Liquid purification or separation – With gas-liquid surface contact means
Patent
1988-09-16
1990-09-11
Fisher, Richard V.
Liquid purification or separation
With gas-liquid surface contact means
210151, 210619, C02F 308
Patent
active
049560824
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to an apparatus for biological purification of wastewater, and more particularly to a centrifugal bio-contactor.
2. Background of Invention
Contaminants and microorganisms usually coexist in wastewater, and contaminants, in this case, become the nutrient of the microorganisms and if there is any solid surface in the wastewater, the contaminants get attached to the surface thereof. Biological slimes are formed, as a result of growth and proliferation of microorganisms on the solid surface. The microorganisms within the biological slimes use contaminant for their growth and proliferate, thereby reducing the contaminants in wastewater. In this case, the wider the contacting area, the more the attached microorganisms. In the processes using attached microorganism for the treatment of wastewater, the rotating biological contactor method and fixed bed method have been typically developed in the art. Especially, the method using a rotating biological contactor for the biological treatment of wastewater involves the use of partially submerged bodies forcibly rotated to exposed the organisms on the contact surfaces to the atmosphere for the absorption of oxygen. Such rotating biological contactor have been known in several forms in the past as illustrated in U.S. Pat. Nos. 3,777,891, 3,827,559, 3,847,811, 3,904,525, 3,997,443, 4,122,011, 4,115,268, 4,444,658, etc. However, in the system of such a rotating biological contactor, because more than a half of the horizontal rotor is exposed to the atmosphere or air, once the biological slimes get thick, the increased weight causes the horizontal axis to be bent or to be broken in many cases and the organisms exposed to atmosphere are very sensitive to cold water. Therefore, operating such rotating biological contactor in low-temperature climates requires a housing to limit wastewater temperature reduction or heat loss.
The inventor engaged in research in order to solve the above problems/disadvantages and concluded that a contactor having a plurality of transverse ribs disposed along the axis with a proper spacing between each of the transverse ribs and a plurality of longitudinal ribs having the shape of an impeller of a pump has the advantage of removing the contaminants of wastewater effectively, because the rotation of the rotor which consists of a shaft and such contactor makes the flow of the wastewater smooth, even if the rotor is submerged entirely in wastewater.
As to the flow of wastewater, Trulear and LaMotta disclose that the removal of the contaminant materials depends on the mass transfer when the water flow is below 0.8 to 0.93 m/sec. (Trulear, M.G. "Dynamics of Biofilm Process", J. WPCF. Vol. 54, pp. 1288-1301, 1983; LaMotta, E. J.," External Mass Transfer in a Biological Film Reactor" Biotechnol. Bioeng., Vol. 18, pp. 1359-1370, 1976) and also Rittman discloses that the faster the speed of the flow of the wastewater, the more the quantity of detached microorganisms (Rittman, B. E., "The Effect of Shear Stress on Biofilm Loss Rate", Biotechnol. Bioeng., Vol. 24, pp. 501-506, 1982). Accordingly, the flow of wastewater which passes over the surface of the biological slimes, has an important role not only in transferring contaminants, but also in controlling the amount of microorganisms. The efficiency of treatment will be increased in accordance with the width of the contacting area and smoothness of wastewater flow. The present invention puts the above theory to practical use.
The purpose of the invention is not only to increase the contacting area and make the flow of wastewater smooth in order to increase the efficiency of the treatment, but also to prevent bending and destruction of the axis due to the adverse effect of cold weather. There are three characteristics in this invention. First, the longitudinal ribs of the contactor are installed like those of the impeller of a pump, in order to make the flow of the wastewater smooth, even if the rotor is submerged entirely in wastewater. Rotating of t
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Fisher Richard V.
Nessler Cynthia L.
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