11.3  Treating sewage for reuse

A lot of water is used for purposes where high-quality drinking water is not necessary.

  • Can you think of water uses where the quality does not have to be of drinking water standard?

  • You may have thought of the washing of outdoor areas (like the house yard), washing of vehicles and gardening, but you could have mentioned anything that does not involve ingestion of the water.

One of the biggest uses of water is in irrigation, not only for food crops but also for landscaping schemes in cities like Addis Ababa (Figure 11.6). For uses such as these, it is possible to use treated sewage effluent to water plants, if this is available. Sewage treatment can be an economical process using a simple system of ponds called waste stabilisation ponds, which are described below. (Note that reuse of the water is only feasible for fully treated sewage; septic tank discharge should not be used in this way.) In Ethiopia the opportunities for reusing treated sewage effluent may be limited at the moment, but future changes could see more sewage treatment systems, which would increase the potential.

Figure 11.6  Volunteers planting trees in Addis Ababa, on World Environment Day, 5 June 2013.

11.2  Using rainwater

11.3.1  Waste stabilisation ponds