In the water treatment industry, maintaining a consistent chlorine residual is crucial. Water tank mixers are essential for keeping chlorine and, at times, chloramines to maintain proper reaction rates and comply with local, state, and federal guidelines.
There are typically only two mixing approaches in municipal water treatment: passive and active. Although there are only two, several factors impact the best water tank mixer for your treatment process. These include the specific application, energy consumption, operational complexity, and cost. This post examines the differences, advantages, and disadvantages of each type of water tank mixer to help you determine which is more suitable for your operation.
What is a Passive Water Tank Mixer?
A passive mixer, also known as a static mixer, operates by utilizing the natural flow of water to mix. It has no moving parts and is typically installed inline within a pipe or series of pipes. As the fluid flows, it passes through a series of fixed, stationary elements that induce turbulence or disrupt the flow, thereby facilitating the blending of components.
Key Features of Passive Mixers:
- No moving parts: The design consists of static structures that force the fluid into different paths or directions, promoting mixing through turbulence.
- Low maintenance: Since it has no mechanical components, this type of system requires minimal, if any, maintenance.
- Energy efficiency: Because passive mixers don’t require an external power source (such as motors), they consume no external energy.
Ideal for continuous flow systems: Passive mixers are the obvious choice for applications where the water elevation in reservoir tanks moves up and down frequently due to water consumption and addition. This allows the water to have sufficient opportunity to move around enough to maintain decent consistency in the residual.
What is an Active Water Tank Mixer?
An active mixer uses mechanical components, such as impellers, paddles, or blades, to agitate and mix fluids. Typically, an electric motor powers active mixers, which stir the tank’s contents or standpipe.
Key Features of Active Mixers:
- Mechanical movement: Active mixers rely on moving parts that physically stir the water, ensuring a more controlled and consistent mixing process.
- Higher energy consumption: Active mixers require motors or other power sources, such as solar power, whereas passive mixers consume no energy.
- Greater mixing control: A constant mixing speed allows for consistent chemical blending within the reservoir or standpipe.
Comparing Passive and Active Mixers
1. Energy Efficiency
Passive Mixer: This device operates without external power, harnessing gravity and the natural flow of water. It is a highly sustainable and cost-effective choice for mixing.
Active Mixer: Active mixers consume energy; however, they provide greater control over the mixing process, which may be necessary for more precise applications and older tanks unequipped for a passive solution.
Winner: The winner is both. Passive mixers are far more energy-efficient but only effective in continuous flow systems, while active mixers work excellently in almost all applications.
2. Cost of Ownership
Passive mixers: Because installing a passive design requires a lot of work, they tend to be cost-prohibitive. However, not needing moving parts reduces maintenance costs, leading to lower long-term operational costs.
Active Mixer: The upfront costs depend on the type of mixer you purchase. Some require regular maintenance, such as lubrication, inspections, and repairs, to ensure optimal performance. However, some reservoir mixers have extremely low maintenance and installation costs.
Winner: Active mixers are generally more cost-effective in terms of initial investment. However, passive mixers are typically maintenance-free.
3. Mixing Efficiency
Passive Mixer: While passive mixers are practical for many applications, particularly those involving continuous flow, they do not work in locations with limited water movement.
Active Mixer: Active mixers provide greater control over the mixing process regardless of how much the water exchanges
Winner: Active mixers offer superior mixing efficiency and precision, especially in applications with limited water movement
Which Makes Sense for Your Application?
When deciding between a passive and an active mixer, consider the specific requirements of your operation:
Passive mixers are often the best choice for processes with enough water movement, and the municipality has the circumstances to shut down the tank for installation.
An active mixer may be more appropriate when consistent mixing is needed to maintain a desired chlorine residual or chloramine residual. Some active reservoir tank mixers can be easily installed, making them a preferred option.
In conclusion, choosing between passive and active mixers depends on your operation’s needs. A passive mixer is likely the best fit if energy efficiency, low maintenance, and continuous flow are vital factors. However, an active mixer will provide the flexibility and performance you need if your process requires precision, control, or high-intensity mixing.
Understanding the advantages and limitations of each type of mixer can help you make an informed decision that balances performance, cost, and operational efficiency.