Contech Engineered Solutions -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.

Category: filters | storm water management | stormwater filters...

MasterFormat: Facility Storm Drainage | Stormwater Utilities

Contech Engineered Solutions
9025 Centre Pointe Drive
West Chester, OH 45069
Tel: (800) 338-1122

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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 incorporates a non-blocking screen.

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.
  • 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

2. Self-cleaning screen

3. Isolated storage sump eliminates scour potential

4. Internal bypass

5. Multiple pipe inlets and 90-180º angles

6. Numerous regulatory approvals


1. Superior pollutant removal

2. Ease of maintenance

3. Excellent pollutant retention

4. Eliminates the need for additional structures

5. Design flexibility

6. Proven performance

CDS Configurations
  • Inline, offline, grate inlet, and drop inlet configurations available
  • Internal and external peak bypass options available
CDS Maintenance
  • CDS provides unobstructed access to stored pollutants, making it easy to maintain.
  • Maintaining a CDS is a simple process that can be easily accomplished 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.
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.

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Pretreatment for Rainwater Harvesting

Our hydrodynamic separation products are ideal solutions for preatreatment to rainwater harvesting. Not only do they improve the overall water quality, they also provide protect the pumps and controls from being overburdened with material that could clog and damage the mechanical system.

Pretreatment to Storage

Our hydrodynamic separators are frequently installed upstream of detention and infiltration systems as pretreatment devices. By capturing the majority of sediment, hydrocarbons and trash and debris upstream of the storage system, maintenance becomes much easier as material is congregated into a smaller device with clear access for cleanout. Additionally, by utilizing pretreatment upstream of infiltration systems, sediment that would have clogged the stone voids in the storage envelope surrounding the storage chamber can be captured before entering the storage system thus extending the longevity of the entire system.

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.

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.