Stormwater Treament Measures

MUSIC simulates the operation of the following different types of stormwater quality improvement facilities:

	Buffer Strips are commonly used as a source control measure, particularly for management of road runoff. They are effective in the removal of coarse to medium-size sediments and can be used as an effective pre-treatment measure for bioretention systems. They also can assist in reduction of peak flows for smaller events and may promote infiltration dependent upon the underlying soil conditions.
	Vegetated Swales are open channel systems which use vegetation to aid the removal of sediment and suspended solids. These systems are subjected to fairly high hydraulic loading and the removal efficiency is dependent on the density and height of the vegetation in the channel. As for buffer strips, the vegetation can assist in reducing peak flows for a range of events (dependent on the swale width and length) and may also be beneficial in volumetric reduction through infiltration, dependent upon the underlying soil conditions.
	Wetlands are an effective stormwater treatment measure for the removal of fine suspended solids and associated contaminants, as well as soluble contaminants. They can also provide significant storage for a range of storm events. These systems use a combination of physical, chemical and biological processes to remove stormwater pollutants. They are commonly used as "end-of-pipe" stormwater treatment systems, but recent research has shown that they are scalable for application as near-source control measures. The model also has the capability to model the reuse of treated stormwater stored in wetland systems.
	Bioretention Systems (also known as biofiltration systems or rain-gardens) promote the removal of particulate and soluble contaminants by passing stormwater water through a filter medium, either for infiltration into surrounding soils, or for collection by an underdrain. This category is thus also used for modelling vegetated infiltration systems, whilst unvegetated infiltration systems are modelled with the Infiltration node (see below). Well designed bioretention systems can provide both flow management and water quality benefits. A range of factors affect the treatment performance of the bioretention systems, including the type and composition of filter media (e.g. loamy sand), the presence and type of vegetation used, and the presence of design enhancements such as the use of a saturated zone to enhance denitrification. In music, the prediction of bioretention system performance is based on extensive research undertaken by the Facility for Advancing Water Biofiltration (see www.monash.edu.au/fawb). It is strongly recommended that FAWB’s Stormwater Biofiltration Adoption Guidelines be consulted when designing (and modelling) bioretention systems.
	Infiltration Systems reduce the volume of stormwater, and hence the frequency of runoff and the mass of contaminants carried, by infiltration into the bed of the basin. In music the Infiltration node is used only to simulate the performance of unvegetated infiltration systems (e.g. using gravel or sand filter media). Vegetated infiltration systems should be modelled using the Bioretention node (see above). In general, the use of vegetated infiltration systems is advocated wherever possible. In unvegetated systems, coarse particulates are deposited on the floor of the basin. Dissolved material and very fine particulates infiltrate into the soil, hence the potential for contamination of groundwater needs to be addressed. Inflows in excess of the storage and infiltration capacity of the basin will overflow and continue downstream. By reducing the volume of surface runoff, infiltration systems help to counteract the increase in runoff volume and frequency that generally accompanies urbanisation.
	Media Filtration Systems are commonly modular or pre-fabricated systems which are used for filtering stormwater. These systems typically use a simple sand media, or a more specialised engineered media, and may be specifically tailored to provide water quality suitable for stormwater harvesting. You can edit the properties of this node to match the specifications of the filtration system being used (such modification should be undertaken only using published and peer-reviewed data).
	Ponds are stormwater treatment measures such as open water bodies (without significant shallow vegetated areas in the predominant flow paths) and ornamental ponds. The treatment of stormwater is predominantly associated with temporary detention to reduce peak flows and facilitate settling of suspended solids. Other treatment processes promoted in pond systems include phytoplankton assimilation of soluble nutrients and ultra-violet disinfection. These processes are currently not explicitly included in the modelling algorithm. The model also has the capability to model the reuse of treated stormwater stored in ponds.
	Rainwater Tanks enable reuse of roof runoff for in-house or garden use. While some settling may occur in the tank, the main contaminant removal process is the diversion of impervious area runoff to pervious areas (via garden use) or to sewer (after in-house use). Effective use of rainwater tanks can reduce the directly connected impervious area of a catchment, and help to counteract the increase in impervious area that generally accompanies urbanisation through reduction in runoff volumes.
	Sedimentation Basins are open water bodies aimed predominantly at the removal of coarse and medium particles. Typically they operate at high hydraulic loading rates, and have fairly short detention times. The treatment of stormwater in sedimentation basins is achieved almost entirely by temporary detention to facilitate settling of suspended solids. No other biological or biochemical processes are simulated within the Sedimentation Basin node.
	Detention Basins are open or closed storages aimed primarily at reducing downstream peak flows although they also offer some removal of coarse and medium particles. Typically they operate at high hydraulic loading rates, and have fairly short detention times. The treatment of stormwater in detention basins is achieved almost entirely by temporary detention to facilitate settling of suspended solids. No other biological or biochemical processes are simulated within the Detention Basin node.
	Gross Pollutant Traps are devices for effective removal of solids conveyed by stormwater which are typically larger than 5 mm. Often, they are used as the first treatment element in a stormwater treatment train. There are many proprietary gross pollutant traps currently suitable for use in urban catchments and information on their performance is becoming available. As for media filtration systems, information on performance of these systems should only be sourced from published and peer-reviewed data.
	Generic Treatment Nodes allow you to define "transfer functions" for flows and water quality for stormwater quality treatment measures which are not explicitly modelled in music. Generic nodes can also be used to model such situations as flow diversion, flow dilution, contamination by sewer overflow, etc.