A process for utilizing the material of ammonium-containing effluent which contains further soluble constituents and, possible additional solids, comprising: a) optionally separating off the solids, b) concentrating the substantially solids-free ammonium-containing effluent to give an aqueous concentrate having an increased content of ammonium and additional soluble constituents, with simultaneous recovery of substantially ammonium-free pure water, c) precipitating ammonium as magnesium ammonium phosphate from the ammonium-containing aqueous concentrate, and d) separating off precipitated magnesium ammonium phosphate with recovery of substantially ammonium-free residual concentrate which at least partially contains the further soluble constituents.