You may have noticed your sewer use fees went up in Bloomington-Normal this year. They rose 15%.
Bloomington- Normal Water Reclamation District [BNWRD] Director Tim Ervin said that’s about $2 per month for the average homeowner. And there will be several more years of double-digit percentage increases.
Over the next several decades, the fees will help pay for $300 million in improvements to the sewage treatment system in the Twin Cities. The state and federal governments are loaning residents the money up front.
There are several reasons.
“Such as aging infrastructure to water quality standards, to increasing the capability of our facilities to handle wastewater,” said Ervin.
Here’s what the money will buy.
Turning dark chunky water clear: unappealing but important
This is a story about poopy water and what we humans in Bloomington-Normal have to do with it to avoid sickening people downstream.
“Sugar Creek starts in Bloomington and then it flows down to the Salt Creek, and then from the Salt Creek it hits the Sangamon River and then it discharges in the Illinois River at Beardstown and from there it heads down to the Mississippi and then to the Gulf,” said Josh Stevens, BNWRD's operations superintendent.
The district operates two wastewater treatment plants, including one in west Bloomington.
“It’s 100 years old and showing its age,” said Ervin. “And we just need more capacity to handle additional wastewater and accommodate future growth.”
The second plant south of the Twin Cities near Randolph also needs a big overhaul to meet federal requirements to reduce phosphorus levels.
The main facility is rated at 22.5 million gallons per day. The plant can handle that through most of the dry season, said Stevens, but with more intense rainfalls, BNWRD must use combined sewer overflow facilities more often for temporary storage of the water — 10-15 times a year of late.
The district put in a combined sewer overflow lagoon in 2008 to try to eliminate direct sewer overflows into the waterway. That has helped, as have Bloomington and Normal municipal efforts to separate storm and sanitary sewers, though the city and town have said it’s unlikely the two will ever be completely separated.
Those measures will help manage peaks and will help treatment processes by keeping the sewage more concentrated when it arrives at the treatment facility.
Treating sewage is a complicated process.
“We do preliminary treatment to get out the heavy grit," said Stevens. "Then we use a process of settling out solids. Then we do a biological process to treat the nutrients we’re required to remove based on our National Pollution Discharge Elimination System Permit we get from the IEPA.”
Headworks
The sewage comes into the main plant on West Oakland Avenue in Bloomington.
The plant has two separate treatment systems; one looks a lot like it did a century ago. The second one is newer, but still needs updates. District engineer Shawn Maurer said both start with what's called "headworks."
“There are just some strong odors in here for the headworks, right? We’re screening off a lot of solids and things, so on a nice warm July day it gets a little ripe,” he said.
There are two huge rotating drums in this building with metal screens.
“As a pair it can put through 35 million gallons a day. Anything bigger than a quarter of an inch will get caught on these screens and brought up and then it goes up this chute here and then it goes through a small washing and de-watering process and then it goes to the dumpster,” said Maurer.
From there, the water goes to settling tanks to remove solids. Right now, the plant has an area grit chamber to do that. That will be upgraded to a vortex solution. Grit tanks settle. A vortex spins the water and forces more of the grit out of suspension. Now, workers use a clamshell bucket to scoop up the solids. Maurer said that's labor intensive. After the revamp, they also won't have to aerate the settling tank anymore.
“The blowers that put the bubbles in the existing aerated grit tanks are very inefficient from an energy standpoint. Vortex grit removal doesn’t require air so that cost goes away for us,” said Stevens.
Pump building
Ah yes, the pump station. It's in a distinguished looking tile roofed building designed by the famous Bloomington-Normal architect Arthur Pillsbury. It has great lines. Inside though, it's really loud.
Josh Stevens said it houses the main inflow pumps for plant one, the newer treatment system.
“This is lifting the water up to our clarifiers along Oakland Avenue there. Once it gets up to that point, it’s gravity flow the whole rest of the way until we get to clarification," said Maurer. "Then it goes under another pumping towards the tertiary treatment and the other UV units on the other side of the plant. This whole building and these pumps, pretty much original design of the plant. These pumps are going to go away and be replaced with a new submersible lift station. It’s going to be more energy efficient in the long run.”
In fact, energy efficiency is a theme for many of the projects the water reclamation district is doing. Ervin said it's the second highest expense behind payroll, $1.5 million a year.
"We're hoping to go to more zero electric use facilities. We're going to be using more solar and low-energy products, different green infrastructure to provide the bulk of the power to the facility," he said.
Distribution building
Once the solids are gone, workers de-water the gunk and give it to farmers for fertilizer — about 2,000 dry tons per year. That's applied to 250-300 acres per year owned by a handful of farmers. Biosolids have nitrogen and phosphorus and are useful organic matter. Ervin said they used to landfill it, which cost money. Now, they only pay the transportation cost.
“Our main goal is to get rid of the solids and distribute the solids in a green way,” said Ervin.
Next up is the distribution building that splits it into the two treatment process streams. The water looks like typical sewage, a light gray color. There's a strong odor, an ammonia sting in the nose.
“The water flows over these weirs into each tank. One tank is filling, and the other tank is draining. Those will automatically flip flop for us,” said Maurer.
The older museum-quality treatment process sends the water to a trickle filter. It's kind of pretty. A series of sprinklers sprays an array of umbrella shaped patterns over a deep bed of rocks.
“We’re going to have to basically put in a whole new type of process on that side of the plant specifically for the biological phosphorus removal which would include aeration tanks,” said Josh Stevens.
The rebuild will demolish the trickle filter. It won't be as pretty. New clarifiers will go there and the space in between the clarifiers and the existing clarifiers will be filled in with aeration basins. For now, the sprays go on and off every so often.
"The higher the flows the shorter the frequency in between, but the idea is to allow a dose, or a rest cycle, so the water can trickle through, and air has a chance to flow through the medium. Underneath, there are under drains where the water that is flowing over this media is collected and then conveyed over to the pump station for our nitrifying bio-towers," said Stevens.
Biotowers
Nitrifying Biotowers — two cylindrical buildings about 30 feet in the air — have millions and millions of species of bacteria. They go nom-nom-nom on unwanted nutrients.
The water drains down, goes into clarifiers, then to another pump house that lifts the water to a sand filter that takes even more contaminants out of the water. Stevens said all told, the treatment plant has about four different stages that require pumping.
"One of the things with the upgrades we're looking to is setting the plant up where we only have to pump it once and then we can flow by gravity and thus eliminate multiple pump stations. That's less maintenance you have. Fewer pumps to maintain, and then it’s less energy we're expending on it," he said.
The water goes from the sand filter to a clarifier. There's more bubbly air percolating up from bottom.
Aeration tanks
OK, back to the tour.
“We’re going to show you where we farm the bugs. Our aeration tanks are up here,” said Shawn Maurer.
Another treatment process the district uses is called activated sludge where millions of bacteria and other microbes are suspended in the wastewater under aeration and used to clean up the water.
UV polishing
And the last stage of all that ends this strange eventful and watery journey does what's called polishing.
“Our UV, ultraviolet disinfection unit is kind of the last pass. Water goes past this, gets disinfected, and goes out to the creek," said Maurer.
Some other treatment districts still use chlorine, though that's becoming rare. There is extra holding time for that method of final treatment and if there is a mistake it can lead to fish kills.
There are big signs in the UV building that say, “Don't look at the bulbs.”
"When the front ones are on you can sometimes see fish up here on the back end of it. Carp and other fish out of the creek will make their way up when the creek is up high, and they will get into the UV channel. Kind of a nice sign that the water is good if the fish are there, right?” said Maurer.
Right now, there are two ultraviolet facilities. The plant upgrade will consolidate those.
All told, it takes six or 11 hours for sewer water to make it from the start to the finish and back into the creek, depending on whether it goes through the treatment that belongs in a museum or the more modern method.
Other projects
BNWRD’s southeast facility at Randolph is currently being renovated with $41 million in state revolving loan funds. That includes a four-megawatt solar farm to help defray energy costs.
BNWRD also is looking to put in five miles of sewer lining on the west side of the community, on the north from Fairview Park to Illinois State University, and on West Market Street down to the BNWRD facility on West Oakland Avenue.
Carp and other fish out of the creek will make their way up when the creek is up high, and they will get into the UV channel. Kind of a nice sign that the water is good if the fish are there, right?”BNWRD Engineer Shawn Maurer
“We put a lining in it. It’s kind of like putting your sock on. Then it’s heated with water, and it forms a new pipe. It allows the wastewater to flow. It brings the pipe up to a new condition, without digging it up,” said Ervin.
The district also is building new sewers down the west side of the community, consolidating with the tiny Clearview sanitary district along U.S. 51 near the interstate exchange, and putting in a new sewage interceptor there.
Over the last decade, that has caused the initial price tag of about $100 million to grow to the current $300 million.
“We’ve added about 15 other projects in the community that are needed, but just have never been done," said Ervin. "Rather than focus on this one facility and neglect the rest of the system, we’re treating it as one system.”
While the water released from the treatment plant isn't potable, Ervin said it is healthy enough to increase species diversity in the creek and on the banks downstream. And being able to do it cheaper, better, and to federal standards, Ervin said, will be worth the money.
