Patent ID: 7842186

Claim:
A method of treating wastewater containing phosphorus and/or nitrogen for removing phosphorus and/or nitrogen from the wastewater, including following steps of: (a) introducing wastewater containing phosphorus and/or nitrogen into an anaerobic reactor, treating the introduced wastewater with anaerobic microorganisms, to produce biogas from organic matters in the wastewater, and then discharging the treated wastewater saturated with carbon dioxide under carbon dioxide partial pressure of 0.2 to 0.5 atm; and (b) introducing the treated wastewater of step (a) into a carbon dioxide stripping apparatus wherein the wastewater is free-fallen to expose the wastewater to ambient condition with carbon dioxide partial pressure of less than 0.001 atm so that carbon dioxide stripping takes place and increase in pH occurs, and then providing proper pH of 8.4 to 9.6 to form struvite, and at least one compound selected from the group consisting of magnesium containing compounds, phosphate containing compounds, and ammonium nitrogen are additionally injected before or during step (b).