Operation of the Manz Slow Sand FilterTM (MSSF)

  • The traditional slow sand filter (TSSF) must be operated continuously or the biological layer (‘schmutzdecke’) responsible for removal of microorganisms will be damaged or killed.
  • Unlike a TSSF, the MSSF can be demand operated.
  • Raw water is added to filter without disturbing surface of media
  • Similar to traditional slow sand filtration, particulate material is captured on or near surface of the very fine filtering media
  • No particulate material is captured within media because the water is not forced into the media as it is in rapid sand filtration or pressure filtration
  • Flow to filter is stopped
  • Water level drains to paused or minimum depth (5cm)
  • Sufficient oxygen diffuses through the shallow layer of water to keep aerobic biolayer alive.
  • Paused depth should NOT be less than 5cm as the biolayer will be disturbed when water is added. Paused depths much greater than 5cm may limit transfer of oxygen to the biolayer impairing its performance. 5cm is considered the optimum.
  • Flow to filter resumes
  • Mature healthy biolayer still present

Development of the Biolayer

Beginning of operation
No biofilm around particles and no biolayer.

Formation of biolayer
(biofilm on the mineral particles, exactly the same as that observed in ‘trickling filters’ used for aerobic treatment of wastewater).

Biolayer thickens
with use and time.

The biolayer will form more quickly with greater concentration of aquatic life in the water and larger quantities of water being treated.

Biolayer thickens
and captured material accumulates.

Biolayer thickens
and captured material starts to restrict flow. 
Flow is unacceptably low and surface layer must be cleaned. Cleaning the MSF will leave biolayer intact.

Research Article: Visualisation of the microbial colonisation of a slow sand filter using an Environmental Scanning Electron Microscope
Electronic Journal of Biotechnology
ISSN: 0717-3458 Vol.11 No.2, Issue of April 15, 2008
© 2008 Pontificia Universidad Católica de Valparaíso -- Chile Received August 28, 2007 / Accepted December 6, 2007

Esther Devadhanam Joubert
Department of Environmental Sciences
Skinner Street Campus
University of South Africa

Balakrishna Pillay
Department of Microbiology
Westville Campus
University of KwaZulu-Natal

click here to view article

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Last updated Saturday November 27, 2010
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