Method and Apparatus for Treating Water

1. Field of the Invention

The present invention relates generally to treatment of water, and more particularly to treatment of waste water utilizing a plurality of adjacent conduit members positioned to receive an air flow or gas flow therethrough to lift and circulate the water to be treated. Preferably, the gas utilized is air or oxygen and provides for aerobic biological treatment of the water. Optionally, particles may be added to the solution to increase the surface area carrying the desirable biota.

2. Description of the Related Art

An early process utilized to purify or treat water such as waste water was the Trickling Filter Process. Initially, this aerobic biological process involved trickling the water to be treated over a bed of rocks. The process evolved to the use of plastic to provide a receptive, enlarged surface area for the biota. Accordingly, greater surface area could be provided in a given volume and the reduction in weight enabled towers as high as forty feet to be employed. The process was further improved by recycling a portion of the effluent back over the biota. However, while the biota cultivated on the plastic surface is efficient and effective in removing contaminants, energy requirements to pump the water and a desirable recycle stream to such heights are substantial.

The Activated Sludge Process was developed after the Trickling Filter Process to provide for more thorough treatment of waste water contaminants and facilitate treatment of large quantities of waste water. Like the Trickling Filter Process the Activated Sludge Process is an aerobic biological process and depends upon providing substantial amounts of oxygen to the micro-organisms comprising the biota. Rapid mixing is essential to contact the micro-organisms with the contaminant which serves as nourishment for the micro-organisms. A clarifier is required in the Activated Sludge Process. Basically, a clarifier provides a quiescent volume which allows the activated sludge in the form of colonies of micro-organisms to settle and thus be conveniently available for removal from the clarifier. Clarified water is removed from another zone of the clarifier. A recent improvement to the Activated Sludge Process involves the addition of activated carbon particles to the reactor. The activated carbon absorbs the contaminants and thus provides a greater resident time for the micro-organisms to consume the contaminants as nourishment.

Rotating biological films or discs were developed as an improvement over the Trickling Filter Process in order to treat large flows and avoid the prohibitive energy demands required to pump waste water to the top of high towers. Typically, large discs rotate at a rate of about 1 to 5 rpm to enable biota to build up on the surface of the disc. Since the disc is partially in the water and partially in the atmosphere, oxygen is supplied to the biota as the disc rotates out of the water to the surrounding atmosphere. Nourishment, in the form of contaminants in the waste water, is provided to the biota as the disc carrying the biota rotates through the waste water. However, the process is limited by the relatively low rate at which the disc can be rotated. Biota colonies carried on the disc are rather fragile and will not withstand substantial disturbance resulting from the discs moving through the waste water in conjunction with centrifugal force resulting from even moderate rotational speeds.

Thus the prior art generally relates to processes which are effective but relatively slow and/or energy intensive in treating water. Accordingly, an advantage of the instant invention is a compact, efficient biological reactor which is effective and efficient in reducing the contaminants in water.

Another advantage of the instant invention is the efficiency resulting from the use of gas to aerate and circulate the waste water over a compact volume having great surface area to support biota growth.

Yet another advantage of the instant invention is the vigorous mixing and aeration of the water to be treated thereby providing oxygen and nourishment in the form of contaminants to the biota growth on the biological reactor.

These and other advantages of the instant invention will become apparent from the following description.

In the drawings:

FIG. 1 is a perspective view, partially cut away of a biological reactor in accord with the instant invention;

FIG. 2 is a section of the biological reactor shown in FIG. 1 along section line 2--2;

FIG. 3 is a perspective view of a typical manifold arrangement as utilized in the biological reactor shown in FIG. 1;

FIG. 4 is a section view of a single conduit and associated manifold of the biological reactor shown in FIG. 1;

FIG. 5 is a cross sectional view of a biological reactor as used in another embodiment of the instant invention; and

FIG. 6 is a cross sectional view of yet another embodiment of the biological reactor in accord with the instant invention.

With reference to the drawings, wherein like components are designated by like reference numerals throughout the various figures, a biological reactor is illustrated in FIG. 1 and generally designated by the reference numeral 10. As illustrated, biological reactor 10 is formed of a plurality of conduits 12, which are open-ended tubular members preferably of circular cross section, but operably of various cross sections such as square, hexangular, etc. It is desirable that conduits 12 be positioned in an adjacent but spaced relationship to provide openings 13 therebetween. Manifold 14 is positioned below conduits 12 and connected to gas inlet 15. Gas inlet 15, in turn, is connected to a pressure source (not shown) for the gas.

Biological reactor 10 is supported and surrounded by enclosure 17. Inlet 19, through which water to be treated is conducted, provides flow into enclosure 17. Water level 20 in enclosure 17 is controlled by outlet 22 which is connected to clarifier 24. Clarifier 24 is an enlarged volume container for after treatment of the water to facilitate separation of sludge entrained with the water flowing through outlet 22 from enclosure 17. While not critical, clarifier 24 is a desirable addition to improve operation of biological reactor 10. Sludge and treated water are separated in clarifier 24 with the treated water exiting through treated water outlet 25 and the sludge, which is primarily micro-organisms, recycling through sludge outlet 26. Pump 28 draws sludge from clarifier 24 through sludge outlet 26 to either, as is determined by the operator, sludge outlet 30, illustrated as a manual valve, or sludge return 32 in enclosure 17.

The operation of biological reactor 10, as illustrated in FIG. 1, will be more readily understood with references to FIGS. 2, 3 and 4. As shown in FIG. 2, manifold 14 is positioned immediately below conduits 12 and spaced therefrom. Manifold 14 is formed of manifold tubes 35 positioned between headers 36 at either end thereof and having defined therein gas orifices 38 positioned with a gas orifice 38 immediately below each conduit 12. Accordingly, as shown in FIG. 4, gas under pressure, and preferably air or oxygen, is provided to manifold tube 35 and metered through gas orifice 38 in a manner such as to agitate and aerate water in conduits 12. The gas aerates and agitates water in conduit 12. The aerated water, being of a lower density than the water in enclosure 17, is displaced upward to the top of conduit 12 and spills thereover in a more or less frothy or aerated manner. Both the inner and outer surfaces of conduit 12 are appropriate for the cultivation of biota. The biota, though fragile, is compatible with relatively strong agitation of the aerated water in conduit 12. Accordingly, both oxygen and nutrition in the form of contaminants in the turbulant water, are rapidly replenished when consumed by the biota. Accordingly, the kinetics, both of growth of the biota, and the consumption of contaminants by the biota, are greatly enhanced.

Another embodiment similar in operation to that of FIG. 1, but employing somewhat different structure is illustrated in FIG. 5. While much of the structure is identical to that of FIG. 1, i.e., inlet 19, water level 20, manifold tubes 35, header members 36 and treated water outlet 25, it is to be noted that the embodiment of FIG. 5 includes an outer tank 45 which surrounds enclosure 17 and defines a volume therewith. Openings 47 are defined through enclosure 17 such that water treated by biological reactor 10 flows from enclosure 17 through opening 47 to the volume defined by outer tank 45. Thus the volume between enclosure 17 and outer tank 45 in effect serves as a clarifier. As discussed with regard to the clarifier of FIG. 1, such volume communicates with treated water outlet 25 and sludge outlet 30 as illustrated. Also, while it is to be understood that biological reactor 10 may be supported in a great number of manners, as shown in FIG. 5, manifold 14 is carried on the floor of enclosure 17 by supports 50. Conduits 12 are in turn supported from manifold 14. Thus it is to be appreciated that the preferred embodiment of FIG. 5, which is particularly adapted to utilize air as the lifting and aerating gas, is the functional equivalent of the embodiment of FIG. 1, but utilizes a clarifier structure which is integral with the flow through the openings 47 to the space defined by outer tank 45 and enclosure 17.

Another embodiment, as illustrated in FIG. 6, is quite similar to the structure discussed with reference to FIG. 5. However, as illustrated in FIG. 6, the normally open upper portions of enclosure 17 and outer tank 45 are closed by top 55 extending thereacross. Also, gas outlet 57, communicating through top 55, is provided to vent gas from the volume enclosing biological reactor 10. This arrangement is particularly useful when substantially pure oxygen is employed as the operative gas. Accordingly, vent 57 is connected to a blower 59 which conducts the treatment gas through line 60 to carbon dioxide absorber 62. Carbon dioxide absorber 62 may be any of the conventional means for this purpose, but is conveniently a tower including, for instance, sodium carbonate, sodium hydroxide, potassium hydroxide or other such aqueous solutions known to absorb substantial quantities of carbon dioxide. As is well known in the art, the carbon dioxide may be desorbed from the solution by changing conditions, such as temperature, to reduce the solubility of carbon dioxide in the liquid.

After excess carbon dioxide, which is a by-product of treatment of contaminants by the biota, is removed, the remaining oxygen is conducted through lines 65 to gas inlet 15 to serve as the aerating gas to carry the liquid up through conduits 12. Makeup oxygen is supplied to the system from a source (not shown) at oxygen inlet 68. A trap 70 is preferably included at water outlet 25 to prevent loss of oxygen with treated water. While the cost and complication of using oxygen is greater than required for atmospheric air, the efficiency of the biological reactor is of course greatly enhanced if pure oxygen is employed. Particularly in instances where weight and/or space is important, i.e., shipboard installations, the use of pure oxygen may be quite desirable.

From the above discussion, it will be apparent to those skilled in the art that the treatment of waste water will substantially reduce Total Organic Carbon, Biochemical Oxygen Demand and Chemical Oxygen Demand, oil and grease, Total Suspended Solids and turbidity. This is accomplished in a rapid and efficient manner primarily as a result of the agitation and mixing of the gas, which provides both oxygen and nutrients to the biota, as the gas carries the water upward through the conduits. While the biota is fragile and may be thrown from a surface by relatively low centrifugal force, resistance to turbulence and agitation is substantially greater. Thus the biota is able to withstand velocities of about 11 feet per second in terms of water flow over the surface thereof. However, somewhat lower flowrates on the order of 0.3 to 5 feet per second are preferred. A range of 1.5 to 3 feet per second is particularly preferred. In any event, though a certain portion of the biota will of course be detached by the agitated and aerated water flowing thereover, such detached micro-organisms serve to initiate new sites for biota growth on any surface not previously cultivated, provide for a certain amount of in situ treatment of contaminants, and are substantially recovered in the clarifier for recycling through the biological reactor.

The method and structure of the instant invention may be further yet enhanced by the addition of properly selected plastic pellants, spent catalytic cracker and catalyst particles, powdered coke or other such particles such as fly ash particles. Such particles may be added in amounts of up to five percent by weight of the charge rate, but preferably 0.05 to 1 percent by weight of the charge rate is preferred. Such particles provide even greater surface area and support growth of biota thereon as the water travels through the biological reactor. A certain number of particles may be adhered to the walls of the biological reactor, thereby presenting even greater surface area. A particularly preferred particle is one having a density only slightly heavier than water thereby providing for flow with the water through the biological reactor yet permitting separation in the clarifiers for recycling and or removal from the treated water.

The nature and advantages of the instant invention will be more readily appreciated with reference to the following examples.

Two activated sludge reactors, each having a five gallon capacity and an annulus clarifier, but one being operated with powdered refinery coke to provide additional surface area for micro-organisms, were each stirred with a one-quarter horse power lightening mixer and ample air supplied thereto by an air diffuser. A biological reactor substantially as described above with reference to FIG. 1 and having a five gallon capacity and an annulus clarifier was prepared. The biological reactor consisted of 144 three-eighth inch OD polyvinyl chloride tubes twelve inches long placed over a distribution box containing 144 one-sixtyfourth inch holes. Each of the one-sixtyfourth inch holes were placed under one of the 144 polyvinyl chloride three-eighth inch tubes with approximately one-quarter inch space between the bottom of the tube and the top of the distribution plate. The reactor tubes were placed with two inches thereof extending above the water line in an enclosure, and accordingly ten inches below the water level. Two cubic feet per minute of air was supplied to the distribution box. Table I summarizes the results of a five day comparison of waste water purification from each of the three reactors. The data presented was collected each day of the five day period and averaged. Feed to each of the reactors was from a common tank and thus the same waste water was provided to each reactor.

As is apparent from Table I, the biological reactor, even without the benefit of added particles such as the powdered coke utilized with one of the activated sludge reactors, in every instance provided substantially improved treatment with almost double the feed rate and almost half the residence time.

A similar comparison to that described in Example I utilizing the biological reactor of Example I was made also utilizing a forty-seven inch rotating disc pilot plant reactor with clarifier. While the biota on the rotating disc had been built up over a two month period and equilibrated with the common waste water feed for twelve days prior to the two day test period, the biological reactor had been cleaned five days before the two day test period and thus the maximum amount of biota may not have been produced. The data from the two day period were averaged and summarized in Table II.

As is apparent from Table II the biological reactor, having lower actual surface area, and lower equivalent surface area calculated upon dynamic blow, again provided improved treatment in every instant. Thus, it is apparent that the dynamic mixing and distribution of nourishment in the form of contaminants and oxygen provides for rapid treatment of the contaminants. Though the biological reactor utilizes energy to accomplish such mixing, the energy is very efficiently used so that the gas, in the preferred embodiment, both aerates the water for purposes of lifting, and also for purposes of providing oxygen to the micro-organisms. Thus, with efficient use of energy and little lift of the water, greatly enhanced treatment rates are accomplished.

Although only several embodiments of the present invention have been illustrated and described, it is anticipated that various changes and modifications will be apparent to those skilled in the art, and that such changes and modifications may be made within the scope of the following claims.