Sewage treatment plants were developed in order to clean waste water in the most efficient way possible. This results in clean water that can be discharged into the surface water. The remaining waste substances are dumped. However, nowadays waste water is also regarded as a valuable source of energy, as well as of raw materials and phosphate.


Humans, animals and plants need phosphates in order to live. Phosphate is an important element for the production of food. If we look at current consumption, the supply of phosphate threatens to run out in only 50 to 100 years' time. 14.9 million tonnes of phosphate from natural sources are used worldwide per year.
Approximately 20 per cent of this ends up in waste water through food production and human excrement. Removing phosphate from the water will alleviate the pressure on this scarce raw material and will mark an important start to recycling. Sustainability is becoming increasingly more important.


In 2008, in the multi-year agreement for "energy-efficient waste treatment management", agreements were made between the Ministry of Economic Affairs, Agriculture and Innovation and the regional water authorities. The regional water authorities are striving for a 2 per cent improvement in energy efficiency per year (a total of 30 per cent between 2005 and 2020), primarily by working more energy-efficiently. The Integral Treatment Plan 2010-2015 of the Vallei & Eem Regional Water Authority includes its ambitions and activities for treating waste water sustainably. These are divided over the basic principles of cost-savings, striving for sustainable and climate-proof systems, and saving energy and raw materials. Through this, the
authority has reduced energy consumption by more than 20 per cent in the last ten years. The Vallei & Eem Regional Water Authority is using innovative techniques to search for new ways of making the sewage treatment plants work energy-neutral at least.

The Energy Factory

In 2009, the Vallei & Eem Regional Water Authority and twelve other water authorities took part in the project ‘The Energy Factory' in which the Amersfoort sewage treatment plant was treated as a business case. Based on the results of this project, the authorities will be setting up twelve large-scale Energy Factories for generating energy and heat from biogas over the coming years. An Energy Factory
is a sewage treatment plant in which the locally generated energy (green electricity) from waste water and sewage sludge is at least equal to the total energy consumed in water treatment. The aim is that, in 2014, sewage treatment in Amersfoort will be organised in such a way that there is an energy surplus and that valuable raw materials are removed from the water for re-use.

Project development

In 2010, the water authority started research that took into account the ambitions laid down in the Integral Treatment Plan. This research is the basis for achieving the objectives of the Omzet●Amersfoort project: treating waste water sustainably and removing valuable raw materials from the waste water for re-use. Various options were considered in order to make the Energy Factory more attractive in terms of energy production and cost level.


At the same time, a subsidy application for building OmzetAmersfoort was submitted to LIFE+, a European funding instrument for the environment. This European subsidy has now been approved. This means that we can realise our ambition of creating more sustainable sewage treatment. The Omzet●Amersfoort project also provides possibilities for (re-)building new or existing water treatment plants as an Omzet throughout Europe.


The aim of the Omzet●Amersfoort project is to contribute to solving the climate problem by treating waste water sustainably and making effective use of raw materials and energy. It is also hoped that the project will contribute to achieving European objectives and to developing policy for less waste, recovery of phosphates, limiting the exhaustion of natural resources, limiting the ecological footprint of water treatment plants, reducing emissions of CO2 and other greenhouse gases, and improving the quality of surface water, as required by the water directive.

The expected results

Raising production of biogas by 60 per cent
Raising the recovery of phosphates to 80 per cent
Reducing sludge production by 17 per cent
Lowering the operational costs of treatment plants by 15 per cent
Maintaining high effluent, and thus surface water, quality

For more information

Project Manager: Henry van Veldhuizen