Crystalactor® is a well-proven technology that purifies water using a crystallization technique, while harvesting valuable resources from the water.


The patented zero-waste Crystalactor® water treatment technology is used as advanced treatment of both drinking water and (industrial) waste water for removal of a large number of heavy metals and other inorganic compounds. The Crystalactor technology is a flexible technology that can be used for treatment of both large and small water flows.

Crystalactor is sustainable and cost-effective: compared to other technologies like precipitation, ion exchange or membrane filtration, it produces a valuable resource as revenue instead of waste and associated costs. Recently, we enhanced the Crystalactor with a smart controller, which was developed in close collaboration with Delft University of Technology and Amsterdam Water Works (Waternet). The advanced controller reduces the chemical, operational and maintenance costs by predictive control of formed pellets.


The heart of the Crystalactor installation is the so-called pellet reactor, partially filled with a suitable seed material such as sand or minerals. Feed water is pumped in an upward direction at a superficial velocity of about 40-100 m/h, which depends on the type of application. To crystallize the target component(s) on the pellet bed, a driving force is created by a reagent dosage and chemical for pH-adjustment. By selecting the appropriate process conditions, co-crystallization of impurities is minimized and high-purity crystals (pellets) are obtained. The pellets grow and move towards the reactor bottom by gravity.

Research and practice have been demonstrating that maximizing the specific surface (m2 pellet surface per m3 reactor volume) near the reactor bottom is the key to a successful operation of pellet reactors. This requires an integrated approach and control of the hydraulic load, reagent dosing of base and supersaturation. .

Crystalactor Animated Process

Intermittently, a quantity of the largest fluidized pellets is discharged from the reactor and fresh seeding material is added (picture 3). After atmospheric drying, readily handled pellets are obtained and the need for sludge dewatering, drying or hauling of sludge is eliminated. These pellets could be transported for reuse and/or commercial off-take, which could contribute positively to the financial balance.


Mr. Rietveld, professor of Drinking Water & Urban Water Cycle Technology of Delft University, explains in attached video the working of softening and crystallization.



Royal HaskoningDHVs’ involvement with crystallization started early in the 1980’s when then we assisted Amsterdam water supply company Waternet in designing the pellet softening plants Leiduin (8,500 m3/hr) and Weesperkarspel (3,300 m3/hr) and took over the patent of the pellet softening process. We still exploit our expertise to date for numerous clients worldwide, as they rely that we mitigate the risks for achieving well-functioning and optimal state-of-the-art operational plants. We prove this as we issue process guarantees for pellet reactors if clients request us to do so. We assisted i.e. Taiwan, as a country, who adopted softening with pellet reactors nation-wide and guided them into this new venture. The technology has the widest range of application in the industry. Crystallization is proving technology for us, because we realized world's largest softening installations, recovered fluoride from sub-flows in the semi-conductor or solar panel industry, recovered phosphate as struvite/calcium phosphate, treated concentrate streams in desalination plants, harvesting heavy metals out of waste-water stream. Many other applications are available on your request.


Nowadays, we still investigating in new developments like salt precipitation for brine minimization and CO2 capturing. We are happy to support you on your specific water challenge and/or new developments, on small and large scale as well. Royal HaskoningDHV will bring you unprecedented crystallization top expertise, validated by more than 30 years of experience in design, construction, testing, commissioning and operating of more than 70 plants across the globe.So, bring-in-the-Dutch” crystallization top-expertise for your own water challenge.

Would you like to know if the Crystalactor is the perfect technology to treat your water? Please send an e-mail or call Aad van Duyvenvoorde on +31651615265.