CDS® Stormwater Treatment

The CDS hydrodynamic separator uses swirl concentration and continuous deflective separation to screen, separate and trap trash, debris, sediment, and hydrocarbons from stormwater runoff. CDS captures and retains 100% of floatables and neutrally buoyant debris 2.4mm or larger, effectively removes sediment, and is the only non-blocking screening technology available in a stormwater treatment device.


Loading. Please wait

Superior Stormwater Trash and Sediment Removal

The CDS is a swirl concentrator hybrid technology that uses continuous deflective separation – a combination of swirl concentration and  indirect screening to screen, separate and trap debris, sediment, and hydrocarbons from stormwater runoff. The indirect screening capability of the system allows for 100% removal of floatables and neutrally buoyant material debris 2.4mm or larger, without binding. CDS retains all captured pollutants, even at high flow rates, and provides easy access for maintenance.

CDS is used to meet trash Total Maximum Daily Load (TMDL) requirements, for stormwater quality control, inlet and outlet pollution control, and as pretreatment for filtration, detention/infiltration, bioretention, rainwater harvesting systems, and Low Impact Development designs.

How CDS Treats Stormwater

  • Stormwater enters the CDS through one or multiple inlets and/or a grate inlet. 
  • The inlet flume guides the treatment flow into the separation chamber where water velocities within the chamber create a swirling vortex.
  • Water velocities in the swirl chamber continually shear debris off the treatment screen, making it the only non-blocking screening technology available in a hydrodynamic separation system. 
  • The combination of swirl concentration and indirect screening force floatables and solids to the center of the separation chamber trapping 100% of floatables and neutrally buoyant debris larger than the screen aperture.
  • Sediment settles into an isolated sump while floatables and neutrally buoyant pollutants are captured in the separation cylinder. All pollutants remain in these sections of the unit until they are removed during maintenance.
  • Stormwater then moves under the hydrocarbon baffle, and the treated water exits the system. The baffle acts as a wall for hydrocarbon containment. It contains previously captured hydrocarbons and prevents the agitation of hydrocarbons when high-flows spill over the diversion weir.
  • During high-intensity events, the internal diversion weir directs a portion of flows greater than the design storm around the treatment chamber and over an internal bypass weir.
  • Treated stormwater exits the CDS via the outlet pipe.

CDS Features and Benefits



1.Captures and retains 100% of floatables and neutrally buoyant debris 2.4mm or larger 1.  Superior pollutant removal
2. Self-cleaning screen 2. Ease of maintenance
3. Isolated storage sump eliminates scour potential 3. Excellent pollutant retention
4. Internal bypass 4. Eliminates the need for additional structures
5. Multiple pipe inlets and 90-180º angles 5. Design flexibility
6. Numerous regulatory approvals 6. Proven performance

CDS Configurations

  • Inline, offline, grate inlet, and drop inlet configurations available
  • Internal and external peak bypass options available

CDS Approvals

CDS has been verified by some of the most stringent stormwater technology evaluation organizations in North America, including:

  • Washington State Department of Ecology
  • New Jersey Department of Environmental Protection
  • Canadian Environmental Technology Verification (ETV)

  • California Statewide Trash Amendments Full Capture System Certified*

  • *The CDS System has been certified by the California State Water Resources Control Board as a Full Capture System provided that it is sized to treat the peak flow rate from the region specific 1-year, 1-hour design storm, or the peak flow capacity of the corresponding storm drain, whichever is less.

CDS Applications

CDS is commonly used in the following stormwater applications:

  • Stormwater quality control – trash, debris, sediment, and hydrocarbon removal
  • Urban retrofit and redevelopment
  • Inlet and outlet protection
  • Pretreatment for filtration, detention/infiltration, bioretention, rainwater harvesting systems, and Low Impact Development designs.

CDS Maintenance

  • Maintaining a CDS is a simple process that can be accomplished in less than 30 minutes for most installations using a vacuum truck, with no requirement to enter the unit.
Contech has created a network of Certified Maintenance Providers to provide maintenance on stormwater BMP’s.

To view documents simply click on (+) before the folder to view contents, then double click document file to open.

Hydrodynamic Separators for Inlet and Outlet Pollution Control

Keep trash and debris out of your lakes, streams and oceans by installing one of our hydrodynamic separators at the inlet or outlet of your drainage system.  Our systems - which include the CDS,  Vortechs, and VortSentry HS - are most effective on sediments, trash and debris, and oil and grease.

Hydrodynamic Separation for Water Quality

Our hydrodynamic separation products (including the CDS, Vortechs, and VortSentry HS) are reliable, easy to install, and offer high-performance, proven, stormwater pollutant removal. The systems are widely accepted for effective solids removal and can be designed to achieve your site treatment goals - including TMDL requirements for TSS and trash.


Treating Stormwater on Industrial Sites with Hydrodynamic Separation

Our stormwater treatment systems can be utilized on industrial sites and help bring sites into compliance with industrial National Pollutant Discharge Elimination System (NPDES) stormwater permits. We have over fifteen years of experience in the stormwater treatment market, and can provide reliable, flexible and cost-effective solutions to assist in meeting environmental permit requirements. Our hydrodynamic separation systems target sediment, trash and debris, and provide spill capture and containment for low density, non-soluble liquids like motor oil. These systems are typically specified as pretreatment upstream of stormwater filtration, infiltration or detention systems.

Bioretention Pretreatment

Keeping LID and GI sites free from fine sediments, oils, trash, and debris while functioning as designed can be time consuming and costly.  The practice of combining LID with treatment systems like the Jellyfish Filter or CDS is becoming more common. Doing so increases water quality, provides a single point of maintenance, promotes proper system functionality, and increases the aesthetic appeal by removing unsightly trash and debris.


CDS Installation Timelapse