A simple sand filter for grey water can be constructed using a barrel or similar container with layers of filtration materials. Here's how:
Construction Steps
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Prepare the Container: Choose a barrel or other suitable container. Ensure it has a drainage outlet at the bottom.
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Base Layer (Gravel): Add a layer of gravel (approximately 1 inch) at the bottom of the container to facilitate drainage.
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Filter Fabric/Mesh: Place a sheet of weed mat or window screen (or other similar mesh filter) on top of the gravel. Cut it to fit the container's shape. This layer prevents the sand from mixing with the gravel.
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Sand Layer: Pour a layer of sand (approximately 10 inches) on top of the filter fabric. This is the primary filtration layer. Use a fine to medium-grade sand.
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Top Layer (Gravel): Add another 1-inch layer of gravel on top of the sand to keep the sand in place when water is added.
How it Works
Grey water is poured onto the top gravel layer. As it passes through the gravel, sand, filter fabric, and bottom gravel, particulate matter and some contaminants are filtered out. The filtered water then exits through the drainage outlet.
Important Considerations
- Grey water source: This type of filter is best suited for relatively clean grey water sources, such as shower or sink water. Water from toilets or containing large amounts of food waste is not suitable.
- Maintenance: Regularly inspect the filter and clean or replace the top layer of gravel and sand as needed. The frequency of cleaning will depend on the volume and quality of grey water being filtered.
- Disinfection: Sand filtration alone does not disinfect the water. Further treatment, such as a chlorine tablet or UV light, may be necessary depending on the intended use of the filtered water and local regulations.
- Local Regulations: Check with your local authorities regarding regulations and permits for grey water systems.
- Plant suitability: If used for irrigation, ensure the plants are suitable for grey water and are not for human consumption.
- Slope: Ensure the discharge area has good drainage and a slight slope for the water to flow away, avoiding pooling which could become a breeding ground for mosquitos.
Summary
Building a sand filter for grey water involves layering gravel, filter fabric, and sand within a container to physically remove contaminants. Consistent maintenance and understanding of the water source and intended usage are vital to successful implementation.
