Filamentous bacteria can cause operational problems for clean-water plants and are typically a symptom of a process upset that needs correction.

Different filamentous morphotypes point to different conditions, and operators can benefit greatly from being able to identify the various strains using phase contrast microscopy and make appropriate process adjustments based on their findings. Midwest Contract Operations, a company based in Neenah, Wisconsin, that provides hands-on technical support to municipalities, utilities and industries, has published an updated handbook of wastewater microscopy emphasizing methods of filamentous identification.

The company provides microscopy interpretation services to clean-water organizations throughout the United States and Canada.

The new 50-page handbook combines images of the most common filamentous organisms with easy-to-use tables and charts to help operators identify the different filament types and the issues they can cause. Ryan Hennessy, microbiology and operations specialist with MCO, talked about the handbook in an interview with Treatment Plant Operator.

: What is your background in plant operations and microscopy?

Hennessy: I worked for seven years at an industrial facility, and for another three years with MCO doing a split between operations and microbiology. I am still involved in operations on a fill-in basis. I took a number of wastewater classes from Moraine Park Technical College and Milwaukee Area Technical College. I have an Advanced Wastewater Operator license in Wisconsin.

: How did you acquire your knowledge of microbiology and filamentous bacteria?

Hennessy: For about 10 years I learned under Dr. Michael Richard, who is a world authority on wastewater treatment microbiology. In the 1980s and 1990s, he and Dr. David Jenkins did a great deal of work on the correlations between the different types of filament and their causes. I reached out to Dr. Richard through some wastewater forums and eventually took the class he was teaching in Oregon. Over the years, I would go to any wastewater plant I could find and take a sample of the mixed liquor. I would take and analyze a picture, send it to Dr. Richard, and he would tell me if my analysis was right or wrong.

: What is the history behind the handbook you have created?

Hennessy: In 2004, Dr. Richard, Dr. Jenkins and Glenn Daigger wrote the third edition of their handbook, which has been a popular tool for identifying and learning the different filaments. Between 2004 and 2020, we have learned a lot through DNA studies and more advanced technologies. Over the past 40 years, there is a really good track record in correlating what we see under the microscope with the actions we take as operators. We’ve also learned that there is a lot more diversity among filaments than we originally thought.

: Who has access to this handbook?

Hennessy: Anybody who wants a copy can have it. Dr. Jenkins as well as many highly esteemed colleagues have seen it; Dr. Richard was deeply involved in writing it.

: What is the value of this handbook for a clean-water plant operator?

Hennessy: If they can identify the filament types and the associated causes, then they can make appropriate corrective changes to the treatment process.

: Why does the handbook include images of glycogen accumulating organisms, phosphorus accumulating organisms, and nitrifying bacteria in addition to filaments?

Hennessy: Under the microscope we’re looking at filaments and also looking at indicator organisms. Everything you look at basically supports the big-picture diagnosis of what you’re seeing. You’re taking pieces of a puzzle and putting them together. The higher life forms, the floc structure, whether you have PAOs, the different filaments, you get a big picture of the sludge characteristics. Then the next step is to decide: Is there a problem or not? The biggest thing is to determine at what point you should act. That’s going to be different for every plant.

: Why did you decide not to include a dichotomous key for identifying filaments?

Hennessy: It is very easy to get on the wrong path with the dichotomous key, because it is highly dependent on staining reactions, which can often be affected by the chemistry of the wastewater. Often in industrial processes the staining reactions can be highly variable. The stains are still important, but when you start with them on the key, there is a lot of room for going down an incorrect route. Also, based on what we have learned from genetic research, the diversity among the different filament types may be a factor in abnormal staining reactions.

: Without the key, what helps users of this handbook make the right determination?

Hennessy: There is a series of pictures showing different morphology traits, like cell diameters, septa (crosswalls), presence of a sheath, branching, and different cell shapes, like sausage, rectangle, ovals, squares and elongated rods. There are also pictures of some of the more common filaments. There are descriptions of all the different filament types, and then there’s an identification table. It’s all built together.

: Why do the identification tools de-emphasize traits such as filament length, location, and shape?

Hennessy: Those traits in filaments are not entirely consistent. For example, a filament that’s typically located in floc may grow dispersed if it is growing fast enough. It’s the same with shape. You can have the same filament type and sometimes it’s curved, sometimes it’s straight, sometimes it can be in the floc.

: Do you offer any other tools that can accompany this handbook?

Hennessy: We provide hands-on training upon request and have a fleet of traveling microscopes. Also, due to the sample volume we work with, we are typically able to bring the majority of the common filament types and good samples for training purposes. From an operational standpoint we have an app to accompany our microbiology reports. The app contains all the different filaments and all the indicator organisms that operators are looking at. Users can pull up that app and follow trends to see which way things are going and determine where the plant runs the best.