Rain water must be stored in ...

Rain water must be stored in closed tanks away from sunlight and atmosphere, leave small vents just to air the tanks, the problem seems to be primarily linked to biofilm formation, this is a frequent issue if the rainwater is stored without pretreatment, surface runoffs do collect some biomass and pathogens, generally originating from avian faecal matter and other organic entrapments in the gutters, You may use bioswale based filtration methods using Rigofill-ST based tanks as receptacles or use Sedipipe/Sedipoint flow separation technology to prevent the fine particles from entering the storage tanks. In some parts of western India, people use rainwater for several months for drinking after storage in beri, khoe and tanka systems.