NOVELTY - The municipal wastewater purification comprises anaerobic biological purification of the wastewater by using a biomass (15-100 g/l) from psychrophilic microorganisms, concentrating the sludge by separating the wastewater and feeding back the sludge into the anaerobic biological purification. The psychrophilic microorganisms exhibit an optimum temperature of less than 25degreesC. The anaerobic purification takes place as single- or two-step methanization process. The biomass is suspended in the wastewater and is immobilized in a bioreactor (111).    USE - For purifying municipal wastewater. The psychrophilic microorganisms are useful for the production of biogas in the wastewater purification and for anaerobic biological wastewater purification (claimed).    ADVANTAGE - The wastewater purification shows slight temperature sensitivity and high purification effectiveness in the dismantling of organic impurities.    DETAILED DESCRIPTION - The municipal wastewater purification comprises anaerobic biological purification of the wastewater by using a biomass (15-100 g/l) from psychrophilic microorganisms, concentrating the sludge by separating the wastewater and feeding back the sludge into the anaerobic biological purification. The psychrophilic microorganisms exhibit an optimum temperature of less than 25degreesC. The anaerobic purification takes place as single- or two-step methanization process. The biomass is suspended in the wastewater and is immobilized in a bioreactor (111). The sludge is concentrated through micro filtration by means of rotation disk filters. Phosphorus precipitates and nitrogen are eliminated from the wastewater after the supply into the anaerobic biological purification. The nitrogen elimination takes place via exchange of the ammonium nitrogen at the zeolite. The zeolite loaded with ammonium-nitrogen is regenerated with regeneration solution. The ammonium-nitrogen is removed from the regeneration solution through air stripping and ammonia is received from the solution. The regeneration solution is again used partly after the air stripping for the regeneration of the zeolite.    INDEPENDENT CLAIMS are included for:    (1) a procedure for the production of biogas from wastewater; and    (2) a device for the anaerobic biological purification of wastewater.    DESCRIPTION OF DRAWING(S) - The figure shows a device for the anaerobic biological purification of wastewater:    Bioreactor (111); (110)    Discharge opening; (113)    Micro filtration device; (120)    Supply inlet. (121)