Small-scale Wastewater treatment system based on Innovative filter Materials


The SWIM project aims to develop an innovative solution for small-scale residential wastewater treatment based on novel recyclable filter materials. The SWIM solution is based on a series of filters that can remove 100% of the phosphorus, 50% of the nitrogen and 99.9% of the bacteria while enabling the recycling of nutrients, in particular phosphorus.
A majority of residential wastewater treatment systems are based on soil treatment units that can filter residual suspended matter but are very poor at capturing nutrients. More advanced systems such as “mini treatment plants” rely on the chemical precipitation of nutrients, which have a number of drawbacks: toxicity, energy requirements, inability to recycle the nutrients once precipitated, prohibitive installation and maintenance cost for a single household. In practice, over 50% of the households that lack connection to the municipal sewer system are not compliant with the EU Water Directive as their sewage system lacks effective tertiary treatment capabilities.

Calculations show that the phosphorus emission from single sewer systems in many countries, for instance Sweden, can be equivalent or supersede all the municipal cleaning plants together. Locally, a single sewer can be the biggest source of phosphorus emissions to the water, and the Baltic Sea eutrophication is partly a direct result of the nutrient pollution generated by these “rogue” sewage systems. The top 3 countries contributing to this phenomenon are Poland (24%), Sweden (19%), Russia (17%) for the nitrogen input and Poland (36%), Russia (14%), and Sweden (13%) for the phosphorus input. Phosphorus is also an essential component in all living organisms and the use of phosphorus fertilizers in agriculture must increase in order to produce more food for the growing population despite the fact that phosphate rock is a limited and rapidly declining resource. It is therefore of great importance to develop and optimize filter materials for removal and subsequent recycling of nutrients from these systems.
The Baltic Sea eutrophication is a European issue, and a Swedish-Polish consortium has been established to tackle the problem of nutrient capture and recycling in small-scale decentralized wastewater treatment systems: four SMEs in Sweden and Poland (Bioptech AB, Bioptech Sp z o.o., Dot-Eko and POMInnO), and a leading edge university (KTH) focusing on environmental technologies.

The SWIM solution is a passive (using gravity when possible – not electricity and pumps) treatment solution that is simpler, cheaper and safer to install and maintain than current solutions, making it the solution of choice for upgrading or installing the 20M of European residential systems required to comply with the EU water directive. The project impact is twofold:

  • Reduced nutrient discharge to water sources, preventing the eutrophication process and therefore protecting aquatic life and water quality
  • Increased recycling of phosphorus that can reduce the use of commercial fertilizers, reducing the pressure on the limited supply of phosphorus, and providing cost-savings to the agricultural industry

Participating countries

Sweden (Bioptech Sweden, KTH)
Poland (Bioptech Poland, Dot-Eko, POMInnO)

Project overview

Project leader


Start date

Status Running

Duration months

Budget 1.4 M€


Norén Anders
Bioptech AB