U.S. patent application number 13/461871 was filed with the patent office on 2012-11-08 for method and apparatus for treating natural gas and oil well drilling waste water.
This patent application is currently assigned to LAKE COUNTRY FRACWATER SPECIALISTS, LLC. Invention is credited to Steven B. Addleman, Francis C. MILLER.
Application Number | 20120279925 13/461871 |
Document ID | / |
Family ID | 47089527 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120279925 |
Kind Code |
A1 |
MILLER; Francis C. ; et
al. |
November 8, 2012 |
METHOD AND APPARATUS FOR TREATING NATURAL GAS AND OIL WELL DRILLING
WASTE WATER
Abstract
A method of treating contaminated water effluent from a well
drilling operation. The method comprises decomposing organic
contaminants in the effluent by bubbling a gas containing ozone
through the effluent; adding a coagulant to increase the particle
size of solid particles contained in the effluent; adding a
flocculant to increase the particle size of solid particles
contained in the effluent, thereby forming flocs suspended in the
effluent; and filtering the flocs from the effluent to produce a
filtrate and flocculated solids. The method may further comprise
adding the coagulant into a stream of effluent flowing within a
first conduit under controlled shear conditions, and adding the
flocculant into a stream of effluent containing pin flocs flowing
within a second conduit under controlled shear conditions. The
method may further comprise delivering the effluent containing the
suspended flocs into a filter through a conduit floating in the
effluent contained in the filter.
Inventors: |
MILLER; Francis C.;
(Livonia, NY) ; Addleman; Steven B.; (Somerset,
PA) |
Assignee: |
LAKE COUNTRY FRACWATER SPECIALISTS,
LLC
Livonia
NY
|
Family ID: |
47089527 |
Appl. No.: |
13/461871 |
Filed: |
May 2, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61481370 |
May 2, 2011 |
|
|
|
Current U.S.
Class: |
210/723 |
Current CPC
Class: |
C02F 9/00 20130101; C02F
1/52 20130101; C02F 1/001 20130101; C02F 2201/008 20130101; C02F
2103/365 20130101; C02F 5/02 20130101; C02F 1/78 20130101; C02F
2101/30 20130101 |
Class at
Publication: |
210/723 |
International
Class: |
C02F 1/52 20060101
C02F001/52 |
Claims
1. A method of treating contaminated water effluent from a well
drilling operation, the method comprising: a) decomposing organic
contaminants in the effluent by bubbling a gas containing ozone
through the effluent; b) adding a coagulant to increase the
particle size of solid particles contained in the effluent; c)
adding a flocculant to increase the particle size of solid
particles contained in the effluent, thereby forming flocs
suspended in the effluent; and d) filtering the flocs from the
effluent to produce a filtrate and flocculated solids.
2. The method of claim 1, wherein the ozone concentration in the
gas is at least one percent by weight.
3. The method of claim 1, wherein the size of the gas bubbles is
less than 500 microns in diameter.
4. The method of claim 1, wherein the pH of the effluent during gas
bubbling is between 3 and 10.
5. The method of claim 1, further comprising causing pin flocs to
form in the effluent by adding the coagulant.
6. The method of claim 5, further comprising adding the coagulant
into a stream of effluent flowing within a first conduit under
controlled shear conditions, and adding the flocculant into a
stream of effluent containing pin flocs flowing within a second
conduit under controlled shear conditions.
7. The method of claim 1, further comprising delivering the
effluent containing the suspended flocs into a filter through a
conduit floating in a portion of the effluent contained in the
filter.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Patent Application No. 61/481,370 filed May 2, 2011, the disclosure
of which is incorporated herein by reference. This invention is
also related to the inventions disclosed in U.S. patent application
Ser. No. 12/914,072 filed Oct. 28, 2010, and U.S. Provisional
Application for Patent No. 60/255,504, filed Oct. 28, 2009, the
disclosures of which are incorporated herein by reference.
BACKGROUND
[0002] 1. Technical Field
[0003] This invention relates to the removal of contaminants from
waste water discharged at a gas wellhead, and more particularly to
the removal of contaminants from drilling water that is used during
the process of drilling a well bore, and that is subsequently
discharged from the wellhead. The waste water may contain
petroleum-based drilling muds. The waste water may be treated as it
is discharged from a well bore, or after it is temporarily stored
in a nearby lagoon or tanks.
[0004] 2. Description of Related Art
[0005] Certain subterranean geologic formations contain significant
reservoirs of natural gas. For example, the Marcellus Shale
subterranean formation, which extends from central and western New
York southwardly through Pennsylvania, West Virginia, and eastern
Ohio, contains significant natural gas deposits. Extraction of this
gas has been made economically and technically feasible by the
utilization of a technology referred to as hydraulic fracturing,
commonly abbreviated as "hydrofracking," or "fracking." This
technology utilizes injection of large volumes of water at high
pressure to fracture the subterranean shale structures, which
causes them to separate and release the pockets of methane gas
contained within the shale strata.
[0006] During the drilling of the wells, drilling mud and treated
water are utilized for lubrication, suspension of drilling wastes,
and as weighting agents to form a plug to restrain the pressure of
the natural gas within the well bore. This drilling operation
produces a waste effluent stream referred to as "pit water." This
pit water is the liquid and semi-solid remnants resulting from the
drilling process typically remaining after the bulk of the rock
cuttings have been removed by conventional means. This pit water
contains contaminants in the form of drilling mud, pulverized rock
cuttings and chemicals from the subterranean structures, as well as
from pretreatment of the water with certain chemicals prior to
performing the drilling along with other debris. As much as one
hundred thousand gallons of pit water may be generated from the
drilling process for each well. Separation of the rock cuttings and
drilling muds from this water is needed.
[0007] The contaminants in this water render it unsuitable for
reuse except in small proportions. Disposal of the water and the
organically contaminated solids contained therein has become an
expensive proposition for the well developers and also a difficult
environmental problem. Treatment of the water with solidification
additives is sometimes used. New environmental regulations, as well
those proposed and likely to be implemented, may severely limit the
ability to dispose of or treat this water by conventional means
within the states of Pennsylvania and New York as well as Texas,
and Idaho among others, and some foreign countries. There is a
significant need by the well developers for technologies which will
treat the water to enable its reuse to a maximum extent, and for
the cost effective and environmentally satisfactory disposal of the
contaminants contained in it.
[0008] The contaminants in this water include many of the following
components: [0009] Sodium chloride. [0010] Calcium and magnesium
(hardness) salts, typically in the bicarbonate and/or chloride
form. [0011] Soluble sulfate salts. [0012] Volatile organic
compounds (VOC) resulting from the degradation of the ancient sea
creatures captured within the shale formation. (The VOCs may
include small amounts of crude oil.) [0013] Residual organic
compounds (ROC) from the water treatment chemicals introduced into
the drilling water to enhance the drilling process. [0014]
Pulverized rock cuttings. [0015] Bentonite clay which may be a
component of the drilling mud.
[0016] The following are also possibly present, but to a lesser
degree: [0017] Barium salts, typically in either the soluble
chloride form or the insoluble sulfate form, which may be a
component of the drilling mud or contained with the rock cuttings.
[0018] Strontium salts, typically in either the soluble chloride
form, or the insoluble sulfate form which may be component of the
drilling mud or contained with the rock cuttings.
[0019] Common practice may provide for some reuse of the pit water
in limited quantities as makeup water for hydro-fracturing water or
other drilling operations, provided that the pit water is from a
"water based" drilling mud operation and it is clarified through
sedimentation, and the soluble contaminants levels are below
predetermined limits. Alternatively, previous disposal of the pit
water has been accomplished by transport to and subsequent
treatment at conventional municipal waste water treatment
facilities and specialized industrial treatment facilities,
provided that the drilling muds utilized are "water based." New and
pending regulations may severely limit this option. "Oil based"
drilling mud may not be treated in significant quantities in
conventional municipal waste water treatment facilities. In fact,
there are considerable limitations to the disposal of "oil based"
pit waters altogether. Most of these pit waters are treated with
thermal technologies, bio-remediation, deep well injection,
addition of solidifiers (such as polymers, sawdust, wood chips,
lime, or vermiculite) and/or evaporation of the water fraction
followed by landfill disposal of the remaining contaminated
solids.
[0020] The sodium chloride is not considered a significant problem
relative to the reuse of the water up to some practical limit that
is determined by the drilling operator. The soluble barium and
strontium salts, and alternatively the soluble sulfate salts, form
insoluble solids during and after the fracking process, which have
been determined to be degradative to the drilling and/or
hydrofracturing process when these materials exceed certain levels
which depend upon the particular operator of the drilling rig.
Elevated levels of these salts limit options for disposal as well.
The soluble calcium salts form hardness scale in the subterranean
shale structures and are similarly limited in concentration but at
higher levels. Both of these conditions may result in the
obstruction of portions of the fissures within the shale strata
created by the fracking process when the water is reused, if the
concentrations of these salts contained in it are excessive. The
presence of the residual or incipient volatile organic chemicals in
the return water results in further difficulties in proper
reformulation of it as fracking water for reuse. The pulverized
rock cuttings and residual mud present in this pit water represent
suspended solids which are unacceptable in hydrofracking or
drilling fluids.
[0021] The removal of certain suspended solids in the waste water
from water based drilling mud is defined in various documentation
and literature. The solidification of the salts may be accomplished
by conventional evaporation technology, gelatinizing of the
solution, or precipitation means. The current method of return
water remediation is to transfer it upon its discharge from the
wellhead into tanker trucks or pits, decant any clarified
supernatant following settling or treatment for reuse, and then
transfer the unusable remaining water and/or sludge into tankers.
The tankers of sludge are then hauled substantial distances to
off-site municipal or industrial water treatment plants, or to
other solidification pits where further solidifiers may be added.
This is expensive, and additionally, it may soon be prohibited in
many jurisdictions (particularly New York, Pennsylvania and Texas)
by new environmental regulations.
[0022] The aforementioned U.S. patent application Ser. Nos.
12/914,072 and 60/255,504 of Miller provide for a modular, portable
and cost effective method and apparatus for treating the frack
water for the removal of the barium, calcium and strontium salts
onsite at the wellhead. However, there remains a need for a
modular, portable, and cost effective method and apparatus for
treating waste water produced from the utilization of oil-based
drilling mud. The separation of the settleable and finely dispersed
suspended solids from the aqueous phase must be accomplished in a
manner such that the solids may be disposed of separately, and the
water may be reused. It is desirable that the process and apparatus
also accommodate the presence of any residual or volatile organic
chemicals, typically including finely dispersed or emulsified
diesel oil or other "oil" components of the drilling mud
formulation, or natural crude oil component brought up from the
wellhead; and residual soluble precipitate-forming salts as
well.
SUMMARY
[0023] The Applicants have developed a method and apparatus to meet
this need. The method and apparatus separate and remove the
settleable and finely dispersed suspended solids from the waste
water from oil based drilling mud operations. The method and
apparatus also removes residual soluble precipitate forming salts
where applicable. The suspended solids are coagulated and
flocculated and then dewatered, which renders the resulting solids
mass suitable for conventional landfill or on site disposal. Any
problematic levels of barium, strontium, calcium and magnesium
salts may be selectively precipitated into their inert forms for
removal and disposal as recited in the aforementioned patent
application Ser. Nos. 12/914,072 and 60/255,504 of Miller. The
soluble sulfate salts are precipitated in the inert barite and
celestite forms which are similarly coagulated and flocculated, and
then dewatered for disposal.
[0024] The product water from the instant process is a sodium
chloride (brine) solution, which is suitable for reuse as a portion
of the makeup water in drilling operations or hydrofracturing
operations. The instant process may include an ozone treatment
process for removal of organic contamination prior to treatment to
improve chemical efficiency and performance. In addition, ozone
treatment, or alternately carbon absorptions, may be utilized
following filtration to remove any residual organic materials.
[0025] More specifically, in accordance with the invention, there
is provided a method of treating contaminated water effluent from a
well drilling operation. The method comprises decomposing organic
contaminants in the effluent by bubbling a gas containing ozone
through the effluent; adding a coagulant to increase the particle
size of solid particles contained in the effluent; adding a
flocculant to increase the particle size of solid particles
contained in the effluent, thereby forming flocs suspended in the
effluent; and filtering the flocs from the effluent to produce a
filtrate and flocculated solids.
[0026] The ozone concentration in the gas is preferably at least
one percent by weight. The size of the gas bubbles is preferably
less than 500 microns in diameter. The pH of the effluent during
ozonation (gas bubbling) is preferably between 3 and 10. For most
pit water effluent mixtures, the ozone treatment will operate in
the range of 10 ppm ozone to 50 ppm ozone concentration with a pit
water effluent average residence time in the apparatus 18 of
between approximately 10 and 30 minutes. The method may further
comprise causing pin flocs to form in the effluent by adding the
coagulant. The method may further comprise adding the coagulant
into a stream of effluent flowing within a first conduit under
controlled shear conditions, and adding the flocculant into a
stream of effluent containing pin flocs flowing within a second
conduit under controlled shear conditions. The method may further
comprise delivering the effluent containing the suspended flocs
into a filter through a conduit floating in a portion of the
effluent contained in the filter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The present disclosure will be provided with reference to
the following drawings, in which like numerals refer to like
elements, and in which:
[0028] FIG. 1 is a schematic diagram of one exemplary embodiment of
the instant process and apparatus for treating waste water from oil
based drilling mud;
[0029] FIG. 2 is a flowchart of the instant process for treating
pit water;
[0030] FIG. 3A is a schematic cross-sectional illustration of a
"box" type filter that may be used as a part of the instant
apparatus, shown during delivery of liquid containing flocculated
solids; and
[0031] FIG. 3B is a schematic cross-sectional illustration of the
filter of FIG. 3A, shown during dewatering of sludge contained
therein.
DETAILED DESCRIPTION
[0032] The present invention will be described in connection with
certain preferred embodiments. However, it is to be understood that
there is no intent to limit the invention to the embodiments
described. On the contrary, the intent is to cover all
alternatives, modifications, and equivalents as may be included
within the spirit and scope of the invention as defined by the
appended claims.
[0033] For a general understanding of the present invention,
reference is made to the drawings. In the drawings, like reference
numerals have been used throughout to designate identical elements.
It is to be understood that the labeling of the vessels, conduits,
pumps, filters, and other process equipment with dimensions,
volumes, flow rates, capacities, materials of construction, and
other specifications is meant to be exemplary only, and not
limiting with respect to the instant apparatus and method. The
apparatus and method may be operated in many other suitable
configurations within the scope of the present disclosure.
[0034] Referring to FIG. 1 (which includes certain parameters that
are recited above, and that are exemplary only and not limiting)
and FIG. 2, an apparatus 10 and a process 100 for treatment of gas
and oil well drilling waste water are shown. The process 100 is
comprised of the sequential addition and timed reaction of
chemicals for the coagulation of the contaminants and their
subsequent flocculation and filtration. The waste water that is
discharged from the wellhead (not shown) may be captured and
directed into a tanker truck (not shown), which may transport the
waste water to a storage tank(s) 12 or alternately a lagoon 14, and
transfer the drilling waste water thereto. Alternatively, the
drilling waste water may be captured and pumped directly into the
storage tank 12 if the drilling waste water treatment apparatus 10
is located near the wellhead. The apparatus 10 may also include or
be installed proximate to the outlet of an ozonation treatment
system. The storage tank 12 or lagoon 14 may be between the
ozonation system and the apparatus 10.
[0035] Some or all of the apparatus 10 may be mounted on a flatbed
trailer or in an enclosed trailer so as to make it transportable as
a tractor trailer rig or smaller tongue style trailer, in a manner
similar to that disclosed in the aforementioned patent application
Ser. No. 12/914,072, and shown in FIGS. 9A and 9B therein. In one
embodiment, most of the apparatus 10 is mounted on or in a trailer,
with one or more "roll-off" box-type filters 52 and 54 being
separately transportable.
[0036] The apparatus 10 is comprised of various tanks, pumps,
filtration device(s) and other equipment for performing
coagulation, flocculation and filtration operations on the drilling
waste water. In step 110, a portion of drilling waste water is
delivered into a tank or tanks 16 for "equalization," i.e.,
accumulation and mixing of the influent stream to dampen out
variations in the chemical and/or physical character of the waste
water.
[0037] In step 115, the equalized waste water may optionally be
treated with ozone, in a suitable source or apparatus 18. Ozonation
115 is used to decompose any organic contaminants contained in the
waste water to carbon dioxide and water. In gas well drilling,
these organic components originate primarily from "oil based"
constituents that are added to the drilling fluids.
[0038] The ozonation treatment requirements are dependent upon the
constituents of the waste water such as metals, bacteria, H.sub.2S,
hydrocarbons, etc., as well as total organic carbon (TOC) and
biochemical oxygen demand (BOD) of the constituents, and
temperature and pH. With the exception of the pH, all of the
variation in constituents may be accommodated by adjustments to the
ozonation process 115. The Applicants have found that for the
ozonation process 115 to work most effectively, the pH level is
generally required to be between 3 and 10 but the system will still
function outside this range. For most pit water mixtures, the ozone
treatment 115 will operate in the range of 10 ppm ozone to 50 ppm
ozone concentration with a pit water average residence time in the
ozone apparatus 18 of between approximately 10 and 30 minutes. Pit
water having elevated level of hydrocarbons and BOD may require the
oxidation/contact chamber in the apparatus 18 to be pressurized and
the dwell time extended. The required pressure may be approximately
in the range of 1 to 5 atmospheres and the dwell time extended to
between approximately 30 and 60 minutes.
[0039] The Applicants have discovered that the size of ozone
bubbles needed to accomplish complete oxidation of contaminants is
important. Diffusion of ozone gas into water from a sintered pipe
or similar device will normally be insufficient for treatment of
the pit water. The use of microbubbles with a diameter of
approximately 5 to 500 microns is normally sufficient. The
microbubbles may be formed by using a venturi contact system such
as is commercially available and well known in the art. However,
pit waters with elevated levels of contamination above 50
milligrams/liter (mg/l) hydrocarbons, 250 mg/l TOC, and/or 500 mg/l
BOD will require the infusion of nanobubbles with a diameter of
approximately 0.1 up to 4 microns delivered under pressure with
lengthened residence time of approximately 30 to 60 minutes. The
concentration of ozone in the ozone/oxygen gas is preferably at the
highest percent by weight available, in the range of approximately
6 percent to 10 percent, in order to optimize the efficiency of the
operation.
[0040] In step 120, a coagulant is introduced from a source 20 into
the drilling waste water, which is a slurry containing suspended
solids such as rock dust and drilling mud. This coagulant forms a
fine "pin floc" of the suspended and settling materials which will
later be formed into a larger floc suitable for efficient
filtration. The optimum coagulant for this application has been
determined to be a metal chloride, such as aluminum chlorohydrate.
Multiple alternate metal chlorides may also be utilized. However,
following extensive testing including ferric chloride as the
coagulant, the Applicants have observed that the aluminum
chlorohydrate is visibly, significantly more effective in terms of
formation of the pin floc under varying conditions and
concentrations of the solids in the pit water. The addition ratio
of the coagulant has been determined to be approximately 0.001 to
0.01 parts of the coagulant per part of the solution, although
higher concentrations may be used if the waste water has higher
percent solids or has been pre-treated to concentrate it. The
coagulant may be introduced to the suspended solids slurry as a
neat (concentrated liquid) material or as a diluted aqueous
solution provided from a vessel 20, depending upon the site
specific requirements and available feed equipment. It may be
delivered through conduit 22 and blended and reacted with the
slurry in either a batch or continuous tank 24.
[0041] Alternatively, the waste water slurry may be provided as a
continuous feed into a moving flow of the slurry in a conduit 26.
The Applicants have discovered that optimum coagulation occurs in
step 130 when the section 28 of the conduit 26 that is downstream
from the coagulant injection point 30 is a corrugated 11/2''
diameter hose which has a length of approximately 20 to 50 linear
feet and the velocity is approximately 4 to 12 feet per second.
[0042] Following the formation of pin flocs by the introduction of
coagulant, an anionic flocculant is added to the slurry in step
140. This flocculant forms the pin flocs into large flocs which are
suitable for efficient filtration. In one embodiment, the optimum
coagulant for this application has been determined to be anionic
polyacrylimide F-303AH as provided by Water Specialists
Technologies, LLC of Sanford, Fla. However multiple alternate
anionic poly acrylimides may also be utilized. The addition ratio
of the flocculant has been determined to be approximately 0.0001 to
0.0005 parts of the flocculant per part of the solution.
[0043] The flocculant may be introduced to the flowing pin floc
slurry in conduit 28 as a diluted aqueous solution in the range of
0.1% to 0.5% concentration depending upon the site specific
requirements and available feed equipment. It may be blended and
reacted with the pin floc slurry into a downstream continuous
flocculation tank (not shown), or as a continuous feed into a
moving flow of the pin floc slurry in a pipe or other conduit 32.
The Applicants have discovered that optimum flocculation occurs in
step 150 when the conduit 32 is a corrugated 11/2 diameter hose
which has a length of approximately 20 to 50 linear feet and the
velocity is approximately 4 to 12 feet per second.
[0044] In step 160, the now flocculated slurry is introduced into a
filtration system 50. The filtration system may be comprised of one
or more active filter(s) 52 and 53, wherein solids are captured on
a filter medium, and then dewatered by the action of inflatable
bladders disposed against the medium. One suitable active filter is
the "DryBox" filtration system sold commercially by Innovative
environmental Products, Inc. of Livonia, N.Y. under License from
Idee e Prodotti S.r.l. of Cavenago Brianza, Italy. This filter is
provided in a multiple solid holding capacities ranging from 5
cubic feet up to 40 cubic yards.
[0045] Alternately, other filtration devices such as a plate and
frame filter press, rotary drum filter, or other such commercial
device may be utilized with the process 100.
[0046] The box filters 52 and 53 may be provided as transportable
"roll off" boxes that are similar to refuse collection boxes.
Referring to FIGS. 3A and 3B, the box filter 52 (as well as box
filter 53) may be comprised of a box-shaped housing 54 having a
bottom wall 56, a surrounding side wall 58 that includes a
discharge door 59, and a displaceable filter bag 60 disposed within
housing 54. The discharge door 59 may be hinged vertically or
horizontally. The discharge door 59 facilitates the emptying of the
dewatered sludge from the filter. Filter 52 is further comprised of
at least one inflatable bladder 62 (shown in dotted line),
comprised of a central portion 63 disposed along the bottom wall
56. The bladder 62 may include an end portion 64 disposed along the
end wall 66 opposite the discharge door 59. The bladder 62 may also
include end portion 68 or portions disposed along the inside face
of the discharge door 59. Bladder section 68 may be an independent
bladder section interconnected to the bladder 62 or bladders by
pneumatic or hydraulic tubing (not shown). The end portions 64 and
68 of bladder 62 may extend up the end wall 66 and discharge door
59 of the housing 54 less than shown in FIGS. 3A and 3B. The end
portions 64 and 68 of the bladder 62 may be comprised of single or
multiple sections disposed on the end wall or discharge door of the
housing 54 interconnected by pneumatic or hydraulic tubing (not
shown).
[0047] Alternatively, the filter 52 may be comprised of a bottom
bladder and one or more independent end wall bladders in place of
end portion 64, and one or more independent discharge door bladders
and two additional side inflatable bladders (not shown) disposed
along the side portions (not shown) of side wall 58. If individual
end wall or side wall bladders are used, they may be made
independently inflatable and deflatable through respective valves
70, 72, and 74, which are controlled by programmable logic
controller 76 or another appropriate control device. Alternatively,
all bladders may be connected to a single air source and all
inflated simultaneously through a single valve 70 as shown in FIGS.
3A and 3B; or bottom bladder 63 may be connected to a first air
source controlled by valve 70, and the end and/or side wall
inflatable bladders may be connected to a second air source such
that bottom bladder 63 is separately controllable from the end
and/or sidewall bladders.
[0048] In the embodiment depicted in FIGS. 3A and 3B, the bladder
62 is inflated and deflated by air supplied and exhausted through
valve 70. The corner portions of bladder 62 may be held proximate
to the juncture of the end wall 66 opposite the discharge door 59
and the bottom wall 56 and proximate to the juncture of the
discharge door 59 and the bottom wall 56 by the lower portion of a
support basket or frame 78, which also supports the bottom and the
vertical sections of filter bag 60 that are disposed along the
bottom wall 56 and the side and end walls 58 of the housing 54.
Referring in particular to FIG. 3B, the profiles of the inflated
bladder 62, and alternate bladder 68 (if provided separately from
bladder 62) are indicated by dotted curves 80, 82, and 84. When the
bladder 62 (and alternate bladder 68 if provided separately) is
pressurized, the bottom portion 62 bulges upwardly while the end
portions 64 and 68 bulge inwardly, resulting in the upwardly and
inwardly displaced filter bag 61 and the dewatering of the solids 2
therein. As the sludge 2 in the filter 52 is dewatered, at least
one outlet 86 permits the drainage of filtrate from housing 54. If
separately operable bladders are provided in the filter 52, the
respective bladders may be operated sequentially to manipulate the
sludge 2 that accumulates on the filter bag 60. Further details on
the construction of the active filter may be as disclosed in U.S.
Pat. No. 7,972,517 of Miller, the disclosure of which is
incorporated herein by reference.
[0049] Referring again to FIG. 3A, to perform the filtration step
160 (FIG. 2) with the active filter 52, floc-containing waste water
is delivered through inlet conduit 34 into the filter 52 from the
floc formation conduit 30. The Applicants have discovered that for
the most effective filtration, it is beneficial to introduce the
floc-containing waste water through a floating conduit 36. The
floating conduit 36 may be made of a buoyant material such as a
foam, or it may be comprised of separate buoyant members (not
shown). In operation, when floc-containing waste water is delivered
into the filter 52, the conduit 36 floats upon the waste water 3
and gently discharges the flocs 4 so as to not disrupt them. (It is
to be understood that more flocs 4 may be present in the waste
water 3 than shown in FIG. 3A, extending to the bottom of the
filter 52.) The Applicants have discovered through experimentation
that in many instances the free cascading of the flocculated solids
from a pipe down into the dewatering box has a tendency to disrupt
the stability of the floc and reduce the filtration performance of
the dewatering operation. Thus the use of a floating conduit 36 to
introduce the floc into the filter housing 54 is beneficial.
[0050] A first portion of filtrate flows through the filter bag 60
by the action of gravity and out of outlet 86 as indicated by arrow
99. A cake of sludge 2 is retained by the filter bag 60.
Subsequently, step 170 is performed in which the sludge 2 is
dewatered. The bladders 62, 64, and 68 are actuated to manipulate
the sludge cake 2, resulting in the discharge of a second portion
of filtrate. The bladders 62, 64, and 68 may be repeatedly inflated
and deflated in programmed sequences, thereby manipulating the
sludge 2 on the filter bag 60 in a manner that maximizes the
dewatering thereof.
[0051] As alternatives to the box filter 52 and other active
filters, various other static style gravity filtration systems
available to the industry may be used as the filtration system 50.
These include common filtration boxes as provided by Rain for Rent
(25 Yard Filter Box) or Flotrend (models RB-25-O-GN-VPF,
RB-20-O-GN, RB-20-C-B and/or RB-25-O-GN-S) and other similar agents
and various applications of the Geotube.RTM. as provided by Marifi
Company. These systems perform substantially the same function as
the box filter 52. However, the "active filtration" process of the
filter 52 is believed to provide enhanced and accelerated
dewatering of the filtered solids and is significantly less
sensitive to problems associated with upsets in the coagulant and
flocculant feed systems. These filters may be configured with a
floating conduit in a manner similar to the floating conduit 36 of
the filter 52. In addition, the Squeeze Tower Press manufactured
and sold commercially by Idee e Prodotti S.r.l. of Cavenago
Brianza, Italy, also an active filtration device, may be suitable
under conditions requiring finer filtration at lower solids loading
rates.
[0052] In step 180, the solid sludge is discharged from the box
filter 52. If the box filter 52 is of a roll-off construction, the
entire box filter 52 may be drawn onto a truck and transported to a
suitable dumping site. The product of the process, based upon the
ozonation and the chemical coagulation, may be suitable for
disposal in a conventional non-hazardous landfill.
[0053] The filtrate that is discharged from the box filter 52 in
steps 160 and 170 may be discharged into a sump tank 40. In step
185, the filtrate may optionally undergo a "polishing" ozonation
process using an ozonation apparatus 42 to decompose any traces of
organic constituents contained therein. Alternately the organic
compounds may also be removed by carbon absorption, or other
suitable means. In step 190, if the filtrate is sufficiently free
of dissolved contaminants other than sodium chloride, it may be
discharged to the environment, or reused as fracking water. In the
event that the clear filtrate contains strontium, barium, magnesium
and/or calcium (hardness) salts in addition to sodium chloride
salt, it is desirable to remove these salts. In such circumstances,
the process 10 may proceed with a subsequent sequential addition
and timed reaction of chemicals for the precipitation of these
inorganic contaminants and their subsequent coagulation and
flocculation and filtration in accordance with the aforementioned
patent application Ser. Nos. 12/914,072 and 60/255,504 of Miller.
This filtrate has been tested and has generally found to be
suitable for use in preparation of the dilute polymer flocculant
solution for the process which will reduce requirements for fresh
water on the site. The suitability is subject to the brine (sodium
chloride) concentration, which is usually less than 40,000 PPM.
[0054] It is, therefore, apparent that there has been provided, in
accordance with the present invention, a method and apparatus for
removal of contaminants from oil and gas well drilling waste water.
Having thus described the basic concept of the invention, it will
be rather apparent to those skilled in the art that the foregoing
detailed disclosure is intended to be presented by way of example
only, and is not limiting. Various alterations, improvements, and
modifications will occur and are intended to those skilled in the
art, though not expressly stated herein. These alterations,
improvements, and modifications are intended to be suggested
hereby, and are within the spirit and scope of the invention.
* * * * *