Apparently it's for prevention of fouling: > Combined low concentrations of copper (5 μg/l and chlorine (50,μg/l have been effective in preventing both micro a

Apparently it's for prevention of fouling: > Combined low concentrations of copper (5 μg/l and chlorine (50,μg/l have been effective in preventing both micro and macro-fouling in over 120 seawater installations since 1987. https://www.researchgate.net/publication/242186534_FOULING_PREVENTION_IN_DESALINATION_PLANTS1 https://www.researchgate.net/publication/242186534_FOULING_P...