ARTICLES Mar 4, 2022

Greywater Reuse

Greywater refers to the wastewater generated from homes or other building except for the wastewater from toilets. This includes shower water, sinks, dishwashers, laundry wastewater etc. This will be relatively clean and has less pathogens compared to blackwater(the sewage water from toilets) and can be reused after treating. Greywater reuse without treatment can also be done within houses, like using the greywater from showers or bathtubs for toilet flushing, and the water from vegetable washing for garden.

For optimal recycling of greywater, it is imperative that greywater be kept separated from blackwater by separate plumbing system. Greywater treatment is less expensive than blackwater treatment and if mixed, they need to be sent to sewage treatment plants. Most greywater is easier to treat than blackwater since it contains less pathogens. The psychological aversion to reuse of treated blackwater also necessitates the separation of greywater for water conservation efforts locally. Greywater from kitchen sinks contain grease and oil, and it needs to be removed before being sent to the greywater tank for treatment. You must have read of the fatbergs causing blockage to sewers due to fats in wastewater. Reuse within households require the fats to be removed, or if not possible the kitchen should be redirected to blackwater plumbing. Benefits of Greywater Reuse

  • Reduced use of freshwater, e.g., flushing and watering of garden/lawn can use greywater instead of freshwater
  • Less sewage flowing to septic tank or sewage treatment plants since greywater is separated from sewage
  • Treated greywater can be used to recharge groundwater as there is no risk of pathogens seeping into water table.
  • Energy conservation due to less demand on sewage treatment plants.
  • Treated greywater can be used for irrigation