Odor Control System

"Your treatment plant stinks again! What are you going to do about it?" 

Whether this complaint comes directly from an offended neighbor, or is routed through a council member or utility board, we know where the buck stops: the WWTP manager.

Odor complaints have become an all too familiar subject to WWTP managers. They are not only expected to manage their plants effectively and efficiently, meeting both regulatory specs and budget requirements – they are also expected to be good neighbors and keep odor under control. This article describes the successful odor control efforts of the South Dearborn Regional Sewer District located in Lawrenceburg, Ind.

 The district provides regional wastewater treatment services for three cities and an international distillery. The 6 mgd  treatment plant is located in an area of high population growth, and is surrounded by many retail operations and other commercial developments. In addition, a heavily traveled state highway runs by the treatment plant.

As the community grew, odor complaints became a sensitive issue, and the district sewer board was committed to solving the odor problem. The results of the district's initial attempts to treat or mask odors from their primary clarifiers were sometimes unsatisfactory, and it became apparent that neighbors' perceptions did not change as long as odors were occasionally present.

As South Dearborn Sewer District Superintendent Dennis Feichtner found, "The district would manage odors well for 62 days in a week and then have an unexpected 'odor event.' Then the telephone calls would start again."

The district evaluated alternative approaches and decided to purchase covers that would work with a ventilation and scrubber system to positively capture, remove and treat odorous gas. With the assistance of the district's consultants, GRW Engineers Inc., decisions were quickly made regarding a blower and scrubber to remove and treat the gas. The district's remaining task was to choose a cover system that captured and contained odorous gas while providing features that best met their operational needs.

After evaluating several cover systems, the district chose covers fabricated and installed by Geomembrane Technologies Inc. (GTI), with customized features to meet their operational needs, while fitting within the constraints of existing infrastructure.

Each clarifier is covered by a high performance coated fabric tensioned over a series of aluminum support arches placed along the length of the clarifier tank openings. This industrial fabric is a proven performer in a wastewater environment and features high strength, durability, and UV protection.

Aluminum walkways divide the fabric covers into manageable sections which are easily detached on three sides and rolled up along the support arches to expose the tank interior for inspection or maintenance. Hatches in the walkways are located at key points to provide access for a single operator to take samples, inspect equipment, tip scum troughs, etc. This easy access to the tank interior is a key feature for the district's plant operators.

They also point out that the need for complete tank access is not always part of a planned maintenance activity. Sometimes access is required quickly because of mechanical problems, and the ability to easily retract the covers without the aid of lifting equipment is a time-saving advantage in an emergency.

A customized cover design also made the GTI system an attractive choice for the district. Constraints imposed by the physical configuration of mechanical and electrical systems associated with the existing clarifiers were addressed by GTI. The cover design was modified to fit within these constraints, rather than requiring the district to incur the additional cost of changing their existing systems.

The district superintendent and plant operators took an active role in planning and installing the entire odor control system. With this assistance, the covers were installed in less than a week without taking the clarifiers out of service. District staff installed a blower and underground piping system between the covers and scrubber, and successfully brought the complete system online. The district is now able to capture and treat odors from its headworks, primary clarifiers and belt press building.

The odor control system has been operational for about one year, and Feichtner is pleased with the project's success.

"Odors have disappeared from our plant," he reports. "The subject of odor complaints used to arise so frequently that it was a standard agenda item at board meetings. With our new odor control system, odor complaints are no longer an agenda item in district sewer board meetings. Now we receive positive comments from the public."