A process for recovering inorganic potassium salts from at least one substrate that is at least partially accessible to an anaerobic and/or aerobic treatment, the process comprising at least the following steps (a), (b), (c), (d), (e) and (f), i.e., a preliminary cleaning comprising the steps (a), (b) and (c): (a) separating solids contained in the at least one substrate that is at least partially accessible to an anaerobic and/or aerobic treatment, (b) removing, by means of stripping, nitrogenous compounds contained in the at least one substrate that is at least partially accessible to an anaerobic and/or aerobic treatment, wherein before performing the stripping the pH value of the substrate is set to a pH value > 9 by addition of at least one inorganic alkaline potassium salt, and (c) anaerobically and/or aerobically treating the substrate that is at least partially accessible to an anaerobic and/or aerobic treatment, wherein the order of the steps (a), (b) and (c) is variable, and a pre-cleaned mixture is obtained after performing these steps (a), (b) and (c), (d) treating the pre-cleaned mixture obtained after performing the preliminary cleaning steps (a), (b) and (c) by means of nanofiltration, thus obtaining a concentrate and a permeate, (e) treating the concentrate obtained according to step (d) by means of electrodialysis, thus obtaining a concentrate (E1-K) and a diluate (E1-D), and treating the permeate obtained according to step (d) by means of electrodialysis, thus obtaining a concentrate (E2-K) and a diluate (E2-D), and (f) treating the concentrates (E1-K) and (E2-K) obtained according to step (e) after at least partially reducing the concentrates in each case independently of one another by means of crystallization, wherein step (f) is optionally repeated once or several times in each case, in order to recover inorganic potassium salts respectively contained in the concentrates (E1-K) and (E2-K) that are different from the inorganic alkaline potassium salts used in step (b), characterised in that the inorganic potassium salts obtainable according to step (e) and contained in the concentrates (E1-K) and/or (E2-K) and/or the inorganic potassium salts respectively obtainable according to step (f) are used for the electrolytic production of the inorganic alkaline potassium salts used in step (b). (a) separating solids contained in the at least one substrate that is at least partially accessible to an anaerobic and/or aerobic treatment, (b) removing, by means of stripping, nitrogenous compounds contained in the at least one substrate that is at least partially accessible to an anaerobic and/or aerobic treatment, wherein before performing the stripping the pH value of the substrate is set to a pH value > 9 by addition of at least one inorganic alkaline potassium salt, and (c) anaerobically and/or aerobically treating the substrate that is at least partially accessible to an anaerobic and/or aerobic treatment, (d) treating the pre-cleaned mixture obtained after performing the preliminary cleaning steps (a), (b) and (c) by means of nanofiltration, thus obtaining a concentrate and a permeate, (e) treating the concentrate obtained according to step (d) by means of electrodialysis, thus obtaining a concentrate (E1-K) and a diluate (E1-D), and treating the permeate obtained according to step (d) by means of electrodialysis, thus obtaining a concentrate (E2-K) and a diluate (E2-D), and (f) treating the concentrates (E1-K) and (E2-K) obtained according to step (e) after at least partially reducing the concentrates in each case independently of one another by means of crystallization, wherein step (f) is optionally repeated once or several times in each case, in order to recover inorganic potassium salts respectively contained in the concentrates (E1-K) and (E2-K) that are different from the inorganic alkaline potassium salts used in step (b),