The components of aluminum, beams, trusses and long span structures required by the demands of large wastewater storage basins can be manufactured in many types of lightweight structural aluminum covers. Components can be custom extruded and fabricated to precise thicknesses that place the material in areas necessary for strength and maximize efficiency. This manufacturing process reduces the amount of materials needed in constructing a large dome or vault, enabling an efficient design and reducing weight and transportation costs. Aluminum domes or flat panel structures installed over large containment areas can be engineered to withstand the weight of snow or strong wind pressures with a minimum of materials used to create a light weight structure.

Aluminum covers can be provided in very low profiles. Due to the strength of aluminum structures, almost any design can be developed over the long spans required. Low profiles reduce the cost of air handling equipment inside treatment systems. For some treatment processes, scrubbers, with fans and blowers, pull air out and through carbon or bio filters to cleanse air before discharge. A flat cover allows for less air above the wastewater to be treated and cleaned. They can also eliminate the need for “confined airspace” entry by personnel. Low profiles decrease the size of blowers and air handling equipment which save energy and increase overall plant efficiency.

Aluminum components are easy to assemble. Welding is not necessary, saving labor and increasing quality control in the field. Aluminum domes are mechanically fastened using riveted, huck fasteners, insuring proper torque and installation. Stainless steel bolted fasteners are also used in discrete locations and throughout various components. Components are shop fabricated, reducing filed labor rates and providing higher quality control. The components of an aluminum dome are broken into manageable pieces for efficient packing and transport. For example, a 130-foot diameter dome can be packed to fit on one truck. The design for easy assembly and transportation of aluminum components is part of a sustainable strategy. One of the major innovations at the Beckton Sewage Treatment plant in the UK is the commitment to the sustainable principle and methodology of lean manufacturing or Design for Manufacture and Assembly (DfMA). This principle substantially reduced the number of construction workers required on site, increased site safety and construction reliability.

Types of Aluminum Covers
There are numerous types of aluminum covers for a variety of applications. Some of the types of treatment basins that benefit from covers include the following:

• Clarifiers (circular and rectangular) are part of the primary sedimentation tank system. Suspended solids pass through screens and filters in a clarifier in the first stage of primary treatment.

• Gravity Thickeners separate sludge through specific gravity or weight.

• Sludge Storage.

• Digesters (aerobic and anaerobic).

• Aeration Basins - typically rectangular.

• UV Basins – requires protection from daylight.

• Tricking Filters – with rotating distributors.

Clear span, truss supported flat covers in Brick Township, New Jersey, are designed to maximize equipment efficiency for sewage treatment. Photo © CST Covers

Some applications for covers require large spans and can be constructed as domes, vaults or flat surfaces depending on the project requirements. In some cases, an aluminum structure is selected to provide a cover over stored material, typically called a stockpile. The vault in Gainesville, Florida, illustrated in this article is 175 feet high and 160 feet wide and covers a coal stockpile.

Aluminum vault in Gainesville, Florida over a coal stockpile. Photo © CST Covers