Multiple Depth Mixing Within a Single Process
Application / Industry: Municipal Wastewater Treatment
Customer Name: Berlin Township, MI
Consulting Engineer: Fleis & Vanderbrink, Grand Rapids, MI
Process Fluid: Municipal Waste Activated Sludge
Process Treatment Method: Sludge Storage Tank No.3
Challenge
When the Township of Berlin needed to convert an existing concrete tank to a sludge storage vessel, a major challenge was that a majority of the storage volume in the tank would be within a sloped wall conical area in the lower one half of the tank.
The operations staff and design engineer wanted to apply a diffused air mixing and oxygen supply system for this process. Typical coarse bubble diffused air systems are installed on a 
common hydrostatic plane so that discharge pressure is the same across the entire system for the blower. This meant the system could only be installed at a depth where the walls were still vertical, to allow for installation of the air distribution piping grid, creating a significant problem for mixing solids in the conical area of the tank.
Since there was insufficient space at the lowest elevation of the cone to install the piping necessary to handle the total airflow demand for the tank, the piping would have to be raised or divided into sub-systems operating on different pressure elevations.
Solution
Knowing that raising the entire manifold elevation would result in solids accumulating in the lower cone, and unable to be re-suspended without air discharged in that area, Tideflex® Technologies Engineers custom-designed a four manifold system with each manifold at a different elevation. Each manifold run had an individual drop pipe and a distribution control orifice plate located at the top flange connection. Tideflex® Engineers sized each orifice to produce the elevation head differential from the lowest manifold, allowing the blower to sense a common pressure across all drop pipes (equal to the lowest manifold) so flow was evenly distributed across all four manifolds.
Results
The multi-manifold configuration produced a completely mixed vessel through the vertical wall zones and the conical zone, resulting in homogeneous fluid concentration. Tideflex® is the only diffused air system manufacturer that provides the design and implementation of multi-level mixing systems for tanks with tapered bottoms as well as check valve diffusers that eliminate maintenance due to clogging of air piping.