Aqua-Swirl®, Stormwater Hydrodynamic Grit Separator

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The patented Aqua-Swirl^® Concentrator provides a highly effective means for the removal of sediment, floating debris and free-oil. Swirl technology, or vortex separation, is a proven form of treatment utilized in the stormwater industry to accelerate gravitational separation. Independent university laboratory performance evaluations have shown the Aqua-Swirl^® achieves a TSS (Total Suspended Solids) removal of 91% calculated on a net annual basis.

Each Aqua-Swirl^® is constructed of High-Density Polyethylene (HDPE), and is therefore modular, lightweight and durable, eliminating the need for heavy lifting equipment during installation. Inspection and maintenance are made easy, with oversized risers that allow for both examination and cleanout without entering the chamber.

Introduction

Aqua-Swirl^® Introduction

The Aqua-Swirl^® Concentrator Conveyance Flow Diversion (CFD) System provides full treatment for the most contaminated first flush, while the cleaner peak storm flow is diverted and channeled through the main conveyance pipe. Many regulatory agencies are establishing water quality treatment flow rates for their areas based on the initial movement of pollutants into the storm drainage system.

The operation begins when stormwater enters the Aqua-Swirl^® through a tangential inlet pipe which produces a circular (or vortex) flow pattern that causes contaminates to settle. Because stormwater flow is intermittent by nature, the Aqua-Swirl Concentrator retains water between storm events providing both dynamic and quiescent settling of inorganic solids. The dynamic settling occurs during each storm event, while the quiescent settling takes place between successive storms. A combination of gravitational and hydrodynamic drag forces encourages the solids to drop out of the flow and migrate to the center of the chamber where velocities are the lowest, as shown from extensive CFD modeling.

A large percentage of settleable solids in stormwater are reported to be small and have low settling velocities. Therefore, the volume of water retained in the Aqua-Swirl^® Concentrator provides the quiescent settling that increases performance. Furthermore, due to finer sediment adhering onto larger particles (less than 200 microns), these larger particles settle rather than stay suspended in the water.

Operation

CFD Configuration

The Aqua-Swirl^® Concentrator Conveyance Flow Diversion (CFD) System provides full treatment for the most contaminated first flush, while the cleaner peak storm flow is diverted and channeled through the main conveyance pipe. The treated flow exits the Aqua-Swirl^® Concentrator behind the arched outer baffle. The top of the baffle is sealed across the treatment channel, thereby eliminating any possibility of floatable pollutants to escape the system. A vent pipe is extended up the riser to expose the backside of the baffle to atmospheric conditions, preventing a siphon from forming at the bottom of the baffle.

Offline Configuration

As recommended by the Center for Watershed Protection and some municipalities, the Aqua-Swirl^® can also operate in an offline configuration providing full treatment of the first flush; however this orientation will require the installation of additional manhole structures for diverging the flow to the Aqua-Swirl^® for treatment and converging back to the existing main conveyance storm drainage system.

Benefits

Custom Applications

The Aqua-Swirl^® Concentrator system can be modified to fit a variety of applications in the field. The angles for inlet and outlet lines can be modified to fit most applications. The photo on the left demonstrates the flexibility of Aqua-Swirl^® installations. Two Aqua-Swirl^® units were placed side by side in order to treat a high-volume of water while occupying a small amount of space. This configuration is an example of the many ways AquaShield™ can use HDPE products to adapt to a variety of applications.

Retrofit Applications

The Aqua-Swirl^® Concentrator system is designed so that it can easily be used for retrofit applications. With the invert of the inlet and outlet pipe at the same elevation, the Aqua-Swirl^® can easily be connected directly to the existing storm conveyance drainage system. Furthermore, because of the lightweight nature and small footprint of the Aqua-Swirl^®, existing infrastructure utilities (i.e., wires, poles, trees) will be unaffected by installation

Easy Installation

The Aqua-Swirl^® system has been designed and fabricated as a modular unit with no moving parts or assembly required on site. This facilitates an easy installation of the system.

Since all of AquaShield™ systems are fabricated from HDPE, the Aqua-Swirl^® is lightweight, and can be installed without the use of heavy lifting equipment. Lifting supports or cables are provided to allow easy offloading and installation with a backhoe. Compared to concrete systems, using an Aqua-Swirl^® can significantly reduce installation costs.

In addition, manufactured stub-outs for the inlet and outlet are provided. This allows the contractor to simply attach the Aqua-Swirl^® directly to the main conveyance storm pipe with rubber couplings. Typically, an AquaShield™ representative is present on-site to assist in the installation process.

Easy Maintenance

Inspection and cleanout of the Aqua-Swirl^® is simple. The chamber can be inspected and maintained completely from the surface. Free-floating oil and floatable debris can be directly observed and removed through the provided service access.

Cleanout of accumulated sediment will need to be performed when the usable sediment storage volume has been occupied. The depth of sediment can easily be determined using a stadia rod or tape to measure the top of the sediment pile and calculate the distance to the water™s surface.

A vacuum truck can be used to remove the accumulated sediment and debris. Disposal of the material is typically treated in the same manner as catch basin cleanouts. AquaShield™ recommends that all materials removed be handled and disposed of in accordance with local and state requirements.