Effective removal the colloid,quasi-colloid particles of surface waters and sewages (chemical pre-treatment of wastewaters) requires coagulation-flocculation processes and traditional solid-liquid phase separation (sedimentation,flotation,sand filtration).The destabilisation of colloid,quasi-colloid dispersions depends on the transformation of three-valent metal ions (Al3+,Fe3+) into metal-hydroxides and connection processes with particles of surface waters and wastewaters.