Increasing Wastewater Lagoon DO: A Case Study

Increasing Lagoon DO: A Case Study

Keeping wastewater lagoon DO (dissolved oxygen) at acceptable levels is crucial in order to maintain proper wastewater lagoon operation. DO plays a crucial role in the treatment process. Without it, the bacterial microorganisms will begin to break down the waste without oxygen, or anaerobically, a slow and malodorous process. This blog will examine a case in the suburbs of Chicago, where a facility went about upgrading their system as a means of increasing wastewater lagoon DO.

Wasco Wastewater Facility was experiencing low DO in their lagoon during the winter (the last time you would expect to see low DO levels). This lead to extremely unpleasant odors, as well as below average treatment of the wastewater. It became apparent that they had a severe problem with their aeration system.

Wasco’s Wastewater Lagoon DO Problem

Five years prior to the winter DO problems, Wasco had installed a fine bubble aeration system. The fine bubble diffusers they installed comprised ½” diameter tubing with perforations that essentially leak air (for information see our Fine Bubble Aeration Factsheet). This system is extremely efficient at transferring oxygen in clean water lab testing. Initially, it kept DO levels high, and promised to be an efficient treatment option. Unfortunately, in practice this didn’t turn out to be the case.

Increasing lagoon DO

Fine bubble lagoon aeration diffusers at Wasco (shown right) struggled to effectively mix due to the nature of the fine bubbles moving slowly in the water column and because they are positioned 3 feet above the floor—this left a dead zone under the diffusers where sludge can accumulate over time. The MARS Lagoon Aerator (shown left), on the other hand, both aerates with fine bubbles and mixes the entire water column, thereby minimizing sludge accumulation.

The fine bubble system failed to properly mix the water column. This resulted in 4–5 feet of sludge buildup. Not surprisingly, this amount of sludge buildup sufficiently clogged the diffusers, a common occurrence for this type of perforated aeration tubing due to the rigid holes in the material filling with solids. As the orifices became clogged, fewer bubbles could be diffused and lagoon DO began to drop below 1 mg/L, while higher backpressures could be seen at the air blower. With only 38 of the 73 diffusers originally installed functioning properly, it became a huge drain on facility time and money as the diffusers and blowers had to regularly be maintained and/or replaced.

Clogged Fine Bubble Diffuser

Clogged Perforated Tube Fine Bubble Diffuser pulled out of the Wasco Lagoon

With lower lagoon DO levels, an intense lagoon odor was beginning to be detected. As a result, Wasco feared that their treatment could be suffering, and, without corrective action, they would likely have wastewater lagoon turnover come spring (an event which would cause the bottom of the lagoon to rise to the top— along with the 4–5 feet of sludge). Clearly this would be problematic for the facility, those operating it, and those living nearby.

If you wish to learn more about the benefits of wastewater lagoon mixing, you should read another blog of ours: Wastewater Lagoon Mixing Alleviates Odor and Sludge Issues.

MARS Aeration: Increasing Wastewater Lagoon DO and Improving Treatment

When looking for new aeration system options, Wasco came across MARS Lagoon Aeration. This was an especially attractive option for their application as it incorporated two different types of bubbles in its treatment:

  1. Fine Bubble Aeration: This element would provide the efficient oxygen transfer necessary to increase the lagoon DO that Wasco had hoped to receive with their original fine bubble diffusers. However, by utilizing self-cleaning EPDM technology, the fine bubble diffusers on the MARS Lagoon Aerator avoid clogging (for more on the different types of fine bubble diffusers, see our Fine Bubble Aeration Factsheet). Moreover, the design of the MARS Aerator was one that would inherently prevent clogging as all of the diffusers are positioned 16 inches above the lagoon floor, so the contact between diffuser perforations and sludge is avoided.The MARS Lagoon Aeration System combines Fine Bubble aeration efficiency with Coarse Bubble Mixing in one Portable Platform.
  2. Coarse Bubble Mixing: This element is designed to provide substantial mixing and water circulation within the water column. As a result, sludge is less able to accumulate at the bottom of the lagoon. Coarse bubble aeration is known to create significant turbulence in the water to keep solids suspended, thereby limiting sludge buildup and possibly even reversing sludge buildup over time (to learn more see our article Wastewater Lagoon Sludge: Treatment or Removal).
  3. Portable Aerating: Furthermore, as the MARS Lagoon Aerator is portable in its design, it could be installed in the Wasco lagoons without taking the lagoon offline. This made the MARS Lagoon Aerator an ideal option for cost effectively retrofitting their lagoon aeration system and increasing their lagoon DO.

Wasco selected MARS Lagoon Aeration because it helped them solve the following problems:

  • Lagoon Dissolved Oxygen vs Temperature

    The Lagoon DO at Wasco was low despite the relatively cold ambient temperatures in winter, a clear indication of failing diffusers. Once the MARS Lagoon Aeration system was installed, lagoon DO increased despite warm temperatures.

    Increased wastewater lagoon DO

  • Improved efficiency of the system and treatment
  • Operation and maintenance became less burdensome in terms of both cost and time
  • No longer concerned about lagoon turnover
  • No longer concerned about lagoon odors

 

Learn more about the MARS Aeration System by downloading the MARS Lagoon Aeration Literature. Take your first step toward efficient and effective lagoon aeration today.

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