Method and apparatus for soil decontamination

A method and apparatus for decontaminating soil which has been contaminated with hazardous hydrocarbons. The apparatus includes a blending or scrubbing unit for mixing the contaminated soil with water and a suitable surfactant to form a slurry; screening apparatus operably interconnected with the blending unit for removing from the slurry particles larger than a predetermined size to form a small particle slurry; a reactor unit operably interconnected with the screening apparatus for reacting the slurry with ozone to form an ozone enriched slurry; an ultraviolet radiation generator for irradiating the ozone enriched slurry with ultraviolet radiation; a static mixer operably interconnected with the reactor unit for mixing a floculating material with the slurry to form a floculated slurry; and a belt-forming press for receiving the floculated material from the static mixer and for forming the floculated slurry into contamination free blocks.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to methods and apparatus for the 
decontamination of solids. More particularly, the invention concerns an 
apparatus for the decontamination of soil which has been contaminated with 
hydrocarbon materials. 
2. Discussion of the Prior Art 
In recent years, the maintaining of the enviornment free from contamination 
by hazardous materials has come to be recognized by ecologists and various 
governmental agencies as being of paramount importance. Accordingly, 
meaningful steps have been taken to control waste disposal, including the 
disposal of hazardous hydrocarbon materials. Similarly, meaningful steps 
have been taken to clean up areas which have become contaminated in years 
past and which constitute health hazards. 
In the past, rather crude and generally inefficient methods have been 
suggested for cleaning up hydrocarbon contamination and particularly for 
decontaminating soil which has become contaminated with hazardous 
hydrocarbons. Typically, these prior art approaches were expensive, highly 
labor intensive and generally unsuitable for the clean-up of large volumes 
of contaminated soils. The present invention, for the first time, offers a 
practical and efficient method for the decontamination of large quantities 
of contaminated soils. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a method and apparatus 
for the efficient decontamination of soils which have become contaminated 
with hazardous hydrocarbon materials such as polychlorinated phenyl (PCB), 
pentachlorophenol (PCP), trichlorocthylene (TCE) and the like. 
It is another object of the invention to provide a method and apparatus of 
the aforementioned character in which large volumes of contaminated soil 
can be decontaminated quickly and efficiently using automatic, easy to use 
equipment which requires a minimum manpower investment. 
It is another object of the invention to provide a method and apparatus of 
the character described which is safe to use and which has as its output 
decontaminated soil compacted into easy-to-handle blocks or brickettes. 
Still another object of the invention is to provide an apparatus as 
described in the preceding paragraph which can be operated by unskilled 
workers and which can be set up on site with a minimum amount of 
difficulty. 
Yet another object of the invention is to provide a method and apparatus of 
the class described which is inexpensive and highly reliable in use. 
These and other objects of the invention are realized by an apparatus for 
decontaminating soil comprising a blending or scrubbing unit for mixing 
the contaminated soil with water and a suitable surfactant to form a 
slurry; screening apparatus operably interconnected with the blending unit 
for removing from the slurry particles larger than a predetermined size to 
form a small particle slurry; a reactor unit operably interconnected with 
the screening apparatus for reacting the slurry with ozone to form an 
ozone enriched slurry; an ultraviolet radiation generator for irradiating 
the ozone enriched slurry with ultraviolet radiation; a static mixer 
operably interconnected with the reactor unit for mixing a floculating 
material with the slurry to form a floculated slurry; and a belt-forming 
press for receiving the floculated material from the static mixer and for 
forming the floculated slurry into contamination free blocks.

DESCRIPTION OF THE INVENTION 
Referring to the drawings, the apparatus of the invention includes blending 
means for mixing the contaminated soil with water and a surfactant to form 
a slurry; first screening means operably interconnected with the blending 
means for removing from the slurry particles larger than about 1/8th inch 
in diameter; and reactor means operably interconnected with the screening 
means for reacting the small particle slurry with ozone. 
In the form of the invention shown in FIG. 1, the blending means comprises 
a process blender, or pug mill, having internally mounted, moving blades 
adapted to agitate the contaminated soil and bring it into a generally 
plastic condition. Pug mill 12 is of standard construction and several 
suitable pug mill units are readily commercially available. 
Operably associated with pug mill 12 are three holding tanks identified in 
FIG. 1 as C-1, C-2 and C-3. These tanks contain suitable surfactant 
solvents which, along with water, can be added to the contaminated soil to 
form a slurry of suitable consistency. While various types of surfactant 
solvents can be used, experience has shown that a mixture of sodium 
hydroxide, sodium laural sulphate and hydrogen peroxide will provide a 
suitable surfactant solvent for successfully carrying out the method of 
the invention. When such solvents are used, tank C-1 will contain sodium 
hydroxide, tank C-2 will contain sodium laural sulphate, and tank C-3 will 
contain hydrogen peroxide. A typical formulation for the soil 
decontamination method of the present invention would be 10 grams of 
sodium laural sulphate and 6 grams of sodium hydroxide per gallon of 
water. This mixture plus hydrogen peroxide is controllably added to the 
process blender using suitable pumping and valving devices to make the 
initial slurry. It is to be understood that, depending upon the type and 
extent of the contamination, various well-known surfactants can be used in 
practicing the method of the invention, including household laundry soap. 
The mixture of the appropriate surfactant solvents in the desired 
proportions and the pumping of the solvent from tanks C-1, C-2 and C-3 to 
the process blender is well understood and can readily be accomplished by 
those skilled in the art. 
The contaminated soil surfactant slurry is continuously metered from the 
process blender by means of a variable speed auger 14 to the first 
screening means. In the present embodiment of the invention, the first 
screening means is provided in the form of a commercially available 
vibrating screen assembly 16 which is adapted to remove from the slurry 
particles of predetermined size as, for example, particles larger than 
about 1/8th inch in diameter. The larger particles which are separated 
from the slurry stream may be crushed into smaller sizes and reintroduced 
into the process blender if their level of contamination is above desired 
limits. On the other hand, if the surfactant contained within the process 
blender has reduced the level of contamination of the larger products to 
an acceptable level, the particles may be stacked as finished product and 
disposed of in a suitable manner. 
Following separation of the larger particles from the slurry stream, the 
slurry is pumped by means of a suitable, commercially available slurry 
pump 18 from the outlet of the vibratory screen apparatus 16 toward the 
reactor means of the invention via a conduit 20 which preferably is a 
steel or plastic pipe having a diameter not less than about three inches. 
In the instant form of the invention, the reactor means comprises enclosure 
means shown here as a large tank 22, recirculating pump means for 
continuously recirculating the small particle slurry through the enclosure 
means or tank 22 and ozone generating means operably associated with the 
recirculating pump means for injecting ozone into the small particle 
slurry to form an ozone enriched slurry. As indicated in FIG. 1, the small 
particle slurry is pumped from apparatus 16 to the top of tank 22 and is 
controllably introduced into tank 22 via a standard type of valve 24 
provided within conduit 20. The slurry passing through first control valve 
24 enters tank 22 at a first inlet port 26 and tends to fall by force of 
gravity to the bottom of the tank. Connected proximate the bottom of the 
tank, is a conduit 28 which includes a second control valve 30. 
Interconnected with second valve 30 is the recirculating pump means 
provided here as a standard commercially available slurry pump 32. The 
output of slurry pump 32 is in turn connected with a conduit 34 which 
terminates at its upper end in a standard type of spray nozzle means for 
generating a slurry spray which is introduced into tank 22 via a second 
inlet 36. Typical pressures within conduit 34 are on the order of about 
sixty to eighty pounds per square inch. 
Disposed intermediate the ends of conduit 34 is an eductor unit 38 which is 
operably interconnected with the ozone generating means of the invention. 
The ozone generating means is here provided in the form of a commercially 
available ozone generator of the character marketed by Ozone Systems, Ltd. 
of El Cajon, Calif. The ozone generator, generally designated by the 
numeral 40 in FIG. 1, cooperates with eductor 38 to continuously mix ozone 
into the small particle slurry being pumped through conduit 34. 
Accordingly, the slurry spray which is introduced to tank 22 at inlet 36 
comprises an ozone enriched small particle slurry. 
The ozone generator may be of various types including generators of the 
type wherein ozone is generated by an excimer laser operating in the 
ultraviolet range. Such a laser is available from Coherent Co. of Palo 
Alto, Calif. An organic dye laser can also be used which is activated by 
an argon laser which excites the organic dye and causes it to lase. 
Forming an additional important aspect of the apparatus of the present 
invention, is the provision of illuminating means which is operably 
associated with the reactor means for irradiating with ultraviolet 
radiation the small particulate slurry spray being metered into tank 22. 
In the present form of the invention, the illuminating means comprises a 
series of ultraviolet lights which produce primarily 254 nanometer 
radiation. These ultraviolet lights are readily commercially available and 
are also obtainable from Ozone Systems, Inc. of Cajon, Calif. The 
ultraviolet radiation generated by the illumination means is destructive 
of ozone and causes a reaction similar to a catalytic reaction in that it 
greatly enhances both the speed and effect of ozone destruction of the 
targeted contaminants. Resident time for the slurry within tank 22 is 
dependent upon the type of contamination and the soil makeup, but normally 
is no more than a few hours. 
As seen in FIG. 1, a second tank 22a is provided for use as a secondary 
back-up to tank 22. Tank 22a is interconnected with conduit 20 via a third 
valve 42. Connected at a lower outlet port 28a of tank 22a is a 
recirculating pump 32a of identical construction to pump 32. Recirculating 
pump 32a functions to recirculate the particulate slurry contained within 
tank 22a via a conduit 34a. Conduit 34a is also provided intermediate its 
ends with an eductor 38a which is operably with ozone generator 40. 
It is apparent that by closing valve 24 and opening valve 42 the small 
particulate slurry flowing through conduit 20 from screening unit 16 will 
flow toward tank 22a. Activation of the recirculating pump 32a and opening 
of valve 30a will cause recirculation of the small particulate slurry 
through tank 22a. By switching ozone generator 40 from communication with 
eductor 38 to eductor 38a, the slurry flowing through conduit 34a can be 
reacted with ozone to form an ozone enriched slurry. As the ozone enriched 
slurry is introduced into tank 22a through a suitable spray nozzle 
provided at the outlet end of conduit 34a, the spray will also be 
illuminated with ultraviolet radiation from the ultraviolet generator 43. 
Operably interconnected with conduits 34 and 34a by means of conduits 50 
and 50a is a second screening means for removing particles larger than a 
second predetermined size as, for example, about 80 mesh, from the ozone 
enriched slurry which may be flowing through the conduits. In the present 
embodiment of the invention, in the second screening means is provided in 
the form of a second vibrating screen apparatus 46. By opening one or the 
other of valves 48 and 48a which are disposed within conduits 50 and 50a 
respectively, the ozone enriched particulate slurry can be directed from 
the reactor means toward vibrating screen apparatus 46 where once again 
the larger particles contained wtihin the small particle slurry can be 
separated out to form a fine particle slurry. 
The particles which are separated from the small particle slurry are 
deposited on a conveyor 52 from which they can be stacked as clean, 
finished product. The remaining slurry is collected in a collection tank 
53. This fine particle slurry is then pumped from tank 53 by a slurry pump 
54 into a surge tank 56 through a conduit 58. As indicated in FIG. 1, the 
inlet end 58a of conduit 58 is interconnected with tank 53 while the 
outlet end 58b of conduit 58 is interconnected with surge tank 56 at an 
inlet 58b port 60 thereof. Tank 56 also includes an outlet port 62 to 
which is connected a conduit 64. Disposed within conduit 64 is a control 
valve 66 which controls the flow of slurry from tank 56 toward a pump 68. 
Pump 68 functions to pump slurry via a conduit 70 toward the mixer means 
of the invention. 
The mixer means functions to mix a floculating material with the fine 
particle slurry to form a floculated material which can readily be formed 
into discrete segments such as blocks of a desired size and shape. In the 
embodiment of the invention shown in the drawings, the mixer means is 
provided in the form of an elongated static mixer 72. As best seen by 
referring to FIG. 2, static mixer 72 comprises an elongated tubular member 
74 having disposed therewithin a series of motionless mixer blades or 
baffles 76. Blades 76 function to cause the slurry to flow along a 
circuitous flow path from one end of the mixer 72 to the opposite end in 
the manner indicated by the arrow in FIG. 2. 
Operably associated with mixer 72 are holding tanks 80 and 82 for holding 
the floculating materials. For example, tank 82 is adapted to contain a 
chemical such as lime, magnesium oxide, diatamaceous earth or various 
combinations thereof which can be controllably added to the slurry flowing 
through the static mixer to provide additional body to the slurry. These 
chemicals are added to mixer 72 through a conduit 84 which is 
interconnected with the inlet of a pump 86. The outlet of pump 86 is 
interconnected with mixer 72 via a conduit 88. The amount of body 
enhancing material contained within tank 82 which is added to the fine 
particle slurry varies depending upon the moisture content of the slurry. 
However, enough body enhancing material is added to provide sufficient 
body to the slurry to enable it to be expediciously processed into blocks 
by the forming means, the nature of which will presently be discussed. 
Contained within tank 82 is a suitable anionic, cationic or nonionic 
combination of polymers which can also be added to the slurry flowing 
through mixer 72 in a manner to effect sufficient floculation thereof to 
permit the separation of soil from the water contained within the slurry. 
The polymer material can be controllably added to mixer 72 by means of a 
valved conduit 90 which is interconnected with the inlet of a pump 92. The 
outlet of pump 92 is interconnected with a conduit 94 which in turn, is 
interconnected with mixer 72. 
The outlet end 72a of mixer 72 is operably interconnected via a conduit 96 
with the previously mentioned forming means of the invention. The forming 
means functions to continuously form the floculated slurry received from 
mixer 72 into discrete segments such as brickettes or blocks of 
contamination free soil suitable for ordinary purposes. In the embodiment 
of the invention shown in the drawings, the forming means is provided as a 
belt-filter press 99 of a standard, commercially available type. An 
appropriate belt-filter press for the present application is obtainable 
from G & W Enterprises of Palmdale, Calif. 
During formation of the discrete soil segments or blocks, any liquid 
remaining within the slurry can be removed from the belt-filter press via 
a conduit 100 which is interconnected with a pump 102. Connected at the 
outlet of pump 102 is a conduit 104 the outlet end of which is connected 
to the top of a recycle storage tank 106. Tank 106 is in turn connected 
with the process blender by a conduit 108. By opening a valve 110 provided 
in conduit 108 and by energizing pump 112, water contained within tank 106 
can be controllably introduced into the process blender as needed and 
mixed with the contaminated soil to be processed by the apparatus of the 
invention. 
The method of decontaminating soil contaminated with hazardous hydrocarbons 
comprises the steps of first loading the contaminated soil to be 
decontaminated by means of a conveyor belt, skip loader or other 
convenient means into the process blender 12. With the process blender 
energized, the contaminated soil is mixed with water and a suitable 
surfactant of the character previously described to form a slurry. After 
appropriate mixing has taken place, the slurry is controllably removed 
from the process blender by an auger 14 and deposited onto screening 
assembly 16 for removal from the slurry of particles larger than a 
predetermined size as, for example, about 1/8th of an inch in diameter. 
The small particle slurry thus formed is transported to one of the two 
tanks 22 or 22a of the ractor means of the invention. The fine particle 
slurry contained within the tank is then continuously recirculated using 
recirculating pump 32 or 32a. As the small particle slurry is recirculated 
through the tank, ozone is continuously introduced into the slurry by an 
inductor 38 or 38a to form a highly ozone enriched slurry. The ozone 
enriched slurry is pumped to the top of the tank where it is reintroduced 
into the tank in the form of a fine spray. An important step in the method 
of the invention is the continuous exposure of the recirculating ozone 
enriched slurry to ultraviolet light. This radiation is destructive of 
ozone and causes a reaction similar to a catalytic reaction in that it 
greatly enhances both the speed and effect of ozone destruction of the 
targeted contaminants. Following exposure of the ozone enriched slurry to 
ultraviolet radiation which is on the order of about one to eight hours, 
the slurry is transported to a second vibrating screen mechanism wherein 
particles larger than a predetermined size, as for example, about 80 mesh 
are removed from the slurry to form a fine particle slurry. The larger 
particles are gathered for suitable disposal or reprocessing. The fine 
particle slurry is then introduced into a static mixer, such as mixer 72, 
which in turn is interconnected with a belt-filter press. As the fine 
slurry travels through the static mixer, a floculating material selected 
from a group consisting of lime, magnesium oxide and diatamaceous earth is 
controllably added to the fine slurry. Also added to the slurry is a 
polymer material selected from a group consisting of anionic, cationic and 
nonionic polymers. The amounts of floculating material and polymer to be 
added to the fine particle slurry depends upon the nature of the soil 
being processed and the amount of water present in the slurry. The 
floculated slurry thus-formed is conveyed to the belt-filter press where 
it is pressed into discrete segments such as blocks or brickettes of soil 
which is now decontaminated and suitable for standard soil uses. 
Having now described the invention in detail in accordance with the 
requirements of the patent statutues, those skilled in this art will have 
no difficulty in making changes and modifications in the individual parts 
or their relative assembly in order to meet the specific requirements or 
conditions. Such changes and modifications may be made without departing 
from the scope and spirit of the invention, as set forth in the following 
claims.