JPS5835118B2 - Two-zone method for biological treatment of wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to treating wastewater having biological oxygen demand (BOD) to remove BOD.

More particularly, the present invention relates to a method and apparatus that makes it possible to use a single vessel for carrying out secondary clarification by deposition of biological reactions and precipitated solids resulting from the biological reactions.

The purification and biological treatment of wastewater from municipal and industrial sources before discharge into natural water systems traditionally consists of four basic steps carried out in four separate treatment tanks or vessels in series. It was something.

A typical treatment plant consists of a plurality of banks of such treatment tanks arranged in parallel to treat water from a common inlet pipe and discharge it from a common outlet pipe.

For example, Hamilton, Ontario, Canada.
The treatment plant in the city is 227,100rrf/
It is designed to treat wastewater at a rate of 28,387.5 gallons/day (60,000,000 gallons/day), and each row of the first clarifier, aeration tank, and clarifier tank is designed to process wastewater at a rate of 28,387.5 gallons/day (750,000
0 gallons/day) and eight such rows are in parallel.

At the Hamilton plant each vent tank is 109.
73 m (360 ft) long, 18.288 m (6
Each clarifier has a width of 0 ft) and a depth of 4.7244 m (15.5 ft).
20 ft) square and 3.048 (10 ft) deep, each vent tank is 2006.7 m2
(21,600 square feet) each clarifier has an exposed surface area of 1337.8 tri) (14,400 square feet).

In such conventional treatment methods, wastewater is first treated in a sand removal tank to deposit heavy (-solid) particles.

Water is conveyed from the sand removal tank to a first clarifier, which consists of a tank that holds the wastewater for a period of time to allow the suspended solid particles to settle and skims any solids and fats and oils suspended therein.

The liquid from the first clarifier is sent to a vented tank containing microorganisms for converting dissolved substances in the liquid into insoluble substances, and air or oxygen is introduced into the tank with stirring to meet the oxygen demand of the microorganisms. Fulfill.

A liquid containing suspended solids and dissolved materials is sent from the vent tank to a first second clarifier, and the clear liquid exits the second clarifier to remove solids from the bottom of the clarifier.

A portion of the sludge-containing liquid in the second clarifier is continuously circulated to a vent tank for further biological treatment and the excess is disposed of.

The present invention provides a method for biologically treating wastewater, in which the biological reaction and the secondary clarification of the biologically treated water are carried out in a single vessel. This method allows economy in plant design and advantageous treatment of wastewater containing a higher concentration of waste material than conventional methods using a separate aeration tank and a second clarifier; The clarification, biological reaction and secondary clarification can all be carried out in a single vessel under suitable conditions.

The apparatus of the present invention offers significant economical advantages over previous apparatus previously used in the scale, allowing for high treatment capacity and for treating wastewater containing relatively high concentrations of waste materials. enable processing.

The method of the invention proceeds as follows.

Finally, a reaction zone is formed at the bottom and a clarification zone is formed at the top into a single reaction clarifier. A liquid mixture containing effective microorganisms for converting into

An oxygenated mixed liquid containing dissolved oxygen is continuously fed into the lower part of the vessel.

This oxygenated mixed liquid is provided by adding oxygen to a mixture of freshly supplied wastewater and a partially treated, substantially carbon dioxide-free mixed liquid recycled from within the vessel.

Controlled agitation is used to maintain liquid circulation in only one part of the vessel, creating an agitated biological reaction zone in which the solids are kept in suspension, while at the same time maintaining liquid circulation in one part of the vessel. The liquid is kept relatively undisturbed to form a clarification zone in which the solids settle and the clarified liquid rises.

The partially treated mixed liquid continuously exits the reaction zone and is added to the oxygenated mixture.

The oxygen in the reaction zone is maintained at a concentration that satisfies the oxygen requirements of the organisms and at the same time is maintained at a concentration below the oxygen concentration in the oxygenated mixed liquid fed into the reaction zone.

The oxygenated mixed liquid is diluted as it passes into the reaction zone to prevent the release of oxygen from the solution and to prevent bubbles from carrying solids from the reaction zone into the clarified liquid.

The clarified liquid is continuously discharged from the container and its flow rate is maintained at the same rate as the waste liquid feed rate.

The method described here allows separate stable clarification zones and biological reaction zones to be kept in the same reaction-clarifier and allows effective clarification of mixed liquids on a continuous basis. enable you to get what you want.

In this way, waste water is continuously introduced into and passed through the system, with successive waste products being removed as clear liquid in the effluent stream.

This is done as follows. The freshly added wastewater is mixed with the partially treated mixed liquid to form a mixture to which oxygen is added.

This oxygenated mixture is passed into the lower reaction zone of the reactor-clarifier where it is continuously circulated in contact with the treatment organisms and contains a concentration of oxygen lower than the concentration of the incoming oxygenated mixed liquid. Mix with mixed liquids.

In this way, the resulting liquid mixture is diluted and the oxygen remains in solution, preventing it from being released as bubbles.

This foam would inhibit the process by causing the solids to float into the clarification zone in which the liquid moves upwardly at a faster rate than the upward movement that occurs in the reaction zone.

The incoming liquid thus becomes part of the liquid in the reaction zone and is in continuous circulation.

A portion of the circulating liquid exits the reaction zone and is returned to mix with incoming wastewater for oxygenation as described above.

When all this is done, the liquid above the reaction zone rises at a rate determined by the rate of addition of waste water from the reaction zone into the relatively quiescent clarification zone, in which the resulting upward flow The movement of the liquid is faster than the movement in the reaction zone so that the solids are deposited and the liquid is clarified as it rises.

The clarified liquid is drained at the rate that fresh wastewater is added to the system.

In short there is a continuous inflow of wastewater into the system and a continuous upward flow of the mixed liquid through a single reaction clarifier with an oxygen injector and a stirrer above it, while the conditions in the vessel A controlled downward force exerted on the solids causes them to settle, thus resulting in clarification.

The oxygen supplied to the biological reaction zone is controlled by careful monitoring to meet the microbial oxygen requirements for efficient metabolism.

The most important thing during maintenance is to carefully control the oxygen supply to ensure that there is no undissolved oxygen in the biological or clarification zone.

It is known that the presence of undissolved oxygen in the biological reaction zone inhibits the secondary clarification of undissolved oxygen in the form of small bubbles.

The reason is that small bubbles rise through the upwardly flowing clarified liquid and carry with them solid particles of waste material so that satisfactory clarification is not achieved.

Furthermore, the oxygen bubbles and the solid particles of waste material carried by the oxygen bubbles tend to entrain the active substances in the biological reaction zone consisting of microorganisms and biologically untreated waste material. It also makes the secondary clarification insufficient.

According to another aspect of the present invention, there is provided an apparatus for biologically treating wastewater, the apparatus comprising: continuously adding wastewater to the vessel in a single vessel to deposit mixed liquid contents therein; an oxygen dissolving device comprising an introduction means for forming a mixed liquid and an injection means for injecting oxygen into a mixed liquid contained in the device, the oxygen dissolving device comprising: the oxygen dissolving device used, directing at least a portion of the mixed liquid through the oxygen dissolving device to dissolve oxygen therein and subjecting the oxygenated mixed liquid to the specified biological reaction in the container; Circulating means for discharging the liquid into the biological reaction zone and the oxygen dissolution device for a time and mixture effective to complete the biological reaction in the biological reaction zone. means for removing separated clarified liquid from the top of the vessel (the circulating means is effective for continuously circulating the oxygenated mixed liquid at a flow rate effective to suspend the solids); Give the liquid a flow velocity considerably higher than that of the clarified liquid flowing upward, and set the flow velocity of the clarified liquid flowing upward so that the sedimentation rate of the suspended solids is much higher than the flow of the liquid in the -L direction. clarification of the liquid) and to control the supply of oxygen to the oxygen dissolution device to meet biological oxygen demand and avoid undissolved oxygen in the biological reaction zone. consisting of the means of

In the method and apparatus of the present invention, the biological treatment of wastewater and the clarification of biologically treated water, known as secondary clarification, are carried out in a single unit having a lower biological reaction zone and an upper clarification zone. Effectively done in one container.

Although it is not absolutely necessary to physically separate these two zones, using a diaphragm to distribute the flow between these two zones will reduce the amount of suspension from the upwardly flowing clarified liquid. It is believed to be useful as it improves the separation of cloudy solids.

The above two zones can be made effective by appropriate hydraulic design, based on the placement of pumping or mixing systems to agitate the lower half of the tank to sufficiently keep all solids in suspension and act as a biological reactor. made in

At the same time, the hydraulic design should be arranged to keep the upper half of the tank agitated and act as a clarifier.

The flow rate of water in the clarification zone is equal to the flow rate of the inflow into the vessel, and the flow rate of water in the biological reaction zone is preferably 10-100 times the flow rate of the influent, preferably 25-50 times optimally 35 ~4
It is 5 times more.

The significantly higher flow rate in the biological reaction zone relative to the flow rate in the clarification zone creates the necessary hydraulic system that allows effective separation of the clarified liquid and from the water in the biological reaction zone. Both are necessary to keep the settled solids in suspension, and the solids must be kept in suspension since settling of solids and accumulation at the bottom of the vessel will result in inhibiting the hydraulic system.

The flow rate and design of the waste treatment system is such that the time spent by the wastewater in the oxygen dissolution device is very low compared to the time spent by the wastewater in the biological reaction zone.

The residence time of the wastewater in the oxygen dissolution device for each cycle of wastewater through the oxygen dissolution device and biological reaction zone is typically 5 to 50 seconds, preferably 10 to 25 seconds, more preferably about 15 seconds.
Seconds.

The total time spent by the wastewater in the biological reaction zone is approximately 0.5-5
The time is preferably about 1 to 3 hours and more preferably about 2 hours.

Despite the pioneering theories in the art, it is virtually impossible to obtain an effective separation of the biological reaction zone and the clarification zone and to avoid the escape of circulating solids into the clarified liquid. It was surprising.

Separation of the high and low flow rate bands can be expected on theoretical models under ideal conditions, but adequate separation can be achieved in aqueous systems with high solids contents and clarified aqueous liquids. It was quite surprising that a continuous separation of .

Furthermore, the method and apparatus of the present invention utilizes a single vessel for effective continuous treatment of water with a higher content of waste material than in conventional systems where aeration and secondary clarification are carried out in completely separate vessels. This was not something that could have been expected.

It should be understood that in the clarification zone, the rate of solids deposition must be greater than the rate of upward flow of liquid to achieve effective clarification.

Therefore, when constructing a container for carrying out the method of the invention, various factors, depending on the conditions of the particular case, must be taken into account, which is within the scope of the skilled worker. be.

As explained in the preamble, it is necessary to carefully control the oxygen supplied to the biological reaction zone to ensure the absence of undissolved oxygen in the form of gas bubbles.

For similar reasons, it is appropriate to use oxygen substantially free of other gases.

Air is not suitable as an oxygen source because it has a high nitrogen content; nitrogen is less soluble in water than oxygen; , it rises into the clarification zone carrying solids upwards.

It is possible to use oxygen-enriched air with a high oxygen content as the oxygen source provided that significant amounts of undissolved nitrogen are not introduced into the system.

Under stable conditions, the solids content in the system increases gradually.

To maintain a constant concentration of these solids, small portions are pumped out at frequent intervals.

The solids may be pumped out over a period of 30 minutes to 24 hours per day, but typically is pumped out over a period of 4 hours per day.

Solids are discharged daily at a rate of about 1.0 to 10%, preferably about 4% of the influent per day.

In a typical operation where the inlet flow is about 60,000 gallons per day, solids are preferably discharged from the biological reaction zone at a rate of 10 gallons per day for only 4 hours. It represents a proportion of approximately 4% of the incoming flow.

It is also within the scope of the invention to carry out the first clarification of the wastewater in the same vessel as the vessel for the biological treatment and the second clarification.

This adds a skimmer to the vessel to effectively skim floating solids and oil from the upper surface of the biological reaction zone, as well as to collect and remove heavy solids that settle rather than remain in suspension. This can advantageously be achieved by providing a conveyor device at the bottom of the container.

A particular advantage of the device of the invention is that it allows the processing capacity per unit surface area of the processing tank to be much higher than in current installations.

In the case of the Hamilton treatment plant described above, the separate aeration tanks and clarifiers in each row can be changed to two single treatment tanks in parallel by the teachings of the present invention, thus reducing the treatment of the current installation. The capacity (ie, the volume of water treated per unit time) can be increased from 50% to over 100%.

In this way, in the example of the Hamilton plant, by changing the current two-tank system to two single-processing tanks in parallel, 28,387.5 〆/day (7
500,000 gallons/eye) processing capacity 41,635~7
1915m”/day (11 million to 19 million
0 gallons/day).

If the tank is modified in such a way that all three treatments (first clarification, biological reaction and second clarification) are carried out in the same vessel, the first clarification tank is also modified to form the processing vessel of the present invention. become.

In this case, the current system of three tanks should be changed to three single processing tanks in parallel to provide a processing capacity that is more than three times the capacity of a single system consisting of three tanks. I can do it.

The process and apparatus of the present invention, which can thus be operated continuously without interruption by careful control of added oxygen, is particularly a significant increase to the processing capacity of current plants and, for a given processing capacity, generally smaller scale. It is clear that it has significant advantages in enabling the construction of new plants.

As used herein, the expression "oxygen dissolution device" or "oxygen contacting device" refers to a device that can be used to contact oxygen and wastewater to dissolve oxygen in the water, and which The housing through which wastewater flows
ng) within which oxygen is dissolved in the wastewater.

A particularly preferred oxygen dissolving device is U.S. Pat. No. 36,434.
No. 03, the apparatus comprises a flow restricting chamber having an upper volume and a lower outlet through which the wastewater flows from the highest at the inlet end to the lowest at the outlet end. is propelled downward at a decreasing speed.

The flow-restricting chamber as described by Peeee (5 peeee) consists of a downwardly flared funnel-shaped or generally conical housing with an intake tube arranged vertically at its upper end and an intake tube to direct the flow downwards. It has a propulsion machine installed inside.

Furthermore, the device includes means for introducing oxygen into the funnel section in the form of a foam disperser.

Other types of oxygen dissolution devices, which are normally located outside the processing tank, consist of tubes sunk vertically into the ground.

This tube is divided lengthwise into two halves by a vertical partition;
The partition begins at the top of the tube and ends above the bottom to provide clearance for flow.

To achieve this arrangement, two vertical tubes may also be installed that are parallel and connect at the bottom.

Wastewater is introduced into one side of the partition where a pump directs flow down the pipe and up the other side.

Oxygen is introduced in the form of fine bubbles just below the pump and these are forced downward by the flow, dissolving as they are carried along with the wastewater.

In another aspect, the present invention provides an improvement in an oxygen contacting device that uses a pump to induce downward flow.

This downward flow must not draw air into the liquid by swirling or other means, since the main component of air is diluted by mixing with nitrogen and oxygen.

This reduces the rate at which oxygen dissolves into the liquid.

A pump is needed to provide the energy to move the water and oxygen through the U-tube.

Inducing spiral flow downward through the U-tube is not a requirement as there are many ways to induce the necessary flow even if a helical effect is not created.

Referring to FIG. 1, the processing apparatus of the present invention also includes a tank 10 having a flow-directing diaphragm 12 disposed therein.

An inlet line 13 feeds the influent inside the flow-directing diaphragm 12 in the upper part of the tank 10, and an outlet 14 for solids is mounted in the lower part of the tank 10 to remove solids.

A weir 16 for overflowing the clarifier is installed at the top of the tank 10, and this has an outflow line 1γ for discharging clarified water.
Connect to.

An oxygen dissolving device 18 is installed within the tank 10 and communicates with an oxygen supply source 22 via an oxygen supply line 20 .

An oxygen measuring device 24 is suspended in the tank 10 and the oxygen analyzer 2
6 and a recording controller 28 to a flow control valve 30 in the oxygen supply line 20 .

A pump 32 is mounted above the oxygen dissolver 18 and circulates the liquid to be treated through the oxygen dissolver in the direction of the arrow.

For example, the pump 32 may be an axial or centrifugal pump when foaming of the wastewater is not a problem and/or an air lift pump for circulation when it is necessary to remove CO2 from the wastewater.

In this case, some of the oxygen from the airlift is captured by the mixed liquid, reducing the overall oxygen gas demand.

Tank 10 defines a biological reaction zone 38 and a clarification zone 40 separated by a separation zone 42 .

Flow-directing diaphragms 12 assist in defining these zones within tank 10.

A plurality of flow diverging diaphragms 34 are installed in the separation zone 42 between the flow directing diaphragms 12 and the upright walls of the tank 10.

Preferably, the diaphragm 34 is comprised of a plurality of inclined tube members.

A flow distributor 36 consisting of a flat member having a plurality of passages therethrough extends between the upright wall of the tank 10 and the oxygen dissolving device 18 and can be positioned above the outlet of the oxygen contacting device 18 in the lower part of the tank 10. suitable.

The oxygen supply circuit consisting of the oxygen meter 24 and associated oxygen analyzer 26, recording controller 28, flow control valve 30 and oxygen supply line 20 is known per se in other technical fields where precise oxygen content control is required. It is of the type.

The oxygen supply circuit controls the supply of oxygen to the wastewater treatment to meet the demands made by the wastewater being treated.

In the oxygen supply circuit, the oxygen meter 24 senses the concentration of dissolved oxygen in the biological reaction zone 38, and the oxygen meter 24 is, for example, of the polarographic cell or galvano cell type and is connected to two different metals immersed in an electrolyte. and is separated from the wastewater in zone 38 by a semipermeable membrane.

Under steady state conditions, the dissolved oxygen concentration is proportional to the electrical current that develops between the two metals in the cell.

A stirrer forms part of the oxygen meter and continuously forces the liquid in band 38 through the cell membrane.

The agitator is preferably made of soft rubber and positioned to wipe the membrane and keep it free of grease.

The current output of meter 24 as a measure of dissolved oxygen concentration is analyzed by oxygen analyzer 26 and amplified to a standard signal range suitable for standard controllers.

Recording control? 17i28 consists of the controller described above combined with a recorder, the recording controller 28 continuously recording the dissolved oxygen readings.

A controller in recording controller 28 compares the input signal to a predetermined set point and sends a signal to flow control valve 30 in oxygen supply line 20 .

If the dissolved oxygen is below the set point, valve 30 is signaled to open and vice versa.

The set point is previously determined by experimentation to determine the biological oxygen demand of the wastewater being treated.

The oxygen dissolver 18 consists of a flow restriction chamber 18a having an inlet tube 18b separated from an intake tube 18c by a tube 18d having a partially conical shape.

Intake tube 18c includes an inlet aperture 18e in its side wall.

At its lower end the chamber 18a has an opening at the outlet 18i.

Part 18d serves in a special embodiment as a connecting part between inlet pipe 18b and intake pipe 18c with different diameters.

A flow directing diaphragm 12 is suitably located substantially centrally in the upper part of the tank 10 and is connected to the oxygen dissolving device 18.
It is made to surround the top of the.

In this manner, the septum 12 helps define a biological reaction zone 38 and a clarification zone 40, with the upper part of the zone 38 being defined between the inner wall of the septum 12 and the outer surface of the device 18;
A band 40 is defined between the outer wall of the diaphragm 12 and the inner wall of the tank 10.

Although the diaphragm 12 suitably comprises an upper cylindrical tube and a lower part-conical shaped housing, the diaphragm 12 may also have a square cross-section at its upper part and a square cross-section at its lower part. It may also have a square cross section with pyramids.

In operation, influent is introduced into tank 10 via inlet line 13 and circulated by pump 32 through oxygen dissolution device 18 and biological reaction zone 38.

The influent enters the device 18 via the inlet aperture 18e and enters the outlet 1
It exits from 8f, passes through band 38, and returns to hole I8e.

The velocity of the liquid in chamber 18a decreases as the liquid moves downward from inlet tube 18b to outlet 18f and the liquid is subjected to turbulence.

Oxygen is introduced from an oxygen source 22 via an oxygen supply line 20 into an oxygen dissolving device 18 where it dissolves in the liquid passing through the device.

The oxygen measuring device 24 detects dissolved oxygen in the wastewater, and the analyzer 26 detects dissolved oxygen in the wastewater.
send a signal to.

Analyzer 26 then sends a signal to a recorder/controller which adjusts a flow control valve 30 on the oxygen line of source 22.

If the dissolved oxygen is below the recorder 28 set point, the oxygen flow control valve 30 opens to allow more oxygen to dissolve.

Conversely, if the dissolved oxygen is above the set point, the flow valve is closed.

The recorder 28 set point may be changed as desired.

Oxygen supplied to device 18 is regulated by valve 30 under command from recorder/controller 28 to biological reaction zone 38.
ensuring that adequate oxygen is provided to meet the biological oxygen demands of the microorganisms within the zone, while at times excess oxygen present as undissolved oxygen in the form of bubbles is present in the biological reaction zone. prevent it from being introduced.

As the liquid rapidly circulates through the oxygen dissolution device 18 and the biological reaction zone 38, the clarified liquid gradually rises upward through the clarification zone 40.

Advantageously, the liquid in the biological reaction zone is circulated for 2 to 3 hours, and the residence time of each circulation of liquid within the oxygen dissolution device 18 is only about 15 seconds.

The apparatus shown in FIG. 2 differs from the apparatus of FIG. 1 in that the oxygen dissolution device is located outside the vessel.

With further reference to FIG. 2, the equipment shown therein is the tank 5.
The tank 50 comprises an influent supply line 52 for supplying influent to the lower part of the tank 50 and a solids outlet 54 in the lower part of the tank 50 for removing solids.

Tank 50 includes a clarifier overflow weir 56 that communicates with an outflow line 57 .

An oxygen dissolver 58 is located in the inlet line 52 to oxygenate the influent introduced into the tank 50.

Oxygen dissolver 58 connects oxygen supply line 60 to oxygen source 62
connected by.

The inlet line 52 enters the tank 50 at an inlet 53.

The port 53 suitably consists of a tube having a plurality of outlet passages into the tank 50 for the inlet fluid to flow from the inlet 53 into the interior of the tank 50.

For example, the inlet 53 can be an endless tube frame having the same shape as the cross section of the tank.

For example, if the tank 50 has a circular cross section, the inlet 53 may consist of a circular tube, and if the tank 50 has a square cross section, the inlet may consist of a tubular square frame.

The outlet 64 is located away from the inlet 53 and is preferably connected to the tank 5.
0 has a similar arrangement with a plurality of holes or passages therein for liquid to enter.

Outlet 64 communicates via pump 68 to recirculation line 66 which communicates with oxygen dissolution device 58 .

The oxygen measuring device 70 is suspended in the tank 50 and the oxygen analyzer 7
2 and a recorder/controller 74 to a flow control valve 76 in the oxygen supply line 60 .

An upper clarification zone 82 and a lower biological reaction zone 84 are defined within tank 50 to be separated by a separation zone 86 .

The apparatus is constructed such that the oximeter 10 and the outlet 64 are located within the biological reaction zone 84.

It is convenient to use a plurality of flow dispersing diaphragms 78 in the separator zone 86 to enhance separation as in the embodiment of FIG.

Conveniently, such a diaphragm 78 comprises a plurality of slanted diaphragms.

In one embodiment, the tubes are inclined at an angle of 60° to the bottom of the tank and are comprised of a bundle of adjacent tubes forming a module; The area is approximately 4 square inches and the tubes are preferably made of synthetic plastic such as PVC or ABS.

Such modules are commercially available, are bundled in parallel, and are rigidly supported by clamping devices.

It is also convenient to use a flow distributor 80 located vertically above the population 53 in the lower part of the biological reaction zone 84.

In one embodiment, the flow distributor (36 or 80)
．． Made from plywood with a thickness of 905 CrrL (0.75 inches), approximately 30% of its total area is occupied by circular holes communicating with passageways, the holes being 5.08 and 7.62
cIrL (2 and 3 inches) in diameter.

The operation of the apparatus shown in FIG. 2 is substantially the same as that described for the apparatus of FIG.

In such a case, it is appropriate to add a means for stripping carbon dioxide to the system.

However, dissolved carbon dioxide in wastewater, when present in moderate amounts, does not affect the implementation of biological treatment, and as opposed to some industrial wastewaters, carbon dioxide It is not necessary to remove it.

However, the presence of carbon dioxide in water can reduce the rate and efficiency of oxygen dissolution.

When it is necessary to improve this efficiency, carbon dioxide can be removed by a single degasser.

One suitable device functions by bringing the wastewater into contact with air, causing carbon dioxide to migrate from the water to the air under equilibrium conditions.

There are several known types of devices for contacting water and air in this way, such as surface aerators.
rator), speakeasy turbine (Submerged
turbine) or air atomizers may be used.

Operating the air atomizer as a carbon dioxide remover is illustrated in FIG.

With further reference to FIG. 3, wetting column 92 and vertical column 94
An air injector 90 is also shown and line 93 indicates a moist air outlet 92.
Connecting lines 96 and 98 connect to column 94, and compressed air feed line 100 connects column 94 to a source of compressed air (not shown).

An air jet 90 is placed in the system shown in FIG. 1 or 2 so that a portion of the recycled wastewater to be treated flows through a line 93 to a humidifier 92 and moves upwardly through a column 94. It is returned to the circulating wastewater in the system via line 96.

Compressed air is introduced into the waste water in column 94 via line 100 to remove carbon dioxide from the water and exit via discharge line 98.

Referring to FIG. 4, there is shown a processing device similar to that of FIG. 2, so that the oxygen dissolution device is located outside the tank.

In FIG. 4, the processing equipment is one tank 210, tank 2
There will also be an oxygen dissolution device 218 and a controlled oxygen supply system 211 located outside the 10 .

Tank 210 includes an inlet line 213, an outlet line 217, and a solids outlet 214.

An overflow weir 216 is located at the top of the tank 210 and communicates with an outflow line 217 for taking out clarified water, and a rotating sludge rake 21
5 is placed at the bottom of the tank 210.

Tank 210 provides a lower biological reaction zone 238 and an upper clarification zone 240.

An oxygen dissolution device 218, illustrated by FIGS. 4 and 5, is located within the inflow line 213.

The device 218 generally includes a partition wall or diaphragm 3 extending between the walls of the tube 300 from the upper end 304 to the lower end 306 of the tube 300.
02, the gap 308 is the wall 3
02 and the end 306, the partition wall 302 is provided between the tube 3
00 into an upstream section 310 and a downstream section 312.

A recirculation thruster 314 is located near the top of the upstream section 310.

A pump 318 is disposed within recirculation line 316 , which communicates between biological reaction zone 238 in tank 210 and inlet line 213 upstream of tube 300 .

A solids outlet 214 is provided in line 316 from which excess sludge is removed.

Oxygen dissolver 218 is connected to oxygen source 262 by oxygen supply line 260 .

Oxygen measuring device 2γ0 is biological reaction zone 2 in tank 210
The flow rate control valve 27 in the oxygen supply line 260 is suspended in the oxygen analyzer 272 and the recorder/controller 2γ4.
6.

Oxygen supply line 2 as further shown in FIG.
60 enters the upstream portion 310 in the oxygen injector 261 which also has an injector ring 263 having a row of holes therein.

The operation of the apparatus shown in FIGS. 4 and 5 is substantially the same as in FIGS.
and as described with reference to FIG.

Influent is introduced into tank 210 via inlet line 213 and oxygen dissolution device 218 and recirculated through biological reaction zone 238 and device 218 by pump 318.

As previously stated, clarified liquid overflows outflow line 217 at the same rate that fresh wastewater is introduced as influent into tank 210 via inflow line 213.

However, the velocity of the recirculating flow can be several times the velocity of the wastewater inflow.

That is, the recirculation stream is comprised of influent water entering from inlet line 213, entering recirculation line 316, and then passing through oxygen dissolver 21.
Enter 8.

The recirculating stream is constantly being recirculated and the clarified liquid is in tank 210.
It has no effect on the speed at which it overflows.

In other words, the flow rate provided by recirculation pump 318 is independent of the inlet liquid rate entering inlet line 213 and the clarified liquid rate leaving outlet line 217.

Therefore, the flow rate of the recirculating stream can be several times the inlet water rate.

Oxygen is introduced into the upper flow section 310 of the device 218 and sent to the lower flow section 312 and from there into the liquid that is sent to the biological reaction zone 238.

Oxygen content is monitored and controlled in the same manner as described for FIG.

As the liquid rapidly circulates through biological reaction zone 238 and device 218, the clarified liquid gradually rises upwardly within clarification zone 240.

Bands 238 and 240 are optionally separated by separator bands and flow distribution diaphragms such as those described in FIG. 1 (42 and 34).

Carbon dioxide must be generated within the biological reaction zone.

It is removed from container 210 through line 316.

This carbon dioxide should be removed.

This can be accomplished by leaving an air jet in the horizontal portion of line 316.

In this way, the carbon dioxide generated within the biological reaction zone is continuously removed.

Flow dispersion means are provided in the inflow line 213 to disperse the flow across the entire cross-section of the tank 210, thus avoiding localized high flow inflows that may disrupt or disrupt the clarification zone. Avoid conditions.

Example 1 A pilot plant was assembled in a laboratory according to the method shown in FIG. 2, and an oxygen dissolution device was installed outside the tank.

The treated wastewater is a synthetic product made with the use of glucose and additive nutrients.

Wastewater flow 1-81681/day (4800G, P,
D, (gal Ions / day) ) Quality Total Biological Oxygen Demand 264 m9/1 (BOD
) Total chemical oxygen demand (COD) 396m9/,/l
? Process Conditions Biological Reaction Zone Mixed Liquid Suspended Solids 2 ep o o omg/
73 (MLSS) Temperature Dissolved Oxygen (D, 0.) Residence Time Clarification Zone Outflow Rate 4tz2. ssy/day/i (383 g/day/sq ft) (equivalent to Is16sz/a) Effluent liquid crystalline suspended solids total BOD Total C0D 19°C 5m9/l], 5 hours 85 mg/l: 95■/1 200m9/73 Although the quality of the flow liquid was not very good in this example, the two-zone method of the present invention was found to be practical.

Sludge consumption was determined by the level of mixed liquid in the biological reactor.

In this example, the MLSS was 26,000 ■/l.

The mixed liquid in this method was also spent sludge.

Example 2 The following description presents data from a representative implementation of the biological treatment of municipal wastewater by the two-zone process of the present invention.

The apparatus shown in FIG. 1 with an oxygen contactor in the tank but without a flow distributor 36 and without a flow distribution diaphragm 34 was used.

waste water flow minimum 1892501/day (50000 G, P, D,) maximum 4163501/day (I G, P, D,) iooo.

average 2838751/day (75000 G, P, D,) quality suspended solids Total BOD Soluble BOD Total COD Soluble COD Method conditions biological reaction zone M, L, S, S.

temperature dissolved oxygen Residence time clarifier Overflow rate 40848.61/B/m” (1o o.

70 m9/1 125 m/sq ft) 70 m9/1 125 m/sq. 1 60 labor/1 250 m9/1 175 m9/1 2500 m/1-16℃ 3 m9/1 3-4 hours sludge (solid 2.1336 m/h (7 feet 7 samurai) )body)
Sedimentation rate Effluent Liquid crystalline suspension Total BOD Soluble BOD Total COD Soluble C0D 20 rI19/t 25 m971 5m9/1 80 ■/1 55 ■/1

[Brief explanation of drawings]

The accompanying drawings illustrate preferred embodiments of the invention. FIG. 1 is a diagram showing an apparatus for carrying out the invention in which an oxygen dissolving device is installed in a container. FIG. 2 is a cutaway showing a different embodiment of the device in which the oxygen dissolution device is located outside the container. FIG. 3 is a diagram illustrating a carbon dioxide degassing device that may be added to the system shown in FIGS. 1 and 2. FIG. 4 is a drawing showing another embodiment of the device in which the oxygen dissolving device is installed outside the container. FIG. 5 is a drawing showing in detail the oxygen dissolving device used in FIG. 1. 10...- Tank, 12... Partition plate, 1
3... Inflow line, 14... Outlet, 16.
..., cough, 17... outflow line, 18...
... Oxygen dissolving device, 18a ... Flow restriction chamber, 18b ... Artificial pipe, 18C ... Intake pipe, 18d ... Connection part, 18e・・・・・・
・Popular opening, 18f... Exit, 20...
・Oxygen supply line, 22...Oxygen supply source, 24...
...Oxygen measuring device, 26...Oxygen analyzer, 2
8...Recorder/controller, 30...Flow rate control valve, 32...Pump, 34...
- Partition plate, 36... Flow distributor, 38...
・Biological reaction zone, 40... Clarification zone, 42.
... Separation zone, 50 ... Tank, 52 ...
...Influent supply line, 53...Inlet, 54.
...solid outlet, 56...weir, 57...
... Outflow line, 58 ... Oxygen dissolving device, 60
... Oxygen supply line, 62 ... Oxygen supply source, 64 ... Outlet, 66 ... Recirculation line,
68...Pump, 70...Oxygen measuring device, 72...Oxygen analyzer, 74...Recorder controller, 76... Flow rate adjustment valve, 78...
...Diameter, 80...Flow distributor, 82...
...clarification zone, 84...biological reaction zone,
86... Separation zone, 90... Air blower, 92... Moisture valve, 93... Connection line,
94...Column, 96...Connection line, 9
8... Discharge line, 100... Compressed air supply line, 210... Tank, 211...
Oxygen retention system, 213...Inflow line, 214...
... Solid outlet, 215 ... Rotating sludge rake, 216 ... Weir, 217 ... Outflow line, 218 ... Oxygen dissolving device, 238 ...・・・
... Biological reaction zone, 240 ... Clarification zone, 2
60...-Oxygen supply line, 261...Oxygen injector, 262...Oxygen supply source, 263...
... Injector ring, 270 ... Oxygen measuring device,
272... Oxygen analyzer, 274... Recording port/controller, 276... Oxygen flow rate adjustment valve, 300... Tube, 310... ...Upper flow part, 312...Downward flow part, 314...
・Recirculation propulsion machine, 316... Recirculation line, 318
······pump.

Claims (1)

[Scope of Claims] 1. A wastewater treatment plant having waste decomposing microorganisms and open to the atmosphere for treating wastewater containing biologically degradable waste to provide clarified effluent and waste sludge. The wastewater is continuously passed through a single treatment vessel, which is oxygenated to maintain microorganisms, and the clarified effluent is continuously overflowed from the vessel. In a wastewater treatment method for removing excess sludge and scum from a container,
(a) forming in the lower part of the container a biological reaction zone having a mixed liquid containing microorganisms that performs a biological reaction to decompose the waste; (b) clarified liquid; a clarification zone is formed in the upper part of the vessel which raises and overflows the clarification zone; (e) and continuously removes a circulating stream of mixed liquid from the reaction zone and transfers this circulating stream to oxygen located outside the reaction zone. The influent wastewater is added to the dissolver, oxygen is dissolved in this stream, and the oxygen-supplemented circulation stream is introduced into the lower part of the reaction zone, which is spaced from the outlet. injecting and directing the wastewater into a circulating flow at a rate varying within a range related to the depth and surface area of the vessel, within a reaction zone effective for biological degradation of the wastewater and biological floc formation and deposition. Oxygen is added to the circulating stream at a rate that provides a residence time and an oxygen concentration within a controlled range below the saturated oxygen concentration in the oxygenated mixed liquid, thus meeting the oxygen demand of the microorganisms. the oxygen and the liquid are kept in contact in the recirculating stream under pressure for a period of time during which the oxygen dissolves in the liquid, and the flow rate of the recirculating stream is several times the wastewater inflow rate. (d) dissolve oxygen added to the recirculation stream;
(e) Diluting the solution by controlling the amount of recycle flow entering the reaction zone to be effective at preventing insolubilization of oxygen in the solution in the upper part of the reaction zone (-1 reaction zone). (f) distributing the flow in the reaction zone so as to reach a substantial zone in the lower part of the reaction zone, so that: (g) achieving controlled agitation that effectively disperses the solids and good access of microorganisms to the biologically degradable waste; Achieving a rising rate of the mixed liquid that is less than the settling rate, thus maintaining the reaction zone and the clarification zone separately in the vessel, and reducing the dissolved oxygen concentration in the reaction zone based on changes in the flow rate and concentration of the wastewater. continuously testing the dissolved oxygen concentration to measure changes and maintaining the oxygen concentration within a controlled oxygen concentration range that substantially avoids bubbling leading to gas foaming within the clarification zone; The oxygen addition rate to the recirculating stream is periodically adjusted to correspond to changes in the oxygen concentration in the reaction zone, and the effluent is continuously discharged from the clarification zone to maintain the same rate as the inflow wastewater rate. 2. A method as described above, characterized in that excess sludge is continuously discharged from the reaction zone and carbon dioxide is discharged from the mixed liquid.2. 10 of the flow rate of the clarified liquid with substantially equal flow rates and the circulation flowing upwardly.
A method according to claim 1 having a flow rate of ~100 times. 3. The method of claim 1, wherein the oxygenated mixed liquid is produced in an oxygen dissolution device located inside the container. 4. The method of claim 1, wherein the oxygenated mixed liquid is produced in an oxygen dissolution device located outside the container. 5. The oxygenated mixed liquid is produced in an ``oxygen dissolution zone separated from the biological reaction zone and the clarification zone'' and the oxygen supplied within the dissolution zone maintains a concentration of dissolved oxygen. 6. A method according to claim 1, wherein the mixed liquid in the reactants is recycled. 6. In an apparatus for the biological treatment of wastewater, in a single vessel, the wastewater is continuously introduced into the vessel. introducing means for forming mixed liquid contents therein by adding;
An oxygen dissolving device comprising injection means for injecting oxygen into a mixed liquid contained within the device, the oxygen dissolving device being adapted to dissolve oxygen into a mixed liquid contained within the device. , directing at least a portion of the mixed liquid through the oxygen dissolving device to dissolve oxygen therein and discharging the oxygenated mixed liquid into a biological reaction zone defined in the container. circulation means for suspending solids in the mixed liquid through the biological reaction zone and the oxygen dissolution device for a period of time effective to complete the biological reaction within the biological reaction zone; providing a flow rate to the mixed liquid that is substantially greater than the flow rate of the clarification liquid flowing upwardly in the mixed liquid and serving to continuously circulate the oxygenated mixed liquid at a flow rate effective to cause the mixed liquid to flow upwardly in the mixed liquid; said circulation means serving to effect clarification of said liquid by adjusting the flow rate of the clarified liquid such that the rate of settling of suspended solids is at least as high as the rate of upward flow of the liquid; means for removal from the top of the vessel and for controlling the supply of oxygen to the oxygen dissolution device to meet biological oxygen requirements and to avoid the formation of undissolved oxygen within the biological reaction zone; A device characterized by comprising means. 7. Means for controlling the supply of oxygen to the oxygen dissolution device comprises an oxygen measuring vessel located within the biological reaction zone and effective for measuring dissolved oxygen in the oxygenated mixed liquid; 7. Apparatus according to claim 6, wherein the device is suitably connected to control means for controlling the flow of oxygen to the oxygen dissolution device in response to signals from the oxygen analyzer and the oxygen measuring device. 8. The device of claim 1, wherein the oxygen dissolution device is located inside the container. 9. The device of claim 7, wherein the oxygen dissolution device is located outside the container.