NPHarvest – Sustainable recycling of phosphorus and nitrogen

The NPHarvest process consists of a pre-treatment process for ballasted sedimentation with lime for removal of particles and recovery of phosphorus as well as nitrogen recovery by ammonia stripping with hydrophobic gas-permeable membranes. The new process has low energy requirements, and uses standard chemicals. The products are pure ammonium salt and hygienically solid material containing phosphorus.

In the testbed RecoLab at Öresundsverket in Helsingborg, source-separated household wastewater is handled in a resource recycling facility that provides environmental benefits in the form of increased biogas production, reduction of organic pollutants and recycling of nutrient fractions with low metal content to agricultural land. Several processes are tested in parallel.

NPHarvest is now being tested on a pilot scale at RecoLab. The technology has been developed at Aalto University in Finland.

Previous tests with NPHarvest performed at the Viikinmäki Wastewater Treatment Plant in Helsinki in 2019 showed that the product qualities comply with legislation/recommended values (Konola, 2019). However, these tests were small-scale and were carried out with incomplete process equipment, which is why trials for a longer period of time and on a larger scale are needed. The parallel comparison with other nutrient recovery processes at RecoLab (struvite precipitation and conventional ammonia stripping) is unique to the study.

The project is part-financed by Svenskt Vatten Utveckling (project number 20-120) and J. Gust. Richert Foundation.

The project will study

  • How effective is NPHarvest technology in terms of economy, recycling rate and product quality in the treatment of sludge liquor compared to struvite precipitation and conventional ammonia stripping at RecoLab?
  • How large is the environmental impact of NPHarvest technology, calculated with life cycle assessments?
  • Is the quality of the recycled nutrient fractions acceptable?

Project members from Sweden Water Research and and its owners

Partners in this project