Don't dump 'wastewater': Tap it for energy, raw materials

The world is wasting valuable resources by not managing wastewater in the right way, according to a researcher in The Netherlands.

In fact, argues Jules van Lier of the Delft University of Technology, developing countries would be better off by not emulating the West’s standard approach to wastewater treatment. Instead, he believes, they should focus on treating wastewater as a source of valuable raw materials and energy.

“Take domestic wastewater in the developing world, for example,” he says. “If we assume a 50 per cent recovery of chemical energy, the potential power you can generate from human excreta would be 200 watt-hours per person per day. Not too much, but this would be enough to light the slums of Africa all night long.”

Decentralised sewage treatment plants using anaerobic digestion technology could also provide a way to irrigate crops in dry regions, according to van Lier.

“A city with 1 million inhabitants with an average water consumption of 100 litres a day can theoretically irrigate and fertilise between 1500 and 2000 hectares of farmland,” he says. “In this way, nutrients from wastewater are put to good use and the farmland also serves as a sand filter to purify the water.”

Van Lier believes wastewater treatment plants will eventually become reprocessing plants that produce water suitable for reuse. That will lead to the closing of process water cycles in the industries, short cuts in the urban water cycle, the recovery of fertiliser, particularly phosphates, from domestic wastewater, and the converting of organic pollution into usable energy.