Shades Mountain Water Treatment Plant Tackles Turbidity, Disinfection

An Alabama water treatment plant achieves excellence despite extreme turbidity fluctuations, disinfection byproduct challenges and a complex distribution system.
Shades Mountain Water Treatment Plant Tackles Turbidity, Disinfection
Shades Mountain plant senior superintendent Darin Roberson, left, and chief operator Wendell Cox.

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Bigger isn’t always better, unless you’re the Shades Mountain Water Treatment Plant.

This 80 mgd facility in Birmingham, the largest water plant in Alabama, has won numerous awards, including the 2014 Best Operated Plant from the Alabama/Mississippi Section AWWA. The operators’ experience and passion for the job are keys to the plant’s success.

“The professionals at Shades Mountain are allergic to average and not satisfied with good,” says Darryl Jones, assistant general manager of operations and technical services. “They are committed to greatness.”

Darin Roberson, senior plant superintendent, adds, “In this field you have to be passionate about the job, and our operators are.”

Recent upgrades and an optimization program have also played a role. An online total trihalomethane analyzer (Aqua Metrology Systems) added in 2012 allowed operators to reduce finished water TTHM levels by 30 percent. The staff has also worked hard to meet a 20 percent turnover goal for the distribution system’s 28 storage tanks. This rate — which means the water completely turns over every five days — is crucial for keeping TTHMs in check.

A switch from lime oxide to liquid lime has improved operations by reducing the potential for sediment associated with quicklime from collecting in the finished water clearwells. The plant also converted from chlorine gas to sodium hypochlorite disinfection, for public safety reasons.

The plant has been part of the U.S. EPA Area-Wide Optimization Program (AWOP) since 1998 to limit the threat of microbiological contamination by reducing filtered water turbidity. “The turbidity goal is more stringent than the regulations,” says Wendell Cox, chief operator. “We try to keep turbidity below 0.05 NTU 95 percent of the time. It’s a challenge because we have 46 filters and raw water turbidity that can change from 10 NTU to 400 NTU in a few hours.”

The optimization program has been successful: Shades Mountain received the Optimized Plant Award from the state Department of Environmental Management in 2011-13 and Best Operated Plant Award for 2013 and 2014 from the Alabama Water and Pollution Control Association (AWPCA).

Improving the plant

The Shades Mountain facility is owned by the Birmingham Water Works Board (BWWB), the state’s largest water utility with four plants that serve some 650,000 customers. Shades Mountain provides just over half the total water produced and is interconnected in the distribution system with the Western (60 mgd), Putnam (24 mgd) and Carson (25.9 mgd) plants.

Built in 1888 as a settling plant, Shades Mountain has been upgraded many times to improve operations and meet regulations. In 2009, it added the sodium hypochlorite facility, which includes four 15,000- gallon storage tanks, a 2,000-gallon day tank and four pumps (Watson-Marlow Fluid Technology Group). The system can switch feed points for flexibility. The climate-controlled building is designed for future on-site generation and enhances safety for nearby schools, hospitals and malls.

Another project, completed in 2012, includes two 6-million-gallon finished water storage tanks, a new pump building with horizontal split pumps (Pentair - Fairbanks Nijhuis), electrical upgrades, a new transfer pump station, a Cal~Flo liquid lime feed system (Burnett) and new chemical injection points. “The new lime system is more efficient than the old one,” says Roberson. “It allows operators to better control the pH and reduce disinfection byproducts. It also requires less maintenance.”

Today, on a 50-acre site, the plant treats an average of 50 to 60 mgd and nearly 80 mgd in the summer. Source water from the Cahaba River is pumped over the ridge of Shades Mountain to the plant, where it undergoes pre-sedimentation, rapid mixing, flocculation, sedimentation with a 4.5-acre earthen-bottom basin, and filtration with dual-media, high-rate filters.

Ferric sulfate is added as a coagulant. Primary disinfection and pH adjustment are completed downstream of the filtered water transfer station, just before the clearwells. A 2,126-foot-long by 12-foot-diameter inclined tunnel, built in 1888, houses the 36- by 42-inch water main that brings water from the plant to downtown Birmingham. Other service areas are supplied by the finished water pump station.

During summer, Lake Purdy supplements the water supply. The plant reduces pumpage during times of peak power demand to reduce electricity costs. The utility’s other plants provide water to various pressure gradients by way of automated pressure-reducing stations and various pump stations.

“The Shades Mountain and Western plants can assist each other in operating the West End booster station, which can be configured to pump to Shades Mountain or Western,” says Cox. “This can reduce pumpage of either plant by 14 mgd depending on the configuration.”

Highly experienced

A staff of 22, including 10 operators, keeps the plant running around the clock. Each eight-hour shift includes a lead operator and an operator I or trainee. Maintenance staff members work Monday through Friday. Two people are on call after hours and on weekends. Roberson, with the plant for 27 years, holds Grade 4 certification. Cox, also Grade 4 certified, has been with the plant for 24 years. Other staff members include:

  • Lead operators (Grade 4): John Gilreath, 31 years; Dewayne Deramus, 28 years; and Jamie Urbanski, 10 years.
  • Operators (Grade 4): Justin Morrow, five years; Christopher Gormley, two years; and Ronald Brock, two years.
  • Trainees: Tommy McRae, Grade 4, one year; Jonathan Bittles, four years; and Annette Robertson, two years.
  • Maintenance: Crew leader James Smith, Grade 4, 18 years; supervisor Jarrod Shotts, Grade 4, 11 years; workers Chris Ashmead, Andrew Smith, Nick Webb, Josh Templeton and Bill Hynes (Grade 4).
  • Solids handlers: Michael Skinner, 41 years; LaTonya Black, four years; Richard Harless, two years; and Jonathan Pearson, one year.

Lead operators monitor and operate the distribution system, inspect and adjust process equipment, perform water-quality analyses, check turbidimeter accuracy, receive bulk chemical deliveries, and supervise the assistant operators. Assistants’ duties include calibrating and verifying lab equipment, collecting and analyzing water samples, collecting bacteriological samples, and doing minor maintenance and housekeeping.

A shadowing program helps trainees learn the ropes from experienced operators. New hires train on maintenance tasks like equipment oil changes and calibration and gravity filter maintenance, then train with an assistant operator on plant operation, and finally with a lead operator on the distribution system.

Meeting challenges

Shades Mountain operators face many challenges, from dealing with turbidity, alkalinity and conductivity fluctuations in source water to simultaneously monitoring the plant and distribution system and interfacing with operators at the other plants.

“The alkalinity and conductivity in Lake Purdy is much higher than in the Cahaba River and requires a higher dosage of ferric sulfate to treat the increase in dissolved solids,” says Cox. Since the river water turbidity can increase to 300 to 400 NTU within hours of heavy rainfall, operators feed a cationic polymer to the pre-sedimentation basin, reducing turbidity to 40 to 50 NTU before primary coagulant is added at the flash mixer.

Monitoring and control of TTHMs poses another challenge, especially since the distribution system contains 11 pressure gradients, 19 remote pump stations and 45 pumps. “Operators have to strike a balance between system demands and meeting the desired turnover every day in each of the storage tanks,” says Cox.

Each shift is assigned a portion of the tanks to cascade, with help from operators at the other plants. “When summer demand is high, cascading has to be balanced with demand,” says Cox. “We do this by having operators at the automated pressure-reducing stations and pump stations move water from other plants into the Shades Mountain plant gradients to keep the water age low. With a distribution system this size, and with a terrain of mountain ridges around valleys, it takes a lot of coordination between plants to keep disinfection byproducts from becoming a problem.”

The plant continuously reduces TOC by 60 percent; the goal is 1.60 ppm or lower at all times. An online TOC analyzer (GE Intelligent Platforms Sievers Series 900) is key to reducing disinfection byproducts. Operators can precisely adjust the chemical dosages to prevent increases in finished water TOC and sustain lower TTHMs leaving the plant. Says Cox, “Operators shift the chlorine application points and optimize coagulant dosages to reduce TOC levels before the water contacts the disinfectant.”

Removing solids

Shades Mountain has one 5-acre settled water basin with no continuous solids removal. Its large size makes it vulnerable to adverse surface currents caused by wind. “If solids are allowed to accumulate, it can cause density currents that result in higher settled water turbidity, which in turn causes extra gravity filter loading,” explains Cox.

Solids are removed from the basin with a Mud Cat diesel auger dredge (Liquid Waste Technology), then pumped to the plant’s solids residuals facility and processed with a plate-and-frame press (Bilfinger Water Technologies). The solids are transported to the utility’s landfill for use as a soil amendment.

“We have to take special care when operating the auger dredge, since moving it too fast can disperse more solids in the water than the dredge can vacuum up,” says Cox. “This can cause an increased settled water turbidity reading in the plant, which could result in problems for the filters if not conditioned properly.”

Birmingham Water is replacing the plate-and-frame press with two centrifuges (Centrisys). Engineer Jeff Cochran tested different dewatering equipment and found that the centrifuge produced the best results in dewatering ferric sulfate solids. “We produce 15,000 to 25,000 pounds of solids per day,” says Cox. “Our team does an exceptional job in processing these and keeping the settled basin cleaned. They always step up and work extra hours when needed to complete the job.”

Training operators

Birmingham Water reaches out to the community in several ways. The Young Water Ambassadors program allows 100 high school juniors and seniors to spend their summers working in and learning about the waterworks and its operations.  

College students can intern through the Ambassadors in Training program while earning college credit. “This is a wonderful program where a young person can work under an operator and find out if this is a career they want to pursue after graduation,” says Roberson. “We’ve had several students come back and work for us. Jarrod Shotts started as an intern through this program.”

The staff is also involved with the Alabama/Mississippi Section AWWA. “We send operators to the national conference so they can see new technology and attend technical programs presented by other water professionals,” says Roberson. “This is where we first saw the online TTHM analyzer we have.”

The future holds new challenges. “At the end of this year, we’ll be constructing a brand-new filter building with 16 dual-media filters so we can treat 80 mgd in one building instead of two,” says Roberson. “The filters will be equipped with air scour technology and configured so that we can switch to granular activated carbon (GAC) in the future.” A GAC pilot test showed that the plant could get an additional 10 to 15 percent organics reduction that would help with any future disinfection byproduct regulations. The plant will also be upgrading the 50-year-old coagulant feeders.

Bad weather is another challenge. “We got hit by a tornado in April 2000 that shut down the plant for several hours,” he recalls. “A tree ruptured the fluoride line and the water ran into the sedimentation basin. That could have been a problem, but we recycled the water back to the pre-sedimentation basin, which diluted the fluoride concentration. Our job is always changing, and I’m proud of our team’s adaptability.”


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