Contaminants will be predominately pathogens and organic chemicals. Biological pathogens may include fungi, cysts such as Giardia and Cryptosporidium, bacteria and viruses. Naturally occurring organic chemicals are predominantly tannins from vegetation in gutters. Synthetic organics are pesticide overspray and air pollution. Inorganic chemicals can be from dust and roofing /tank materials such as zinc, copper, and lead solder.
Treatment methods should be preceded by a first flush system directing initial rain flows to drain.
Treatment solutions may include coarse filtration, sub micron filtration, organic reduction and disinfection. Inorganic contamination will usually be addressed through first flush and correct materials choice.
Typically applied technologies include:
Coarse filtration - self cleaning screens or bag filter or cartridge filter
Fine filtration - self cleaning ultrafilter or 1 micron cyst rated cartridge
Organic reduction - activated carbon, anion resin
Disinfection – chlorine, ozone, ultraviolet irradiation