By Lucy Allen
Active tank mixing increases tank longevity and improves water quality.
Municipal water tanks and reservoirs are valuable assets for healthy, thriving communities. They represent a sizable capital investment and are a critical component to the quality of your potable water supply. Ensuring clean drinking water is important to the overall health and safety of your community. Here are the top five reasons to consider an active water tank mixer.
1. Safe Drinking Water Maintained
In order to maintain water quality, water in a storage tank must be moving. Static water conditions in a water tank can cause issues in all seasons. In winter, static water freezes, damaging the tank and its coating. During summer, temperature and chemical stratification can impact both the tank and water quality. These issues can lead to increased water age and reduced chlorine residuals, which can cause an increased risk of biofilm and increased production of disinfection byproducts.
A mixing system is an operator’s best tool to help maintain water quality. By adding a mixing system to your water tank, you can help ensure your water tank’s integrity by reducing interior headspace temperature and reducing steel corrosion, as well as maintain overall water quality.
2. Avert Water Tank Quality Issues
There are many tank mixing systems, but the two most common are active and passive. Determining the appropriate mixing system for your water tank is the first step, and an active tank mixing system should be your primary consideration.
Active mixing systems keep water circulating inside the tank continuously 24 hours a day, 365 days of the year, regardless of water volume in the tank. They’re smaller and more sustainable than passive mixers, as they provide operators with more mixing power, independent of drain and fill cycles. They’re also less expensive, easier, and faster to install and can be easily removed for tank inspections and ongoing maintenance.
Seasonally, active tank mixers deter some of the most critical water tank issues, including ice formation and stratification. Through continuous mixing, ice is unable to form, and stratification can never develop. This significantly reduces physical damage from ice formation and minimizes the potential for biofilm growth and disinfection byproducts. The result is homogeneous water quality throughout the tank, reducing water age and increasing water quality.
3. Ease Of Installation
Tanks and reservoirs come in many styles, shapes, and sizes. It’s critical to ensure you have the proper tank mixing system in place to meet the unique needs of the distribution system you are managing while keeping ease of installation and serviceability in mind.
Active mixing system selection should offer various mounting options to meet the unique tank or reservoir application. Regardless of the size and placement, active mixing systems should be easy to install in new or existing tanks, without using cranes or draining the tanks. Additionally, they should be easily removable for tank inspection and maintenance.
When determining the size and placement of your active tank mixer, you’ll also want to carefully review the warranty and the NSF rating.1 Both are critical components to ensure your mixing system provides years of service and the electrical and material quality to maintain the system integrity.
Before and after images showing the thermocline layer eliminated by effective mixing.
4. Effective Water Blend Cycle
Once your active tank mixing system has been installed and is continuously mixing your water supply, it’s a best practice to ensure that your tank is mixing effectively, because consistency equals quality.
One method of ensuring effectiveness of your active mixing system is to look at the blend cycle. The blend cycle is the time it takes to mix the water to a homogeneous temperature during tank cycling. For instance, during daily operations, if it takes two hours to refill the tank, then the active mixer needs to be able to reblend the new water with that already in the tank in two hours.
You can also visibly see whether your tank is actively being mixed by looking at the exterior of your tank. In the summer months, examine at your water tank. Do you see a sweat line? Is there mold growing on the tank in that area? If so, it’s indicating that the water below is colder than the water above the thermocline (sweat line). Other ways to test whether your tank is being mixed is to use a temperature data string inside the tank, or an aerial drone that can capture thermal imagery to determine if there is thermal stratification.
5. Cost-Effective Problem Prevention
While active tank mixing is critical for water quality, regular inspection and maintenance of your water tanks and mixing system are critical. Inspections help assess safety and security issues, structural and coating conditions, and obvious sanitary concerns, and notifies the operator of any needed tank service.
The American Water Works Association has determined a standard schedule of inspection. Visual inspection of your tanks should happen regularly, at a minimum on a monthly basis. Your tanks should be drained, washed, and professionally inspected at least every three years, if not more often. Your mixing system and ground fault breakers should be checked to make sure they are within manufacture recommendations.
About The Author
Lucy Allen is the municipal business development manager for Kasco Marine. She has more than 15 years of experience in the water and wastewater industry and is an expert on water tank mixing. Learn more at kascomarine.com/certisafe.