In Roermond a CoRe pilot installation is now producing a stream of very clean water from 2 m3 of pre-screened WWTP influent. In this TKI project, Royal HaskoningDHV, BLUE-tec, the Limburg Water Authority Company (WBL), the Vallei and Veluwe, and the Rijn and IJssel Water Authorities, KWR and Allied Waters are jointly investigating whether CoRe – Concentrate, Recover & Re-use – can also make a valuable contribution in practice to the recovery of water, energy and raw materials from wastewater. A chat with Andries Vonken (WBL) and Frank Oesterholt (KWR).
First extract as much clean water as possible from the wastewater. Then extract as much value as possible from the concentrated waste stream in the form of raw materials or energy – and then reuse both the clean water and energy in useful applications. That is the objective of the CoRe approach: Concentrate, Recover & Re-use. Following small-scale testing during 2017-2020 at three Water Authorities, the technology – based on forward osmosis (water to the draw solution) and reverse osmosis (recover the water from the draw solution under pressure) – was further developed and scaled up to a pilot installation capable of processing 2 m3 of wastewater per hour. At the end of last year, within the framework of a TKI Water Technology project, the pilot installation was set up at the WBL site in Roermond.
Running on wastewater
Following an extensive test and configuration phase with clean water, this CoRe pilot installation has for a short while now been running on pre-screened influent. ‘It took longer than we had hoped,’ says Frank Oesterholt, who is responsible for the project at KWR. ‘Among other things, we wanted to use this pilot research to test which cleaning regime and which cleaning frequency were optimal for the required chemical cleaning, air-water flushing and osmotic backwash. To do so, we wanted to start with a high frequency and then adjust it down on the basis of our findings. The cleaning procedures however proved to be more complex and time-consuming than we had foreseen, so that the start-up took longer.’ The configuration of the drum screen, which is used to pre-treat the wastewater, also took more time. Oesterholt: ‘But after having recently started to run on settled influent from the WWTP, it appears that the membranes foul a little less rapidly than we had expected: we might therefore need to clean them less frequently.’
The installation will remain at the WWTP in Roermond until the end of this year. As strategic advisor in water treatment at the Limburg Water Authority Company (WBL), Andries Vonken is involved in the project. Since the concept fits in so well at WBL, he was also involved in the previous research over the last few years which ultimately led to this pilot. ‘CoRe dovetails in so many ways with WBL’s mandate and ambitions. We stand, for example, for clean and ecologically healthy water – and CoRe can contribute to this, because it also provides a means for the removal of organic micropollutants. We also strive not only to discharge our treated water into surface water, but also to actually find useful applications for it – which is also something that could be done extremely well and entirely locally with the CoRe technology. Water reuse is an important motivation behind our participation in this pilot: a large part of Limburg consists of drought-sensitive high sandy grounds, and reusable water could be a good alternative source for both agriculture and industry, today and into the future.’
‘We stand for ecologically healthy water – and CoRe can contribute to this.’
The modular set-up of CoRe also fits in perfectly with the vision WBL has of its wastewater infrastructure and technical treatment assets. Vonken: ‘Our area has billions of euros of wastewater infrastructure, both above and underground; and here, too, we are faced with the need for extensive overhauls. We started thinking about the replacement issue a few years ago, and we concluded that we wanted to operate in a far more flexible, future-proof and sustainable manner. This was the origin of the Verdygo® concept: a modular building philosophy, which resulted in standardised modules with equipment, usually built above-ground in standard containers and above-ground tanks. In this ‘plug and play’ philosophy, we can quite simply integrate CoRe for the treatment of (partial) wastewater streams – as soon as the installation is scaled up further to 20 or 50 m3 per hour. CoRe can provide a welcome addition to our treatment techniques, on the basis of which we of course continuously make choices depending on the costs, environmental impact and sustainability of the overall system.’
Research on wastewater
Now that the installation is running with wastewater, other research questions arise, for instance concerning how clean the water that CoRe ‘extracts’ from the waste stream is. Oesterholt: ‘We would like to show that this technique does actually remove organic micropollutants such as pharmaceutical residues, and also to know whether, and how many, small molecules such as ammonium come with the clean water. In this project we will not yet be testing which techniques could be used as subsequent steps in the treatment of the concentrated wastewater stream, but we do want to know how high the levels of certain concentrations can rise in the stream. If you know how much nitrogen, phosphorus or chemical oxygen demand occurs in the stream, you can determine whether you can for instance use digestion as a subsequent step, which allows you to generate much of the energy you need for the reverse osmosis in CoRe.’ Vonken adds: ‘And naturally we also want to know how stably and autonomously the installation can run, and how robust this technology is.’
Vonken: ‘An endurance test provides valuable information, because you want to know about the impact for example of variations in temperature or wastewater composition. You also want to find out how well this process can be autonomously or remotely operated. WBL attaches a great deal of importance to innovation, and we see this pilot research as a sensible investment.’
After the completion of this TKI project, the pilot installation will return to KWR, and can be used in new research projects. Oesterholt: ‘CoRe can be perfectly well used for a wide variety of wastewater streams, including in industry, and we aim in the years ahead to further improve the technology because it is excellently suited for a circular economy.’
Source: TKI Water Technology