Screening Find out more about Hydro International

  • Storm King®
  • Hydro Jet® Screen
  • Hydro-Static® Screen
  • Heliscreen®

Storm King®

An advanced vortex separator with a self-cleansing, non powered screen designed to effectively capture a wide range of sewer solids.

The Storm King® is a vortex separation chamber with the option to incorporate unique, non-powered, self-cleansing swirl cleanse screening technology. The Storm King® is ideal for satellite treatment at overflow sites and has been shown to save municipalities up to 50% on overall project costs when compared to conventional solutions.


  • Floatables control, sedimentation and disinfection of CSOs
  • Upgrades to existing CSO facilities
  • New satellite CSO facilities
  • Treatment of excess wet-weather flows at WWTPs
  • Stormwater treatment at centralized stormwater treatment plants



  • Effluent meets and exceeds primary treatment equivalency for BOD and TSS removal
  • Vortex chamber can be used for disinfection
  • Screening down to 4mm for debris, floatables, gross solids and neutrally buoyant material
  • Save up to 50% on CSO project capital costs
  • No moving parts
  • No external power source needed
  • Low system headloss
  • Minimal maintenance required


Flow is introduced tangentially into the side of the Storm King® causing the contents to rotate slowly about the vertical axis.

The flow spirals down the perimeter allowing the solids to settle out. This process is aided by rotary forces, shear forces and drag forces at the boundary layer on the wall and base of the vessel.

The internal components direct the main flow away from the perimeter and back up the middle of the vessel as a broad spiralling column, rotating at a slower velocity than the outer downward flow. By the time the flow reaches the top of the vessel, it is virtually free of settleable solids and is discharged to the outlet channel. Prior to discharge, the overflow passes through the swirl cleanse screen.

The swirl cleanse screen captures all floatables and neutrally buoyant material greater than 4mm. The air regulated siphon provides an effective backwash mechanism to prevent the screen from blinding.

The collected solids and floatables are then discharged by gravity or pumped out from the base of the unit to the sanitary sewer. 


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Hydro Jet® Screen

Award winning, non-powered, self-cleansing technology.

The Hydro-Jet Screen is a self-activating, self-cleansing, CSO screening system with no moving parts and no power requirements. A compact device with high hydraulic throughput, the Hydro-Jet Screen is perfectly suited for small to medium size CSO sites.


  • Retrofit existing facilities
  • New CSO facilities
  • Satellite treatment sites
  • Floatables control for CSOs and collection systems


  • No moving parts or power requirements
  • Self-activating & self-cleansing
  • Low headloss
  • High throughput of 3.5 MGD per screen panel with small footprint
  • Low capital and life cycle costs
  • Upgradeable to tighter screen specifications
  • Pilot unit can be taken to your site


Dry weather flows pass through the Hydro-Jet® Screen chamber via the dry weather channel and continues to a downstream treatment plant.

During wet weather events, the flow increases as runoff drains into the combined sewer system. The water level in the dry weather flow channel rises as the Reg-U-Flo® Vortex Valve limits the flow passed through the continuation flow outlet.

Water in the dry weather flow channel rises until it spills over the weir wall and flows down through the angled self-cleansing screen.

As the water level under the screen rises to the crest of the siphon, the pocket of air trapped between the water surface and the screen creates a backwash mechanism.

Debris is lifted off the screen and carried down the screenings channel, which is returned to the continuation flow.

The siphon breaks, discharging the screened effluent to the receiving water body while drawing the water level in the overflow spillway down


The Hydro-Jet® Screen provides screening to 6 mm in two directions, to intercept and retain aesthetically offensive material and gross solids at all states of flow up to the peak storm flow with the material being returned to the continuation sewer. The dynamic, self-cleansing screen cleans itself using a patented, siphon initiated backwash cycle and as such requires no external power and has no moving parts.

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Hydro-Static® Screen

Removal down to 4mm provides cost effective floatables control. 

The Hydro-Static® Screen is a non-powered screening technology suitable for sites with infrequent overflows.

With a small footprint and a low capital cost, the Hydro-Static® Screen offers an economically sustainable screen for projects with limited budgets.


  • CSO sites with infrequent spills
  • Floatables control within collection systems
  • Retrofits or new CSO screening facilities



  • No moving parts or power requirements
  • Economical screening solution
  • Patented flow-modifying components provide partial cleansing
  • Components can be pre-installed in a precast concrete chamber
  • Mesh screen panels are coated in a non-stick polymer and corrugated to increase flow-through capacity


During dry weather conditions the flow to the treatment works will pass underneath the screens in the dry weather flow channel.

In a storm event the inflow rate to the chamber will exceed the outflow rate causing water levels to rise within the chamber and spill through the screens (red arrows).

The Hydro-Static® Screen is mounted over the dry weather flow channel so that the flow passes up and through the screen during a storm event. Solids and floatables are trapped below the screen and returned to the sanitary continuation flow (brown arrow). Screened effluent is discharged to a receiving waterway (blue arrow).

An emergency overflow weir is incorporated into the screen should the peak design flow be exceeded.


The Hydro-Static Screen provides screening to 6 mm in two directions, to intercept and retain aesthetically offensive material and gross solids at all states of flow up to the peak storm flow with the material being returned to the foul sewer after the storm event. The screen requires no external power and has no moving parts. A spray bar system can be provided where requested.

The Hydro-Static Screen is unique because of flow modifying components which enhance the naturally occurring recirculation patterns and therefore reduce the blinding effect when the screen is in operation.

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Compact, high efficiency screening under surcharged conditions

The Heliscreen® is a compact powered CSO screening system with the ability to operate under surcharged conditions. With low headloss and a small footprint, the Heliscreen® is ideal for retrofit installations with hydraulic or physical site constraints.


  • New CSO facilities
  • CSO retrofits
  • Sites constrained by hydraulic levels or chamber dimensions
  • Facilities with low maintenance requirements


  • 100% of screenings retained on the sanitary side of overflow weir
  • Operates under surcharged conditions
  • Low headloss
  • Compact design
  • Ability to handle high concentrations of screenings
  • Handles high concentrations of screenings down to 6 mm in diameter
  • Self-cleansing
  • Easy to install and maintain  


Water flows into the chamber and begins to flow through the Heliscreen’s semi-cylindrical stainless steel perforated screen.

Water levels in the chamber rise, initiating the rotation of a helical brush mechanism on the influent side of the screen. The spinning helical brush scrubs solids away from the screen and into the continuation flow while the effluent is discharged to a spillway. The screenings and continuation flow are carried on for further treatment.

As the water level continues to rise, spill flow and continuation flow pipes become surcharged. Excess flows are bypassed over the back plate/emergency overflow weir. Unlike most CSO screens the powered motor of the Heliscreen sits above the back plate to ensure that the device will continue to operate even in the event of surcharges.


The Heliscreen is an automatic self-cleansing storm overflow screen which prevents the introduction of aesthetically offensive material and gross solids, greater than 6 mm in two directions, into a receiving watercourse. The Heliscreen is continually brushed clean to ensure the foil does not bind and that the flow is discharged freely. The system has a unique ability to operate effectively under flooding conditions.

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Hydro International: Heliscreen® Hydro International: Heliscreen® (196 KB)