The small clean-water plant in Hardin County Water District 1 has seen many changes and upgrades.

Its team has had to blend old with new and demonstrate ingenuity to meet stringent effluent limits the state of Kentucky has imposed. Wastewater system supervisor Stacy Miller and his team are responsible for wastewater treatment and collection in the city of Radcliff, in the central part of the state.

Cross-training of teams for both treatment and collection, as well as a “solve more than one problem” approach for each new project, have helped the plant to meet its objectives, optimizing treatment efficiency and reducing cost.

Old meets new

Radcliff, a city of “hills and hollers,” has a population of 23,000 and a collection system that includes 48 lift stations. The Radcliff wastewater treatment plant handles 2.5 mgd on average and is designed for 4 mgd. Over the years, the plant has gone through several upgrades and iterations.

The activated sludge plant has a preliminary treatment building with two bar screens (Huber and Arlat) followed by a grit chamber with an air blower that forces the grit onto a screw conveyor. The wastewater continues to a splitter box that directs it to three oxidation ditches. 

Two of the ditches, each with 1.42-million-gallon capacity, were installed in 1984; a third was added in 1998 with a capacity of 1.49 million gallons. The plant operates on two ditches, holding one in reserve. Within the ditches, Hach probes constantly monitor dissolved oxygen, TSS, ORP and temperature in real time.

Improved RAS pumping

The plant’s mechanical return activated sludge system is fairly new; it replaced a set of tubes that would siphon sludge out of the clarifiers and into a wet well, from which it would be pumped back to the oxidation ditches. Operators found that the siphon tubes plugged up frequently, especially with rags or debris.

The new mechanical return activated sludge (RAS) pump station includes three 100 hp wet-dry Grundfos pumps with variable-frequency drives. These pumps constantly deliver RAS to the aeration process. The three pumps provide redundancy, ensuring an uninterrupted RAS flow. In addition, the waste activated sludge system has been automated for ease of operation.

“We have a lot more control over our treatment process with the new RAS station,” Miller says. “Because ours is an activated sludge treatment system, the plant’s success hinges upon the efficiency and reuse of its microorganisms and biology. Now we have a nonstop return.”

After the oxidation ditches, the wastewater enters two secondary clarifiers, followed by two 66,500-gallon final clarifiers. These smaller clarifiers typically operate one at a time to remove debris, scum and floating solids that passed through the first set of clarifiers. From there the effluent enters a TrojanUV3000Plus disinfection unit, installed during a 2017 upgrade. The effluent then flows down an aeration ladder before discharge to Mill Creek.

Special challenges

Since the health of Radcliff’s collection system plays a huge part in the functioning of the treatment plant, the district staff has had to deal with inflow and infiltration (I&I) from rain events in fall through spring. The plant has seen peaks flows of 15 to 20 mgd, well over design capacity and with potential to wash the plant out.

To combat this, the district upgraded the preliminary treatment building with the addition of a large concrete splitter box. All influent now enters the plant through this structure, which includes a manual gate that operators can raise or lower depending on how much water they want to divert to three equalization basins with a combined capacity of 5 million gallons.

Controlling influent flow is just one part of the solution; Miller and his team have established an I&I mitigation program. They aggressively inspect all lines using a CCTV contractor and use the information to develop a program to rehabilitate or replace damaged lines. In-house crews perform weekly lift station inspections; some that serve larger populations are checked daily.

Radcliff has nearly completed the installation of SCADA to its system to give operators real-time information from 31 key lift stations. Being built on karst topography, Radcliff has always struggled with sewer system overflows. A $9.6 million federal grant transferred from a neighboring water district has been invested mostly to upgrade lift station capacity and to enhance collection system capacities.

“Our water table here is very high, and we have a quite a number of lines that are deep,” Miller says. “That makes it a perfect storm for problems in the collection system.” The gravity system in many areas was laid deep enough to allow basements to tie in. Therefore, in maintaining the collection system, the district has challenges. The district is now keeping a running list of vitrified clay lines that are the most susceptible to damage, placing them on a priority list for cured-in-place pipe lining, if viable, or replacement with PVC pipe.

More simple solutions

In another example of problem-solving, Radcliff operators came up with a solution for an ongoing issue with algae constantly growing on the aeration ladder. They rejected chemical treatment as too costly and instead installed brushes and rakes on the clarifiers, but the algae kept accumulating. They ultimately solved the problem by installing aluminum sheeting to block sunlight from the aeration ladder; the algae immediately stopped growing.

Miller observes, “When it comes to finding solutions to problems, or where we believe we may need some type of upgrade or improvement, we have a process of working with our engineering manager and outside consultants to go through the problems with us and see what can be designed to solve multiple problems at once.”

Miller is the newest member of plant staff, having been promoted from Radcliff’s sister facility. His seasoned team includes William Bishop, Scott Johnson and Frank Raymer, all with Class 3 wastewater operator and collection certifications.

The collection team includes Jason Atcher and Michael Shanahan, both also heavy equipment operators, and collections technicians Daniel Young and Andy Alvarez. Cole Davis, a master electrician, is the plant maintenance and controls specialist.

Construction curveballs

Although upgrades have improved plant treatment efficiency, they have not been without challenges. Miller and his team are proud of their ability to stay in compliance through all the construction projects.

“We’ve been able to accomplish what we have because of this team’s ability to understand the collection system as well as the treatment,” Miller says. Everyone on the team has helped with projects in the collection system, reducing variability in the plant and delivering quality treatment even during the most disruptive times of upgrades.

“I came in green with novice knowledge of this plant and system,” Miller says. “My saving grace has been empowering the team to find solutions. I stay involved and contribute, but my team members’ ability to identify problems and offer solutions has allowed us to overcome our most daunting challenges. Our personnel are definitely the greatest tool in the toolbelt.”