THE PILOT PLANT TREATMENT OF SWINE WASTES
BY THE DEEP SHAFT METHOD
Kunlo Is hi mam, Professor
Ginshiro (Kama. Associate Professor
Akikuni Ushikubo, Professor
Department of Liberal Education
Tokyo University of Agriculture
Setagaya-ku, Tokyo 156
Japan
Frank M. D'ltri, Professor
Institute of Water Research and
Department of Fisheries and Wildlife
Michigan State University
East Lansing, Michigan 48824
INTRODUCTION
Wastewater treatment facilities have usually been designed according to the traditional engineering practices that rely on biological or physical-chemical processes to remove both dissolved and particulate organic matter. The deep shaft process for biological treatment of wastewater was developed
recently by modifying the basic aerobic fermentation technology devised by the Agricultural Division
of Imperial Chemical Industries, Ltd., to produce single cell protein from methanol [1,2]. The major
change involved modifying the fermenter design by increasing the length of the reactor to over 100
meters. Because of the solubility of a gas is directly proportional to its pressure (Henry's Law), the additional length allows more oxygen to dissolve in the water as well as providing a much longer contact
time. As a result, the oxygen transfer efficiencies are higher than can be achieved with conventional
activated sludge aeration systems, but still lower than the air-aeration system proposed by Hashimoto
and Chen [3].
The wastewater and activated sludge are circulated in the reactor through the air lift pump principle by injecting compressed air into the riser section at a fixed depth below the surface. The compressed air circulation forces the aerated liquid through the downcomer section to the bottom of the
shaft where it re-enters the riser pipe and flows upward. While most of the compressed air rises to the
top of the reactor and is released to the atmosphere, the amount of oxygen that dissolves in the water
is substantially increased as a result of depth. As the liquid travels upward in the riser section, dissolved carbon dioxide, nitrogen, and unused oxygen are forced out of solution by the decreasing
hydrostatic pressure. The result is that the spent air is eliminated from the mixed liquor-activated
sludge. It leaves the riser through the open non-pressurized head tank and then reenters the
downcomer. A portion of the mixed liquor-activated sludge equal to the influent flow rate, is continuously diverted from the top of the riser into a sedimentation tank while the remainder is recirculated to
the downcomer [4,5].
The wastewater, air, and solids are subjected to a turbulent mixing and are treated throughout the
shaft. This promotes efficient oxygen dissolution combined with improved contact between the bacterial and organic substrates.
The advantages of the deep shaft wastewater treatment method over the conventional activated
sludge system are: much higher organic loading capacity, reduced retention time, more efficient
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