The Town of Normal is making progress on an experimental project to remove ammonia from town water by using bacteria.
The pilot project began about a year ago. Water Department Director John Burkhart said if it works at scale, the town could save some costs on chlorine, adding the EPA requires water producers to have plans in place to deal with ammonia and may eventually regulate it more tightly.
The town is now collecting data, though Burkhart said it took longer than hoped to get the number of bacteria growing to what's called a steady state, at a stable effective level to remove the ammonia. The pilot project is small.
"Roughly two 55-gallon drums in size. We're talking about running a quarter to a half gallon per minute through it," Burkhart said on WGLT's Sound Ideas. "In comparison, we're running upwards of five million gallons a day right now."
Burkhart said the Village of Morton has used the process at scale for about a year. Normal's population is roughly three times that of Morton, according to 2020 census figures. And Morton has had challenges.
"As they increased flow through the plant [due to a sudden demand event] their biological system really struggled. It's nothing mechanical. You are growing these organisms and have to give them time to consume it. If you speed flow up through the plant faster than that can be done, you can see more ammonia on the backside," said Burkhart.
He said as long as water workers are prepared for increased flow, they can deal with the excess chemically instead of biologically.
The town is providing data to the Illinois and U.S. Environmental Protection Agencies. Burkhart said the agencies may require a full year of data from the pilot project before issuing a permit, instead of the nine months currently available.
"If they are comfortable giving us a permit, then we'll start looking at full-scale design," said Burkhart, adding he did not have reliable cost estimates for a system to process all town drinking water with the bacterial treatment.
"We thought we could do this with what they call one contactor. That hasn't been the case. That has been part of the problem in the slowness of getting to a steady state. We had to add a second contactor. We know the system is going to be bigger. We're not sure how much yet. That is going to increase the cost," said Burkhart.
He said some of the components in the town well water slowed the action of the bacteria to remove the ammonia.
"Just the hardness, the iron, components that are naturally there, nothing that is harmful," said Burkhart. "They can slow the growth of those microorganisms.
The town would like to see finished ammonia level at 0.5-0.7 ppm. The naturally occurring ammonia varies among the town's five wells that are considered in the Mahomet Aquifer.
"Typically, we'll see ammonia levels in that water from 2.0-2.5 ppm. The rest of our wells are shallower, they are a lot lower. They may be around 1.0-1.5 ppm," said Burkhart.
If they can get it there, said Burkhart, they can still use chloramines as a disinfectant. Adding more chlorine also would remove some ammonia, which he said could be useful for peak flow times.
“We don't need 100% removal,” he said.
Burkhart said wastewater treatment facilities have used bacteria to remove ammonia for a long time, but it's relatively new for the drinking water side. He said keeping some ammonia is good because ammonia can neutralize excess chlorine.
How thirsty are the Twin Cities?
Demand for water varies considerably seasonally. Peak water demand in Normal in the last couple years is more than six million gallons per day, said Burkhart. That typically happens in late August or early September when college students come back to town and while people are still watering lawns and filling pools.
Bloomington's peak demand days historically have had a broader distribution.
"Over the past 20 years, the peak day has occurred from mid-June to early September: eight in June, seven in July, five in August, and one in September," said the city water department. The historical peak day is 21.0 million gallons per day, set in 2005. For the past 10 years, the peak day is 18.9 MGD, set in 2023.
In Normal, average daily use last year was four million gallons. In Bloomington it was 11.1 million gallons. Bloomington said water production decreased from 2005 to 2016.
"This reflects a common trend during this time period when the water usage declined due to changeover to water- efficient plumbing fixtures. Since 2015, the average daily production has returned to the historical upward trend to the 11.1 MGD in 2023," said the city.
