Mother Nature + Mt.View-Edgewood Water Co. + TMS = The Best Water in the Nation
Imagine having the best tasting water in America. Mt. View-Edgewood Water Company (MVEWC), located in the state of Washington, won this top honors in the 13th National Rural Water Association’s Great American Water Taste Test held in Washington DC.
Additional honors went to Mike Craig, MVEWC Field Manager, who was recognized as the “Water System Operator of the Year.” This highly coveted award, presented by Evergreen Rural Water of Washington State, recognizes the top water system operator in Washington for superior achievement.
Since 1925, the Mt. View-Edgewood community has worked together to build a member-owned utility that provides quality drinking water and fire protection. MVEWC does not add any chemicals to its water. The water is delivered to customers without chlorine, fluoride or any other chemicals. The water is filtered slowly and naturally through glacial gravels deep beneath the earth’s surface. The aquifer does not contain naturally occurring elements that affect taste, acidity or hardness. MVEWC’s staff is focused on problem prevention, operational best practices, design and continuous improvement to deliver the best-tasting water nature has to offer.
Challenge
MVEWC’s water storage consists of two steel tanks (South Reservoirs), which provide a combined total of 1.2 million gallons of storage; and one steel 1.0 million gallon reservoir (North Reservoir). Built in 2000, the North Reservoir is 80 feet in diameter and 32 feet tall. It was designed with a 16 feet tall inlet riser pipe and an outlet pipe placed 180 degrees opposed to the inlet.
Computational Fluid Dynamics (CFD) by Red Valve determined this configuration is prone to stratification and short-circuiting. In summer, inlet water is colder and denser, therefore it is negatively buoyant and it sinks. Although the physical separation of inlet and outlet pipe makes intuitive sense, science proves that it does not improve mixing and it does not prevent the tank from stratifying and short-circuiting. The key to achieving complete mixing and improving water quality is the proper design of a multi-port mixing system that distributes the inlet flow momentum through the tank and ensures inlet jets reach the water surface during summer negatively buoyant scenarios.
During investigative sampling (at the discharge), the North Reservoir had a Total Coliform positive result and a Heterotrophic Plate Count (HPC) of 250 colony-forming units per milliliter (cfu/ml). Follow-up in-tank sampling indicate HPCs at over 30,000 cfu/ml at the top. The HPC is normally between 0 and 8 for their system. MVEWC determined that the tank was severely stratified, causing the elevated HPCs throughout the tank.
Solution
MVEWC turned to Red Valvle to solve the problem. Using data from MVEWC, along with CFD and field-validated models, Red Valve engineered a Tideflex® Mixing System (TMS) to ensure complete mixing within the North Reservoir.
The inlet riser was converted into a multi-port TMS with three Tideflex® Inlet Nozzles. The quantity, size, relative stiffness, elevation and discharge angles were designed based on CFD and field-validated models. MVEWC normally cycles the tank daily between 21 feet and 29 feet, recognizing that sufficient turnover to minimize water age is very important for ensuring that quality water is being delivered to MVEWC customers.
The TMS uses differential pressure in the distribution system as the only energy source to mix the tank, so there no need to pay for energy twice. Tideflex® Inlet Nozzles used within the TMS have a variable orifice that enables maximized jet velocity at all flow rates. Higher inlet jet velocities will produce circulation patterns within the tank that not only maintain water quality by mixing the entire tank, but also help prevent ice formation in cold weather. The TMS is truly a green technology and the all-elastomer construction of the Tideflex® Inlet Nozzles renders the system maintenance free.
Results
“After proper mixing with the Tideflex® Mixing System, we eliminated the Coliform and the HPC dropped to 7,” says Field Manager, Mike Craig. “We test our reservoirs monthly for HPC and they continue to pass well below the standards.”
“Mother Nature provides us with a pure, naturally filtered product,” adds Craig. “It is our job to make sure we preserve that quality. Keeping our water pure from the source to the tap makes more sense than allowing it to become contaminated and then trying to purify it with chemicals.”
The Mt. View-Edgewood Water Company and Red Valve company are clearly proud of their achievements. MVEWC is one of many TMS success stories in which Tideflex® Technologies finds the perfect solution and products to fulfill tank mixing needs.
The Tideflex® Mixing System can be custom designed for every tank based on tank style, material, volume, dimensions, flow rates and volume turnover. Using data provided by the utility or engineer, Red Valve creates a free TMS Design Report for every tank that includes a TMS general arrangement drawing, CFD modeling, specifications, manifold hydraulics, Mixing Analysis (showing how much turnover is required to achieve complete mixing) and Water Age Analysis (providing the average water age under current or proposed operation).