What type of pollutants can be present in rainwater?

Harvested Rainwater can be used for several purposes including drinking. Before the rainwater is harvested, it may come in contact to several surfaces and materials. In general, the following types of pollutants can be found in rainwater:

• Gross Pollutants – These pollutants virtually harbor other pollutants such as various chemicals and micro-organisms that are carried by surface runoff from the catchments. Some examples of gross pollutants are listed:
  • Litter
  • Plant Debris
  • Float-able Materials
• Sediments – Sediments are common components of rainwater collected from any surface. Sediments act as vehicles for other pollutants such as heavy metals and hydrocarbons etc. Major sources of sediments are:
  • Construction Sites
  • Roadways
  • Parking Lots
  • Industries
  • Areas with exposed soils
• Oil & Grease – Oils & Grease include a wide range of organic compounds. Sources of such pollutants include:
  • Catchment Surfaces that have been exposed to leaks and breaks in machines or appliances.
  • Catchment Surfaces that are exposed to kitchen waste, waste oil.
  • Catchment Surfaces that have been exposed to cleaning and maintenance of machines.
• Nutrients – Nitrogen & Phosphorus are often found in rainwater collected from any roof. The presence of these nutrients on roofs is due to deposition of particulate matters that are generated by automobile emissions, industrial processes, etc. The presence of these nutrients is harvested rainwater is beneficial for using in lawn irrigation.