Practitioners Of Sustainability


Uses for non-potable 'green' water might include:

  • Swimming baths
  • Laundries
  • Toilet Flushing
  • Parks & Irrigation
  • Sewer Jetting
  • Public Area Cleansing
  • Heating/Cooling cycles for Buildings

Green Water

Green Water is a generic description for water that has been treated to a quality suitable for provision as a non-potable supply, usually, but not exclusively in parallel with a potable supply, for industrial, residential or public use (examples might include toilet flushing, horticultural/irrigation purposes, laundries, industrial processes or washing, heating/cooling functions.)

[Green water’ is sometimes mistakenly referred to as ‘grey’ water. This should not be the case – ‘grey’ water is untreated wastewater from baths, basins and showers. Green water is treated.]

The Green Water “Standard” has the following characteristics:

  • is clear (<2NTU), free of pathogens (<10cfu/100ml), and conforms to criteria for tertiary treatment, typically < 10mg/l BOD, < 10mg/l Suspended Solids and < 5mg/l NH3
  • should be clearly identified as a separate supply, not for human consumption, by the use of a green tinged vegetable dye at a specified dilution (1:20,000)
  • Rainwater and storm run-off water, when blended with treated water from other derivation would also qualify as ‘green water’ when treated to the Green Water “Standard”.

Potable water is provided for the purpose of drinking and must meet all the Drinking water Quality Regulations. Private supplies of Green water to more that a single household are regulated by Local Authority Environmental Health Departments. They have a requirement to sample the water at a specified frequency.

Non-potable Green Water is not yet regulated in the UK and can be treated (or not) to meet specific end-use. There is a Duty of Care by agreement between the supplier and the provider of a service (e.g. the Local Authority) to ensure that the agreed standard is complied with.

The Green Water is distributed through distinct green pipe work developed by AWS which cannot be inadvertently connected with the drinking water system.

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