Sand filters are being increasingly used in many parts of the country for storm water management. Each builder in Kerala is now trying to use the best rain water harvesting method in his projects. The water thus collected can be used for a number of purposes after proper filtration. After installation the maintenance of these filters is also very important.
Sand filters are generally thought to be one of the higher maintenance BMPs, but a recent study has shown that only 49 hours a year is required for field activities. Extended detention basins serving comparable sized catchments require much greater maintenance. In sand filters most of the maintenance includes routine removal of trash and debris as the outlet riser from the sedimentation basin can become clogged. In the sand media the hydraulic failure from clogging happens before the pollutant breakthrough. Generally only the top layer of sand becomes clogged while the rest of it remains in relative pristine condition. The clogging of the filter generally occurs after 2-10 years of service. The top 2-3 inches of the filter media is removed when the clogging occurs which restores most of the lost permeability.
The maintenance activities include inspections half yearly for standing water, sediment, trash and debris and finding out the potential problems. The accumulated trash and debris in the sedimentation basin from the riser pipe and the filter bed should be removed during regular inspections. During the wet season after a large rain event the facility should be inspected to determine whether it is draining completely within 72 hours. The accumulated sediment in the sedimentation basin should be removed every 10 years or when the sediment occupies 10 percent of the basin volume, whichever is less.
Sand filters are generally thought to be one of the higher maintenance BMPs, but a recent study has shown that only 49 hours a year is required for field activities. Extended detention basins serving comparable sized catchments require much greater maintenance. In sand filters most of the maintenance includes routine removal of trash and debris as the outlet riser from the sedimentation basin can become clogged. In the sand media the hydraulic failure from clogging happens before the pollutant breakthrough. Generally only the top layer of sand becomes clogged while the rest of it remains in relative pristine condition. The clogging of the filter generally occurs after 2-10 years of service. The top 2-3 inches of the filter media is removed when the clogging occurs which restores most of the lost permeability.
The maintenance activities include inspections half yearly for standing water, sediment, trash and debris and finding out the potential problems. The accumulated trash and debris in the sedimentation basin from the riser pipe and the filter bed should be removed during regular inspections. During the wet season after a large rain event the facility should be inspected to determine whether it is draining completely within 72 hours. The accumulated sediment in the sedimentation basin should be removed every 10 years or when the sediment occupies 10 percent of the basin volume, whichever is less.
