Wastewater from process industries has long been difficult to purify without producing large amounts of waste in the form of sludge and other by-products. By taking a more circular approach where the water is purified using natural processes, waste management problems can be resolved while the contents of the water can be used to create value. RISE has developed a new type of mobile pilot system that makes it possible to quickly scale up results from the lab and carry out biological purification on site.
At RISE’s prototype workshop in Uppsala, Johan Andersson M.Sc.Eng., and his colleagues have worked extensively over the last few years to create a pilot system that can be used to purify wastewater from mines and other process industries by means of a new type of biological treatment. The method, which is globally unique, could change our view of wastewater. Instead of viewing it as a problem, it can be considered an important resource and a crucial factor in a sustainable, bio-based economy.
– “We used a mobile biogas system the size of an intermodal container, which we converted into a water purification system and which can be transported to different sites,” says Andersson. “In the pilot facility, together with Fortum Waste Solutions and LKAB, we developed a method that both biologically purifies the water from the mining industry and enables it to be reused.”
Natural process instead of chemicals
There is increased awareness of the need to protect our waters, and more stringent regulations are in place pertaining to what industries and other operations are permitted to release into the environment. Sweden, for example, has strict requirements for sulphate emissions, a problematic substance found in pit water and wastewater from the process industry. To purify this water, various types of chemicals are currently used, but it is often difficult to bring them down to the low levels required. Furthermore, enormous volumes of sludge are produced, which need to be dealt with.
Karin Willquist from RISE’s Bioprocesses and Environmental Services unit is researching how biological methods can be used to purify process water and believes the future looks bright for the technology:
– “Today’s methods work in terms of purification, but create considerable waste problems. If chemical methods were used to remove particles from water across Europe, it would produce a 320 km high mountain of waste – which is the same height as 1,000 Eiffel towers stacked atop one another.”
Biological purification employs a natural process instead, consisting of microorganisms grown in a lab. Sulphate-reducing bacteria, which absorb sulphate in oxygen-free environments, are added to remove sulphate from the incoming water. The sulphate is converted into hydrogen sulphide, which can then be used if the water is to undergo further treatment.
It’s a brilliant technology and very timely
Unique in the world
The pilot system built at LKAB in Svappavaara has proven successful, despite some challenges. The method has demonstrated that clean water can be produced with a 95% reduction of sulphate, and is deemed to have the potential to save tremendous volumes of water. In addition to sulphate, the method was also able to remove uranium and nitrate from the water, and the positive results have attracted national and international attention. The project was one of three nominated in innovation contests, including the Swedish Mining Innovation Award 2019.
– “Our strength was the broad expertise possessed by the project team, and the fact that we managed to convert our biogas system into a treatment system in a short space of time. With a robust control system and a high degree of automation, it worked very well technically,” says Andersson.
Viewing wastewater as a resource
A major advantage of biological purification is that substances in wastewater can be used as a resource. When sulphate is converted into hydrogen sulphide, it becomes possible to use the substance in various ways.
Fortum Waste Solutions strives for seamless waste management in all types of operations. Since pit water from the mining industry has been a problematic area, there is significant potential for biological purification and the new pilot system developed together with RISE.
– “It’s a brilliant technology and very timely,” says Thomas von Kronhelm, Head of Research at Fortum Waste Solutions. “It’s inexpensive, scalable and enables sulphate to be reduced and sulphur to be recycled. We want to help scale up and commercialise the technology.”
Fortum believes the method can be made commercially viable. To do so, it must be shown that substances extracted from the water can be used as a product, thereby eliminating waste. According to von Kronhelm, the sulphate conversion process also needs to be accelerated:
– “It looks good, but we have to verify that it remains stable over time. RISE possesses a great deal of expert knowledge of system technology and microbes, and here at Fortum we understand how to scale up and implement. So we complement each other in the project.”
Challenge at low temperatures
The greatest challenge involves carrying out biological purification in low temperatures. In this, the RISE and Fortum project is totally unique in that pit water has been successfully purified in temperatures as low as 5 °C. The solution will now be scaled up in the SO4Biored pilot project together with mining and smelting company Boliden.
“Biological purification is gaining considerable momentum,” says Willquist. “There is major interest from smelting plants, the pulp and paper industry, and the food industry. Our strength lies in the fact that we have developed a method that allows customers to perform tests in the lab to see whether it works with their wastewater. If a positive result is achieved, we can quickly set up a pilot system on site at the customer.”
