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News: Plant Spotlight

Plant Spotlight: City of Shelby WTP

Monday, April 23, 2018   (0 Comments)
Posted by: Kyrie Hoover
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Sedimentation Basins and WTP Operations Building

 

 

Raw Water Pumps at Pump Station # 2


 

Operations Staff

 

 

Filter Pipe Gallery

 

 

Filter Gallery

 

 

Original Raw Water Pump Station and Intake

 

Originally published in the Spring 2018 issue of NC Currents magazine.

General

The City of Shelby is located in
Cleveland County and has a current
population of approximately 20,323.
Known as the “City of Pleasant Living,”
Shelby is located in western North
Carolina about 65 miles west of Charlotte
along US 74. Shelby was incorporated
in 1843 and named for Colonel Isaac
Shelby, a Revolutionary War hero at the
nearby Battle of Kings Mountain.


The City of Shelby is a full service utility
community. The Shelby utilities system is
a municipally owned and operated public
utility system that provides residential,
commercial, and industrial customers with
water, sewer, electric, and natural gas.
The City currently operates one
WTP and one WWTP. The WTP serves
the City of Shelby and nearby Boiling
Springs. The distribution system has
220 miles of water line with two pressure
zones and includes four elevated water
storage tanks with a total capacity of
2.25 million gallons (MG) of storage.


The source water for the water treatment
plant is the First Broad River, which is a
tributary within the Broad River Basin. The
river originates in the foothills of the South
Mountains. The City of Shelby also has a
secondary intake at the Broad River.

 

History

In 1953, construction began on the
original WTP that included four filters
and a production capacity of 4.0 million
gallons per day (mgd). J.N. Pease was the
consulting engineer for the project.
In 1959, plant upgrades at the WTP
included the addition of four filters, and
increased the production capacity to
8.0 mgd. J.N. Pease was the consulting
engineer for this project as well.
In 1992, plant upgrades at the WTP provided two additional sedimentation basins, conversion to dual filters, new raw water intake, and new chemical storage and brought the production capacity to 12 mgd. The daily flow is approximately 6 mgd. McGill Associates was the consulting engineer for the project.


The Shelby WTP is ISO 14001 Environmental Management System certified, becoming one of the first
WTPs in the state of North Carolina to
achieve this certification. Both the water
treatment plant and the First Broad
WWTP facilities are ISO 14001 certified.

 

Process Flow Components

• Two permanent raw water intakes
• Influent screening
• Five (5) raw water pumps
• Three raw water storage lagoons –
19.0 MG
• Rapid mix – chemical injection
• Flocculation –
12 vertical flocculation mixers
• Sedimentation with tube settlers
• Dual media filtration – eight filters
• Chlorine disinfection
• Clearwell – 8 mgd
• High service pump station –
six pumps
• One booster pump station with
new booster station in the process of bidding
• One new 0.750 MG tank under construction

 

Raw Water Intake Structure and Reservoirs

 

The primary water source is the First Broad River with a permitted withdrawal rate of 18 mgd. Raw water is withdrawn from one of two raw water pump stations and then pumped to a series of three raw water reservoirs for temporary storage. Capacity of the two lower reservoirs is 14 MG. The upper reservoir provides an additional 5 MG of storage. Flow is then gravity fed from the upper reservoir into the rapid mix chamber at the head of the plant.


The secondary water source is the Broad River near Boiling Springs, with a permitted withdrawal rate of 9 mgd. This 30-inch line was installed as an emergency backup source after the drought of 2002.

 

Flocculation, Sedimentation, and Filter Operation

 
After the water leaves the rapid mix chamber, it enters the flocculator basin where the coagulation chemical (See Chemical Feed and Disinfection below) is further mixed, allowing the “floc” to Sedimentation Basins and WTP Opeerations Building Raw Water Pumps at Pump Station # 2 24 NC Currents Spring 2018 fully form. There are six vertical type flocculators in use per side, for a total of 12. Each flocculator turns at a lower speed so as not to break up the formation of the “floc.”


After the “floc” has been formed, the flocked water is drawn into the sedimentation basins allowing formed “floc” to settle or drop out. The majority of the “floc” settles here, reducing the load on the filters. The sedimentation basins also incorporate tube settlers that decrease settling time and improve performance. The settled water enters the filters from the sedimentation basins where the remaining “floc” is removed. There are eight filters for filtering settled water. These are Roberts Filter dual media filters comprised of anthracite, sand and gravel, doubling the filtering capacity from 2 ft2/min to 4 ft2/min from a conventional sand filter. The filters are also equipped with wheeler bottoms, rotary surface sweeps, and washwater troughs. The pipe gallery instrumentation includes filter effluent turbidimeters and flow meters. The original marble filter consoles are located above the pipe gallery on the main floor of the filter building. The original controls have been upgraded to electronic digital controls.

 

From each console, a manual backwash can be initiated. Standard operating procedure is to perform this function at the filter console so the operator can see the backwash in progress.

 

 

Chemical Feed and Disinfection System

 

 Coagulation is achieved through the addition of aluminum sulfate (alum) at the flash mixing chamber just prior to the flocculation basins. In addition to this, sodium hydroxide (caustic soda) is added at the flash mixing chamber to adjust the pH.

 

 Pre-chlorination is fed prior to the filters and post-chlorine disinfection occurs after filtration and prior to the 8-MG clearwell. The clearwell provides adequate water storage and ensures the required chlorine contact time to disinfect potential pathogens.

 

 In addition to this, carbon is added for taste and odor and ortho-phosphorus is added to provide a protective coating along the interior of the distribution system piping. Finally, hydrofluosilicic acid (fluoride) is added for protection of the consumer’s dental enamel.

 

 The chemical additions, from raw water to distribution, are tested in the lab, 24 hours a day, 7 days a week. Tests include pH, chlorine, turbidity, hardness, alkalinity, and fluoride.

 

SCADA System and Controls

 
Prior to 1992, the plant was equipped with a control panel with circular chart recorders and manual switches and indicator lights. In 1992, the plant installed a QEI QUICS supervisory control and data acquisition (SCADA) system to monitor the plant and distribution system. This system is still in use today but is being phased out to make room for a newer SCADA system. This system consists of computer monitors, Rockwell Human Machine Interface (HMI) software and a communication network that incorporates Allen Bradley programmable logic controllers (PLCs). The future plant upgrade includes plans to install automation of the filters in Phase II of the WTP upgrades.

Plant Staff

 
The WTP currently employs a total of 11 plant personnel, including seven certified operators and four facilities maintenance workers. All of the operations staff is trained to run the required laboratory analyses.

 

Personnel Development Programs and Certification Programs

 
The City offers continuing education classes to their employees and pays for all training and certifications for operators. In addition to this, the City provides cross training of staff for those interested in career development.

 

Challenges

 
Drought of 2002
The drought of 2001-2002 resulted in the First Broad River running dry. The City was able to maintain service through innovative cooperation of City staff and other municipal governments. From this process, the City began the planning of improvements of the raw water capabilities and partnered with Cleveland County to install a new raw water line to the Broad River. The Broad River Secondary Intake involved the construction of a 30-inch waterline from the Broad River southeast of Boiling Springs to the City of Shelby WTP. Since this installation, the water line has not been activated but is available for water supply emergencies. As a result of this drought, the City improved drought and emergency response plans for the future.


Loss of Textile Industry – 1990s
The large textile base dwindled in the 1990s, resulting in significant water sales decline that reduced capital funds for plant and system improvements. The City began to look at ways to cut costs and begin the process of attracting new manufacturing to Shelby. The City also worked very closely with Cleveland County to develop this approach. Through funding opportunities and improved water and sewer infrastructure in Northwest Shelby, the City
purchased properties with the County to develop the Foothills Commerce Center Industrial Park. Since 2010, Shelby has been able to attract a diverse manufacturing base of companies that has resulted in the creation of jobs, increased tax base and increased water and sewer revenues.

Some of these include:
• Schletter
• Clearwater Paper
• KSM Castings
• IVARS
• Greenheck Operations Staff

• Mafic
Due to this resurgence of industry, the finished water demand has increased from an average of 4.0 mgd to 6.06 mgd. Finished water demand is expected to exceed 7.0 mgd in 2019 with the Clearwater Phase II Expansion.

 

Future Plant Expansion

 
Since 2010, the City has developed a Water and Sewer Asset Management Plan and also conducted a thorough evaluation of the WTP. The 2016 plan has established three phases of water plant upgrades totaling over $20 Million. In 2017, the City and its consulting engineer, HDR of the Carolinas, began design for the Phase I improvements, with construction to begin in 2019. This will include:
• New clearwells – existing
clearwell to be abandoned
• New high service pump station
• Filter valves replacement
• Building improvements –
structural and ventilation

 

Summary

 
The City of Shelby WTP has experienced its fair share of challenges over the last 20 years. The loss of textile manufacturers in the 1990s and the 2002 drought were huge challenges for the water treatment and maintenance staff. However, things continue to improve with the resurgence of new businesses and the implementation of a drought and emergency response plan. Staff will continue to make periodic updates to the City’s Water and Sewer Asset Management Plan to continue to plan and implement infrastructure improvements and evaluate potential hurdles associated with utility management.

 

The water plant staff has also worked diligently to attain and maintain their ISO Environmental Management System certification. They are proud of this accomplishment and for the job that they perform every day to bring safe and quality water to the City of Shelby.

 

For additional information: Contact:
Michael Mull - Water Plant Supervisor/ORC
Phone: (704) 484-6885
mike.mull@cityof shelby.com

 


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