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Test of ventilation in septic tank
Photo: Maja Englund

Function in on-site soil and infiltration beds for wastewater treatment

This two project, "Function in small on-site soil and infiltration beds for wastewater treatment in field" and "Function in small on-site soil and infiltration beds for wastewater treatment in field – competition", investigated the status of small on-site soil treat-ment systems for wastewater in field to find out if there were any common problems.

The purpose of the studys was to find out if there were any common problems in soil treatment systems and to suggest if they could be prevented. This after that several projects pointed out the occurrence of functional problems, such as clogging and decreasing purification.

Some of the result shows:

  • soil treatment systems with very high levels of water (≥ 11 cm) or very high levels of sludge (≥ 5 cm) in the distribution pipes indicate high water levels in other parts of the plant, which suggest that the plant is not working as it should.
  • It is importent that the size of the soil-bed is dimensioned correctly in field.
  • Larger water-loading installations should not be discharged to the soil treatment system.
  • The age of the soil treatment system can be a "natural" cause of very high water levels
  • To be able to make a control, control points are needed. If, for example, if ventilation pipes are not available, ventilation in the bed cannot be controlled. The same goes for control of the groundwater level, that is imopssible without a reliable measurement point.

One of the goals of the project was to propose measures to reduce the occurrence of functional problems. Some of the proposals are:

  • The different constructions in the soil treatments system must be possible to check
  • There sould be at Follow-up control of conditions in permits for exampel teh size of the bed and the distance to groundwater.

It is important to remember that the performed inspections only provide a momentary-view of the soli treatment system and not the operation of the soli treatment system over time. Following some soli treatment system over a longer period would give a better picture of the function over time and a better idea of how sludge and water levels can vary in different parts and with different seasons. There are also no studies on how, for example, different levels of sludge and water in distribution pipes affect the purification process in the STS. This needs to be studied in the future to increase knowledge and provide guidance on what measures can be taken in different types of functional problems.


Project name

Function in soil treatment systems



RISE role in project

Project manager

Project start


3 år


va-guiden, Uppsala kommun, Örebro kommun, Bollnäs kommun, Södertälje kommun, Ekerö kommun, Kungsbacka kommun, Miljöförbundet Blekinge Väst, Vara kommun, Herrljunga kommun, Marks kommun, Lilla Edets kommun, Svenljunga kommun, Hörby kommun, Värnamo kommun


Havs- och vattenmyndigheten

Project members

Supports the UN sustainability goals

6. Clean water and sanitation
Elin Ulinder

Contact person

Elin Ulinder


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