Keeping the system running
Marshall’s Wastewater Treatment facility works round-the clock to treat sewage. A plan in the works to upgrade the facility would help keep things running.
It’s a big, complicated, and smelly job. But collecting and treating the city of Marshall’s wastewater is a vital job for both the health of the community and the Redwood River.
The city’s Wastewater Treatment Facility, located on Erie Road on the north edge of town, normally handles a flow of about three million gallons of sewage a day, said Marshall Wastewater Facility Superintendent Bob VanMoer. In addition to operating and maintaining the plant equipment, the city wastewater department’s 13 employees are also responsible for the wastewater collection lines and lift stations around Marshall.
“Most of the equipment is running 24-7, so it gets a lot of wear and tear,” VanMoer said.
Over the past 25 years, the wear and tear has taken a toll on some of the older equipment at the plant. That’s why an estimated $8.68 million construction project to upgrade the Wastewater Treatment Facility is in the planning stages.
“They’re working on the final design now,” VanMoer said.
In November, the Marshall City Council approved an agreement with engineering firm Bolton & Menk to design the updates.
The project would make needed updates to some of the plant systems and expand others to help keep things running smoothly, VanMoer said.
The wastewater plant can usually handle Marshall’s needs. Situations like the July 3 storms, where extreme amounts of rain fell on already-saturated ground, are an exception, he said. (They’re also an example of why sump pumps should not be connected to the sanitary sewer, he added.)
The planned plant updates are the first phase of a two-part plan, VanMoer said. In Phase 1, “We’re pretty much rehabbing old equipment,” some of it dating back to 1993, he said. The plan would also add some equipment to help ease bottlenecks in the wastewater treatment process. A second phase of the plans would start if Marshall gets new nitrogen limits for its wastewater.
Sewage being treated at the wastewater plant goes through several processes to separate out solid waste and to get pollutants out of the water, VanMoer explained. Besides filters and other water treatment equipment, the plant has several different structures called clarifiers, where solids are allowed to settle out of the wastewater. The sludge separated from the water is also treated to make fertilizer, and stored for future application on farm fields.
Several items in the upgrade plan would refurbish or replace pumps and other equipment at different clarifiers at the plant. An additional clarifier would also be built to help accommodate the flow of wastewater at the plant, VanMoer said. The estimated construction cost for the new clarifier is about $1.2 million.
Other upgrades focus on the plant’s trickling filter system. From the outside, the trickling filters look like two round concrete buildings. On the inside, VanMoer said, the buildings hold structures that look a little like plastic hay bales.
“There’s a big sprinkler system on top,” trickling wastewater down through the plastic media, he said. Bacteria grow on the plastic and help filter the water as it goes through the system.
The upgrade plan would rehab one of the plant’s two trickling filters, at an estimated cost of about $1.1 million. Typically one filter is in use while the other serves as an emergency backup, VanMoer said.
Another part of the plan would refurbish equipment for the wastewater plant’s aeration basins. The blowers and diffusers that help aerate the wastewater are in definite need of replacement, VanMoer said.
“It’s all needed,” he said of the planned upgrades. But replacing the blowers and diffusers was among the highest-priority needs.
Upgrades to the aeration system would cost an estimated $1.2 million.
Other upgrades would also include replacing some equipment used for treating the sludge removed from wastewater and turning it into fertilizer. Plus, an additional biosolids storage tank would be built, VanMoer said. The estimated cost for the new biosolids storage would be about $2.1 million.
VanMoer said the wastewater treatment upgrades are separate from a water-softening project being planned by Marshall Municipal Utilities. The MMU project would focus on water coming into Marshall utilities, and focus on cutting back the need for water softener salt in local homes.
VanMoer said cost estimates for the wastewater facility upgrades weren’t final, but so far the total construction estimate was about $8.68 million. The project is qualified to receive a low-interest loan from the Minnesota Public Facilities Authority, VanMoer said. He said over the past two years, the wastewater department has included the planned upgrades in its budget process, so the project shouldn’t have a big impact on future wastewater rates for Marshall residents.
“Those numbers are built into the rates,” he said.