12th December 2005 at 12:30 pm #643
Hi Rakhi,
The diffuser plate is essential to break the force of the water being poured into the filter. Without the plate, the water would seriously disturb the top sand layer, and damage the important biological layer. Regarding flow rate, actually the strong point of the BSF is that it can be used intermittently. Hence, the flow rate can vary during startup, or as a result of partial blocking over time as the filter media gets plugged by dirt. In principle though: the slower the better, as this provides more time for particles to settle and gives more time for the biological layer to consume pathogens.
Regarding particles of course and fine gravel at the bottom of the filter: these are only necessary to stop the sand media itself from blocking the outlet pipe. Water that percolates down trough the sand in all parts of the filter can easily find its way through the gravel to the outlet piple.
Regarding your question on what good microbes are: that is not my field at all but I would imagine that these are numerous organisms of different types – as long as they are not pathogens.
Finally, the height of the actual sand media (excluding the gravel layer) is best kept to around 50 cms as research has shown this to be an optimim minimum height to assure best filtration. Higher sand column is of course possible. The width of the filter can be altered without problems: this will only affect flow rate, e.g. the wider, the higher the flow rate.