Aluminum Covers

Sustainable Odor Control Covers for Wastewater Treatment
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Sponsored by CST Industries, Inc.
By Celeste Allen Novak AIA, LEED AP
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Growing Wastewater Problem in Manchester, NH

With a growing population, Manchester, New Hampshire also had a growing wastewater problem. Camp Dresser & McKee engineering firm provided a comprehensive approach to odor control at the Manchester water pollution control facility, reviewing the complete system in order to propose solutions to the problem. The source of odors came from a numerous parts in the wastewater treatment process. These included odors from:

• Septage receiving, both at discharge and when stripped from the downstream process.

• The Crescent Road pumping station.

• Open tanks and channels.

• Sludge storage and dewatering.

• Multiple hearth incinerators.

As a short-term solution, the engineers were able to suggest operational changes. These included the increase in fuel and oxygen in the multiple hearth furnaces, reducing storage times, increasing make-up water to gravity thickeners, and other alternative practices. As an intermediate solution, the engineers recommended the construction of stand-alone septage receiving facility to receive, screen, store and meter septage into plant effluent. Odor control will be provided by the containment of septage in covered storage. The long-term improvements required the development of a new influent pumping station that would sequester highly odorous air and provide activated carbon control and later biofilters before allowing ventilation to the atmosphere.

Additional long-term improvements included changes to the primary facilities by the installation of aluminum primary tank covers for storage containers. Because the biological processes require clear, uninterrupted spans, the engineers designed truss supported aluminum covers that were supported from the exterior walls. These covers had to meet a 60 psf snow load, 30psf live load, pressurization of 2 in w.g. vacuum and 80 mph wind load with a deflection limit of L/240.

The aluminum covers and truss supported system were designed to expand and contract. A camber was designed into the flat cover to allow for drainage of rain and snow. The lightweight aluminum trusses were assembled from manufactured components on an adjacent area. Fully assembled trusses were raised in place by cranes and placed on the walls of the storage tanks. Aluminum plates were installed along with access hatches for observation of the treatment process. A large system of ductwork connected the treatment storage tanks. These were attached to the aluminum covers. Make-up air vents were also incorporated into the cover system. Before becoming operational, all air header piping was pressure tested. The covers were also tested for air pressure. Air filtration of the covers tested at 0.02cfm per square foot meeting the requirement for air tightness. Other testing, balancing and sampling were completed before the system was operational.

Construction began in December of 1997 and the system was operational by August of 1998. The contract was met within budget with a 2 percent increase in change orders. This large system includes one of the largest biofilters in New Hampshire providing a sustainable solution to waste management.


The Aluminum Industry and Sustainability

The consistent process improvement by the aluminum industry shows progress towards the development of a production processes that have reduced greenhouse gas emissions per ton of products. The 2011 American Aluminum Industry Sustainability Report “Aluminum: The Element of Sustainability” documents both the advances in sustainable production as well as the challenges.

Once produced, aluminum can be recycled repeatedly without loss in quality and strength. In taking a life cycle approach to the production of this material, the industry has made consistent improvements. According to this report,iii the primary energy demand in energy production decreased by seventeen percent and cumulative greenhouse gas emissions have decreased by seventy-two percent. The results are even larger for secondary aluminum production as primary energy demand decreased by fifty-eight percent and cumulative greenhouse gas emissions decreased by sixty-five percent. To offset these energy demands, the advantages of aluminum against other materials such as wood, steel, or concrete, comes from the continued recycling. In addition, the industry estimates that there is:

• “87 percent neutralization of energy consumption associated with all aluminum production via energy savings through aluminum’s use in road vehicle down-weighting in 2009; and.

• 92 percent neutralization of cumulative greenhouse gas emissions associated with all aluminum production via GHG avoidance through aluminum’s use in road vehicle down-weighting in 2009.iv

There are also challenges that the aluminum industry is facing when moving toward continued improvements in sustainability and performance. These include finding innovative ways to reduce energy and resources during primary production. The industry is also reviewing the wastes involved in the entire life cycle of this product, from mining, to casting operations research is ongoing to streamline the production of aluminum to reduce harmful production systems. One of the biggest challenges is the reduction and/or elimination of the by-products of bauxite refining. The North American Aluminum Association has joined other global organizations to find solutions to these and other difficult problems.

In addition, the industry is working on end-of-life solutions for aluminum materials. To reduce the amount of aluminum in landfills, the industry is reviewing data collection on materials, the possible development of material “bar codes” and other strategies to encourage recycling and re-use through a life-cycle inventory. Structural aluminum can be specified with up to seventy—five percent recycled content depending on the source of the materials, and manufacturers can supply data to that effect that can be used when documenting the sustainability of a project.

One of these strategies includes a commitment to the design challenge from the Department of Environmental Protection to Design for the Environment (DfE). The International Aluminum Association maintains a website that provides general information on aluminum and life cycle assessments including statistics on aluminum reuse and recycling. Designing for recycling is a new strategy for engineers and architects. By designing systems that can be deconstructed for re-use, the environmental benefits of the re-use of the material can be assured.

With this 2011 report, the aluminum industry has provided a published commitment to sustainability and in the future will be developing the following initiatives to help practitioners to meet sustainable targets. These include:

• “Regular and streamlined data collection of annual energy and material consumption and environmental emissions and releases from the industry’s production facilities in the region;

• Data and information collection on the use phase of major categories of aluminum products in terms of functionality, use pattern, service life, energy and material demand for maintenance, and quantifiable potential overall benefits brought to the society compared to alternative materials;

• Regular and optimized data and information collection on recycling of products in major market sectors;

• Data and information analyses on the life-cycle performances of the material;

• Development and monitoring of a sustainability matrix in the region, including environmental, economic and social aspects;

• Push for appropriate regulation and legislation on recycling; and.

• Active communications with stakeholders and the general public. v

These commitments and future actions are only the beginning of the movement toward responsible design through choosing a sustainable material. However, manufacturers also must commit to sustainable practices. Some of these include incorporating DfE and DfMA similar to those used in the Beckton Sewage project.

Truss supported covers in Oregon.

Truss supported covers in Oregon.

Photo © CST Covers


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Originally published in December 2013