During the expansion of a large municipal drinking water treatment plant, 18 INVENT Hyperclassic® Evolution7 mixers and three Cyberpitch® mixers were installed. The existing plant was reconstructed in order to increase capacity and energy efficiency.
INVENT’s distribution partner was able to lay out and recommend suitable mixers to optimize coagulation and flocculation. Also, with the help of high-resolution, realistic flow simulation, processing steps were modeled and optimized.
One challenge during the layout was to improve mixing in the supply tank. The goal is to achieve a spontaneous equalizing of the charge on the particles’ surface so that colloidally present particles can grow into flakes. Cyberpitch mixers mix with high velocity and energy. They use a refined angled-blade, which accelerates water not only in an axial, but also in a radial direction. This helps to evenly stir in the flocculation agent.
Hyperclassic Evolution7 mixers are employed in the flocculation tanks in order to remove, for example, particles causing turbidity or solute organic matter. This is achieved through agglomeration of suspended or colloidal particles. Subsequently, the water passes through sedimentation, flotation and filtration phases.
Subscribe to our Newsletter!
The latest environmental engineering news direct to your inbox. You can unsubscribe at any time.
The design of both mixers meets the requirements of drinking water treatment very well. The power units are dry installed above the water’s surface and therefore do not come into contact with it. Food-grade oil in the power units and oil trays prevents water contamination.
With the help of the mixers, all prerequisites for the optimal formation of flakes can be fulfilled and undesirable impurities can be separated. By rotating close to the bottom of the tank, their eight integrated and specifically optimized transport ribs generate a radially external bottom flow. This flow is particularly turbulent close to the bottom, so it efficiently stirs up sediments to prevent sedimentation of particles in the flocculation tank.
Additionally, incidences of short circuit flows are eliminated. Due to the fact that the flow on the water’s surface is directed towards the drive shaft, all particles are evenly mixed throughout the tank so that almost all of the particles come into contact with the flocculation agent, agglomerate and form flakes.
Due to the mixer’s large diameter, its optimal geometry and low rotational speed, shear forces are minimized. This enhances agglomeration of the flakes and avoids loading the flakes. The bigger and more stable these flakes are, the more easily they can be separated in the subsequent purification steps.
INVENT is represented in Ontario by Pro Aqua, Inc. This article appears in ES&E Magazine’s February 2018 issue.
