JPS62106897A - Device and method of treating waste water - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD This invention relates to improved wastewater treatment systems, particularly the control of anaerobic systems for high intensity wastewater treatment.

BACKGROUND OF THE INVENTION Many types of anaerobic systems have been devised to treat wastewater containing various biodegradable substrates and nutrients, as described in the following US patent publications.

3.640,846; 3,724,542; 3,81 s857; 3.994.780; 4,043,936; 4
,067.801;4.100,023;4.1
34,111+50° Since all of these systems operate under ambient or atmospheric conditions, there is often a limit to the amount of infusate that can be efficiently passed through the system. Physically transporting gaseous targets across biological membranes has a significant impact on the anaerobic decomposition of organic wastes. Anaerobic biomembranes are highly porous materials that typically contain rapid formation of microbubbles of carbon dioxide or methane, which impede the transport of nutrients and substrates to organic cell locations.

Transport of coenzymes and other metabolic target products is also limited. When the concentration of these substances increases beyond a certain level, production inhibition and/or accumulation of toxic substances at cellular locations occurs.

Molecular hydrogen (H2) is an important intermediate in controlling the complex intermediate species reactions that occur during the anaerobic decomposition of wastes in fluid media. Molecular hydrogen is released into solution by a group of microorganisms and used by methanogens to reduce carbon dioxide to methane. Furthermore, as the partial pressure of the solution increases, substrates such as ethanol, propylate and butylate esters convert to methane, forming undesirable free energy levels. Therefore, when operating under atmospheric pressure conditions, it is necessary to maintain the partial pressure of H2 within a very narrow range for efficient total methane production.

In solution, sulfides are formed from sulfates and sulfur-containing compounds present in the wastewater. This increases the toxic level of sulfide in biological membranes to the point where the effectiveness of anaerobic bacterial systems is adversely affected.

As explained in more detail below, many of the critical factors that shape the complex metabolic interactions of the various species involved in the anaerobic process are achieved by limiting the headspace pressure above the wastewater during treatment. Can be controlled or adjusted. By operating below atmospheric pressure, the gas pressure in and around biological membranes can also be alleviated by making them less soluble in wastewater.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an overall improvement in anaerobic reactors for high-intensity wastewater treatment.

Another object of the present invention is to provide an improved vacuum reactor system that improves biomembrane performance in anaerobic wastewater treatment systems.

Yet another object of the present invention is to provide overall control of the operation of a reduced pressure anaerobic reactor to optimize the removal rate of the system over a wide range of injectate flow rates.

Yet another object of the present invention is to reduce the gas solubility in anaerobic reactors and to allow continuous operation of overloaded systems by rapidly and efficiently removing inhibiting and toxic gases from solution. .

A further object of the present invention is to reduce the operating pressure of the anaerobic reactor to facilitate the removal of microorganisms that are trapped in biological membranes and interfere with the release of coenzymes and thus the removal of metabolic wastes. be.

The above and other objects of the present invention include an airtight reactor containing a predetermined amount of waste water, a shaft rotatably mounted within the reactor, means for rotating the shaft at a desired speed, and a biomembrane of anaerobic microorganisms. a plurality of spaced apart contactors fixed to the shaft for support and partially immersed in wastewater to sequentially pass the biomembrane wastewater and head space, fluidization means for passing the wastewater to the reactor; , a detection means for detecting the load on the reactor, and a control means responsive to said detection means for regulating the pressure in the headspace, thereby maintaining the reactor at an optimum operating level. This can be achieved by a treatment device for wastewater containing organic substrates.

Embodiment of the invention The present invention will be described in detail below with reference to the accompanying drawings.

Referring first to Figures 1-3, an anaerobic reactor 10 for treating high strength wastewater containing all anaerobically decomposable nutrients and organic substrates is illustrated.

The reactor system contains carbohydrates, fats,
It is provided with an air/liquid tight housing 11 capable of containing a predetermined amount of waste water 12 containing biodegradable substances such as proteins, alcohols, acids, etc. Although the housing is partitioned into a large number of equally volume compartments or compartment stages 13 to 13 by the partition plates 14 to 14, depending on the situation, it may be desirable to vary the size of each stage.

The partition plates 14-14 extend upwardly from the floor 15 of the reactor housing to a height that is slightly above the normal water level 16 of the wastewater maintained within the housing. by this,
The formation of a continuous and relatively uninterrupted ridge 17 above the wastewater ensures that the pressure above the stage where anaerobic activity is occurring is the same. As will be explained in more detail later, during the anaerobic treatment of wastewater, the headspace gas pressure is lowered to a predetermined reduced pressure under fully controlled conditions to reduce the volumetric C for more efficient wastewater treatment.
Increase OD removal rate and local COD removal rate. COD
is the chemical oxygen demand of nutrients and substrates.
It is an abbreviation for "loxygen dema-nd" and is well known as a measure of wastewater strength.

The unit is +rq/L.

A suitable water bearing is provided in the housing with a horizontal shaft 20 connected to a variable speed drive motor 21. In the housing, is there a gap between /yaft? A plurality of contactors 26 to 23 are provided. Each contactor consists of a plastic disc fixed to a shaft for rotation as a unit. The same number of disks are contained within each reactor membrane and approximately 50-80% of each disk is submerged in the wastewater.
Position the disc. In fact, a whole colony of biomass anaerobic microorganisms grows on the surface of each disc that can nourish the degradable nutrients and substrates present in the wastewater. Partial rotation of the shaft removes nutrients and substrates as the partially immersed disk sequentially deposits biomass through the wastewater and head B', while the remaining rotation drives process gases into the headspace. It will be done. This allows for a controlled feeding system within the system, which solves many of the problems associated with 7 stems that are completely flooded with biomass.

The injectate is delivered into the reactor housing via a supply pipe 25 connected to the discharge side of the injectate pump 27 . By driving this pump with a variable speed motor 28, the amount of injectate wastewater supplied to the housing is tightly controlled. First, the impeller 61 fixed to the p1 shaft 20 transports the injected liquid to the mixing chamber.
The injectate is premixed by the injector and the waste water contained in the housing is left in an agitated state. Through openings 32-32 (FIG. 2) formed in the partition plates separating each treatment stage, all of the waste water is conveyed between each treatment stage and finally out of the housing via a discharge line 63. Separation of each treatment stage by a partition plate allows the concentration of nutrients and substrates in the wastewater to be reduced as the wastewater flows laterally through the housing. Tapering the concentration gradient can improve removal rates while minimizing reactor space. To increase the operating capacity of the reactor, an auxiliary injectate delivery system 65 is provided that can introduce feed injectate into one or more processing stages. A bypass line 37 is provided to divert a portion of the infusate exiting the infusate pump to the bottom of the housing below each processing stage.

This line is connected into the note processing stage by a supply line 38 extending through the floor of the housing and a remote control valve 39. These valves allow for selective control of the raw material injection liquid introduced into each processing stage.

A vacuum pump 40 is connected to the headspace of the reactor through a line 41 and a vacuum control valve 42 that can adjust the headspace pressure within the reactor housing. Infusion pump motor and pressure cassette 4
A suitable microprocessor would program the controller 45 to adjust the functions of both the vacuum control valve 46 and the vacuum control valve 46 in response to data from the flow sensor 47. A pressure sensor is provided in the ceiling 48 within the reactor housing and measures the total headspace pressure within the housing. The injectate flow sensor is mounted within the injectate line 25 and is adapted to measure the flow rate of incoming wastewater. The speed of the infusate pump and the pressure within the housing are regulated by a controller to maintain optimum operating conditions over a wide range of load conditions.

Example The present invention will be explained in more detail below with reference to Examples.

In this example, a reactor of the above type with an internal volume of &5 tons was used. The reactor was approximately 60 cm long and was divided into four equal volume treatment stages using fixed partitions. Each partition plate has 1.
A total of eight 88C1rL openings were provided. 1.2 for each processing stage
A total of 10 contactors with a diameter of 12.70 mm and a wall thickness of 0.318 mm were installed at 7 wet intervals.

The nominal surface area for biomass attachment of the contactor disc was approximately 1.14-1, and the rotational speed of the shaft was 17 rpm.

The entire reactor was operated with about 70-80% of the disk area immersed in waste water. Head pore pressure was monitored with a pressure gauge and wastewater flow rate in the reactor was regulated by controlling pump speed. During operation, the reactor was maintained at a temperature of 32°C to 38°C. The exhaust gas is released using a vacuum pump, and the water displacement method is used.
The substrate used for the carbon source was sucrose, and sodium bicarbonate and mineral nutrients were added to the injectate to give an injectate of known constant strength.

The reactor was operated at different mass loading/pressure conditions. The results are shown in the table below.

It can be seen that a high yield was actually measured despite the reduced pore pressure. This is due to toxicity during system start-up and over long periods of time.
Recommended when recovering from a yock. CO under reduced pressure
Not only was the D removal rate improved, but the C
The utilization rate of OD has improved. There was a linear relationship between pore pressure and mass COD removal. Under reduced pressure conditions of 0.54 atm, C0D3000-5000 per ton of injection liquid
At the load (2), the removal rate of the first treatment stage approximately doubled. C0D
At 8000 cm/t of injection liquid, the removal rate was improved by 77%. For example, the first two treatment stages yield approximately 62% of the total COD removal rate, and the linear relationship between pressure and removal rate allows for mass removal rate and local removal rate to increase with increasing load and pore vacuum. It can be seen that there is considerable improvement as a function of both.

Under reduced pressure conditions, the concentrations of propionic acid and butyric acid in each stage of the reactor are higher than at low pressure. Under stress conditions, these high concentrations of acids lower the redox potential, lower the acid equivalent, and reflect the full capacity of the bacteria to remove all toxic accumulations of molecular hydrogen. Vacuum operation helps alleviate metabolic inefficiencies exhibited by the presence of propionate and butyrate. As a result, during depressurization operations, CO
The D removal rate can be greatly improved, and pH problems associated with start-up loads and shock organic loads on anaerobic systems can be minimized. Furthermore, high pH values at reduced pressure can increase the organic loading of anaerobic systems under vacuum operation without the toxic effects associated with low pH values.

As can be seen from the previous table, the measured yield of the reactor ranges from 0.16 at atmospheric pressure conditions to 0.3 at 0.54 atm.
It ranges up to 5. The measured yield is here defined as the mass of volatile suspended solids in the effluent relative to the mass of COD removed throughout the reactor during the steady-state period. In either case, the yield observed under reduced pressure is greater than that under atmospheric pressure. The COD concentration of the injection solution is approximately 8000/
Under high loading conditions of l, the methane yield was significantly higher at o and 54 atm.

It was observed that the removal of COD was almost completed in the first three stages of the reactor. Removal rates in the first three treatment stages were analyzed using local removal rates in both linear and non-linear loading ranges. FIG. 4 shows COD removal 111? against COD 47 supplied to the reactor. /contactor rr? /day) are all plotted. The curve approaches an asymptote between 50 and 125 at different pore pressures. /
rr? The removal rate varies linearly over the brow range to a marginal removal rate.

The slope of the straight part of the curve shown in FIG. 4 (removed COD/supplied COD) t is plotted as a function of pore pressure in FIG. As is clear from these data, the local removal rate increases substantially as the pore pressure decreases.

The linear portion of the straight portion of the curve is determined by the following relational expression.

M, = MAC(1,06-0,497p)-k(20
, 59p-2, 65) (In formula 11, M = C0D removal f
fi (j/rr?/day), MA=C fed to the reactor
OD amount (?/, r? 7 days), C, - a constant related to the source characteristic of the injectate, and p = absolute head pore pressure (atmospheric pressure).

The constants C and k can be determined experimentally from empirical data for each wastewater; for easily degrading wastewaters such as sugar the value of the constants is approximately to, and for more complex wastewaters less than 10.

When the limited COD local removal rate shown in FIG. 4 is plotted against the pore pressure shown in FIG. 6, a clearly linear relationship is obtained. Again, the data shows that the limiting COD removal rate varies linearly with pressure over a wide load range. The ultimate COD removal rate in this range, that is, the limit COD removal rate is determined by the following relational expression.

MR=C(155,8-51.6p) where MR,C
and p are as described above.

The data obtained show that headspace depressurization of the reactor improves both local and volumetric COD removal rates. These removal rate improvements are linearly related to applied pressure and are therefore easily applicable to computerized control systems of the type described. As can be seen, the controller allows adjustment of both the load on the reactor and the vacuum maintained within the reactor, thus continuously maintaining the system at optimal operating conditions.

This particular application ensures relatively constant replenishment of the wastewater injection fluid. Therefore, the flow rate of the injectate is a clear indication of the load on the system. Flow sensor 47 is adapted to send flow data to controller 45 via data line 56. Similarly, the pressure within the housing is monitored by vacuum sensor 46 and this data is sent to the controller by data line 59. The pressure within the housing, as seen from the flow rate delivered to the system, can be set using the vacuum control valve 42, thus maintaining the entire system at the desired operating point for optimum efficiency. Control signals are sent from the controller to the valve by control line 60.

As can be seen, reduced pressure operation of an anaerobic reactor improves COD removal under high load conditions. Furthermore, because both the linear COD removal rate and the limited COD removal rate vary linearly over a relatively wide operating range, optimal operating conditions can be accurately estimated and the reactor can therefore be easily tuned for optimal efficiency. Shock load, pH, H2, H2S
Existing reactors in systems currently operating at overload due to target toxicity can be easily modified for reduced pressure operation, thus alleviating the problem. Additionally, vacuum operation allows for rapid biomass growth even during start-up, allowing for faster recovery from long-term toxic conditions.

Although the present invention has been described in terms of specific embodiments above,
The present invention is not limited to this.

[Brief explanation of drawings]

FIG. 1 is a side view showing the entire cross section of a reactor which is an embodiment of the present invention, FIG. 2 is a sectional view taken along line 2-2 in FIG. 1, and FIG. FIG. 4 is a graph showing the responsiveness of the reactor of the present invention according to the local COD removal rate at different pore pressures, and FIG. 6 is a graph showing the slope of the straight line portion of the curve shown, and FIG. 6 is a graph showing the maximum COD removal rate as a realizable function. DESCRIPTION OF SYMBOLS 11... Reactor, 12... Waste water, 16... Treatment stage, 14... Partition plate, 17... Clearance, 20... Shaft, 21... Motor, 23... Contactor, 27...
・Pump, 28... Variable speed motor, 40... Vacuum pump, 42... Vacuum control valve, 45... Controller, 46...
...Pressure sensor 47...Flow rate sensor.乍・１ふ卦辷斤 5 sho 0 hi DT and mu 1 ka too

Claims (13)

[Claims] (1) An airtight reactor containing a predetermined amount of wastewater, a shaft rotatably mounted within the reactor, means for rotating the shaft at a desired speed, and a shaft for supporting the biofilm of anaerobic microorganisms. a plurality of spaced apart contactors fixed to and partially immersed in the wastewater to sequentially pass the biological membrane through the wastewater and the head space; fluidization means for passing the wastewater through the reactor; a detection means for detecting such loading; and a control means responsive to said detection means for regulating the pressure in the head space, thereby maintaining the reactor at an optimal operating level. Treatment equipment for wastewater containing substrates. (2) The apparatus according to claim 1, which performs fractional COD removal by adjusting the operating level of the reactor according to the following relational expression. M_R=M_AC(1.084-0.48p)+k(1
6.24p-6.44) In the formula, M_R=COD removal amount (
g/m^2/day), M_A=COD supply amount (g/m^2
/day), C, A = constant related to the source characteristic of the injectate, and p = absolute headspace pressure (atmospheric pressure). (3) The apparatus according to claim 1, wherein the operating level of the reactor is adjusted according to the following relationship to remove maximum COD. M_R=M_AC(155.8-51.6p) where M
_R=COD removal amount (g/m^2/day) M_A=COD
Feed rate (g/m^2/day) C = constant related to the source characteristic of the injectate, and p = absolute headspace pressure (atmospheric pressure). 4. The apparatus of claim 1, wherein said fluidizing means includes a variable speed injectate pump for regulating the flow rate of injectate entering the reactor housing. (5) The apparatus according to claim 1, further comprising means for stirring the wastewater contained in the reactor. 6. The apparatus of claim 1, wherein the reactor housing includes a series of partition plates dividing the housing into a plurality of processing stages. (7) The patent claim applies the same headspace pressure to each treatment stage by extending each partition plate upwardly from the floor of the reactor housing to a height between the wastewater level and the ceiling of the reactor housing. A device according to scope 6. (8) A step of sending wastewater to an airtight reactor, a step of sequentially passing a series of contactors supporting the biological membrane through the wastewater and the head space above it, a step of applying reduced pressure in the head space, and an injection liquid applied to the reactor. A method for treating wastewater containing anaerobic nutrients and substrates, comprising the steps of: detecting a load; and controlling pressure in the headspace in response to the load to maintain the system at a desired operating level. (9) The method according to claim 8, wherein the operating level of the reactor is adjusted according to the following relational expression for fractional COD removal. M_R=M_AC(1.084-0.48p)+k(1
6.24p-6.44) In the formula, M_R=COD removal amount (
g/m^2/day), M_A=COD supply amount (g/m^2
/day), C, A = constant related to the source characteristic of the injectate, and p = absolute headspace pressure (atmospheric pressure). (10) The method according to claim 8, wherein the operating level of the reactor is adjusted according to the following relationship to remove maximum COD. M_R=M_AC(155.8-51.6p) where M
_R=COD removal amount (g/m^2/day) M_A=COD
Feed rate (g/m^2/day) C = constant related to the source characteristic of the injectate, and p = absolute headspace pressure (atmospheric pressure). (11) The method according to claim 8, further comprising the step of sequentially partitioning the reactor into multiple stages. (12) The method of claim 11, including the step of mixing the injectate before passing it through the first stage. 13. The method of claim 11, further comprising the step of adding infusate to one or more predetermined stages.