THE United Nations in a recent report said that in a world where the demand for water continues to grow and the resource is finite, treated wastewater can help meet the needs for freshwater as well as for raw materials for energy and agriculture.
The use of wastewater largely depends on the extent of treatment done. Wastewater treated from conventional facilities can be used for watering golf courses and landscaping or for irrigation purposes. According to the UN report at least 50 countries around the globe are now using treated wastewater for this purpose, accounting for an estimated 10 per cent of all irrigated land. Further treatment means it can also be used as cooling water for power plants.
Using more advance treatment like dual-membrane (via microfiltration and reverse osmosis) and ultraviolet process, wastewater can be good enough for drinking and cooking. An example of this is Singapore’s NEWater, reclaimed water produced by Singapore's Public Utilities Board. The water is potable and is consumed by humans, but is mostly used by industries requiring high purity water. NEWater is now able to supply up to 40 per cent of Singapore's total daily water demand, up from 30 per cent, with the opening of Singapore's fifth NEWater plant last January.
Perhaps the best example of wastewater treatment and re-use is the water used by Astronauts in space such as those on the International Space Station who have been reusing the same recycled water for over 16 years. According to NASA, Astronauts will not be able to carry enough water for long-duration flights. They must be able to recycle the water they use for washing their hands and brushing their teeth. They must also recycle their sweat and urine.
The UN report further said that in addition to providing a safe alternative source for freshwater, wastewater is also a potential source of raw materials, noted the report. Owing to developments in treatment techniques, certain nutrients, like phosphorus and nitrates, can now be recovered from sewage and sludge and turned into fertilizer. It is estimated that nearly 22 per cent of the global demand for phosphorus (a depleting mineral resource) can be met by treating human urine.
At home, some wastewater can be used without treatment. It is called Greywater, the water used from your bathroom sinks, showers, tubs, and washing machines. It is not water that has come into contact with feces, either from the toilet or from washing diapers. Greywater need not go into the septic tank because it can be used immediately.
The easiest way to use greywater is water ornamental plants or fruit trees. Greywater can also be used to irrigate vegetable plants as long as it doesn’t touch edible parts of the plants. It can also be used for washing floors, cars and other areas in the house that do not need clean, fresh water.
Remember, water is a precious resource. Use it wisely.