The Bio-Sand Filter and ‘Ideas at Work’
Improving water quality for the rural community is a continuing priority in Cambodia and has been recognised in its Millennium Development Goals (MDG’s). Part of these improvements has seen a focus on household treatment methods to improve biologically contaminated water. One of these is the Bio-Sand Filter (BSF). IaW are always keen to take the lead in introducing and improving technologies based on good practice and user feedback. IaW recognised opportunities because of manufacturing and practical disadvantages of the conventional square BSF units. We decided to introduce the first round units to Cambodia because of a number of benefits they have. These are:
- A significant reduction in mould materials – easier to handle and transport to the production site
- Lower overall mould unit cost
- Ease of moving the unit on the ground – the unit can be ‘rolled’ by one person,
- As much as 20% less concrete required than conventional square units – cost savings all round – by cutting corners!!
- A more aesthetically pleasing design
Bio-Sand Filter mould components
The mould unit is an all steel construction manufactured to a high quality and finish. The main parts of the mould unit are shown in the exploded view below, these are:
1) the puller, 2) an inner mould, and 3) outer mould.
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The mould is simply bolted together, turned upside down and fitted with a copper outlet pipe. A concrete mix is then poured in the mould and compacted down. After several hours the puller is used to remove the inner mould after which the outer mould can be removed revealing the finished filter shell. The filter is then filled with sand and gravel layers.
The Bio-Sand Filter unit
Contaminated water is poured into the unit at the top. The water passes through the diffuser plate and the sand and gravel layers. Head pressure pushes water through the copper pipe in the base to the outlet point. Biological contamination is reduced through the actions of adsorption; mechanical filtering, predation (biological layer’) and natural die off. The typical flow rate of the unit is around 60 litre/hour.
Dimensions of the finished filter:
Outer diameter: 35cm
Inner diameter: 30cm