Sludge Watch ==> Minnesota - Water Treatment Sludge - the Other Sludge

[Maureen Reilly]

Sludgewatch Admin:  There are two kinds of municipal sludges - sewage sludge 
and drinking water treatment sludge.  The source water for municipal treated 
drinking water is often treated with lime to remove impurities. This sludge 
needs disposal.  It has little nutrient value to farms....but agricultural 
disposal is cheap.  See story below.

.........................................................................

Sludge: murky waters
Written by April Scheinoha
Thief River Falls Times
Oct 10, 2006 at 10:56 AM


It was a muddy task Sept. 26 during an adjourned meeting of the Thief River 
Falls City Council. It was muddy because the council apparently doesn’t know 
what it wishes to do and muddy because the subject matter was lime sludge. 
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About 35 people attended the public informational meeting, which was held to 
help the council decide whether it wants to proceed with one of three lime 
sludge management projects or proceed with none of them. Each project has an 
estimated price tag of at least $3.4 million. The council has yet to 
formally vote on the matter.
The issue has been sitting in the Utilities Committee, where council members 
were waiting for some sort of solution, said Acting Mayor Dave Carlson, who 
noted the costs for the project are probably increasing every day.
There are no grants available for this project, said Utilities Director Arlo 
Rude, who noted there are no-interest loans that are available. For those 
loans, the city’s project has received a score of 10. Other projects have 
received 180 or 190 points, meaning that they are more likely to be funded 
with the loans.
Water systems with violations usually score big points, noted Brian 
Bergantine of consulting firm Advanced Engineering and Environmental 
Services Inc.
Carlson said that city leaders are examining the project at all angles and 
are at the beginning of determining how they wish to proceed.
“We’re certainly wide open to alternatives,” said Carlson, who noted the 
public informational meeting won’t be the last meeting the city will hold on 
the project.
Water treatment
Currently, water is taken out of the Red Lake River and goes through the 
water treatment process. During this process, lime is used. “Lime is used to 
soften the water, and it removes minerals from the water,” Rude said.
As part of the water treatment process, sludge is created and flows to the 
three ponds near the water plant. Gravity causes lime, chemicals used in the 
water treatment process, and sediment from the raw water to settle at the 
bottom of the ponds. Lime sludge is created by this mixture of lime, 
chemicals and sediment.
Water also accumulates in the ponds and is later recycled. Rude estimated 
that recycled water to be 5 percent or less of the water flowing into the 
water treatment plant.
Lime sludge
Approximately six million gallons of lime sludge are generated annually by 
the city. That amount accounts for about 1.8 percent of the total annual 
water flow, according to information provided at the meeting.
The lime sludge is removed once a year from the sludge ponds and then hauled 
to city-owned fields near the Thief River Falls Regional Airport. One 
hundred fifty loads of lime sludge were hauled to the airport fields this 
year, Rude said Sept. 27. He noted that amount was a typical annual amount.
The city budgets $60,000 a year to haul the lime sludge to the fields near 
the airport, Rude said at the meeting.
The fields are currently rented to local farmers, and lime sludge 
application is scheduled when there are no crops on the fields, Rude said.
The city uses an average of 60 acres of land a year for the application of 
lime sludge, said Water Distribution Foreman Wayne Johnson.
Carlson asked Rude how long the lime sludge can be spread on the fields. 
Rude responded that it
depends on the volume of lime sludge generated by the water plant.
Capacity is also limited at the ponds. As the city grows, it is expected 
that the amount of lime sludge will increase and exceed the capacity of the 
ponds, Rude said.
Council candidate Larry Rohlf asked where the city sat if it decided to do 
nothing with regard to the capacity of the lime sludge ponds. He also asked 
whether it’s an issue that the city should be concerned about now or 15, 20 
years from now.
The city hasn’t made a projection, replied Rude, who added that it was hard 
to predict whether the city has five, 10 years until lime sludge exceeds the 
capacity of the current ponds.
Coping with the lime sludge
In 2002, Advanced Engineering found three possible methods for the city to 
cope with lime sludge. Those potential methods included a fabric filter belt 
press, a filter press and ponds.
As the name implies, a fabric filter belt press would take moisture out of 
the sludge with a filter, according to Rude. The sludge would then be hauled 
somewhere else. That project is estimated to cost $3.44 million.
With a filter press, the mud is pumped between a series of steel plates and 
moisture is squeezed out, Rude said. Then the sludge would be hauled 
somewhere else. That project is estimated to cost $3.9 million.
The filter press process is labor intensive since workers have to remove 
sludge from the machine’s plates since the plates don’t come clean, 
Bergantine said.
The ponds project is estimated to cost $3.7 million. If ponds were used, the 
three ponds would be similar to the existing ponds and constructed adjacent 
to the wastewater ponds, said Rude, who noted they would be sized to provide 
10 years of sludge discharge.
A lift station and two underground force mains would have to be constructed 
as well, according to Rude. Workers would have to directionally bore under 
the Red Lake River in order for the lime sludge and water to be moved to the 
proposed location of those ponds.
If city leaders decide to do any of those projects, they would also have to 
decide what to do with the sludge. “The sludge that is available from the 
sludge processing needs to be disposed of or used in some way,” Rude said in 
his presentation.
There are three possible disposal methods for the lime sludge – applying it 
on land, using it in a landfill or using it for a mono-fill operation (such 
as a pond).
“Land application is not a very viable alternative,” Rude noted in his 
PowerPoint presentation. He said the city looked at the Grand Forks, N.D., 
and MarKit landfills. Given issues with the future location of the Grand 
Forks landfill, Rude noted that landfill wasn’t a viable place. He added 
that MarKit was interested in the city’s lime sludge, but was concerned with 
the amount of water in the sludge. A MarKit representative has taken a 
coffee can of the lime sludge to determine whether MarKit wishes to use the 
sludge.
With a mono-fill operation, the sludge would be placed in a “land storage 
area,” such as a pond. “When a pond is full of sludge, the city will need to 
determine if capping the pond with clay and building another pond is 
required. If no other use for the sludge is available, then capping and 
building another pond is required,” Rude noted in his presentation.
Given the costs associated with each project and the disposal of the lime 
sludge, it is possible that the city may raise its water rates. Potential 
fee increases were shown at the meeting.
The public’s suggestions
At the meeting, attendees had a number of suggestions for the council and 
raised questions that seemed to suggest that the city should change the way 
it is currently handling lime sludge.
Council candidate Emery Lee questioned why the city didn’t haul the lime 
sludge more than once a year.
The airport fields are only available in August and September, replied Rude, 
who noted that there are chances of weather problems if the lime sludge was 
hauled from October to May.
Crop rotation and airport security are other issues that the city deals 
with, Johnson noted.
Resident Jim Burkholder asked whether it would be more feasible for the city 
to rotate the fields, much like a farmer rotating the crops that are planted 
in a particular area. “Would it be more favorable to the city to do that 
than to wait for the farmer to take his crop off?” he asked.
The city should be able to have any rental scheme it wants, Rude responded.
Residents also suggested other areas where the lime sludge could be applied 
to land or where the potential ponds could be located. Planning Commission 
member Don Barron suggested that the lime sludge should be applied to 
city-owned land one-fourth of a mile west of Thief River Falls.
Rude replied that a farmer rents that property.
Barron also suggested that the ponds be constructed in a 35-acre wooded area 
along Pennington Avenue, near the water treatment plant.
Rude said the city needed enough land to continue building ponds.
Burkholder suggested that the city construct ponds along Pennington Avenue 
and across from the water plant.
Storm sewer goes through that area, which was a wetland, Rude noted.
What now?
What city leaders plan to do about the lime pond issue remains to be seen. 
The matter will continue to be studied by the Utilities Committee.
It is believed that the Utilities Committee will recommend a course of 
action sometime in the future. Carlson told audience members that he 
couldn’t give them a timeline as to when that recommendation will be made.
Mentioning that it should be determined whether the city is producing more 
lime sludge and/or water, Carlson said, “I think starting at Ground Zero and 
looking at plant operations is the number one step.”

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