Omohundro - AdvancingMWSWater

Omohundro WTP

History of Nashville Water System

Nashville had what could be considered, a water system as early as 1826, consisting of a pump at the foot of Spring Street (now Church Street), which pumped water into a reservoir on the north side of Church Street, just below the present 5th Avenue. Wooden pipes delivered water from the reservoir to the square. However, this system burned in 1830, and a second water system was constructed on the grounds of the old General Hospital Building on Hermitage Avenue in the fall of 1833. This system functioned for many years, but muddy water from the Cumberland River was an ever-present challenge.

After several cholera outbreaks, the Board of Health determined in 1876 a sufficient amount of water was being secured, but the quality of the water was sub-standard. It became apparent in 1887 that a new reservoir was necessary.

What is now known as the 8th Avenue Reservoir was constructed on Kirkpatrick’s Hill, and a new pumping station was built at the “Upper Island,” near the natural filtering galleries in the Cumberland River. Both were completed in 1889 and remain in use today.

The 51 million gallon reservoir divided into two 25.5 million gallon compartments by a cross wall, allowed for muddy water to be pumped into one chamber for settling and then allowed to flow into the other basin through a weir on the cross wall for storage and distribution.

In 1908, the use of alum and hypochlorite of lime began to facilitate settling of particles and sterilization of the water, and in 1920, chlorine replaced the hypochlorite of lime for disinfection.

A grit chamber was installed near the pumping station in 1921, and the first filtration plant began operations in 1929. This complex, known as Omohundro, now treats up to 90 million gallons of water per day and sends clear disinfected water to the 8th Avenue Reservoir for storage.

In 1953, the pumping station was modernized by removing the coal-fired steam boilers and turbines and converting them to electrically powered equipment. Much of the original equipment is still being used today.

Nashville’s second water treatment plant, K.R. Harrington, was placed into service in 1978 and also treats up to 90 million gallons of water per day.

A detailed history of the Nashville water system can be found on the Metro Water Services About Us page, and additional information about the Omohundro Water Treatment Plant can be found below.

Existing Water Treatment Process

Omohundro WTP is a conventional water treatment plant with pumping, rapid mix, flocculation, sedimentation, filtration, clearwell storage, and disinfection with sodium hypochlorite. An illustration of the existing treatment process is below.

Pilot Plant

In April of 2018 MWS began a Pilot Plant project to explore new
water treatment technologies. Piloting, or testing, different treatment options prior to full scale implementation is the best way to ensure we get the data needed to make critical decisions
about the future of water treatment at MWS. Full scale water treatment plants were modeled using smaller scale equipment to collect data on which treatment option performs the best with our source water. The pilot plants were located at the K.R. Harrington Water treatment plant and the list of piloted treatment options includes pre-ozone, post ozone, granular activated carbon (GAC) filtration, ultraviolet (UV) treatment, biologically active filtration (BAF), and different combinations of these treatment techniques. Data collection concluded at the end of September 2019 and each piloted option was evaluated using the following criteria.

WATER QUALITY

Finished water Total Organic
Carbon (TOC) improvements

Reduction of formation of
Disinfection By-Products
(DBPs)

Removal of taste and
odor compounds
2-methylisoborneol (MIB) and
Geosmin

Effectiveness in removal of
a broad range of Emerging
Contaminants

PROCESS

ENHANCEMENTS

UPRONT CAPITAL COST

OPERATIONS AND MAINTENANCE COST

PROCESS AND OPERATIONAL ENHANCEMENTS

EASE OF OPERATIONS

Findings were analyzed with the support of the MWS Water Master Planning Group, and GAC was selected as the treatment option that most effectively allocates resources and meets water treatment needs now and into the future.

Water Treatment Process Improvements

The Process Improvements Project will replace aging facilities with new state-of-the-art pumping, flash mix, flocculation, sedimentation, filtration, clearwell storage, and chemical facilities, and add an advanced treatment process: post-filter granular activated carbon (GAC) contactors. Post-filter GAC contactors provide protection against taste and odor compounds and emerging contaminants that are difficult to remove with conventional processes. In addition to treatment process improvements, the treatment capacity will be increased by 67% from 90 million gallons per day (mgd) to 150 mgd. An illustration of the new treatment process is below.

Resilience & Reliability

In addition to treatment process and capacity improvements, a major objective of the project is to improve treatment resilience and reliability. This includes building a treatment system for future risks, protection of Nashville’s water supply from extreme weather events, including flooding, and replacing aging infrastructure with modern facilities.

Project Description

Increase water treatment capacity by 67%.
Build a water system for future risks.
Protect Nashville’s drinking water supply from extreme weather events, including flooding.
Replace aging infrastructure systems with modern facilities.

Enhanced Treatment

The Granular Activated Carbon (GAC) contactor system will play a pivotal role in addressing contaminants of emerging concern, advancing water quality, and safeguarding public health and well-being.

Capacity Expansion

Flood Mitigation

Proactive measures will be implemented to fortify the plant and enhance its readiness to withstand potential future floods.