Blackwater Recycling System

Blackwater Recycling Systems

Blackwater, which is sometimes referred to as sewage  is the wastewater that comes from toilets, garbage grinders, and dishwashers. This is different from greywater because it contains bacteria, pathogens, and food particles, which can rot and is more difficult to treat than greywater. The wastewater that comes from showers, washing machines, and sinks is considered greywater because, even though it has particles and contaminants, they are not considered dangerous.  (, 2007). However, in areas where proper toilets and washing facilities do not exist it is likely that even laundry wastewater may contain harmful pathogens or bacterias. Thus, in some areas such as in Monwabisi Park all wastewater should be treated as blackwater.

In a blackwater recycling system, all of the blackwater is routed to an initial tank via gravity. The blackwater is given time to settle and a primary colony of bacteria goes eats away at the waste for 24 hours similar to a normal septic system. Then the settled blackwater goes into another tank that is divided into 3 chambers; Aeration, Sludge settling and Irrigation (Green Living Tips, 2009).

  • Aeration stage: water and air are injected into the tank at timed intervals so that the contents of the tank are churned. Bacteria in the tank then settle so they can feed on the sludge in the tank. When that is finished, the water is moved to the sludge settling chamber
  • Sludge Settling Chamber: the results of the aeration stage are then piped into a sludge settling chamber. A bacteria biomass mechanism forces sludge downwards and the partially treated water upwards to be collected and sent on to the irrigation chamber stage
  • Irrigation Chamber: The remaining effluent passes into the irrigation chamber. Here, it is clarified and chlorinated, which is the last step of the process. The water can then be piped into ground irrigation systems for use in gardens.

The water that is recycled from blackwater recycling systems should never be used as drinking water or on food crops because they could still contain harmful bacteria. It can be used for watering lawns or non-food gardens.


Watering lawns and non-food gardens are not the only benefits of a blackwater recycling system. It is also benefits the environment in many ways such as:

  • Energy conservation: The removal of harmful bacteria from blackwater in processing plants is expensive and uses a lot of energy.
  • Water conservation: Using recycled blackwater to water lawns and non-food gardens helps to conserve the fresh water that would otherwise be wasted.
  • Natural resource conservation: Plants that are grown using recycled blackwater do not need fertilizer because the water is already nutrient rich and the plants feed off of them, this eliminates the need for polluting the environment with fertilizing chemicals.
  • Habitat protection: Recycling blackwater lessens the chance of the wastewater seeping into natural habitats.


Just as there are advantages of recycling blackwater, there are also some disadvantages. These disadvantages include:

  • Cost: These systems can be expensive to install, maintain and repair if something goes wrong.
  • Odor: Some people say that there is not a bad smell, but others say that they can smell sewage all the time.
  • Maintenance: Maintaining the system can be a bother, it requires maintenance about every three months by the company that installed it and there may or may not be a charge for each visit depending on the company. (, 2007)

Read More about Composting Options for the Sanitation Facility

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