carbon to produce biogas and a pretreated stream, wherein the biogas comprises at least methane and carbon dioxide;
• upgrading the biogas produced by removing a majority of the carbon dioxide;
• using the upgraded biogas to generate electric power to offset part or all of electric power used at a water treatment plant that is treating the wastewater stream;
• and
• flowing the pretreated stream to an anoxic tank operating under anoxic conditions.

A system for treating wastewater to simultaneously remove organic matter, nitrogen, and phosphorus with energy recovery, the system comprising:

• a pretreatment tank that receives plant influent wastewater and that comprises anaerobic microorganisms that react with the plant influent wastewater to produce, at least, biogas comprising methane, excess sludge, and a pretreated stream;
• an anoxic tank that receives the pretreated stream and return activated sludge and mix them to form a mixed liquor;
• an aerated tank that receives the mixed liquor from the anoxic tank, wherein the aerated tank operates under microaerophilic conditions, to simultaneously effectuate nitrification, denitrification, phosphorous release, and phosphorus uptake in the aerated tank;
• and
• a membrane tank that separates plant effluent wastewater from activated sludge, a portion of which is recycled to the anoxic tank as the return activated sludge.