N.V. Slibverwerking Noord-Brabant (SNB) operates the largest sludge incineration plant in the Netherlands. The company processes municipal sewage sludge of six shareholding water boards and sludge of various external clients. Sludge is a by-product of waste water treatment plants.
Alone, and together with its partners, SNB seeks innovative ways of contributing as much as possible towards an efficient wastewater chain. This is done through,for example, research into the possibilities of recycling by-products.
SNB works continuously on initiatives to recycle valuable raw materials from sludge. For example, SNB supplies its phosphate containing incineration ash for the production of fertilisers and other phosphate products. A neighbouring company uses CO2 from the flue gas of SNB as a resource for the production of paper.
In November 2010, the shareholders approved the business plan of 2010-2015. In this plan, SNB has presented a clear vision about the processing of sewage sludge, and the realisation thereof. In addition, SNB has explicitly stated its key values. In 2014, SNB is working on the continuation of the business plan for the period 2015-2020.
SNB maintains three basic starting points for the processing of sewage sludge:
- Sludge consists of nutrients which are necessary to provide food to people. SNB seeks to recycle these nutrients and utilise them as much as possible. This contributes towards the sustainability of society.
- There is energy present in sewage sludge. SNB converts this energy into electricity.
- Sewage sludge plays an important role as an absorbent of contaminants in wastewater. This prevents them from ending up in the surface water. SNB strives to prevent these contaminants from still ending up in the environment during the processing. It also constantly works towards the optimisation of sludge processing.
SNB plays an active role as a partner in the total wastewater chain, in order to continually process sewage sludge against the lowest chain costs, with minimal emission into the environment, and the maximum recycling of energy and raw materials.
SNB also plays an active role in innovations in the wastewater chain. According to SNB, this can only be achieved through close involvement with the water boards, and by consciously and actively initiating cooperation with all parties ivolved.
Total wastewater chain
The wastewaterchain begins with the production of wastewater ends with the final processing of sludge, including recycling of energy and the recycling of waste materials from sludge. All the separate segments of this chain have influence on each other need to be geared to one another to realise an efficient total wastewater chain.
Continuity is of great importance in sludge processing. If sludge is not processed continiously, it leads to problems in society.
Wastewater chain costs
Together with its partners, it is the aim of SNB to achieve the lowest posssible costs in the wastewater chain. The purpose is to impose a minimal burden on the tax payer regarding the total costs of wastewater treatment.
SNB aims to gain as much energy as possible out of sewage sludge, and when possible, recycle the raw materials present in sludge. Moreover, SNB aims to prevent the emission of any harmful elements into the environment. SNB strives for a sustainable processing of sewage sludge: the sludge processing of today must not have any negative consequences on life in the future.
SNB collaborates with many national and international parties, within and outside the wastewater chain. Together with them, SNB strives for an efficient and sustainable wastewater chain. These are, among others: the Dutch Nutrient Platform, the Deutsche Phosphor-Plattform (DDP) and the European Sustainable Phosphorus Platform. Moreover, SNB works with other sludge processors, on individual basis and within the Vereniging Afvalbedrijven (Dutch Waste Management Association) and its German counterpart, the Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall (DWA).
Phosphate (P205) is one of most important raw materials for food production. The demand for phosphate is always on the increase. That is because of the increasing world population, the increase in meat consumption, and the growing of energy crops. These are crops that grown for the production of biofuel.
What is phosphate
Phosphate (P205) is a compound of phosphor and oxygen. Humans, as well as animals and plants, need phosphate in order to live. Humans and animals acquire phosphate through food, while plants get it from the ground. Phosphate compounds play an important role in the DNA of humans, and in the production of energy in humans, animals and plants. For example, the molecule adenosine triphosphate (ATP) is an important storage medium for energy in our body. Phosphate stabilises the oxygen level in our blood. The largest quantity of phosphate is found in our bones and in our teeth.
The phosphate problem
It is clear that we need phosphate to prevent a food problem. However, Europe is strongly dependent on the import of phosphate. Almost the entire stock has to come from outside the continent. A resulting problem is that the available phosphate rock is becoming more and more contaminated with cadmium and uranium.
In the Netherlands, due to the high use of (artificial) fertilisers in the past years, there is an excess of phosphate in the soil and on surface water. Nonetheless, it can run out if it is not supplemented.
What is the solution? Recycling phosphate from sewage water is an efficient and environmentally friendly way of recycling phosphate. This can take place at various places in the wastewater chain.
- At the toilet, through decentralised sanitary (collecting urine separately).
- At the wastewater treatment plants (WWTPs), by letting the phosphate react into struvite.
- At the sludge incinerators, by recycling phosphate from the sludge incineration ashes.
SNB receives more than a quarter of the Dutch phosphate through its sewage sludge, and strives to recycle these essential raw materials on basis of recycling phosphate via sludge incineration; the method with the highest returns.
Scientific research shows that worldwide around 14.9 million tons of phosphate rock is mined. By recycling phosphate through sludge treatment, we can cover 20% of the worldwide demand for phosphate.