Featured Video: Smelly Lagoon? Diagnosing and Correcting Lagoon Odors

As weather begins warming up for spring, many lagoons system owners have to manage odor issues and water turnover. In this week’s featured video, an experienced “Lagoon-atic” describes what causes lagoon odors and the best practices to manage them.

The most dreaded odors from lagoons systems are caused by sulfur dioxide and hydrogen sulfide gases. These gases emit a rotten egg odor that often leads to complaints from locals in the area. Under oxygen-stressed conditions, insufficient dissolved oxygen (DO) levels favor anaerobic digestion of biological oxygen demand (BOD) and sludge by sulfur bacteria.

This video also discusses the earthy smell of a healthy lagoon and other odor causing problems a lagoon may experience. Grassy odors indicate high levels of algae favored by warming temperatures, long detention times, excess sunlight, and excess nutrients. As spring approaches the solubilization of solids from the sludge blanket can cause nutrient release. This issue can be corrected by a reduction in the sludge blanket. Fishy odors may result from cyanobacteria growth under conditions with warm temperatures, high nutrient levels, thermal stratification, and still water. The longer water remains still, potential for cyanobacteria growth increases. Cyanobacteria can be reduced with chemical control, aeration, circulation, and ultrasonic waves. 

Spring time has potential to pose many odor issues for lagoon systems. Operators can maintain a healthy lagoon by ensuring sufficient DO levels, controlling sludge buildup, and mixing.

What's That Smell? Eliminating Wastewater Treatment Odors

With all this talk about public awareness of hidden water system infrastructure, it is important to point out that there are times when public awareness is definitely NOT on your side. And one of those times is when there is a stink that just doesn't go away.

Odors are generated from every phase of wastewater management including collection, treatment, and disposal, and they can cause all sorts of public relations issues, putting pressure on an utility to resolve the problem in a timely way. Certainly, managing odors is one of the most important - and yet most challenging - aspects of wastewater treatment. 

Why so challenging? Because in part there are many odor control technologies available but no single ideal solution. Some systems, like this Brownsville Public Utilities Board plant in Texas, solve odor problems by placing covers over wastewater tanks and channels and then blowing the smelly hydrogen sulfide gas through a biological tower. Others such as this Bridgeport, CN Water Pollution Control Authority plant, capture odorous offgas with coated fabric covers and treat it with a carbon system. Still others use a combination of  different measures, such as activated sludge diffusion, carbon adsorber sytems, pump station chemical feed systems, coverings and plant operation modifications. 

But fixes like these don't come easily, or cheaply. And sometimes, the problem is even more complex. Consider this story of a system in Saline, MI that has been the subject of neighbor complaints for years. Even after odor studies and abatement work, the smell just keeps getting worse. 

How can a smaller system then, with its limited funding and manpower, address odor problems effectively? The cheapest way to control odors is at their source, according to this Science Daily article, but sometimes that is simply not possible. Fortunately, researchers from the University of British Columbia may have recently developed a solution. 

Many wastewater facilities use anaerobic digestion, but is is expensive to acquire and maintain the associated odor control and biogas safety equipment needed. A much more cost-effective way to mitigate odors, these UBC researchers have discovered, is to revisit metal salts treatment. Simply adding new combinations of these common commercial metal salts during the fermentation process dramatically improves offensive odors, and also improves their ability for remove water from digested sludge. It is these unique doses/formulas and point of addition during the fermentation process that really amplifies the effectiveness of this new approach. Moreover, the cost of adopting their technique is minimal, so smaller systems can afford to test it out. 

In the meantime, if you need a quick primer on odor generation and management, the Water Environment Federation (WEF) has a 7-page factsheet explaining the problem and outlining advantages and disadvantages of various mitigation strategies. 

You can also keep an eye out for odor events right here on WaterOperator.org. For example, this Iowa training later in the month troubleshoots lagoon odor issues. Just type "odor" in the keyword search box on the event calendar page. 

Want to brainstorm with other wastewater professionals? Attend WEF's Odors and Air Pollutants Conference 2018 in Portland, Oregon in March, 2018. With sessions ranging from "Optimizing Hydrogen Peroxide Dosing" to "Odor Control Scrubber System Planning and Design," there will be many opportunities to learn in-depth solutions to any smelly situation.