AbstractPurification of waste water containing ammonia – Comparison of proces and costs.The present case study compares three processes for reduction of ammonia in liquid effluents with respect to process engineering and treatment costs: stripping with steam, stripping with air, and liquid membrane technology. The specific purification costs are estimated for plant capacities between 1 and 50 m3/h, for NH3feed concentrations between 50 and 2000 ppm, and for waste water feed temperatures between 5 and 80ßC. Moreover, the NH3exiting concentration is varied between 1 and 500 ppm. In the standard case, the estimates are based on a decrease to 5 or 50 ppm NH3in the waste water. Two cases are considered: in one, it is assumed that the ammonium sulphate solution produced by all three processes must be evaporated down to a disposable form. Alternatively, it is assumed that the ammonium sulphate can be used without further work