Four years ago, Ph.D. scientist Arnoud de Wilt investigated the use of microalgae, in combination with bacteria and light, for improved micro-pollutant degradation in wastewater. This photo-bioreactor was very effective in breaking down different medicine residues in wastewater. However, implementing his idea proved to be challenging due to less favorable conditions for microalgae growth in The Netherlands. Therefore, in the last stage of his research, de Wilt focused on using ozone in combination with bacteria to degrade these compounds. The extra biological treatment step demonstrated a more efficient removal of micro-pollutants compared to just ozone treatment. Hence, implementation of this new cost-effective technology in current wastewater treating plants is promising.
Conventional wastewater treatment facilities are not designed to remove pharmaceutical residues. As a result, these components end up in surface water, threatening ecosystems as well as drinking water supplies. ‘Chemical or physical treatment for the removal of pharmaceuticals in wastewater is expensive and consumes significant amounts of chemicals and/or energy’, Arnoud de Wilt says. ‘We wanted to make these treatment processes more sustainable by combining them with biology.’ During the last year of his Ph.D., De Wilt decided to focus on ozone in combination with bacteria. Just ozone treatment to degrade micro-pollutants is not cost-effective, among others due to high amounts of background organic matter in wastewater: a lot of ozone is consumed by degrading this fraction. De Wilt’s first step was therefore to add a biological treatment step to remove this organic matter, so less ozone was required for
effectively degrading pharmaceuticals. This resulted in a reduced ozone demand of more than a third, offering an excellent starting point to continue the research and further improve the process. ‘The combination of ozone and biological treatment is even more interesting, since EU regulations will require the removal of more phosphorous and nitrogen’, says de Wilt. ‘Most likely, this can also be achieved by this biological step.’
Mature the technology
After finishing his Ph.D., De Wilt was employed at Royal HaskoningDHV.
This consultancy firm was interested in continuing de Wilt’s Ph.D. research. With a supplementary grant from the Minister of Economic affairs, Royal HaskoningDHV invested in an extension of his research. A new Ph.D. scientist was hired, while de Wilt was in charge as supervisor. ‘The overall aim is to mature the technology and bring it into practice’, says de Wilt. ‘My Ph.D. research was mainly an academic exercise. Now we aim to build a pilot plant where we will bring theory and practice together.’ However, before the technology can be implemented, several key questions need to be answered: Which reduction in ozone demand can be achieved? What are additional benefits of the combined treatment? Who is going to use the technology? How can it be implemented in current wastewater treatment plants?
De Wilt aims for the implementation of an additional step in existing water treatment plants to remove pharmaceuticals. However, currently, there is no legal obligation. Only in Switzerland, there is legislation enforcing the removal of these compounds. This increased the costs of wastewater treatment roughly by five to ten euro per person per year: the price of just three to four cappuccinos per year, as the Swiss state.
In The Netherlands, amounts of pharmaceuticals present vary between different locations. Several dozens out of ca. 320 wastewater treatment plants are marked as so-called ‘hotspots’, meaning the effluent contains concentrations of these compounds which negatively affect the receiving surface waters.
These plants should be upgraded first with such an additional cleaning technology. ‘In four years time, I hope we have managed to implement
an efficient and cost-effective technology to remove these micro-pollutants, together with additional nitrogen and phosphorous removal,’, says de Wilt. ‘The hotspots should of course be prioritized. This is important to keep our surface water clean and our drinking water safe.’