WATER SENSITIVE URBAN DESIGN & CONSTRUCTED WETLANDS
OFF-LINE SECONDARY TREATMENT SOLUTION
Sand Filters are typically used in water-sensitive urban design (WSUD) as a component of a treatment train to remove pollution conveyed in stormwater runoff before discharge to receiving waterways or to underground storage for collection and reuse.
Sand filters operate in a similar manner to Bio-retention systems, with treated stormwater percolating downwards through a filter media and then being intercepted by perforated pipes located at the base of the media for conveyance downstream. Prior to entering the filter media (typically sand), flows must be subjected to pre-treatment to remove litter, debris and coarse sediment. This is typically achieved via an ‘inlet chamber fitted with a primary treatment litter basket as part of the system.
Although not commonly used today they still do have their application where site conditions, such as space limitations, or drainage grades, limit the use of bio-retention systems.
The range of Ecosol Sand Filters is able to be custom built to suit most applications and can be easily retrofitted into existing drainage networks. Ecosol Sand Filters are designed to remove and retain gross pollutants, sediment, free oils (hydrocarbons) and other attached particulate pollutants such as Nitrogen, Phosphorous and heavy metals present in stormwater runoff. The system is unique as it provides both primary and secondary treatment of stormwater flows within the one device.
The Ecosol Sand Filter is a multi-chamber engineered pre-cast concrete system consisting of:
An inlet chamber with removable filtration basket designed for pre-treatment (primary treatment) of stormwater flows. Pre-treatment of stormwater entering an infiltration system is critical as it minimizes the potential for clogging of the infiltration media;
A fore-bay chamber to reduce flow velocities entering the systems;
A secondary filtration chamber consisting of a sand filtration media with ponding for removal of finer particulate pollutants conveyed in stormwater flows (secondary filtration); and
An overflow chamber ensuring adequate discharge at peak flow eliminating the potential for scouring of the secondary infiltration media.
Ecosol’s Sand Filter series are predominately installed as off-line systems.
SAND FILTER KEY FEATURES AND BENEFITS
Compact, cost efficient stormwater treatment solution for high density commercial developments
Supplied as a complete system housed in its own pre-cast pit ready for installation
Easily maintained by vacuum truck
Durable robust product engineered for the environment in which it operates
Treats 100% if incoming flows up to its designed TFR
Provides both primary and secondary treatment of stormwater within the one device
At Urban Asset Solutions we can site measure, fabricate, install and maintain your Sand Filter making the whole process seamless.
The Ecosol Sand Filter is a multi-chamber engineered pre-cast concrete system consisting of an inlet chamber with a removable primary filtration basket into which stormwater enters from a conventional underground pipe. At Urban Asset Solutions we can design, manufacture or construct on site, a system specific to your catchment area and drainage design. Further we can commission, regularly inspect and maintain the system on your behalf.
The table below provides a guide on typical product configurations.
Urban Asset Solutions supplies the engineered layers of filter media, essential for secondary treatment of stormwater run-off separately once site conditions have stabilised. As a general guide these layers consist of the:
Drainage layer (clean washed, fine gravel such as 2 – 5mm screenings) designed to avoid migration of the filter media into the drainage layer.
Infiltration layer designed to filter and retain particulate bound pollutants conveyed in stormwater run-off
The table below provides a guide on typical media volumes for the above product range.
Ecosol Sand Filters are designed to treat stormwater runoff for typical developed urban catchments of 100 – 2000m2 (bases on a 100% impervious catchment). Ecosol designs each Sand Filter specific to site constraints such as space limitations, impervious catchment area and annual rainfall intensity ARI. Typically most Ecosol Sand Filters are designed to treat between 1.4 – 2.0L/s/m2 of bed area with ponding depths of 200 – 300mm respectively.
The below table provides an indicative guide of the treatable flow rates achievable for our standard pre-cast concrete system configurations.
Ecosol SAND FILTER TYPICAL MEDIA BED DIMENSIONS & TREATABLE FLOW RATE
Infiltration Bed Dimensions
Bed Area (Length x Width) (m2)
Ecosol Sand Filter Typical Media Bed Dimensions and Treatable Flow Rate - 2018
When designing the Ecosol Sand Filter careful consideration was given to ensure the system is able to be maintained easily. Multiple access points over each chamber have been incorporated into the design, eliminating the need for direct physical access inside the unit.
As with all filtration systems the Ecosol Sand Filter should be cleaned regularly. The cleaning frequency and the cost depends heavily on catchment conditions and rainfall. One of the key advantages of the Ecosol Sand Filter is that the primary filtration basket can be manually cleaned. As this is most likely to need regular maintenance, having the ability to clean it manually significantly reduces ongoing third party maintenance costs. The Secondary Treatment chamber containing captured coarse sediment and hydrocarbons will need to be cleaned at recommended intervals with a small vacuum truck removing all retained contaminants with each clean.
The tables below provides broad guidelines about the typical activities necessary to monitor and maintain your Ecosol Sand Filter to ensure it continues to perform to its designed specification.
Remove by either manual or vacuum method all captured and retained gross pollutant from within the pre-screening inlet litter basket
Every 3 months or immediately after storm event
Inlet Forebay Chamber (Sediment and Hydrocarbon Sump)
Remove by vacuum method all retained free floating hydrocarbons and settled settlement
Every 3 months or immediately after storm event
Secondary Treatment Chamber (Sand Bed)
Remove the top 50mm of sand and replace with an approved clean washed sand
Every 6 months or earlier if there is a noticeable reduction in the infiltration rate
Remove by vacuum method all sand and drainage media and replace. During this process flush out all underdrain filtration pipes to remove any accumulated sediment and replace the protective geofabric and engineered media
Every 24 months
Outlet/Over flow Chamber
Remove by vacuum method any sediment or debris from within the outlet chamber
Every 24 months
Inspect all structural elements to ensure structural integrity
Ensure all inlets and outlets from the system are free of any debris