The presented report deals with the characterization and optimization of coagulation of wastewater effluent from three wastewater treatment plants – Podlázky WWTP, Kvasiny WWTP and Solnice WWTP, which are to serve as a source of raw water for process water production for Škoda auto, as. The report is designed as a basis for implementation of pilot tests and subsequent design of the technological line of the planned water treatment plant, where coagulation and subsequent separation of the suspension by flotation is planned as the first stage of water treatment.