We recently received a contribution from Mathur, an Internet user wishing to draw our attention to the need to explore alternative ways of producing energy in order to power drinking water production and treatment facilities. Here is his message:

“Power and water go hand in hand. Especially for India, we should concentrate on using human and animal waste, make biogas and convert it to power, which in turn should be used for water treatment and desalination.”

The issue is a core concern for members of the water industry. It was also one of the main issues discussed at the World Water Forum in Istanbul. According to a study presented at the Forum, recycling one cubic meter of wastewater consumes between 1 and 6 kWh, while the desalination of one cubic meter of water requires, depending on the method used, between 4 and 8 KWh.

As Mathur rightly underlines, it is possible to produce energy with the sludge output by wastewater treatment plants via incineration and methanisation. In France, the recycling of household waste is the 3rd most important renewable source of electricity after hydropower and wind, and the 4th ranking source of heat after wood, biofuels, and heat pumps. The energy produced can obviously be used to power water production and treatment plants or be sold.

It is also possible to minimise the energy requirements of drinking water production facilities. In desalination for example, the development of state-of-the-art technologies such as the reverse osmosis process has helped optimise the levels of energy consumption. Powering plants with "green" energy is another way of limiting those requirements. SUEZ ENVIRONNEMENT is working in that direction: one instance is the energy consumed by the future desalination plant in Melbourne, Australia, which will be 100% renewable, being output by a new wind farm located in the State of Victoria. That is already the case in Perth, where 100% of the energy requirements of the desalination plant are supplied by a wind farm located 200 km further north.

The relationship, however, also works in the other direction… there is energy in water as well. Wastewater and sewage sludge can be used produce energy and heat based on a variety of processes, including digestion (methanisation), co-digestion, pyrolysis, and gasification. For example, at the Upstream Seine plant at Valenton, France, dried sewage sludge is used for self-energy production on-site and to produce a non-fossil alternative fuel or organo-mineral fertilisers (depending on the quality of the sludge).

As Mathur rightly points out, energy self-sufficiency for water utility infrastructures is a major issue for the research and development efforts of their operators, such as SUEZ ENVIRONNEMENT.