Water Technologies & Solutions case study

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CS1523EN.docx May-15

duck river drinking water treatment plant Application: Lake Water treatment for community drinking water

Capacity: 11.6 – 14.25 MGD

Location: Tullahoma, TN

Commissioned: 2004

challenge

The Duck River Utility Commission (DRUC) draws water from Normandy Reservoir to provide drinking water to several local communities. Because of increased demand, it was deemed necessary to expand the existing conventional surface water treatment plant and double its capacity. In 2004, SUEZ provided a ZeeWeed* membrane system for the new treatment process, utilizing five membrane trains with a potential for future expansion.

At the time of install, the onsite membrane tanks were coated with a concrete treatment in an effort to protect them from various chemicals used in the treatment process. Within months, this concrete treatment had dissolved, exposing the bare concrete. Shortly afterward, the concrete began to break down. In some areas, over ¼ of an inch of surface cover was lost, revealing the aggregate, and forcing facility personnel to literally shovel sand off the floor of the tank into buckets.

solution

DRUC contacted other membrane plants and coating manufacturers for recommendations. An epoxy coating had been installed successfully at a plant in Sweetwater, Texas, which also uses ZeeWeed membranes. This was a form of epoxy that is tolerant of moisture during application, adheres well to surfaces, and can be over coated after longer periods of curing.

Several vendors were solicited for bids on the repair project but the epoxy coating was selected due to its purported properties and its success at the Sweetwater facility.

Prior to the application of the epoxy coating, the ZeeWeed membranes were consolidated into four of the five trains. The empty tank walls were thoroughly cleaned by pressure washing, and then dried with blowers and heaters. A priming coat was applied to the tanks, followed by multiple finish coats. The treatment was allowed to cure for one to three days. Once the curing time was completed, the membranes were reinstalled into the tank and the train put back on line. This process was repeated until all five trains were complete.

It has been two years since the coating was applied and according to the site manager, the coating has been performing very well. During membrane repairs, or if the cassettes are removed from the tank, the coatings and all surfaces are inspected for damage or coating failure. Any minor issues found since installation were attributed to the damage previously done to the concrete and were easily repaired.

process overview

The Duck River Utility Commission (DRUC) had a conventional surface water treatment plant with a 7.5 MGD capacity. In 2001, DRUC decided to upgrade its water treatment plant with the addition of ultrafiltration (UF) membranes. In 2004, SUEZ installed ZeeWeed 1000 membranes into new tanks. The ultrafiltration membrane has a nominal pore size of 0.02 microns and is capable of removing suspended solids and most viruses, resulting in excellent effluent quality. After an initial clarification process, the feed water was passed into the membrane tanks. The membrane modules were arranged in five trains, three cassettes per train.

Page 2 CS1523EN.docx

Effluent from the membrane tanks was sent to GAC contactors before exiting the system to the clear well tank. With the installation of the ZeeWeed membranes, the plant’s capacity was increased to 11.6 MGD, with a possible future expansion to 14.25 MGD.

c

Before Breakdown of concrete before coating applied

Priming Coat Final coat