Operation

The Aqua-Filter™ treatment train is designed to provide a high level of water quality treatment through the use of a swirl chamber (Aqua-Swirl™) for pretreatment followed by a filtration chamber for secondary treatment. The offline Aqua-Filter configuration uses a separate diversion structure, or weir device located upstream of the unit. The diversion structure is designed to direct only the designed water quality treatment flow through the Aqua-Filter system. Twin or multiple Aqua-Filter system configurations can be implemented to allow for higher treatment flow capabilities beyond that of a single unit.

The two treatment steps of the Aqua-Filter operation are described below.

Step 1. Pretreatment

The swirl chamber provides pretreatment by capturing and retaining coarse sediment, debris and free-floating oil. The captured (settled) particles are retained in the swirl chamber, while the treated flow exits the swirl chamber behind an arched inner baffle. The top of the baffle is sealed across the treatment channel to eliminate floatable pollutants from escaping the swirl chamber. Water is retained within the swirl chamber between storm events to a level equal to the invert elevations of both the influent and effluent pipes.

Step 2. Filtration

The pretreated water is then evenly distributed across the horizontal filter bed and allowed to permeate downward through the filter media. While downflow filtration designs are most commonly used, custom upflow designs can be used where there is little vertical difference between the inlet and outlet elevations.

The filtration chamber utilizes a number of filter media rows based on the specified treatment capacity. Each filter media container measures two feet (0.6 meters) long, one foot (0.3 meters) wide, and 0.5 feet (0.15 meters) thick. The filter containers are stacked one on top of another in an alternating configuration such that each filter row is one foot (0.3 meters) thick. Each row of filter media contains 12 filter containers and occupies an area of 12 square feet.

The filter media is capable of removing fine-grained sediment, heavy metals when bound to particulate matter and residual oil. Perlite is the most commonly used filter media in the Aqua-Filter™. Other filter media such as granular activated carbon (GAC), leaf compost, zeolite and various media blends are also available to meet site-specific discharge criteria.

Installation

Since all Aqua-Filter systems are fabricated from high-performance materials, the units are durable and lightweight and can be installed without the use of heavy lifting equipment. Lifting supports or cables are provided to allow easy off-loading and installation with a trackhoe. Compared to concrete systems, using an Aqua-Filter can significantly reduce installation costs.

Four routine underground installation steps for the Aqua-Filter are summarized below. It should be kept in mind that the Aqua-Filter can also be installed above grade to meet custom installation needs.

Excavation and Bedding. The trench and trench bottom shall comply with ASTM D 2321, Section 6, Trench Excavation, and Section 7, Installation. The unit is installed on a stable base consisting of Class 1 stone materials per ASTM D 2321, Section 5, Materials, and compacted to 95% proctor density. Additional bedding should be tamped around the “under-center” of the filtration chamber up to the springline to provide adequate support.

Pipe Connection Devices. Manufactured stub-outs for the inlet and outlet piping are provided to allow for simple attachment of the device to the stormwater conveyance pipe with rubber couplings. AquaShield furnishes the coupling between the swirl and filtration chambers. This only requires the contractor to supply rubber couplings to attach the pipes to both the swirl chamber and filtration chamber stub-outs for the system to function properly

Buoyancy (if required). All Aqua-Filter systems are supplied with anchor feet at each end of the filtration chamber to provide additional surface area to counter any buoyant forces exerted on the system. Concrete can be poured directly onto the anchors if necessary to provide additional resistive force. Note: The swirl chamber includes an octagonal base plate to counter any buoyant forces (see Step 3 of the Aqua-Swirl Installation summary).

Traffic Loading. The Aqua-Filter is constructed from Polymer Coated Steel (PCS) and designed to support HS-25 traffic loading. A traffic rated frame and cover is installed using a slip-fit and reinforced concrete ring to ensure no load is transferred to the riser.

Maintenance

AquaShield™ recommends that periodic system inspections be performed to determine whether the disposal of captured material is needed to ensure proper operation of the Aqua-Filter treatment system. It is important to keep in mind that all BMPs require some degree of maintenance. Maintenance cycles are ultimately dependent on site-specific pollutant loading conditions.

An Inspection and Maintenance Manual is furnished for each project installation for an end user(s) to track and document system operations. The unit should be inspected and cleaned at the end of construction regardless of whether it has reached its capacity for sediment or oil storage.

The filter media containers are the only components of the system that require replacement. The replacement of filter containers is generally needed if the filter media is observed to exhibit a dark brown or black color, and if a noticeable excessive accumulation of sediment, oil or other materials occurs across the filter bed.

AquaShield recommends that confined space entry techniques be used to perform tasks associated with filter replacement or entry to the filtration chamber for any other reason. A built-in ingress/egress ladder is provided in the filtration chamber and extends downward through the riser to the base of the filtration chamber and near the outlet opening. Proper health and safety protocols should be followed during all maintenance events. We also recommend that all materials removed during the maintenance process be handled and disposed of in accordance with all applicable federal, state and local guidelines.

Essential elements of an Aqua-Filter maintenance event include the replacement and disposal of the filter media containers, as well as vacuuming of floatables, oil and sediment from the swirl and filtration chambers.

The filter media containers are the only components of the system that require replacement. The replacement of filter containers is generally needed if the filter media is observed to exhibit a dark brown or black color, and if a noticeable excessive accumulation of sediment, oil or other materials occurs across the filter bed. Filter replacement activities can be performed without the on-site assistance of an AquaShield representative.