Liquid purification or separation – With gas-liquid surface contact means – With separator
Patent
1998-03-09
2000-06-20
Upton, Christopher
Liquid purification or separation
With gas-liquid surface contact means
With separator
210194, 210197, 210220, 210616, C02F 308
Patent
active
06077424&
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
The present invention relates to a method for aerobically treating liquid-waste and a treatment tank used in the method. More particularly, the present invention is concerned with a method for maintaining in an aerobic treatment tank carriers having microorganisms immobilized thereon and aerobically, biologically treating liquid-waste, such as sewage, human excrement and industrial organic liquid-waste. The present invention is also concerned with a treatment tank used in the above-mentioned method.
CONVENTIONAL TECHNIQUE
In recent years, as liquid-waste treatment techniques, an activated sludge method, a biomembrane method and an immobilized microorganism method have been known. From the viewpoint of efficient utilization of land, it has been desired to develop a liquid-waste treatment method which is space-saving, and a method for an aerobic treatment of liquid-waste utilizing carriers having microorganisms immobilized thereon, the improvement of performance of such carriers has attracted attention. The present inventors previously developed a liquid-waste treatment apparatus shown in FIG. 9, in which carriers having microorganisms immobilized thereon are utilized. In the liquid-waste treatment apparatus of FIG. 9, liquid-waste is introduced from an inflow pipe 7 into one end of a treatment tank 1, aerated in the treatment tank 1 and discharged from an outflow pipe 8 as a treated liquid. In the treatment tank 1, carriers 2 having microorganisms immobilized thereon are maintained in a floating state due to fine air bubbles supplied from an air-diffusing means 3, such as a diffuser, an air-diffusing pipe or the like.
The air-diffusing means 3 is disposed on a bottom surface of the treatment tank 1. Air is supplied under pressure from a blower 4 through an air pipe 5 to the air-diffusing means 3, which supplies numerous fine air bubbles into the liquid-waste from a position in the vicinity of the bottom surface of the treatment tank 1. The supplied air bubbles rise through the liquid-waste and partly dissolve in the liquid-waste. The carriers 2 in the liquid-waste are pushed by the rising air bubbles and rise in the treatment tank 1, and settle due to their own weight in a region in which no rising of air bubbles occurs. Thus, the carriers 2 float in the liquid-waste while circulating therethrough. A carrier-separating device 6 is disposed in the treatment tank 1 at an end thereof opposite to the inflow pipe 7. In the carrier-separating device 6, the carriers are separated from the treated liquid discharged from the treatment tank.
In the prior art, as aeration apparatuses for a liquid-waste treatment in which air is diffused through and mixed with the liquid-waste, there have been known an apparatus in which a surface of the liquid-waste is agitated and an apparatus in which air is supplied from a large number of small holes and diffused through the liquid-waste. In addition to the above-mentioned apparatuses, there has been known an underwater agitation type aeration apparatus (an aerator provided with an impeller) having an air-diffusing mechanism on a discharge side of the impeller, which is disclosed in, for example, JP-B2-61-36475, JP-B2-61-36476 and JP-B2-61-38000 (Examined Japanese Patent Publications), and U.S. Pat. No. 4,512,936 (U.S. Patent).
The treatment tank 1 of FIG. 9 is advantageous in that the oxygen-dissolving efficiency of the air-diffusing means 3 is high and that breakage of the carriers 2 does not occur because the agitating force of the air-diffusing means 3 is small. However, the treatment tank 1 of FIG. 9 has the following disadvantages.
(1) The carriers 2 having microorganisms immobilized thereon flow in a horizontal direction, together with a liquid to be treated, from an inflow end (the left end of the treatment tank of FIG. 9) to an outflow end of the treatment tank 1, so that the distribution of carriers becomes non-uniform, such that the concentration of carriers is low in the vicinity of the inflow end of the treatment tank
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Concurrently filed U.S. Patent Application corresponding to PCT/JP96/01364, Filed May 23, 1996, entitled "Carrier-Separating and Liquid-Collecting Mechanism for Liquid-Waste Treatment Apparatus" by Noboru Katsukura et al.
Katsukura Noboru
Mishima Koji
Nakagawa Sota
Nishii Akinori
Tochikubo Eiji
Ebara Corporation
Upton Christopher
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