A treatment train approach combines more than one treatment control to reduce the risk of harm from erosion and sediment and from dust.
A treatment control is a specific type of control measure designed to treat pollutants by removing, reducing or altering them as part of a management system.
Water run-off can carry a range of pollutants, including sediment and other fine particles. The controls you use depend on the pollutant and the level of treatment you want to achieve.
You can design a treatment train to address both:
- water quantity – by detaining high-volume flows and slowing down their velocity
- water quality – by removing a range of sediments, pollutants and nutrients from run-off before it's discharged into receiving catchments.
Treatment train processes include:
- screening – for example, pre-filtering technologies, litter baskets or gross pollutant traps
- sedimentation – for example, sediment basins or ponds
- adhesion and filtration – for example, bioretention systems, infiltration systems and wetlands
- biological uptake – for example, wetlands and biofiltration systems.
When to use a treatment train
Use a treatment train:
- if your land use activities could result in erosion, sediment, dust deposition and run-off
- to improve water quality, reduce run-off volumes or control water flow
- to improve visual and amenity outcomes for the community.
There are 3 treatment stages. Treatment controls in each stage depend on the size of pollutant they filter. Coarser sediments generally need to be removed first so that treatments targeting finer sediments can operate effectively.
Each stage can have one or more treatment controls, depending on:
- concentration of pollutants in the water
- types of pollutants to be removed
- water quality objectives.
1. Primary treatment stage
Screens and coarse filters remove litter, coarse debris and coarse sediment. Examples of primary treatment controls are:
- buffer strips
- grassed swales
- sediment basins
- ponds
- litter traps
- porous and permeable pavements.
2. Secondary treatment stage
Secondary treatments improve water quality by using settlement or filtration to target fine sediments and attached nutrients. Examples of secondary treatment controls are:
- swales
- infiltration trenches
- porous paving.
3. Tertiary treatment stage
The tertiary stage involves enhanced sedimentation and filtration. It removes dissolved pollutants (usually nutrients) through biological uptake. Examples of tertiary treatment controls are:
- wetlands
- bioretention systems.
Considerations and requirements
Choose treatment controls based on the hazards specific to your site and the level of risk of your activities. The selection and order of treatment controls is important.
The design and location of treatment systems need to suit the physical constraints of the location, catchment and flow pattern. Learn more about site planning and management.
Consult a qualified professional to make sure your treatment controls are appropriately designed and installed. Learn more about working with a consultant.
Conduct post-installation inspections of treatment controls and maintain them as required. Regularly review the effectiveness of the treatment train to confirm it's meeting set objectives – for example, for water quality. Adjust your treatment controls if you identify improvements you could make. Learn how to check and maintain controls as part of your risk management process.
Plan how you will remove and dispose of accumulated sediments and pollutants, in line with site waste treatment measures. Sediments will build up over time, so you must conduct regular maintenance to remove the accumulated sediment to:
- maintain treatment efficiency
- minimise the risk that sediments trapped in the system will be absorbed back into the water.
Treatment train systems retain much of the pollution load passing through them, particularly sediments and products of biodegradation. They may need partial reconstruction or complete replacement after a period of time.
Example of a treatment train
There are various configurations for treatment trains, depending on your circumstances. Below is a simple example to improve water quality with 3 treatment controls.
Primary treatment control: swales
- A vegetated buffer receives run-off carrying coarse sediment particles and dissolved pollutants, such as nutrients.
- Water slows down as it enters the vegetation. Sediments settle out, and water infiltrates the soil.
- The vegetation takes in nutrients from the water.
- Water leaves the swale with reduced levels of sediment and nutrients.
Secondary treatment control: sediment basin
- A sediment basin receives run-off carrying sediment particles and dissolved pollutants.
- The basin slows run-off and holds water to increase the amount of sediment deposited in the basin from the water.
- Water leaves the basin with reduced levels of sediment.
Tertiary treatment control: wetland
- Run-off is received by a wetland with multi-stemmed vegetation, such as shrubs, ferns, and mallees.
- Water slows down as it enters the vegetation, reducing erosion and increasing infiltration.
- The vegetation lets fine particles settle out as sediment and reduces the amount of trapped sediment that is absorbed back into the water.
- Wetland vegetation takes in dissolved nutrients and pollutants from the water.
- Water leaves the wetland with reduced levels of fine sediments and nutrients.
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