- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 18 Feb 2022
Black water recycling
Water is an increasingly scarce resource. As the population increases, and climate change makes rainwater patterns less predictable, it is becoming more important that we reduce the amount of water we consume and discharge into the sewerage infrastructure. In addition, the treatment of water to make it suitable for drinking and other uses consumes a considerable amount of energy. Treating water to make it suitable for ‘drinking’ just to use it for purposes that do not require this level of treatment, such as watering gardens, washing cars or flushing toilets, is extremely wasteful.
Environmental concerns, utilities bills and the imposition of restrictions such as requirements for sustainable urban drainage systems and hosepipe bans mean that people are increasingly looking to re-use or re-cycle water.
- Fresh, potable water or ‘drinking water’ is sometimes referred to as ‘white water’.
- Wastewater from showers, baths, washbasins and washing machines that is not considered to be potentially dangerous is referred to as ‘grey water’.
- Water from toilets that may be contaminated with hazardous material is referred to as ‘black water’ (or sometimes brown water, foul water, or sewage). Some definitions of black water also include water from kitchen sinks, dishwashers and waste disposal units which may contain food particles.
Despite this contamination, black water can be recycled and re-used. Typically this re-use is for applications such as watering landscape (although generally not crops) or for flushing toilets (Ref Thames Water, Recycled Londoners’ sewage keeping Olympic Park green). It is also possible, although expensive, to make black water suitable for drinking.
- Reduce water use.
- Conserve energy and reduce utilities bills.
- Reduce loads on local sewerage systems.
- Contribute to sustainability standards such as LEED.
However, it can be:
- Difficult to manage and maintain.
- There can be perception and stigma issues.
- It requires a separate, clearly identified pipe network.
- Long payback times combined with small storage volumes mean it can be less effective than other water-conservation measures.
It is possible to recycle black water at a domestic scale, but this is not common due to the expense involved, despite the fact that many remote domestic properties already have septic tanks to deal with sewerage locally. Generally, the process is only adopted on larger sites, or for multi-home developments.
Treatment is generally by a process of settlement, bacterial break down, filtration, aeration, and chemical treatment. This can include the use of reed beds. For more information see The Green Age, Recycling Domestic Sewage.
 Related articles on Designing Buildings Wiki
- Flood and Water Management Act.
- Green roof.
- Greywater recycling at the Millennium Dome.
- Hosepipe ban.
- Marine energy and hydropower.
- Passive water efficiency measures.
- Planning for floods.
- Rainwater harvesting.
- SuDS - is there light at the end of the tunnel?
- Sustainable urban drainage systems.
- Types of water.
- Waste water.
- Water consumption.
- Water engineering.
- Water quality.
 External references
Featured articles and news
Myths and top tips.
CLC plans to ease impact of construction inflation.
BG 50 & VDI 2035 – your questions answered.
Will the way we heat homes change when winter comes ?
Can XR technology be leveraged in design & construction?
Or are you capping.
Digital gaming competition for UK students aged 16 to 18.
Heritage protection in England vs Australia.
Three-quarters of fire doors fail inspections
The role of geoparks, biospheres and world heritage sites.
Just one month to go ! Find out more here.
A new gallery for the University of Huddersfield.
What will it take to stop it ?
To celebrate world bee day 2022 !
Not forgetting part F and the new part overheating part O.
As energy prices jump up in cost.
With people in the UK from Ukraine.
Industry leader Steve Murray takes on role.
An abundant and versatile building material.
600,000 heat pump installations targeted per year by 2028.
Helping prevent those unwanted outcomes.