Reduced emissions from onsite waste water treatment

Individual sewage accounts for about 15 percent of the emissions of nitrogen and phosphorus into the Baltic Sea. In lakes and bays the local contribution from private households could be even higher. These emissions lead to the eutrophication of the sea. In a project led by IVL Swedish Environmental Research Institute, individual sewages are to be tested in order to improve their ability to treat waste water from both excessive nutrients and pharmaceutical residues.

The three-year project Optitreat (Optimization of small wastewater treatment facilities) will be carried out by researchers in Sweden, Germany and Poland. Three typical individual sewage systems and their different control parameters such as residence time, pH and oxygen level will be tested to assess how well the various systems are when it comes to purifying the water from nitrogen, phosphorus, antibiotic resistant bacteria, drug residues and substances from hygiene products. In addition, the project has access to over 200 tests that have never before been compiled, which will provide a good statistical basis for the project's conclusions.

The aim is then to optimize the individual sewage plants based on the results; both in terms of fertilizing and the spreading of infectious substances, but also drug residues, antibiotic resistance, and household chemicals.

The study will also compare the current regulations for private sewage systems in Sweden, Germany and Poland and develop good examples of how to regulate the maintenance of the sewage installations in the best way possible. The capacity of the systems and the correct maintenance of the sewage system are prerequisites for a successful and efficiency treatment.

Optitreat is funded by the Swedish research foundation Mistra through the Baltic Sea BONUS program, an collaboration between Russia and the eight EU countries around the Baltic Sea.

Project facts


  • Period: 2014-2017

Partners: 5