Meeting Challenges Is All in a Day's Work for the Water Plant Team in Central City, Kentucky

A plant in western Kentucky finds creative ways to deal with the challenges of an aging workforce and excess treatment capacity.

Meeting Challenges Is All in a Day's Work for the Water Plant Team in Central City, Kentucky

Jordan Hooper, left, operator, and Jeff Ford, head of maintenance, perform routine maintenance work on the scraper motor for the sedimentation tanks.

The Central City (Kentucky) Water Treatment Plant was on the point of filling a major new demand when a change in federal rules took it away. That left the plant with greatly expanded capacity but not enough customers.

At the same time, the attractiveness of employment in larger cities made it difficult for the plant, in western Kentucky, to find and retain qualified operators.

With innovation and persistence, the Central City team faced the problems down and overcame them. The capacity issue and its associated issues are under control, and an effort to develop operator candidates locally has dramatically dropped the average age of the team.

Along the way, the Central City team picked up the 2018 Drinking Water Plant of the Year award from the Kentucky Water and Wastewater Operators Association. In addition, the late Marvin “David” Dossett, the plant’s former lead operator, received the Kentucky Water and Wastewater Operators Association’s 2018 Earl T. Mitchell Award for his dedication and integrity.

The next generation

It was Dossett who began the program to develop a source of new operators. “Central City is a small town, but unfortunately we have a large plant that requires Class IVA operators,” says Ronald Mobley, chief operator.

Under Kentucky regulations, that classification is at the top of the system and requires a bachelor’s degree in science or engineering along with a year’s experience in a large plant. The unfortunate part is Central City’s location: It’s only about an hour’s drive from Evansville, Indiana, and Paducah and Bowling Green, Kentucky. All are much larger cities with big plants and bigger budgets for salaries.

In 2014 the mayor agreed to start an in-house training program; Dossett set up the standards and procedures for it before he died. The state provided an emergency allocation “because we were down to me and four operators trying to run 24 hours a day, seven days a week. Basically it was killing us,” Mobley says.

Another issue was age: The average for the team in 2014 was 52. Both problems were solved by hiring young local people, and the best place to find them was the local high school. So the first step was to set up a booth at the school’s career day. That produced one recruit, Austin Amos, who is now a Class III operator and will soon test for Class IV.

The next year, Amos went to the career fair and recruited Jordan Hooper who recently passed his Class IIIA exam. At the funeral for Dossett, Mobley began talking to Dossett’s grandson, David McDowell. He is now at the Central City plant and recently passed his Class I exam.

In addition to these people and Mobley, who is Class IVA, team members are Jeremy Leach, lead operator, Class IVA; Jason Lacefield, who handles information technology, Class IVA; Gary Dennison, second shift lead operator, Class IVA; Jeff Ford, Class IIIA, maintenance lead; and Matt Mathis, trainee.

Starting slowly

Training proceeds in stages. “The great thing is, David left an amazing set of procedures and guidelines for me,” Mobley says. “I love science and math, so it’s easy for me to get trainees excited, and they seem to respond well. And the city has been generous enough to allow the extra expense.” 

In the first year of employment, the goal is to not overload trainees. They spend some time with Ford in maintenance, learning basics such as how to rebuild a pump. Occasionally they receive a few hours of instruction.

As the time approaches for the first set of operator exams, training periods increase. Employees who reach Class II certification work alone for one shift each week, but a Class IV operator is on call. “We want to give them that one a week so they get used to the pressure of working by themselves,” Mobley says.

All the new hires have dropped the median employee age from 52 to about 35. When Mobley came on board, only one plant operator was from Muhlenberg County, where Central City is located. Now all the operators are from the county except Mobley and Leach, and those deep local roots make it less likely they will leave.

“Until a few years ago, all utilities did was steal employees from each other,” Mobley says. “If someone offered you more money, you’d leave. That’s no way to build a stable crew, and to be successful you need a stable crew.”

The employee-poaching problem was made worse by a statewide shortage of Class IV operators. “Most are older, in their 50s or 60s, and the pay is not what it needs to be for that much training,” Mobley says. “There is a risk that one of the people we invest in will be lured away, but if you don’t try, you can’t improve. I think we have a program that works, and so far it has paid off for us.” 

Conventional process

Water for the Central City plant is drawn from an intake about a half-mile north of the plant on the Green River. Potassium permanganate is fed at the intake. A 20-inch pipe brings raw water to a three-compartment splitter box with flash mixers. Carbon comes in just before the splitter.

From there, water is treated with heavy polyaluminum chloride for coagulation before it flows into two twin step-down flocculation chambers and then a pair of four-chamber, zero-sludge sedimentation basins. These are a new design that came with an expansion several years ago. The basin bottoms are shaped so that settling solids flow into pits. An arm slowly sweeps the bottoms, and every four to six hours the pits are emptied.

Chlorine is injected into the water after it comes out of the sedimentation basins and before it goes over the weirs. Filtration is done in six rapid sand filters of standard construction with rock, anthracite and sand. Filtered water enters a small clearwell and then is sent to a pair of larger clearwells — glass-lined tanks with a combined 1-million-gallon capacity. Two high-service pumps (National Pump) push the water out into the distribution system.

Flagging demand

Combined with the local market, the upgraded and expanded plant produced the other major challenge for Central City. The plant serves almost all of Muhlenberg County through water districts that buy from the city.

Among the customers of those districts are several coal companies. The largest customer, responsible for 50 percent of demand, is the Tennessee Valley Authority, the federal corporation that provides electricity to part of Kentucky and parts of six other states.

In 2009, the city ran up against a development limit: The plant could meet existing demand but no more, and no new businesses or coal mines were allowed. So the city worked with rural development agencies to get funding and authorization to expand the plant to a design capacity of 7 mgd with an expected average of 5 mgd.

As that was happening, the federal government began encouraging power plants to abandon coal and switch to natural gas. That greatly reduced demand for water from the water districts, which began aggressively following water-loss reduction programs. All this plus a slight rate increase dropped demand to about 3 mgd, where it is today. Unused capacity led to a problem: Violation of the limits on disinfection byproducts because water was sitting too long in the system.

Seeking solutions

“We tried to do some short-term things, but when the demand didn’t return, we had to face the market as it was,” Mobley says. For short-term fixes, the team looked at all the treatment steps upstream of the filters. They were more aggressive in using potassium permanganate. They used carbon daily and were aggressive in feeding it. They moved the chlorination point back to almost at the filters.

“Our primary process became optimized, but we were still having trouble,” Mobley says. “We were barely in compliance at the plant site.” After finding that half the chlorine residual was lost in the Central City distribution system, they shut down three tanks. That left 2 million gallons of storage in the city and 1 million gallons at the plant.

They did more experiments to find the best location for the chlorine injection. Every four hours they sample chlorine concentration upstream of the filters. A second chlorine analyzer on the effluent side of the clearwells tells operators how much the chlorine has degraded. As a result of testing, they added a second chlorine injection point just upstream of the high-service pump. The two injections and continuous readings from the analyzers allow operators to fine-tune the chlorine concentration just before water leaves the plant.

In the end, the plant was running at half its allowed byproduct concentration. Yet one challenge remained: While the plant was meeting its limits, byproducts were still above limits in the city.

The final change was shifting to a 20-hour run instead of 24 hours.

Before that change, the team found the storage tank in the northern part of the city was turning over only about 11 percent of its water each day. The other tank, in the southern part of the city, was turning over about 30 percent because that’s where some large customers are. Shutting the plant off for four hours and letting the SCADA system control demand resulted in about a 30 percent turnover in the north tank and almost 50 percent in the south tank.

The Central City team is not resting. With the help of a consultant, they recently finished a study of water aging in the entire distribution system. The intake site is getting sluice gates. New equipment will monitor corrosiveness of the water leaving the plant, and there is a lab upgrade in progress to add equipment and some space.

It’s all designed to adapt the system to low flows not likely to increase anytime soon. If the recent past is prologues, the plant team will pass the test with flying colors.


Dealing with low flows

When you have to run a large system at much less than its design capacity, there are problems that can’t be avoided. “You just can’t take a 5.3 mgd flow and cut it to 2 mgd without having some issues,” says Ronald Mobley, chief operator at the Central City (Kentucky) Water Treatment Plant.

To help cure a water-age problem in the distribution system, the water plant is shut down for four hours a day to force greater turnover in the tanks. With the plant off, the flow through the city is typically only 600 to 800 gpm, but a large customer on the system was demanding about 2,000 gpm. When that customer shut off its valves, they slammed shut. A hydraulic shock wave came back along the pipe.

“We were having pipes — a few — actually blow holes in their tops,” Mobley says.

One help in finding and solving the problem was the SCADA system. It allows operators to watch demand trends, Mobley says. Operators saw a flow and then sudden large spikes.

Another part of the water-age solution had been to shut down some storage tanks. But when the large customer put demand on the system, customers in another part of the city lost pressure.

The answer to the hammering and pressure loss involved putting one tank back into service. But when it was put back into the system, the water-age problem returned in that area. Engineers are still working on a short-term fix for that one, Mobley says.



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