21 apr 2017

At the Apeldoorn sewage treatment facility belonging to Vallei en Veluwe Water Authority, successful tests are currently being conducted for the large-scale extraction of Nereda® alginate. This raw material originates from sludge left behind after wastewater has been treated using Royal HaskoningDHV’s Nereda®. treatment technology. Nereda alginate is a substance with unique characteristics and potentially high-quality applications. By extracting this and other raw materials such as phosphate from wastewater, water authorities are taking concrete steps towards achieving a circular economy.

The tests are aimed at discovering the best way of extracting the raw material. The results of the trials will be used to build the first two full-scale alginate factories. These will be located in Zutphen and Epe and are expected to be up and running by late 2018 or early 2019.

Part of the extracted alginate from the trial setup will be used to further test various applications of Nereda alginate – for example, as an adhesive in a fertiliser pellet. Other adhesives are currently being used for this purpose, but the amounts need to be increased at least tenfold.

Unique characteristics

What makes Nereda alginate so special? It is a sustainable raw material with a number of unique characteristics. It can retain but also repel water. This means it can be widely used – for example, in the horticulture and the paper and concrete industries. It can be used as a thickening agent or an adhesive, as a coating or as a stabiliser. Various market parties have already shown interest in using the alginate – as a concrete coating, for example.

Alginate pilot Apeldoorn | Nereda, Royal HaskoningDHV

Image: the test installation in Apeldoorn, NL


However, the necessary adjustments need to be made in the legislation and regulations in order to market the product. Raw materials extracted from wastewater have a ‘waste status’, so there are strict requirements that prevent them from becoming circular. Tanja Klip-Martin, Dyke Warden for the Vallei en Veluwe Water Authority: “I believe that the status of extracted raw materials should be made equivalent to that of primary raw materials. On condition there are no risks to public health when they’re deployed, because we don’t want to throw out the baby with the bathwater. It is only then that we will have an equal playing field and that the Government’s aim to make the Netherlands circular by 2050 will become realistic.”

At the moment, alginate is extracted from seaweed. That is currently being done in Asia. It is a relatively expensive process. Because of this, the use of this type of alginate is mostly limited to the medical sector (including moulds for false teeth, alginate plasters). The alginate in the sludge pellets left behind after treating wastewater with a Nereda installation is more sustainable, more economical and therefore more broadly deployable on the market.

The extraction of alginate is consistent with the objective of the water authorities to turn their wastewater treatment facilities into energy and raw material factories.

The NAOP National Alginate Development Programme

The extraction of Nereda alginate from wastewater is part of the NAOP National Alginate Development Programme. In this programme, the water authorities, the Foundation for Applied Water Research (STOWA), engineering firm RoyalHaskoningDHV and Delft University of Technology are working closely together. They are all contributing the knowledge and expertise required for the extraction, processing and marketing of Nereda alginate. From laboratory research to full-scale extraction. In this way, the water authorities, the science sector and the business sector are working together to achieve a sustainable, circular economy.

Full-scale Nereda alginate facilities will ultimately be built at the Rijn en IJssel Water and Vallei en Veluwe water authorities. They expect to save costs by processing 25 percent less sludge and selling the unprocessed Nereda alginate.

What is Nereda?

Nereda is a new, sustainable wastewater treatment technology in which the purifying activated sludge forms granules and not flakes. This means that sludge settles much faster and easier. The technology has a high purification yield, takes up minimal space (no large sedimentation tanks necessary) and consumes relatively little energy. Moreover, Nereda alginate can be extracted from the sludge granules.