Sand is used as a filtering media in many water treatment systems and facilities. This is also an eco-friendly method of treating waste water and the process is quite simple. It is cost-effective method that can be used by many industries. The basic principle is that water is percolated through a sand bed which removes the contaminants from the water.
There are different types of sand filtration. There are rapid sand filters, semi-rapid sand filters and slow sand filters. Rapid and semi-rapid sand filters require pumps and chemicals for the process. A flocculent which is the chemical used in these filters will facilitate flocculation. The chemical causes the particles suspended in the water to combine and therefore deposit in a process called sedimentation. When it comes to slow sand filters, the process doesn’t use any chemicals. The system is not pressurised. Sometimes, activated carbon can be used to aid the process. Also, you don’t need to use electricity for slow sand filters.
The process of filtering water through sand has been used for a long time. This can be used in residences as well as wastewater treatment plants. Rapid filters can be used to filter wastewater by stimulating biological activity to take place and break down organic matter. Water goes through the filter vertically. It is caught at the bottom with drains and directed to more treatment processes. In some cases, the water is allowed to penetrate into the ground. But it should be ensured that the water is free from contaminants so that it will not cause any environmental pollution. The slow sand filter can be used to produce safe drinking water. When the water passes through the sand, there are physical and biological processes that take place which contribute to removing pollutants from the water. With time, bacteria, algae and other micro-organisms can grow on the sand and these microorganisms will contribute to the filtering process. However, the layer of sand can become impermeable after some time when contaminants cause a blockage. When this happens, the sand will need to be cleaned by reversing the flow of water.
You cannot use chlorinated water in sand filters because it will have a negative effect on the microorganisms that are in the filter. This will affect the filtering process. The sand filters are best used for water that has low turbidity and a low algae percentage. The water should not be discoloured. When there is a high algae content or clay, it can clog the filter. The slow sand filter can be used in a residence. It will reduce the number of bacteria in the water and will improve the appearance of water as well. A sufficient quantity of water will be produced for domestic use and maintenance of the system is also quite low. However, the filtered water will need further treatment as the sand filter is not very effective against viruses. When the sand is routinely cleaned, the layer of microorganisms can deteriorate and the effectiveness of filtering can decrease.