11.1  Why do we need to use water efficiently?

Water is a precious resource and has to be conserved in order that future, increased water demands due to population and industrial growth (as is happening in Ethiopia) can be satisfied. Increasing economic prosperity also results in higher water use per person. As people become more affluent and have a piped water connection in their home, they are likely to purchase and use more domestic appliances that require significant quantities of water, such as washing machines and dishwashers. Personal bathing also tends to increase and people shower more frequently. Increasing demand means that more water will need to be supplied, bringing with it the costs and challenges of developing new water sources.

There are other costs to consider. Producing drinking water in water treatment plants requires significant inputs of energy and chemicals, so saving on water use will also save energy and chemicals.

  • How are energy and chemicals used in drinking water treatment?

  • You may recall from Study Session 5 that energy is used to pump raw (untreated) water to the treatment plant. Energy is used in the various treatment units at the plant, and finally energy is used to pump the treated water into the distribution system.

Chemicals such as aluminium sulphate and ferric chloride are used as coagulants, and chlorine is used as a disinfectant.

The water produced by the plant is treated so that it is clean and safe for drinking and cooking with but, as you know, it is also used for many other purposes, some of which do not need water to be of potable quality. It makes sense to avoid using fully treated drinking water for purposes that do not need it. It is also important to note that using less water has economic benefits for consumers, since their water bills will be lower!

Learning Outcomes for Study Session 11

11.1.1  Technical options for minimising drinking water use