Process to avoid the formation of black spots on the walls of the underground water basins

摘要

New method to prevent the formation of black marks on the sides of sunken basins contg. water contaminated by copper ions comprises treatment with a metal sulphide with a solubility in water at least equal to that of copper sulphide. Pref. the metal sulphide is a sulphide of Cd, Pb, Co, Ni, Zn, Fe or Mn, pref. Zn. The water in the basin is circulated over a bed of particles contg. the metal sulphide in the presence of a flocculating agent (a mixture of aluminium hydroxide and aluminium chloride). The method is used for basins coated with a water-proof membrane, pref. plasticised PVC.