Microporous diffusion apparatus

Abstract

Apparatuses for removal of volatile organic compounds in a soil formation include a microporous diffuser for injecting air and gaseous ozone as bubbles into water in the soil formation. The gaseous ozone is present at concentrations to effect removal of volatile organic compounds by the gaseous ozone reacting with the volatile organic compound(s). Injection of air and gaseous ozone is controlled by a timer to allow separation of bubbles by size. In various embodiments, a plurality of microporous diffusers may be controlled by a single timer or each of the plurality of microporous diffusers may be controlled by one of a plurality of timers.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application
where:

• • Vm=rate of mass transfer
  • Kg=coefficient of diffusion for gas
  • A=area through which gas is diffusing
  • C_S=saturation concentration of gas phase in bubble
  • C=initial concentration of gas phase in bubble volume

Table 2 gives Henry's Constants (H_c) for a selected number of organic compounds and the second rate constants (R_c) for the ozone radical rate of reaction. The fourth column presents the product of both H_c and R_c (RRC) as a ranking of effectiveness. In actual practice diffusion is rate-limiting, resulting in the most effective removal with PCE (tetrachloroethylene).

TABLE 2
REMOVAL RATE COEFFICIENTS FOR THE
MICROBUBBLE/OZONE PROCESS - C-SPARGE
	Ozone K2
	Second order	K1	Rate
Organic	Rate Constanta	Henry's	Removal
Compound	(M−1 SEC−1)	Constantb	Coefficient
Benzene	2	5.59 × 10−3	.0110
Toluene	14	6.37 × 10−3	.0890
Chlorobenzene	0.75	3.72 × 10−3	.0028
Trichloroethylene	17	9.10 × 10−3	.1540
Tetrachloroethylene	0.1	2.59 × 10−2	.026
Ethanol	.02	4.48 × 10−5	.0000008
Rc · Hc = RRC
aFrom Hoigne and Bader, 1983
bFrom EPA 540/1-86/060, Superfund Public Health Evaluation Manual

Elimination of the Need for Vapor Extraction

The need for vapor control exists when vapors of VOC's partitioned from the dissolved form into the microbubbles, reach the unsaturated zone, releasing vapors. Without reaction with a decomposing gas, such as ozone, a large mass can be transmitted in a short time, creating potential health problems near residential basement areas.

The combined extraction/decomposition process has the capacity to eliminate the need for vapor capture. If the ozone-mediated decomposition rate exceeds the vertical time-of-travel, vapors will either not be produced or their concentration will be so low as to eliminate the requirement for capture. By controlling the size of microbubbles and matching them to suitable slow rise times, the need for vapor control is eliminated.

The rise time of bubbles of different sizes was computed for water, producing the upwards gravitational velocity (Table 3). The upwards velocity provides the positive pressure to push the bubbles through the porous media, following Darcy's equation. By determining the rise rate in the field, the rise time, proportional to upwards pressure, can be calculated. The bubble size is very important. Once a bubble exceeds the pore cavity size, it is significantly retarded or trapped. Pulsing of the water phase provides a necessary boost to assure steady upwards migration and reduction of coalescence.

TABLE 3
		TIME (MINUTES FOR
	UPWARD	UPWARDS MIGRATION
BUBBLE	VELOCITY	(3 METERS) (Coarse
DIAMETER	IN WATER	Sand and Gravel)
10 mm	.25 m/s	19 min
2 mm	.16 m/s	30 min
.2 mm	.018 m/s	240 min

Elimination Rate of PCE Relative to Ozone Content

The reaction of ozone with tetrachloroethene (PCE) will produce degradation products of hydrochloric acid, carbon dioxide, and water. By adjusting the ozone concentration to match the dissolved PCE level, the PCE can be removed rapidly without excess ozone release to the air or release of PCE vapor into the unsaturated zone.

Accordingly, the object and purpose of the present disclosure is to provide microporous diffusers for removal of contaminants from soil and associated subsurface ground water aquifer, without applying a vacuum for extraction or relying on biodegradation processes.

Another object of the present disclosure is to provide multi-gas systems to be used in combination with the microporous diffusers to promote an efficient removal of poorly biodegradable organics, particularly dissolved chlorinated solvents, without vacuum extraction.

A further object of the present disclosure is to provide that remediation occurs by destroying organic and hydrocarbon material in place without release of contaminating vapors to the atmosphere.

The instrumentalities will be described for the purposes of illustration only in connection with certain embodiments; however, it is recognized that those persons skilled in the art may make various changes, modifications, improvements and additions on the illustrated embodiments all without departing from the spirit and scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional schematic illustration of a soil formation showing an apparatus according to an embodiment.

FIG. 2 is an enlarged piping schematic of the apparatus of FIG. 1 showing the unique fine bubble production chamber.

FIG. 3 is an electrical schematic for a three well system (Model 3503 or 3603) of the apparatus of FIG. 1.

FIG. 4 shows an internal layout of a control module box for a three well system (M-3503 or M-3603) of FIG. 1.

FIG. 5A shows the geometry of a bottom panel on the control module identifying external connections and ports for three well units (M-3503 & 3603) of the apparatus of FIG. 1.

FIG. 5B is a left side view of FIG. 5A.

FIG. 6 is a schematic illustration of a soil formation showing the apparatus of FIG. 1.

FIG. 7 is a perspective view of a bubbler sparge unit for groundwater treatment shown partly in section.

FIG. 8 is a front view of the bubbler sparge unit of FIG. 7.

FIG. 9 is a top elevational view of the bubbler sparge unit of FIG. 7.

FIG. 10 is a bottom elevational view of the bubbler sparge unit of FIG. 7.

FIG. 11 is a front elevational view of the bubbler sparge unit of FIG. 7; the broken line shows the bubbler sparge unit in situ for groundwater treatment.

FIG. 12 is an alternate embodiment of a microporous Spargepoint® assembly of the apparatus of FIG. 1.

FIG. 13 describes Series 3500 & 3600 systems.

DETAILED DESCRIPTION

The present instrumentalities are directed to sparging apparatus for injection of an oxidizing gas in the form of small bubbles into aquifer regions to encourage in situ remediation of subsurface leachate plumes. In particular, microporous diffusers inject multi-gas bubbles into aquifer regions to encourage biodegradation of leachate plumes which contain biodegradable organics, or Criegee decomposition of leachate plumes containing dissolved chlorinated hydrocarbons.

Referring to FIGS. 1 through 6, there is shown a C-Sparger® System (10) consisting of multiple microporous diffusers (26) in combination with an encapsulated multi-gas system, the system (10) consists of a master unit (12) and one or more in-well sparging units (14). Each master unit (12) can operate up to a total of three wells simultaneously, and treat an area up to 50 feet wide and 100 feet long. Actual performance depends upon site conditions. Vapor capture is not normally necessary.

In an embodiment, as shown in FIG. 1 and FIG. 2, master unit (12) consists of the following: a gas generator (16), a gas feed line (15), a compressor (18), a power source (19), a pump control unit (20), and a timer (2). Master unit (12) must be firmly mounted on 4×4 posts (40) or a building wall (42) near in-well sparging units (14). A heavy-duty power cable (44), not over 50 feet in length, may be used to run from the power source to master unit (12).

Referring to FIGS. 1 and 2, in-well sparging unit (14) consists of a casing (56), an inlet screen (50), an expandable packer (52), an upper site grout (54), an outlet screen (58), and lower grout (62). Each in-well unit (14) includes a fixed packer (24), at least two microporous diffusers (26), a water pump (28), ozone line (30), check valve (32), and fittings (34). As shown in FIGS. 1 and 2, diffuser (26) employs a microporous diffuser in place of a standard slotted well screen to improve dispersion of bubbles (60) through soil shown at (84) and to improve rate of gaseous exchange. A normal 10-slot PVC well screen contains roughly twelve percent (12%) open area. Under pressure most air exits the top slits and radiates outward in a star-like fracture pattern, evidencing fracturing of the formation.

Referring to FIG. 2 there is shown a fine bubble production chamber (46) positioned in the well casing (56) between the upper well screen (50) positioned immediately below fixed packer (24) consisting of a removable closure plug and the lower plug (48) consisting of the fine bubble production chamber (46) containing bubbles (60) including upper Spargepoint® (26) positioned above lower well screen (58) including pump (28) and check valve (32). Referring to FIG. 4 there is shown the internal layout of the control module box (12) including an AC/DC power converter (71), and ozone generator (72), well gas relays (73) (three wells shown), a compressor (74), a master relay (75), a main fuse (76). There is also shown a programmable timer controller (77), a power strip (78), a gas regulator and pressure gauge (79), together with a solenoid manifold (80), a ground fault interrupter (81) and a cooling fan (82).

Spargepoint® diffusers include several unique configurations as follows:

a. A direct substitute for a well screen comprising 30% porosity, 5-50 micron channel size and resistance to flow from 1 to 3 PSI. This configuration can take high volume flow and needs a selective annular pack (sized to formation). The use of high density polyethylene or polypropylene is light-weight, rugged and inexpensive.

b. A microporous diffuser can be placed on the end of a narrow diameter pipe riser KVA 14-291. This reduces the residence time in the riser volume.

c. A shielded microporous diffuser which is injected with a hand-held or hydraulic vibratory hammer. The microporous material is molded around an internal metal (copper) perforated tubing and attached to an anchor which pulls the Spargepoint® out when the protective insertion shaft is retracted. The unit is connected to the surface with 3/16 or ¼ inch polypropylene tubing with a compression fitting.

d. A thin Spargepoint® with molded tubing can be inserted down a narrow shaft for use with push or vibratory tools with detachable points. The shaft is pushed to the depth desired, then the Spargepoint® is inserted, the shaft is pulled upwards, pulling off the detachable drive point and exposing the Spargepoint®.

e. A microporous diffuser/pump combination placed within a well screen in such a manner that bubble production and pumping is sequenced with a delay to allow separation of large bubbles from the desired fine “champagne” bubbles. The pressure from the pump is allowed to offset the formation back pressure to allow injection of the remaining fine bubbles into the formation.

Improvements

In the present apparatuses an improvement comprises several new equipment designs associated with the Spargepoint® diffusers. Most important is the submittal for HDPE porous material with well fittings and pass-through design which allows individual pressure and flow control as shown in FIGS. 7-11.

Secondly, the push-probe points have been developed for use with pneumatic tools, instead of drilling auger insertion.

Improvements on C-Sparger®/microporous Spargepoint® diffuser. One of the major pass-through Spargepoint® problems in horizontal sparging is the even distribution of air bubbles. If an inlet is attached to the end of a screen, the pressure drops continuously as air is released from the screen. The resulting distribution of flow causes most bubbles to be produced where the connection occurs with flow alternating outwards. The end of the screen produces little or no bubbles.

To allow even distribution of bubbles, either individual Spargepoints® are bundled (spaghetti tube approach) or the Spargepoints® are constructed in a unique way which allows interval tubing connections with flow and pressure control for each Spargepoint® region within the proposed arrangement. Tubing connected to a Spargepoint® passes through the Spargepoint® internally without interfering with the function of producing small bubbles on a smooth external surface. The tubing penetration reduces the internal gas volume of the Spargepoint®, thereby reducing residence time for oxidative gases (important since ozone has a certain half-life before decomposition), and allows three to four Spargepoints® to be operated simultaneously with equal flow and pressure. Each Spargepoint® can also be programmed to pulse on a timed sequencer, saving electrical costs and allowing certain unique vertical and horizontal bubble patterns. Spargepoint® diffusers can be fitted with an F480 thread with internal bypass and compression fittings, FIG. 12. Some advantages are as follows:

(1) fits standard well screen;

(2) allows individual flow/pressure control;

(3) reduces residence time; and

(4) allows for casing/sparge instead of continuous bubbler.

Use of injectable points configured as molded, 18 Inch×40 inch HDPE molded into ¼ inch pp tubing or HDPE tubing allows a smooth tube to be inserted into a push probe with a detachable point. Use of “Bullet” prepacked Spargepoint® diffusers with a KVA “hefty system” prepacked sand cylinder and bentonite cylinder placed over tubing and porous point is advantageous. Also use of a porous point reinforced with inner metal tube (perforated) to allow strength throughout tubing resists disintegration of plastic during insertion.

Use of pressure/flow headers: Rotameter/mirror: A mirror placed at an angle in a well hole to allow site of a flowmeter reading scale to a point.

It is well recognized that the effectiveness of treatment is dependent upon the uniformity of gas dispersion as it travels through the formation. A porous structure, with appropriate packing, matches the condition of the pores of the soil with thirty percent (30%) pore distribution. The dispersion of bubbles as a fluid can be checked using Darcy's equation.

The use of microporous materials in the Spargepoint® to inject gases into groundwater saturated formations has special advantages for the following reasons:

• • 1. Matching permeability and channel size;
  • 2. Matching porosity;
  • 3. Enhancing fluidity, which can be determined in situ.

The most effective range of pore space for the diffuser material selected depends upon the nature of the unconsolidated formation to be injected. The following serves as a general guide:

• • 1. Porosity of porous material: thirty percent (30%);
  • 2. Pore space: 5-200 microns;
    • a. 5-20 very fine silty sand;
    • b. 20-50 medium sand;
    • c. 50-200 coarse sand and gravel.

The surrounding sand pack placed between the Spargepoint® and natural material to fill the zone after drilling and excavation should also be compatible in channel size to reduce coalescing of the produced bubbles.

The permeability range for fluid injection function without fracturing would follow:

• • 1. 10⁻² to 10⁻⁶ cm/sec, corresponding to 2 to 2000 Darcy's; or
  • 2. 10⁻² to 10⁻⁶ cm/sec; or
  • 3. 100 to 0.01 ft/day hydraulic conductivity.

Permeability is defined as a measure of the ease of movement of a gas through the soil. The ability of a porous soil to pass any fluid, including gas, depends upon its internal resistance to flow, dictated largely by the forces of attraction, adhesion, cohesion, and viscosity. Because the ratio of surface area to porosity increases as particle size decreases, permeability is often related to particle size see Table 3.

Claims

1. An apparatus for removal of volatile organic compounds in a soil formation comprising:

a diffuser for injecting air and gaseous ozone as bubbles into water in the soil formation, the gaseous ozone at concentrations to effect removal of volatile organic compounds by the gaseous ozone reacting with the volatile organic compounds,

wherein injection of air and gaseous ozone is controlled by a timer to allow separation of bubbles by size,

wherein the bubbles range in size from about 5 to 200 μm.

2. The apparatus of claim 1 wherein the air and gaseous ozone are mixed and injected into the water as bubbles with an initial bubble size in a range of about 5 to 200 μm.

3. The apparatus of claim 1 wherein the timer periodically pulses the injected air and gaseous ozone.

4. The apparatus of claim 1 further comprising a bubble sizing chamber.

5. The apparatus of claim 1 further comprising a pump for agitating water to disperse the bubbles through the soil formation.

6. The apparatus of claim 1 wherein the diffuser has a pore size selected to match a porosity of a surrounding soil formation.

7. The apparatus of claim 1 further comprising:

a casing;

a packer disposed through the casing; and

an outlet screen coupled to the casing.

8. The apparatus of claim 7 wherein the outlet screen is coupled to the casing at a lower portion of the casing and the apparatus further comprises an inlet screen coupled to the casing at an upper portion of the casing.

9. An apparatus for removal of volatile organic compounds in a soil formation comprising:

a plurality of diffusers for injecting air and gaseous ozone as bubbles into water in the soil formation, the gaseous ozone at concentrations to effect removal of volatile organic compounds by the gaseous ozone reacting with the volatile organic compounds,

wherein injection of air and gaseous ozone is controlled by at least one timer to allow separation of bubbles by size,

wherein the bubbles range in size from about S 5 to 200 μm.

10. The apparatus of claim 9 wherein the plurality of diffusers is arranged in series.

11. The apparatus of claim 9 wherein the plurality of diffusers is controlled by a single timer.

12. The apparatus of claim 9 wherein each diffuser is coupled to one of a plurality of timers.

13. The apparatus of claim 9 wherein the air and gaseous ozone are mixed and injected into the water as bubbles with an initial bubble size in a range of about 5 to 200 μm.

14. The apparatus of claim 9 wherein the timer periodically pulses the injected air and gaseous ozone.

15. The apparatus of claim 9 further comprising a bubble sizing chamber.

16. The apparatus of claim 9 further comprising a pump for agitating water to disperse the bubbles through the soil formation.

17. The apparatus of claim 9 wherein microporous material of the diffusers has a pore size selected to match a porosity of a surrounding soil formation.

18. The apparatus of claim 9 further comprising:

a casing;

a packer disposed through the casing; and

an outlet screen coupled to the casing.

19. The apparatus of claim 18 wherein the outlet screen is coupled to the casing at a lower portion of the casing and the apparatus further comprises an inlet screen coupled to the casing at an upper portion of the casing.

20. The apparatus of claim 18 wherein the packer is disposed through the casing between the inlet and outlet screens.

21. A method of treating a groundwater or soil formation in situ, comprising: injecting gaseous ozone and air through porous materials to produce bubbles in the groundwater or soil formation at concentrations sufficient to react with, and effect removal of, one or more contaminants in the groundwater or soil formation,

wherein the step of producing bubbles comprises producing bubbles encapsulating ozone and air to convert the contaminants from a dissolved state to a gaseous state and encapsulating the contaminants as a vapor therein.

22. The method of claim 21, wherein the bubbles encapsulating air and ozone increase a transfer rate of the contaminants from a dissolved state to a gaseous state.

23. The method of claim 22 further comprising the step of decomposing the contaminants with the encapsulated air and ozone.

24. The method of claim 23 wherein the step of decomposing the contaminants decomposes the contaminants at a rate that exceeds a rise time of bubble formation.

25. A method of treating a groundwater or soil formation in situ, comprising: injecting gaseous ozone and air through porous materials to produce bubbles in the groundwater or soil formation at concentrations sufficient to react with, and effect removal of, one or more contaminants in the groundwater or soil formation,

wherein the step of producing ozone bubbles comprises increasing a half-life of the ozone.

26. A method for remediating contaminants in a groundwater or soil formation in situ, comprising: injecting a multi-gas oxidizing agent into the groundwater or soil formation through one or more tubes such that the multi-gas oxidizing agent produces bubbles in said groundwater or soil formation that react with the contaminants and encapsulate the contaminants as vapor inside the bubbles.

27. The method of claim 26, wherein the step of injecting further comprises the step of injecting the multi-gas oxidizing agent through a slotted well screen at said groundwater or soil formation.

28. The method of claim 26, wherein the step of injecting further comprises the step of injecting the multi-gas oxidizing agent through a diffuser at said groundwater or soil formation.

29. The method of claim 26, wherein the multi-gas oxidizing agent comprises air and ozone.

30. The method of claim 26, wherein the gaseous bubbles increase a half-life of the ozone.

31. The method of claim 26, wherein the bubbles have reduced bubble sizes to increase surface area to gas volume ratios.

32. The method of claim 26, wherein the bubbles have an initial bubble diameter in a range of about 5 to 200 μm.

33. The method of claim 26, wherein injecting produces the bubbles encapsulating ozone and air to convert the contaminants from a dissolved state to a gaseous state.

34. The method of claim 33, wherein the bubbles increase a transfer rate of the contaminants from a dissolved state to a gaseous state.

35. The method of claim 34, further comprising the step of decomposing the contaminants in the encapsulated air and ozone.

36. The method of claim 35, wherein the step of decomposing the contaminants comprises decomposing the contaminants at a rate that exceeds a rise time of bubble formation.

37. The method of claim 26, wherein the step of injecting produces bubbles with a diameter slightly smaller than a pore size of the soil formation.

38. The method of claim 26, wherein the step of injecting the multi-gas oxidizing agent further comprises injecting the multi-gas oxidizing agent through a slotted well screen surrounded with porous materials to produce bubbles.

39. The method of claim 26, further comprising decomposing the contaminants in said groundwater or soil formation by ozone interaction with double bonded carbon atoms of the contaminants.

40. The method of claim 26, said groundwater or soil formation containing chlorinated hydrocarbons.

41. The method of claim 26, said groundwater or soil formation containing organic and/or hydrocarbon material.

42. The method claim 26, wherein the step of injecting the multi-gas oxidizing agent comprises injecting aerated and ozonated water.

43. The method of claim 26, further comprising intermittently agitating water in said groundwater or soil formation.

44. The method of claim 26, further comprising periodically pulsing the injected multi-gas oxidizing agent.

45. The method of claim 26, wherein the porous material comprises a material selected from the group consisting of PVC, HDPE porous material, sand, and gravel.