Potable water

Used for consumption, i.e. drinking and food preparation and certain household tasks like showering.

Identifying potable water is based on three categories:

  1. Physical
    1. Physical and chemical parameters include heavy metals, trace organic compounds, total suspended solids, and turbidity.
    2. Physical parameters affect the aesthetics and taste of the drinking water and may complicate the removal of microbial pathogens.
  2. Chemical
    1. Physical and chemical parameters include heavy metals, trace organic compounds, total suspended solids, and turbidity.
    2. Chemical parameters tend to pose more of a chronic health risk through buildup of heavy metals although some components like nitrates/nitrites and arsenic can have a more immediate impact.
  3. (micro-)Biological
    1. Microbiological parameters include coliform bacteria, E. coli, and specific pathogenic species of bacteria (such as cholera-causing Vibrio cholerae), viruses, and protozoan parasites.
    2. Originally, fecal contamination was determined with the presence of coliform bacteria, a convenient marker for a class of harmful fecal pathogens. The presence of fecal coliforms (like E. Coli) serves as an indication of contamination by sewage.
    3. Additional contaminants include protozoan oocysts such as *Cryptosporidium sp.*, Giardia amblia, Legionella, and viruses (enteric).
    4. Microbial pathogenic parameters are typically of greatest concern because of their immediate health risk.

Clean water

Used for certain household tasks like flushing the toilet and washing dishes and irrigation (edible plants, like leafy greens).

This is mostly rain water or very clean (!) river water. When in doubt, treat river water as greywater.

Greywater

Used for irrigation (trees, perennials, …) and certain household tasks like cleaning and laundry.

Greywater usually contains some traces of human waste and is therefore not free of pathogens. The excreta come from washing the anal area in the bath and shower or from the laundry (washing underwear and diapers).

The quality of greywater can deteriorate rapidly during storage because it is often warm and contains some nutrients and organic matter (e.g. dead skin cells), as well as pathogens.

Stored greywater also leads to odour nuisances for the same reason.

Blackwater

Used for nothing as it should be treated before anything.

Any water that is contaminated with fecal matter is considered blackwater.