Africa Energy Indaba

Grey Water Recycling

Re-use of recovered water

Grey Water Recycling refers to water that is recovered as a by-product of cleaning and other uses in the building and then reused in the same functions or other purposes like garden irrigation.

Care must also be taking to ensure that the recycled water does not contain harmful toxins that may present a health and safety risk to your building users and the environment. These contaminants typically include bacteria, suspended and/or, dissolved solids, acids, alkalises and synthetic bacteria. The Water Act in South Africa (1998), states that it is illegal to discharge contaminated wastewater to the sewerage and storm water systems.

The Grey Water recycling system is made up of one or more tanks that includes a filtration system. The size is dependent on what process is needed to recycle the water and how much water can be recycled. Systems are available for all types of buildings. A well designed piping system serviced by a pump will ensure that the system works economically. Depending on the water flow rate, some systems employ mechanical filtration to remove the suspended dirt to protect downstream equipment such as valves. If needed, additional treatment to remove or protect specific Greywater contents may include sand filtration, bleach, ozone or UV light.

Useful Information

Reduces Water Consumption

Total water consumption can be dramatically reduced as fresh water is not being wasted on garden irrigation, etc but rather the grey recycled water.

Payback Period

Depending on the type of system and the cost of water in the region, a payback period of two to three years is achievable.

Custom System Designs Are Required

The type, design and layout of a building grey water recycling system depends on what function the water is used for (washing, cleaning etc) and the waste water content that exists after such functions have been performed. Each system must be customised to suite specific building needs.

Piping Design & Layout

Design and layout of the piping in the grey water system will directly affect performance.

Regulations & Safety

Regulations require that mixed wastewater is discharged to the appropriate drain system (i.e. storm or sanitary drains).

Special Treatment May Be Necessary

Some Greywater systems may need to add chemicals to kill harmful microorganisms or may need special treatment to remove harmful toxins.

Looking Ahead...

In the future, some regional and local governments may require permitting and monitoring of grey water systems.

Biological Implementation

Grey water recycling systems also include biological systems (plant systems as treatment ponds, constructed wetlands, living walls, activated sludge systems etc.

Best Practice

It is not advisable to include any water containing fat deposits (from staff kitchens or canteens).

Benefits Of Garden Irrigation Integration

The diluted residues, soaps etc in the water can provide useful sulphates and nitrates which some experts say is more beneficial to the garden than clean tap water.

Maintenance & Servicing

The system requires maintenance and monitoring which includes periodic water quality testing.

Installation Options

Storage tanks can be below or above ground

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