Maximum flow rate & maintaining static water level?

[Guest]

#588

What is the maximum design rate for the vertical flow of water through the filtering medium and what is the user told about maintaining the correct static water level?

[Adriaan]

#591

Flow rate: we never made vertical flow rate an issue in our project design and have not evaluated the performance of the filters in this regard. When the sand is new (or recently washed), the flow rate will be high. Depending on the amount of water filtered and the turbidity of the water, the flow rate will fall progressively. However, it is important to note that a slower flow rate will have no negative impact on the quality of the water, rather to the contrary: a slower flow rate will increase the time during which the schmutzdecke can be active on the water passing through. In all cases in the field (rural Africa), users of the filter did not find flow rate an issue to bother with and maintenance (washing of the sand) was done mostly when the output of the filters became too slow for convenience. Often, ‘slow for convenience’ meant little more than a trickle that over the course of several hours still provided sufficient water for the family.
Adriaan

[Guest]

#592

The filter medium is 50 cm altogether. 5 cm concrete, 5 cm rough sand and 40 cm fine sand, which is the actual filter matrix. Once the filter is installed the user should not move it anymore. If they have to remove sand for cleaning purpose, they have to make sure after they applied the clean sand again, the remaining water level on top of the sand will be 5 cm again (not more and not less). The filter is design in a way that it hold the level itself. The use only must not use more than 50 cm sand for it.
Cleo

[Adriaan]

#595

Maintaining correct static water level: this is not an issue at all due to the particular design of the filter, in which the pipe at the bottom of the filter media is led up to a spout 3/4 up the filter. Thus static water level is automatically achieved. This is the one major technological advantage of this filter design (which Mr. Manz invented), as this guarantees that the schmutzdecke never dries out or is drowned under too much water so as to prevent access to sufficient amounts of oxygen (risk of anaerobic activity).
Adriaan