The present invention relates to a process for treating a wastewater comprising an ammonium ion species and a phosphorus ion species. The process comprises the steps of: (i) treating the effluent in a first stage of the process to convert the phosphorus to a phosphorus-containing salt; (ii) treating the wastewater in a second stage of the process to convert the ammonium ion species to gaseous ammonia; (iii) removing the struvite and/or other phosphorous containing salts from the effluent; and (iv) removing the gaseous ammonia from the wastewater.