In Sweden, a new large pilot plant to extract nitrogen from wastewater is being built at the Hammarby Sjöstadsverk wastewater treatment plant (WWTP) in Stockholm. Together with EkoBalans Fenix AB (EkoBalans), a nutrient recycling company, IVL Swedish Environmental Research Institute (IVL) will test and optimize new technology that hopefully can be utilized by many other WWTPs across the country.
Currently, the recovery of nutrients from wastewater is almost exclusively carried out by spreading sludge from treatment facilities onto arable land. But while almost all the phosphorus separated ends up in the sludge, only about 15 percent of the nitrogen present in the wastewater does, the rest is separated to the air in gaseous form or is discharged into the outgoing water flow.
Conversion of effluent nitrogen requires a lot of energy and in addition to nitrogen gas, the high-potency greenhouse gas (GHG) nitrous oxide (NOx) is also produced – a gas 300 times worse than carbon dioxide (CO2).
Recycling nutrients from wastewater is a topical issue in the industry, not least in light of the sludge inquiry currently in progress. Unfortunately, discussions around recycling requirements have been pretty much restricted to phosphorus extraction. The recycling of nitrogen from wastewater is just as important, if not more so, as conventional nitrogen fertilizer production gives rise to elevated greenhouse gas emissions at the same time as fossil energy reserves needed for nitrogen production are limited, said Klara Westling at IVL Swedish Environmental Research Institute.
Pilot to optimize and evaluate
Lund-based Ekobalans company has developed a method to recover nitrogen from wastewater. Unlike other technologies, this method delivers a solid product that has higher nitrogen content. Together with IVL, Ekobalans will conduct tests to optimize and evaluate this technology.
To facilitate this, Ekobalans has installed a large pilot plant at the Hammarby Sjöstadsverk WWTP at Henriksdal.
The development of this technology and its assessment is of value to all municipal treatment plants – not only in Sweden and the other Scandinavian countries. Many communities across the world are ramping up efforts to enable circular resource flows, and nitrogen is one of the most important of these – one that both impacts and is impacted by local communities, said Gunnar Thelin, Development Manager at Ekobalans.
According to the researchers, nitrogen extracted from wastewater is a neglected and underutilized asset. Significant resources are spent on nitrogen production to ensure safe food production at the same time as huge efforts are made to remove nitrogen later in the chain to prevent harmful emissions to the environment.
The project is striving to break this linear process by addressing both of these issues simultaneously to leverage circular nitrogen management.
We hope this will not only enable us to evaluate the technology but also to raise the discussion around nutrient recovery to a more inclusive and holistic level. We would also like to see more stakeholders engaging in ongoing projects and tests, commented Christian Baresel, Manager at Hammarby Sjöstadsverk.
In the experiments, we will examine the recovery of nitrogen from concentrated streams, such as nitrogen-rich water from the sludge drainage, but also from main municipal wastewater flows themselves.
The latter contains a greater proportion of nitrogen and if it is possible to recover this at this stage sewage treatment will be much more compact and efficient compared to today. To this end, parallel trials are underway testing new resource-efficient purification solutions.
