Abstract: A process for the treatment of cooling waters, particularly in thermal power stations, without or--optionally--with partial acid decarbonization of the make up water, the improvement wherein the make up water is mechanically coarse-clarified and the hardness is then stabilized with scale inhibitors. The scale inhibitors are then removed from the blow down and are optionally recovered.

Abstract: Preventing corrosion and scale formation in water re-circulating systems by adding to the water to be circulated from about 5 to 100 g/m.sup.3, based on the weight of the water to be circulated, of a compound selected from the group consisting of those of the formula ##STR1## and the water-soluble salts thereof and then circulating said water in said system, R being hydrogen, alkyl, alkenyl or alkinyl having up to 4 carbon atoms; phenyl; cycloalkyl having 3 to 6 carbon atoms; benzyl; phenethyl or ##STR2## wherein R' is hydrogen, alkyl having 1 to 4 carbon atoms or carboxyl, R" is hydrogen or methyl and R'" is carboxyl.

Abstract: Preventing corrosion and scale formation in water re-circulating systems by adding to each cubic meter of the water being re-circulated from about 5 to 100 grams of a compound selected from the group consisting of those of the formula ##EQU1## and the water-soluble salts thereof R being hydrogen, alkyl, alkenyl or alkinyl having up to 4 carbon atoms; phenyl; cycloalkyl having 3 to 6 carbon atoms; benzyl; phenethyl or ##EQU2## wherein R' is hydrogen, alkyl having 1 to 4 carbon atoms or carboxyl, R" is hydrogen or methyl and R'" is carboxyl.