2.4.1 Case Stories

2.4.1 Case Stories

1. Biological lamella separation by means of BIO-BLOK® 80 HD G

Technical information Biological lamella separation
Type BIO-BLOK® 80 HD G
Client Hjørring Kommune (Municipality)
DK-9800  Hjørring
Tel.: +45 98 98 63 35 / Fax: +45 98 98 64 72


Biological Lamella Separation
Principle drawing


Brief description of plant and process
Sæsing Renseanlæg (wastewater treatment plant) is a mechanical biological plant that is dimensioned for a load of 250 PE. The dry weather volume of water is approx. 60m3 per day corresponding to maximum 5.4m3 per hour. The demand on outlet for BOD5 and SS is 20 mg BOD5/l and 30 mg SS/l respectively.

The problem was too high outlets of suspended substances and BOD5.

It was decided to replace the filter medium in one of the existing biological rotor filters with the filter medium BIO-BLOK® 150 HD. At the same time, the filter medium BIO-BLOK® 80 HD G was installed in the existing final sedimentation tank as shown above (please see principle drawing).

This lamella filter causes that the water in the final sedimentation tank gets a more steady progress, and at the same time, the biofilm that grows on the lamella filter attracts the flocs that are difficult to settle. This results in the fact that fewer flocs etc. run over the overflow edge. Furthermore - as an additional gain - through the biofilm on the BIO-BLOK® 80 HD G, a biological reduction of BOD and N is achieved.

Treatment results
In 1997 Hjørring Municipality has worked on improving Sæsing Renseanlæg as there during the last few years have been problems with meeting e.g. the demands with regard to suspended substances. The result is an obvious improvement of the outlet quality so that the demands on this plant are now being met.

Please see the curves below for SS and BOD5 which show a reduction of SS from average 34 mg SS/l to average 7 mg/l corresponding to an improvement of approx. 80%. Naturally to that a reduction of BOD5.

Outlet Figures
Outlet figures for Sæsing Wastewater Treatment Plant, Denmark


BIO-BLOK filter media
Photo 1: Sæsing Wastewater Treatment Plant


BIO-BLOK filter media
Photo 2: Sæsing Wastewater Treatment Plant


BIO-BLOK filter media
Photo 3: Sæsing Wastewater Treatment Plant