BIOROCK L and one BIOROCK E installation for 5 houses in Sweden

BIOROCK L and one BIOROCK E installation for 5 houses in Sweden




The renovation of a small group of unsewered dwellings requires the connection of 5 houses to two BIOROCK wastewater treatment units. The clients were equipped with concrete septic tanks and wanted to upgrade to a sewage treatment system with very limited maintenance and running costs however ensuring a top final effluent discharge quality.




Concrete septic tanks were provided by clients are retrofitted with two BIOROCK Units with pumped outlets. One BIOROCK L and one BIOROCK E are positioned next to each other for a total capacity of 25 PE. The effluent is pumped from the existing septic tanks and discharged to the treatment units. The volume of wastewater discharged has been calculated to be in line with each treatment unit's capacity. Two Phosphorous removal filters complete the installation before final water discharge.

Proper aeration is provided by electrical fans to reduce the high of the aeration pipes. This option was not a problem for the clients as a small power source access was available on site for the pumping and uplifting of the treated water at ground level after treatment.

Primary tanks were of adequate volumes, thickness, and in good condition. The installation of the BIOROCK pre-filter was possible, as well as ventilation of the existing septic tanks. These tanks have been emptied before suitability tests were carried out.

The site was accessible; leaving sufficient room for the installation which started after the competent authorities gave their consent.

 Treatment results: 

Treated water effluent quality after 1 year of operation was excellent:

  • BOD 7 = 5 mg/L
  • N-tot = 24 mg/l
  • P-tot = 0,36 mg/l (after P-tot filters final polishing)


The installation was carried out by the client's contractor under supervision by Evergreen Environmental Solutions.

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