Celebrating 40 Years of the Flygt ‘Banana Mixer’ and a New Era of Efficiency

When it comes to plant efficiency, every gain counts. From cost and time to environmental considerations, all areas of operation can benefit. Here, Nils Renman, Global Product Manager for Flygt mixers at Xylem, outlines the importance of mixer technology and the viability of modern replacements and upgrades following a special anniversary.

Mixing is essential to effective wastewater treatment. It blends wastewater from different time periods and sources into a more consistent composition. It also prevents the formation of sediment, keeping all particles suspended and distributed throughout the system, improving the efficiency and optimisation of downstream treatment processes. Mixing is also used to enhance the removal of certain nutrients, using bacteria to consume nitrogen and phosphorous. 

As a process, it presents a number of challenges to wastewater plants. First and foremost, it can be extremely energy intensive with implications for cost and environmental sustainability. At the same time, maintenance costs for older or sub-optimal systems can be high.

40 years of progress

Just over forty years ago, Flygt introduced a revolutionary, low-speed mixer. Equipped with yellow, backswept propeller blades, it quickly earned the ‘banana mixer’ nickname. Its distinctive design was developed to address many of the toughest and most important requirements of mixing – namely thrust, low energy use, and minimal clogging.

Fast forward to today and Flygt continues to innovate and push boundaries with a range of adaptive and single-speed mixers. The modern systems provide excellent turndown and efficient mixing for any application size, eliminating settling problems while also providing the ability to adapt output thrust for changes in process conditions. 

Retrofitting for improved efficiency 

As an energy-intensive process, anything to make mixing more efficient can deliver substantial benefits to the plant. Improvements in mixing technology have delivered a step change in performance, with many Flygt systems reducing energy consumption by up to 30%. This is the result of greater efficiency in both the propellers and motors used. Reductions are further increased with adjustable (adaptive) speed mixers, which can vary their speed to suit process conditions, minimising energy use to only what is needed.

Retrofit of an existing mixer system is an easy and cost-effective way of benefitting from these technology advancements. As an example, Flygt Low-speed mixers with induction motors can easily be upgraded to include a motor with IE3 equivalent efficiency, rather than buying a new complete IE3-powered mixer assembly.

Across Europe, many customers have successfully upgraded ageing installations to include IE3 motors, with much-improved performance and energy efficiency. Such upgrades reuse the existing hydraulics, while introducing a ‘naked’ IE3 mixer including a new gearbox and IE3 equivalent motor. In many cases, the existing propeller is still in excellent, functional condition after 10-15 years of use, making it far more cost-effective to simply upgrade the existing installations to achieve higher mixing efficiency and lower consumption.

Adaptation: modern models

For low-speed mixers – that are often operated 24/7 – Flygt offers a wide range with innovative solutions that are far more efficient and effective than legacy units. This includes single-speed mixers with and without IE3 equivalent motor efficiency, as well as adaptive mixers with IE4 equivalent motor efficiency. All models are available with two- or three-bladed propellers in a range of diameters to perfectly match output requirements.

The adaptive mixers offer substantial energy savings thanks to their operation with variable speed, adapting output thrust to process changes, optimising energy use while maintaining effective mixing. 

Banana-versary 

As celebrations wrapped up for the ‘Banana Mixer’s’ 40th anniversary year, it is clear to see the evolution of mixer technology and the innovations driving operational advantages in wastewater treatment. From the original ‘Banana Mixer’ to today’s adaptive systems, Flygt continues to support customers with cost-effective, efficient, and high-performance products. With reduced maintenance costs and substantial energy savings, operating costs can be significantly lower in the medium-to-long term. Whether considering a complete replacement or retrofitting existing systems, there are Flygt solutions for every plant.