A North Carolina Water Plant Earns the Area-Wide Optimization Award

Operators at a North Carolina plant adopt new technology and climb a steep learning curve to tackle variable turbidity in source water.

A North Carolina Water Plant Earns the Area-Wide Optimization Award

When the staff at the City of King Water Treatment Plant applied for the North Carolina Area-Wide Optimization Program Award, they never expected to win.

“When we heard about the award five years ago, we thought there was no way we would win, but we figured we would try,” says Ben Marion, plant supervisor.

The award, from the North Carolina Department of Environmental Quality, recognizes water systems for outstanding turbidity removal. The King plant won for 2017. “We went from six to eight turbidity violations a year to none in the last three years,” Marion says. “We turned things around by adding equipment that allowed us to simplify the treatment process.” Average 2017 finished water turbidity was 0.02 to 0.08 NTU.

Operator challenges included varying source water turbidity, especially during heavy rain. In 2017, the average source water turbidity was 54.2 NTU and the maximum was 963 NTU. Operators also had to deal with a steep learning curve on new equipment. The plant boasts excellent finished water TOC: In 2017 the raw water TOC averaged 2.5 mg/L, and the finished water averaged 0.7 mg/L.

Conventional plant

The 3.0 mgd conventional treatment plant was built in 1967. It serves about 25,000 customers in King and the towns of Tobaccoville, Pinnacle, Rural Hall and Pfafftown. Plant staff includes Marion, supervisor; Mark Danley, assistant supervisor; four full-time operators; and a belt filter press operator. The plant operates around the clock.

Raw water from the Yadkin River is treated with polyaluminum chloride in a flash mixer before flocculation and sedimentation. The water is sent to four dual-media filters (Leopold - a Xylem Brand) and then enters the clearwell and is dosed with caustic soda and orthophosphate.

The finished water is stored in four inground storage tanks. Before distribution, it is chlorinated with sodium hypochlorite and then sent to three inground storage tanks before being pumped to one of three water towers.

Any wastewater generated is collected in a sludge decant tank. The clean water is dosed with sodium thiosulfate before discharge. Sludge is dewatered in a belt filter press, and the filtrate is returned to the head of the plant. Dried sludge is hauled off site for disposal and given away to farmers and to citizens to use for gardening.

Simplifying treatment

The plant received capacity upgrades in the 1970s and 1980s. In 2014, it switched from alum to polyaluminum chloride (DelPAC 2000 from USALCO). “Before then, whenever we had a major rainstorm that raised turbidity levels to 800 NTU or higher within 30 minutes, we had to run jar tests and then wait for the results,” Marion says.

The operators would feed 100 ppm alum, but the settled water turbidity was in the 6-10 NTU range. “The DelPAC 2000 simplified the process by using only one chemical for coagulation instead of the normal alum and pre-caustic combination,” Marion says. “The DelPAC 2000 has built-in alkalinity and pH adjustment, so no caustic feed is needed to raise the pH after the coagulant is dosed.”

Another improvement added in 2014 was a benchtop LCA-2 laboratory charge analyzer (Chemtrac). “It measures the negative surface charge of particles and predicts through a titration process the amount of PAC to feed to neutralize the charge,” Marion says. This allows operators to adjust chemical doses in minutes during heavy rain.

In 2015, another upgrade added a new raw water intake and pump station with two new vertical turbine pumps (Pentair - Fairbanks Nijhuis) and a static flash mixer (SPX). All these pumps have variable-speed drives (Eaton). Other additions included:

  • Two sedimentation basins with hoseless vacuum sludge collection
  • Two filters (Severn Trent) with an air scour system (United Blower)
  • Two vertical turbine pumps (Pentair - Fairbanks Nijhuis)
  • Chemical feed pumps (Milton Roy).

In 2016, the plant upgraded the SCADA to an InfoScan system with Dorsett Technologies software. “The system was designed around the specs that we wanted,” Marion says. “All dosages and chemicals are entered into the system, and the software increases or decreases the chemical feed rates based on the flow-through calculations done by the software.” 

Operators still control the raw and filtered water flows, and filters are backwashed manually, but everything else is automated. The high-service pumps and all distribution pumps are controlled based on tank levels. Operators watch water demand in real time and adjust the plant flow to match demand.

Trial and error

While the upgrades improved plant performance, the operators were challenged. “The equipment vendors trained the operators during startup, but a lot of the learning was through trial and error,” Marion recalls. “I played with the equipment and collaborated with assistant supervisor Mark Danley. We tweaked it and got feedback from the equipment controls. Only then did we pass this knowledge on to the operators.”

Source water turbidity is always a concern. “It varies widely,” Marion says. The plant lies in an area of farmland and Yadkin River tributaries. “It is a long river that starts up in the mountains. We’re in the middle, so we catch everything.”

The operators rely on many online monitors and constantly look at the raw and finished water turbidity, and streaming current numbers. An alarm sounds when the raw water NTU reaches 50. When it reaches 100, the operators conduct a five-minute jar test. They enter the dosage results into SCADA and wait five minutes to see where the streaming current is. The SCADA automatically boosts the feed based on the flow. “There was a steep learning curve for the operators to master all this,” Marion says.

A winning team

Marion has high praise for his team: “There has been a huge improvement from where we started to where we are now. Our operators have thoroughly learned the water treatment process and how it works. They take pride in the plant and enjoy coming to work. And now, with the recent Area Wide Optimization Award recognition, they come to work with heads held high.”

Marion holds Class A surface water treatment, Grade 1 biological, Grade 1 physical/chemical, and total coliforms and E. coli certifications. He also holds a bachelor’s degree in engineering technology from the University of North Carolina at Charlotte. Team members are:

  • Danley, Class A surface water treatment, total coliforms and E. coli certification.
  • Ronnie Gallimore, belt filter press operator, Class C surface water treatment total coliforms and E. coli certification.

Water plant operators Denise Shelton, Class C surface water treatment, distribution, Grade 2 biological, Grade 1 collections, total coliforms and E. coli certification; Kim Sutton, Class A surface water treatment, total coliforms and E. coli certification; Larry Thompson, Class C surface water treatment, total coliforms and E. coli certification; and Clayton Inscore, Class C surface water treatment certification.

The operators do rounds every four hours and lab sampling every two hours, along with spot-checking the SCADA numbers. Gallimore handles all process water that goes back into the environment. He also performs all equipment and grounds maintenance. As a certified operator, he fills in when needed.

Danley supervises the operators, oversees daily operations and maintenance, and takes care of all distribution and quarterly sampling for the plant. He also performs relief work for each operator and some maintenance.

Ongoing challenges

Marion expects fluctuating turbidity to remain a challenge for the operators. “It just comes on so quickly, and while it’s not as hard to deal with as it used to be, we always have to be on our toes,” he says.

In 2018, “There was a lot of rain for much of North Carolina, and 5 inches fell within a week in early August. Raw water turbidity jumped from 8.0 NTU to 950 and averaged about 500 NTU throughout the week.” Using the new plant equipment, lab and process equipment, and SCADA, the operators maintained settled turbidities at less than 2.0 NTU.

Total trihalomethanes and haloacetic acids are another concern. “We test for these quarterly within the distribution system — two tests near the elevated tanks and two tests at the farthest points in the system,” Marion says. “Bimonthly, we do control sampling to make sure the quarterly results are within range and also to catch and correct any TTHM and HAA5 problems before the required monthly reporting.”

Plant staff members take part in community events. Marion says, “We attend job fairs to get students interested in working at the plant. We usually do a small presentation, and we have literature for students to take home. It’s a perfect job for someone who wants to work right out of high school.”

Marion volunteers twice a year with the North Carolina Waterworks Operators Association, teaching math, maintenance, distribution and safety classes to operators. “This helps them to learn firsthand from someone with experience in the field, doing exactly what they do every day.”

Marion is excited about the future: “The area is growing rapidly and I see us expanding to 6.0 mgd capacity in the next five years. I see our young people coming through the ranks and also two people retiring. When I started here seven years ago, I was learning from those who were retiring, and now I will be the senior person.”

One thing that won’t change is the team’s dedication: “You see police cars and fire trucks drive by, and they are available 24/7. And, we’re here 24/7 too, making sure the water we provide is the best.”

A new idea

Operators at the City of King Water Treatment Plant rely on two methods to check their coagulant dosages during turbidity events: jar testing using the benchtop Chemtrac LCA, and online monitoring using the Chemtrac DuraTrac 4 Streaming Current Analyzer.

Mark Danley, assistant supervisor, and Ronnie Gallimore, operator, came up with a new idea to check to make sure both units were correct. “They pulled a sample from the flash mixer in a 2-liter jar and placed the sample under the LCA,” says Ben Marion, supervisor. “This sample provided a charge straight from the source at which the coagulant and raw water meet. This charge should match close to what the streaming current charge should be, as well as what the LCA jar test should be.”

By knowing what dosage was fed at the time of the sample collection, operators now have a third method for checking that the dosages are correct. Marion says, “This method is now used by all our operators when turbidity events hit.”


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