Design Consideration for Effective Odor Control Cover Systems

Odor complaints need to be taken seriously. Here, find out what you should consider when it comes to the design specifications of an odor control system.

This content is sponsored by Geomembrane Technologies Inc. Sponsored content is authorized by the client and does not necessarily reflect the views of COLE Publishing. View our privacy policy.
Design Consideration for Effective Odor Control Cover Systems
The basic concept for an odor control cover system is straightforward: Cover a wastewater tank to capture odorous offgas, and then remove and treat the odors.

Interested in Tanks?

Get Tanks articles, news and videos right in your inbox! Sign up now.

Tanks + Get Alerts

A common side effect of wastewater treatment processes is the unpleasant odor that can linger near the plant, annoying neighbors, who then complain.

Often, the wastewater treatment plant was built many years ago in an isolated part of town. Over the years, the town’s population grew until subdivisions were developed next to the treatment plant. The new neighbors, offended by the odors, expect a resolution and know how to have their complaints taken seriously. Odor complaints become a political problem that must be solved, budgets are allocated to study and solve the odor problem, and professional consultants are retained. Odor sources are identified and odor levels are quantified. Solutions are explored.

Potential solutions often include:

  • Manage the neighbors’ complaints. Explain to the public the treatment plant is a necessary part of the town and is helping to fuel the local economy.
  • Stop foul air production by introducing new treatment technologies, fine-tuning the treatment process or adding chemicals to the wastewater.
  • Stop foul air from being bothering neighbors by intercepting and treating/masking odors with fogging/deodorizing systems, diluting odors by adding buffers, containing odors with covers or capturing odors with covers and then withdrawing and treating the captured foul air.

Potential solutions are evaluated in light of certain basic realities:

The treatment plant cannot be moved.

  • Utilities do not have unlimited resources, and there are many competing demands for budget allocations.
  • The treatment plant is a complex system that must be maintained so it can continue to function.  Any odor control solution must let plant workers do their jobs efficiently, effectively and safely. Often, periodic access to the tanks for inspection and maintenance is an important consideration.
  • The right solution is identified. For some applications, the right solution is to capture and treat odorous air (i.e., foul air is captured under a gastight cover and is then withdrawn and treated). This article presents considerations in the design of odor control cover systems.

General design components
The basic concept for an odor control cover system is straightforward: Cover a wastewater tank to capture odorous offgas, and then remove and treat the odors.

For the purposes of this article, an odor control cover system is considered to have the following components: a fresh air inlet point, gastight cover, foul-air withdrawal point, blower with ductwork and an odor treatment system. 

1. Fresh air inlet point
This element is often initially overlooked. The general design concept is that fresh air is drawn under the cover, mixes with foul air, and this mixture flows along under the cover until it is withdrawn. A fresh air inlet is therefore required. This is typically located at one end of a cover system, and the foul air withdrawal point is located at the other end.

2. Gastight cover
From the designer’s point of view, the desire is to have a cover that is sufficiently gastight with these considerations:

  • Foul air does not escape through leak points and lead to odor complaints.
  • Excessive fresh air does not infiltrate through leak points along the cover, creating relative dead spots upstream where offgas could collect in concentrations that could potentially damage concrete or equipment under the cover.

The gastightness of a cover is important because less leakage means foul air can be removed using a smaller blower and ductwork, thus reducing capital and operating costs.

From the treatment plant staff’s point of view, the desire is to have a functional system that controls odors while allowing workers to do their jobs operating and maintaining the plant. This often involves full access below the cover for inspection and maintenance.

3. Foul air withdrawal point
The foul air withdrawal point is the point where ductwork connects to cover system. The connection detail could be a duct stub, flanged duct or flexible coupler.

4. Blower and ductwork
As noted above, the gastightness of a cover is important because less leakage means foul air can be removed using a smaller blower and ductwork, thus reducing capital and operating costs.

5. Odor treatment system
Once foul air is captured and conveyed in a ductwork system, it can be treated by various technologies such as a biofilter, wet scrubber, carbon filter, proprietary media, etc.

Design Considerations
1. Gastightness
The gastightness of a cover is crucial to effective odor control. Most covers can be made sufficiently gastight through the use of ample caulking, gaskets and anchors, but it is important to note that there can be a trade-off between gastightness and ease of access.

2. Access
Full or partial access below the cover for inspection or maintenance is often desirable. With some covers, achieving the full access required in some applications means the cover has to be either disassembled and removed in pieces, or lifted off as one unit using a crane. This requires resources and assumes the cover removal is scheduled in advance as a planned maintenance activity. Full access in an emergency can be difficult. However, some covers are designed to provide quick and easy full access and gastightness. Ultimately, the choice of cover style depends on access requirements of the application, but choosing a cover designed to provide ease of access and gastightness can be beneficial in terms of design and operation.

3. Safety during access
Worker safety is always important at treatment plants and this certainly applies when covers must be opened for maintenance. If a cover is being manually disassembled and removed, the removal work necessarily creates openings through which workers could fall. This safety issue should be assessed and managed through the cover system design.

4. Cover height
The height of the cover profile is an important consideration in choosing a cover system. Some cover systems have a flat profile, some have a low profile arched shape, and some have a high profile arched shape. A flat or low profile results in less air space below the cover and allows use of a smaller mechanical system if the foul air withdrawal design is based on number of air changes per hour. A higher profile cover accommodates equipment protruding from the tank and might allow workers to walk under the cover if the environment under the cover is safe for them to work in, but it can require a larger mechanical ventilation system, which is more costly to install and operate.

5. Penetrations
Typically, covered tanks will have various penetrations through the cover, which can include pipes (discharge, aeration, water, etc.), valve operators, instrumentation, etc. All penetrations should be identified and coordinated with the cover manufacturer.

6. Site-specific customization
Almost every cover includes custom-designed elements. Factors that might influence a site-specific cover design include:

  • A tank opening with an irregular shape.
  • The presence of equipment that protrudes into the area to be covered.
  • Varying wall heights around a tank perimeter.
  • Specific locations where inspection access is required.

About GTI
Geomembrane Technologies Inc. (GTI) offers custom-designed structurally supported cover systems that securely cover tanks to help resolve odor issues while providing easy access to internal components.

For more information, visit our website at or contact Brent Howe, vice president of product management at or 506/449-0993.


Comments on this site are submitted by users and are not endorsed by nor do they reflect the views or opinions of COLE Publishing, Inc. Comments are moderated before being posted.