sludge mixers minimize scum formation, distribute heat throughout the digester, completely mix the digester contents and evenly distribute volatile acids and nutrients. Several types of sludge mixers are available to pump large volumes of sludge through draft tubes. Type EDT Mixer External Draft Tube (EDT) mixers are self-contained units which provide a tangential flow pattern within the digester. They are the most efficient system available for high rate digestion.

Maximum energy input occurs at the periphery of the tank near the surface and bottom of the digester tank. Discharge is at the digester surface to enhance surface turbulence and prevent scum accumulation. Easy access for maintenance is achieved by mounting the mixer outside of the tank. Removal of the drive assembly for maintenance is achieved without losing digester gas or dewatering the tank.

Type RDT Mixer Roof-Mounted Draft Tube (RDT) mixers are mounted on the digester cover with the draft tubes and drive assemblies both being easily removable. For maximum mixing capability, several RDT mixers can be distributed around the cover on large digesters. Flow can be directed upward or downward with periodic reversing of direction. Types RDT-V and RDT-L incorporate telescoping extensions at the bottom of the draft tube.

With the type RDT-L, flow is pumped downward through the draft tube toward the digester bottom. The Type RDT-V discharges tangentially at the digester bottom. In large diameter digester applications, an RDT mixer can be installed at the center of the digester tank to operate in conjunction with the EDT mixers at the tank periphery to give additional scum breaking and mixing capacity.

Eimix Mixing Propeller is designed specifically to eliminate accumulation of stringy and fibrous material on the propeller which can cause bearing and seal damage and drive motor overload. Flow is directed away from the hub by the specially designed propeller blade which also permits operation in either upward or downward flow without changing the pumping rate.

 Benefits

• Rotating equipment and draft tubes are supplied as a unit - easy installation 
• Forward and reverse operation - alters flow and increases system flexibility
• Specially designed propeller - eliminates accumulation of debris
• Machined lower mechanical oil seals - decreases maintenance costs
• Large diameter draft tube and propeller - provides low head loss and effective utilization of mixing energy
• Heat exchange jackets - effective digester heating for low cost
• Mixers are located at the tank periphery and/or on the digester cover - more effective sludge mixing and easy access
• Strong surface agitation - effective scum break-up
• Can be worked on while the digester remains in service - easier maintenance
• High degree of mixing intensity - eliminates short circuiting and increases the active digester volume 

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