At the Nov. 16 Board of Aldermen meeting, Steve Womack with Maintenance Systems, Inc. (MSI) provided the board with an update on the city’s lagoon systems, citing issues with lagoon systems (LS) one, four, six, and eight.
“We gave them LS-one, LS-four, six, and eight, which needs to be replaced and upgraded to handle what we have now and for future growth,” Womack told The Star-Herald. “We're in the process of meeting with the engineering firm, with Gardner Engineering, to discuss upgrading the system.”
Though detailed costs are not yet available for the upgrades, costs would likely run to hundreds of thousands of dollars if the recommendations were all completed at once.
Womack said the supervisory control and data acquisition (SCADA) system, part of the HAWK system used in the wastewater department, needs to be upgraded at several city lift stations so MSI can receive a more accurate reading of how much water is being drained and from where it is entering the system.
LS-One, the city’s main lift station, has five pumps and motors that transport wastewater from the city to the lagoons. Womack estimated that these pumps are 30-35 years old, and he recommended the board to make LS-One their top priority due to its deterioration.
He explained that bottom plates holding pumps over the lift station were starting to rot due to accumulation of hydrogen sulfide, and compressors on the pumps have ongoing issues. Weather heads with enclosures over the pumps make it easier for hydrogen sulfide to get trapped inside.
“It's good to keep some of the weather out, but it holds that hydrogen sulfide in there,” Womack told the board. “And when you get into your different little contactors and relays, that hydrogen sulfide eats them up, and they can't make good connections.”
Suction pipes are also suffering from tuberculation, mounds of reddish-brown iron-oxide in the pipes’ interior, caused by bacteria-driven corrosion.
“After a while, you can see the tuberculation on the outside,” Womack told the board. “You have the same tuberculation on the inside, which will go from a shotgun bore down to a rifle bore, which puts strain on your pumps and your motors. We have a lot of that going on at several of them.”
Womack said control panels at all stations, part of the SCADA system, are dated. With numerous people wiring boards over 35 years, some have been bypassed, hindering MSI from receiving SCADA data.
“We're not getting our ratings on our SCADA. Which most of these are very old components, and you can't get some of the data out of those components that you can get with the new stations,” said Womack.
MSI has revamped two of the city’s 10 lift stations, including one near the trailer park on Knox Road where a new control panel was installed.
“It's fairly simple — no fancy bells and whistles. These are stainless panels, and we get them away from the lift stations, so gases won’t get to them,” said Womack.
He said another problem to look out for is sealing off conduits, preventing gases from coming back into the conduits when going down into the well-way.
“Most of the stations, they didn't think about that back in the day,” said Womack. “They just shoved that conduit in, crossed their fingers, and went on.”
A visual was shown to the aldermen of the other renovated station, now equipped with variable frequency drives (VFD). Womack said these drives are compatible with any SCADA system the city has or may have.
“You can float a laptop in the bottom of these VFDs and get all the information off your pumps — runtimes, how they're cycling, and rain events,” he said.
The pumps will also work on a curve, meaning a pump pumping 350 gallons per minute would likely pump around 325 gallons per minute after a year. After five years, pumps may be pumping 250 gallons per minute. But the VFDs provide a fix to keep stations running efficiently.
“With these VFDs, you can go in there and change the hertz on them, and you can get maximum run out of those motors,” said Womack. “And they do it in a way where it won’t kill the motor. So, they're very good and a lot of people use them at a lot of stations.”
Womack added that solid waste has accumulated in the pumps at LS-One, derived from grinder stations pushing the ground-up solids along to other pumps.
“What I would suggest and highly recommend is you put a muffin monster there to grind all of that up. You know, those pumps are big, and you don't want to pump it into the lagoon because you're filling it up with trash,” said Womack. “Most of them have a bar screen and any other particles like tampons and plastics that are ground up. Some of that, you could go to the bar screen and take it and clean it out.”
Womack said the SCADA system is important because sewer backups in the system rarely happen 8 a.m.-5 p.m. on weekdays.
“We all know nothing happens between 8 and 5. It's late at night on weekends. Which, our guys are doing a good job, checking these pumps, but in the middle of the night, if they go down, let's say in a rain event, we're going to have sewer backed up in the system pretty heavy,” said Womack.
To solve this problem, MSI plans to get the SCADA system running properly, acting similarly to a burglar alarm, where wastewater superintendent Howard Sharkey or MSI will be alerted if the system gets backed up.
Womack said if the city tried to bid out jobs for all of these projects at once, prices would likely be through the roof. He recommended a plan where the city could gradually add new control panels, pumps, and motors over time.
“If you piecemeal it together just like you would with your city workers, I mean, we can do a lot of the work. If you piecemeal it together, you're not going to spend that much money.”
