Abstract: The present invention relates to an efficient method of removing nitrogen and producing struvite from nitrogen-rich wastewater. Additionally, the present invention provides an economical method of removing nitrogen while producing a large quantity of struvite from nitrogen-rich wastewater with an appropriate usage of a solution containing phosphorus ion and a solution containing magnesium ion and/or calcium ion.

Abstract: The present invention provides 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 a 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) injecting 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 without addition of alkaline substance, and then providing proper pH of 8.4 to 9.6 to form struvite.