| 3 min read | by Doug Marrin, |

The City of Dexter held an open house Thursday, October 17, 2019, to celebrate and share recent improvements to the newly refurbished and updated wastewater treatment plant (WWTP) with the community and its neighbors.

I know, I know, at first mention it doesn’t sound really exciting. What’s the big deal? Turn the tap on and water comes out. Flush the toilet and away it goes taking its burden with it to become someone else’s problem. We don’t give it a second, or number-two thought. Out of sight, out of mind. However, you might be surprised to learn that at $5.6 million, the wastewater treatment plant upgrade is Dexter’s largest capital improvement project to date.

I showed up early for the open house to get a private tour from Dan Schlaff, Superintendent of Public Services for Dexter, and Lead Utility Operator Eric Hartman. We started at the headworks building. “There’s an odor,” Dan warned me opening the door. I wasn’t too impressed, but I grew up on a farm. I noticed a trio of nice ladies wrinkling their noses. City slickers, I thought in a Jack Palance voice.

Dan Schlaff (left) and Eric Hartman

The headworks was one of the two big projects in the upgrade. This is where the preliminary treatment of wastewater begins. The upgrade was urgently needed because Dexter had squeezed all it could from the 1977 equipment which was far beyond its expected life. One of the huge pumps broke in 2017 and the City just couldn’t hold it any longer. They called in F&V Engineering, who specializes in such things, to bail them out.

“The equipment was failing,” Dan shouted above the working machinery. “We were down to one blower and the gradient around it was failing. The concrete was failing. The equipment and structuring were well-past their expected lifetime. We were at a point something had to be done.”

“The City of Dexter entered into a design-build agreement with F&V Engineering to execute the improvements,” shouted Eric. “The design-build model was different than previous improvement projects at the WWTP as control of the construction stays with the engineering firm instead of being relinquished to a general contractor.”

Inside the headworks building, where the magic begins

“You usually don’t find that in an engineering firm, at least not in my 35 years of experience,” said Dan. “I think that’s what made this project so successful.”

“It was determined that a completely new headworks system would be a slightly higher cost than a repair, but it would provide benefits to the other treatment systems at the plant while reducing energy use,” Eric shouted above the whirring machinery.

They were tag-teaming me with a lot of information. Eric went on to describe the choreographed movements of things like a coarse grinder, a fine particle grit removal system, submersible pumps, and something he called a “one-quarter inch screen” in the new headworks. I tried to connect Eric’s technical narrative to the NASA-looking room around me, clean, shiny and impressive. I was in over my head, figuratively speaking.

Bacteria added to munch away on the impurities

“Is this where the turds go?” I hollered above the noise. I didn’t expect it all to be so complicated.

“This is where everything goes,” Dan explained, politely coming down to my level.

I repeated the question. For some reason, this was important to me, enquiring minds et al. I was looking down at the gray water flowing through the concrete channels beneath the steel grates. I didn’t see anything floating. Old black water, keeping on flowin’ …

“The solubles are all dissolved into the water by the time it reaches here,” Dan said correctly guessing my thoughts.

We walked over a couple of steel grates as we moved around the room. I was troubled on the bridge over this water that some hidden flaw in the steel would suddenly give way under my weight and I would plunge into the depths below never to be seen again, like when driving over the Mackinac Bridge. What a way to go.

After the preliminary treatment in the headworks building, the water then moves on to primary treatment which is similar to the first stop – removing insoluble particles from the water.

“After receiving primary treatment, the water is mostly free of solids and moves on to secondary treatment,” Eric explained showing me a large holding tank of cloudy water. “In this process, bacteria are used to remove dissolved material from the water. Capturing these dissolved materials in bacteria cells allows them to be removed as a solid by settling into a sludge blanket similar to primary treatment.”

Bacteria added to munch away on the impurities

I asked him to repeat that part and he explained that after the bacteria gorge themselves on the water’s impurities, they sink to the bottom which I’m sure is why there is a rule about not swimming for a couple of hours after eating. This sludge is then moved to a “solids handling digester” where it receives further treatment to become fertilizer.

The water continues its day at the spa getting spruced up and rejuvenated to the tertiary treatment, or physical filtration in layman’s terms, for a final polishing up to remove any leftovers that might have eluded the process thus far. The tertiary filter system is the other large part of the plant’s upgrade.

“Tertiary improvements were needed as the existing sand filters were also original 1977 equipment that had exceeded their expected useful life and were not capable of reducing phosphorus levels to current standards,” explained Eric. “The system designed by F&V Engineering and City staff is capable of meeting the current phosphorus standards while reducing energy consumption.”

The last stage of treatment has the water being disinfected of any lingering bacterial pathogens and is oxygenated to ensure the water will support the aquatic life in Mill Creek and Huron River to where it was headed.

Teritary filtration system

I felt as though I should salute or something as the water left the treatment plant for reassignment in the wild. I didn’t realize that wastewater treatment was a catch-and-release program. I had learned a lot.

Thank you for your service, I thought in Mike Rowe’s voice as the water cascaded back out to the watershed. It had come a long way since its arrival from the sewers of Dexter to its transformation back to agua hermosa that would soon be free and rollin’, rollin’, rollin’ on the river. Of all the s#!t jobs I’ve ever been given, this one is by far the best, and oddly fascinating.

“I am grateful for this experience as it was rewarding to see the collaboration with City staff, City Council, equipment representatives, trade contractors, F & V, and also other municipalities who shared their time and experiences with equipment options,” said Eric. “The collective efforts from this large group is why I believe the project was completed in such a short period, on time and most important of all on budget.”

So rest easy Dexter. Everything is smoothly moving along, regularly just as it should with a healthy system.