The Downstream Defender® Select separator is the new generation of hydrodynamic vortex separator for treatment of stormwater run-off to protect the environment and meet water quality requirements.
Its customisable performance and extended range of chamber sizes allows engineers to tailor their drainage designs to meet specific pollutant removal standards – with the system capturing and retaining sediment, oils and floatables from stormwater runoff over a wide range of flows and in a small footprint.
Targeted pollutants include:
- Coarse and fine sediments, retained up to four times the treatment flow rate;
- Litter and debris;
- Liquid hydrocarbons (oils), plus option for enhanced retention;
- Sediment bound metals.
Applications cover:
- Areas requiring a minimum of 50% TSS removal;
- Highways, parking lots, industrial areas and urban developments;
- Pre-treatment to ponds, storage systems, green infrastructure;
- Areas where high solids and rubbish capture are a must.
The Simple Index Approach (SIA)
The Downstream Defender® Select is an integral part of the Simple Index Approach. Outlined in CIRIA C753 The SuDS Manual, this is a water quality design method for sites with low- to medium-risk pollution hazard levels. Sites with a high-risk pollution hazard level should consider a more precautionary approach.
The approach assigns pollution hazard indices to given land use for three pollutant groups - total suspended solids (TSS), metals and hydrocarbons. SuDS components are then selected until their combined pollution mitigation index score is greater than the pollution hazard index for each pollutant group.
Sizing
Designed for versatility, the Downstream Defender® Select accommodates various inlet pipe sizes and up to three inlets - eliminating the need for complex pipe connections, couplings or additional chambers.
The Downstream Defender® can be sized for different treatment goals and objectives. For design purposes, the selected model’s Treatment Flow Rate should be greater than or equal to the site’s Water Quality Flow Rate.
The hydraulic capacity of the selected model should be considered with respect to the peak discharge flow rate from the site.
If there is no treatment objective, just betterment, do not use a treatment flow rate and only compare the hydraulic capacity to the peak discharge flow rate.
There is an online tool available via the Roadstone website to assist in the design and assess the suitability of the system for a project.
Case Study – UCD Science Centre
UCD required a high-performance drainage solution for its O’Brien Centre for Science redevelopment - one that could manage surface water sustainably while meeting strict water quality standards.
The system needed to complement SuDS features such as green roofs, swales and open drains, and ensure pollutants were removed before discharge to the campus network and surrounding water bodies.
The Downstream Defender® was installed as a compact, high-efficiency pre-treatment device within the overall drainage strategy. It was positioned upstream of attenuation systems, effectively capturing sediments, hydrocarbons, floating debris and organic matter.
Its small footprint makes it ideal for space-restricted urban environments, while its lightweight plastic construction enabled fast, crane-free installation - reducing programme time and cost.
Learn more about the Downstream Defender and our other Stormwater solutions here or click here.