DRAFT TUBE CHANNEL APPROACH TO POULTRY PROCESSING
WASTEWATER TREATMENT
J. L. Gruette, Manager
G. M. Westphal, Process Design Engineer
Waste and Water Treatment
Mixing Equipment Co., Inc.
Rochester, New York 14603
A large poultry processing company, located in central Pennsylvania, had to undergo
an extensive upgrading of its waste treatment facilities due to an increase in plant production capabUity and a tightening of the plant discharge criteria as imposed by the Pennsylvania Department of Environmental Resources. This paper details the selection of the
LIGHTNIN™ draft tube channel as the most cost-effective design, the process design
criteria, the start up, and the operating history of this industrial waste treatment plant.
BACKGROUND
The basic concept of the oxidation ditch was developed by Pasveer in HoUand in the
early 1950s. The original concept was buUt around simplicity, both from a design standpoint and also from an operational standpoint. Since the initial development, there have
been many modifications made to allow more flexibUity in design to both improve process
performance and also reduce construction and operating cost.
The initial design had a number of drawbacks which became increasingly critical on
scale up to larger sizes:
1. The use of brush aerators for oxygen transfer and flow development limited the depth of the
oxidation ditch to approximately 5 ft to ensure adequate mixing for dissolved oxygen distribution and blending in of the influent waste.
2. The brush aerator design consisted of horizontal rotor shafts with bearings that were exposed
to the splash and spray generated by the aerators. This type of design has generated a high
percentage of downtime associated with the operation of the equipment.
3. The depth limitation of 5 ft increases amount of land area required and consequently the
capital cost of the entire system.
4. The use of brush aerators increased the amount of waste cooling due to low ambient temperatures. This created additional mechanical problems for the brush aerators and the cooling
effect decreased the removal efficiency of the biological system. This limited the use of oxidation ditches in cold weather climates.
With the development of the nitrification/denitrification process during the early 1960s,
additional advantages were found for the oxidation ditch with respect to power
consumption and process design. Through the use of a low F/M ratio, and the attendant
high sludge age, nitrification normally occurs to a significant extent in oxidation ditch
systems. By taking advantage of the denitrification reaction occuring in the anoxic zone, a
sizable amount of BOD is removed which decreases the total oxygen requirement.
In the late 1960s, the LIGHTNIN organization began development of a mechanical
submerged turbine aerator called the draft tube aerator. It was designed to generate a large
volume of controlled flow, using the liquid flow to drive compressed air to the bottom
of complete mixed activated sludge systems for improved oxygen transfer efficiency. This
new system was built around an airfoil type impeller, pumping axial within a draft tube
modified to permit high hydraulic efficiencies. Low pressure compressed air was introduced
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