Valuable source: Wastewater is usually seen as a dangerous by-product, which is collected in pipes and gutters and flows into ‘a dump-hole somewhere in the ground'. However, in recent decades, the treatment technologies for removing the harmful components from wastewater have become increasingly effective. And as Professor Jules van Lier points out in his inaugural speech, "on closer examination, wastewater is actually a mixed stream of valuable raw materials from previous economic and/or domestic activities."

Western luxury: 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 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. According to Van Lier, this will lend an entirely new impetus to the process that could lead to the application of new reprocessing technologies, especially in areas where waste water treatment is still seen as a ‘Western luxury’.

Excreta and wastewater: "Take domestic wastewater in the Developing World, for example. If we assume a 50 percent recovery of chemical energy, the potential power you can generate from human excreta would be 200 Wh per person per day. Not too much, but this would be enough to light the slums of Africa all night long." A decentralised sewage treatment plant could also be of great value to agricultural ferti-irrigation in dry regions. "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. In this way, nutrients from wastewater are put to good use and the farmland also serves as a sand filter to purify the water."

Ten million hectares: "We still have a lot of hurdles to jump before we get to this stage, of course. But we mustn’t forget that the current situation has led to ten million hectares of farmland worldwide being irrigated with untreated or barely treated wastewater. More than ten percent of the world’s population eats products that are irrigated with wastewater!"

Amman: According to Van Lier, a city like Amman should really opt for decentralised treatment plants (with anaerobic treatment systems) that yield an extra 5 to 6 MW of electrical power. This power could then be used to drive irrigation pumps, for example. "Unfortunately, Amman has gone for a traditional ‘Western’ treatment plant. This is a common phenomenon in non-Western countries. There is little interest in potential alternatives that are often more robust and suitable for these regions.