USES FOR DESALINATED
OIL FIELD BRINE
Beneficial Use of Desalinated
Oil Field Brine
Many areas of the state have water shortages and would
welcome a new source of fresh water that could be used
to supplement municipal supplies. Figure 6 shows almost
one-third of Texas counties have unmet water needs.
Additionally TWDB anticipates a significant increase in
demand for fresh water resources in the next 20 years.
Accordingly, this section summarizes potential uses of
water produced from oil field brine and the applicable
regulations that such usage must meet.
Areas in West Texas with significant oil and gas
production (and brine production) will be the most
likely candidates for beneficial use of produced water.
As Figure 6 shows, a significant number of produced
water facilities are producing brine of less than 10,000
TDS. This represents the most affordable potential
resource. To consider the feasibility of treating oil
field brine, we have concentrated on this less costly
opportunity, produced water which represents
approximately one-third of the brine produced in Texas.
Appendix 1b contains a list of production wells
in Texas discharging brine of less than 10,000 ppm tds.
The list is arranged alphabetically by county, with
Field names alphabetized within a county.
Affordable desalination and supplemental use by
municipalities represents a logical and beneficial use
of the resource. Distribution and/or storage of
desalinated water, either in surface lakes and ponds or
in subsurface aquifers, are a significant issue that
must be considered when evaluating PWDS economics [40].
Technology is available that allows pre and
post-treatment required to assimilate or blend
desalinated water into the local water supply system.
For example, Odessa's average daily water use has
averaged 12 million gallons/day in winter and 29.5
million gallons/day in summer [37], with a peak of 34.9
million gallons used on June 26, 2002. The difference in
water use in the summer is predominately landscape
irrigation. Corresponding daily brine disposal in Ector,
and neighboring Midland, and Winkler Counties Texas in
2002 has been slightly more than 4,000,000 gallons of
water per day according to county records, or 25% of the
water used on landscape irrigation in the city. Most
other areas of Texas reflect the same water usage.
Texas A&M has been
investigating the potential for rangeland and habitat
restoration programs in West Texas. The results of
analyses focusing on restoration of rangeland systems
may provide a prioritization where habitat enhancement
would be most efficient. Of significant interest will
be the development of cooperative programs with
other environmental agencies and introduction of the
technology to determine their opinions on use and
acceptance. Hand in hand with this opportunity is the
potential to use desalination as a way of enhancing the
quality of impaired streams in Texas.
Potable Uses
The highest level of water treatment is associated with
human ingestion. The Texas Commission on Environmental
Quality has responsibility for the quality of water
discharged into the public sector. A project involving
potable use of treated brine produced by oil and/or gas
wells must meet the same permitting requirements as a
municipal drinking water system. by the TCEQ [38]. The
applicable TCEQ Rule pertaining to public drinking water
systems is TAC Chapter 290, Section 42(g). This section
states that “other” treatment processes will be
considered on an individual basis. Based on input from
TCEQ staff, a licensed professional engineer must
provide “pilot test data or data collected at similar
full-scale operations” of the proposed system
demonstrating that the system would meet applicable
Drinking Water Standards [39]. The pilot test must be
representative of the actual operating conditions that
can be expected over the course of a year, meaning the
test must be done during the time of the year that would
place the most strain on the treatment system.
Additionally, proof of a one-year manufacturer’s
performance warrantee or guarantee assuring the plant
will produce treated water that meets minimum state and
federal drinking water standards is commonly required by
the State as a condition of an operating permit.
Figure 10 shows the distribution of brackish produced
water sites in the USGS database for
Texas. The brines are shown with EPA classified counties
with unmet water needs [35].
Therefore, if this water was to be used as an
independent potable water source, among other drinking
water standards, TDS levels must be reduced to the
Environmental Protection Agency’s secondary standard of
500 mg/L. Permitting for waters with a TDS greater than
500 mg/L may be available if this water is the only
potential potable resource for a community. However, if
the high TDS water were to be blended with another
public water supply (PWS) and then distributed, the
required level of treatment could be less. The caution
in this situation would relate to the salt-loading on
the primary PWS infrastructure during blending.
A
point of contention existed in previous years regarding
the discharge of RO concentrate from desalination
facilities. If the saline concentrate is a waste stream,
then the RO facility operator must get a permit from
TCEQ for a Class 1 disposal well. However recently [42]
an agreement between the TCEQ and the TRC was made
regarding the use of the brine concentrate in oil field
brine injection wells for enhanced recovery.
Discharge to Supplement
In-Stream Flow
The Texas Commission on Environmental Quality (TCEQ)
monitors the condition of the state’s surface waters,
and assesses the status of water quality every two years
and submits their assessment to the U.S. Environmental
Protection Agency (EPA). The report is published on
the TCEQ Web site as the
Texas Water Quality
Inventory and
303(d) List
(Inventory
and List). Requirements for the Inventory and List are
codified in the federal Clean Water Act, Sections 305(b)
and 303(d). Further requirements are set out instate law
in Title 30 of the Texas Administrative Code (30 TAC),
and in rules and guidance established by the TCEQ [36].
Discharges to surface water designated as Waters of the
State must meet Texas Surface Water Quality Standards (TSWQS
) as contained in TAC Chapter 307.Without a specific
stream or amount of discharge set, it is difficult to
outline all necessary regulations one must follow.
Figure 11 shows the location of impaired streams with
O&G sites nearby. With proper treatment and regulatory
approval, one of the uses of fresh water from
desalination would be to augment stream flow. More
detailed maps at higher resolution are given in Appendix
2 for each Regional Water Planning District.
The permitting process, done through the TCEQ Water
Quality Division, is conditional on two key variables,
the receiving stream ambient quality and the volume of
the discharge. The TSWQS identify individual water
quality standards for each stream in the State, and
these standards are based on the use category a
particular stream is assigned. A discharge, once
dilution has occurred, must not hinder the water quality
standards set for the receiving stream.
Most
notable for brine, TCEQ Guidance Document RG-194,
Procedures to
Implement the Texas Water Quality Standards,
provides a section entitled, “Screening Procedures and
Permit Limits for Total Dissolved Solids”. This document
states, “Concentrations and relative ratios of dissolved
minerals such as chloride and sulfate that compose total
dissolved solids (TDS) will be maintained to protect
existing and attainable uses”. The screening procedure
is applied to all domestic dischargers with an average
permitted flow of 1 million gallons per day (MGD), all
industrial majors, and all industrial minors that
discharge process water. The screening procedure is
divided into categories based on the type of receiving
stream: intermittent stream, perennial stream,
intermittent stream within three miles of a perennial
stream or intermittent stream with perennial pools,
lake, and bay or wide tidal river. The equations used
take the following into consideration:
·
TDS
criterion of the receiving stream (as defined in the
TSWQS)
·
Harmonic mean flow of the receiving stream
·
Effluent flow volume
·
Effluent TDS concentration
·
Effluent concentration at the edge of the human health
mixing zone
For
discharges to freshwater, a screening procedure is used
to determine whether a total dissolved solids (TDS)
permit limit or further study of the receiving water is
required. If screening demonstrates elevated levels of
TDS, then appropriate permit limits are calculated.
Figure 11 shows an
overlay of BPW production near surface waterways with
impaired quality. Texas Water Planning Districts are
shown in various colors (from TCEQ). Impaired surface
waters are from U.S. Corp of Engineers. Detailed maps
for each Water Planning District in the state are
included in Appendix 2 and show the impaired waterways
juxtaposed with oil fields producing brine of less than
10,000 ppm tds.
Livestock Uses
Another potential use
of the brine-produced water is livestock drinking water.
There are very little, if any, regulations to follow
here. If the owner of the livestock is amenable to using
a water supply, he is allowed to do so. A typical rule
of thumb, though, is a TDS limit of 6,000 mg/L for this
purpose. This is the TDS concentration TCEQ employees
use when gauging if a particular stream is suitable for
livestock use.
Irrigation
Necessary treatment
levels of water to be used for crop irrigation is driven
by the salt tolerance of the crop or landscape. TCEQ
Rules, TAC Chapter 309, Subchapter C (Land Disposal of
Sewage Effluent) provides the following table regarding
crops.
Table 3. Salt Tolerance of Various Crop Plants
|
Relatively
Nontolerant |
Moderately
Tolerant |
Relatively
Salt Tolerant |
Highly Salt
Tolerant |
|
TDS:
1,280 mg/L to 2,560 mg/L |
TDS:
2,560 mg/L to 4,800 mg/L |
TDS:
4,800 mg/L to 6,400 mg/L |
TDS:
6,400 mg/L to 9,600 mg/L |
|
Field Crops:
Field bean
Cowpeas Corn (field) |
Field Crops:
Sorghum (grain)
Rye (grain)
Castorbean
Soybean |
Field Crops:
Cotton
Sugar beet
Wheat (grain)
Oats (grain)
Rice |
Field Crops:
Barley (grain)
Rape |
|
Forage Crops:
White clover
Alsike clover
Red clover
Ladino clover
Crimson clover
Rose clover
Burnet clover |
Forage Crops:
Tall fescue
Meadow fescue
Orchard-grass
Millet
Sour clover
Birdsfoot trefoil |
Forage Crops:
Wheat-grasses
Sudan grass
Sweetclover
Alfalfa
Ryegrass
Rye (hay)
Wheat (hay)
Oats (hay) |
Forage Crops:
Alkali sacaton
Bermuda grass
Barley (hay)
Rhodesgrass
Blue grama
Panic grass |
|
|
Information received from the Texas A&M Soil and Crop
Sciences department provided the following information
on salinity tolerance of turf grass:
|
Table 4.
Salt Tolerance of Various Grass
Species
|
|
Common Name |
Threshold TDS1 |
50% Growth2 |
|
Bermudagrass |
Less than 960 |
8,800 |
|
Creeping Bentgrass |
0 to 1,920 |
- |
|
Kentucky Bluegrass |
0 to 1,920 |
1,920 to 2,560 |
|
Perennial Ryegrass |
1,920 to 8,000 |
6,400 to 8,000 |
|
Seashore Papsalum |
Less than 960 |
14,400 |
|
St. Augustinegrass |
Less than 960 |
18,400 |
|
1. TDS level at which the grass begins to slow
growth due to salts.
2. TDS level at which growth is slowed to 50%
of that in salt free environment. |
Additionally, when irrigating with something considered
reclaimed water, care must be taken regarding the
potential for runoff to waters of the state. This can be
avoided with the use of modern management practices.
Aquifer Recharge
Aquifer Storage and Recovery (ASR) refers to the storage
or banking of fresh water in aquifers [40], and is an
effective way to manage water resources for irrigation,
ecosystem preservation and restoration, and drinking
water supply. ASR has a very high potential for use in
conjunction with PWDS. ASR facilities have been used in
the United States for over 30 years, those in Florida
becoming operational in 1983. Currently, there are seven
ASR facilities operating in Florida and at least twelve
undergoing operational testing. The facilities are being
used to inject and recover treated and untreated
groundwater, partially treated surface water, and
reclaimed wastewater. Some of the issues these pilots
are trying to resolve include are source water quality,
regional changes in aquifer flow and pressure,
target storage volume (TSV)
efficiency,
and
water quality changes.
Use of treated brine
for aquifer recharge could increase groundwater
availability. However, if the water is to be stored in a
potable aquifer zone, the water must be treated to
drinking water standards. Therefore, the section above
titled “Potable Uses” would apply. There is also
potential for the recharge of non-potable aquifer zones,
however, the potential for this to be beneficial is low.
One
potential attraction for aquifer recharge is that it
could be used for water rights transfer from party to
party. Such offsets are accepted in the Columbia River
Basin where a one-to one- replacement of fresh water is
required for permits to be issued for new fresh water
usage (26, 43).
Barriers to Adoption
The barriers to adoption of desalination of waste water,
brackish ground water and oil field produced brine
include political issues, community perception issues,
and technical issues. The Governor and the TWDB have
provided leadership for the State in developing
desalination programs in Texas. However, lack of public
funding, environmental, and regulatory issues related to
desalination of produced water (and other inland saline
waters) inhibit technology advancement of this resource.
Public perception and acceptance of the advantages of RO
desalination is unclear. Cost reduction advancements in
technology are slowed by a lack of a clear “path to
market” of new products and processes. Supplemental
state government funding for demonstration projects
(both sea water desalination and inland BGW
desalination) is lacking. With these issues affecting
the market for commercial development, it is clear that
a more concerted effort is needed to develop new water
resources from desalination, address conveyance issues
associated with water transfer, and be prepared to meet
the demand for the new resource if it were to be made
available. Some selected issues are discussed below.
The Texas Commission on Environmental Quality has been
working with other state agencies to streamline
regulations for the permitting process for disposal in
deep-underground injection wells of brine produced by
desalination operations. Applicants for permits to
dispose of brine from desalination in injection wells
must meet the current requirements for disposing of
hazardous waste in Class I injection wells, including
brine from desalination if it is classified as a waste
material from “either industrial or municipal
facilities”. Since injection wells have been used for
disposal of salt water associated with oil and gas
operations for almost a century, (as Class 2wells), it
is hoped that new cooperative efforts in desalination
will allow deep injection wells into oil and gas fields
for brine byproduct use in enhanced oil recovery
operations. Recent private meetings between TCEQ and the
TRC may have removed the roadblock.
Local issues that communities would identify as barriers
include the perception that desalinated produced water
is not pure enough for consumption by humans or
livestock and that there might be environmental
drawbacks to its use for plants, range, and habitat
sustainability. It is suggested however that advanced
technology and an improved regulatory climate will
increase the likelihood of adoption of PWDS by water use
groups in the state.
General Regulatory
Requirements
Desalination of sea water and brackish ground water and
subsequent use by municipalities would be regulated
through NPDES permitting through TCEA [38]. Ramirez and
Lee [39] describe the Texas TPDES permitting process,
including the Clean Water Act requiring every industrial
or municipal facility that directly discharges
pollutants into streams, lakes or the ocean to have a
wastewater discharge permit.
In the context
of a seawater desalination facility, the TPDES permit
application process would serve to ensure that
discharges of brine concentrate will not have
significant adverse effects on the receiving waters.
Despite the delegation of NPDES permitting authority to
the State of Texas, EPA continues to exert influence
over coastal activities. The Submerged Lands Act of 195394
gave coastal
states title to "lands beneath navigable waters,"
and granted
state jurisdiction over coastal waters for the
"territorial sea."
However, the
federal government, in the Submerged Lands Act, also
retained "all its navigational servitude and rights in
and power of regulation and control of said lands and
navigable waters for the constitutional purposes of
commerce, navigation, national defense, and
international affairs."
Because of this,
the federal government still has the ultimate authority
to regulate activities involving discharges into coastal
areas. The United States Supreme Court has consistently
upheld the federal government's right to regulate
coastal activities.
Because of this
and provisions of the Clean Water Act, TCEQ must provide
EPA with a copy of each TPDES permit it issues, and EPA
may object to any such permit issued by TCEQ.
EPA also
continues to have the authority to enforce any permit
violations against any discharger.
Moreover, a
TPDES permit only lasts for a maximum of five years
(although it could be less), and EPA has the right to
review each permit renewal application at the end of its
term.101
There are
numerous other agencies that may be provided a draft
TPDES permit for review depending on the nature and
location of the discharge.
A
TPDES permit incorporates the general requirements of
the Clean Water Act, Code of Federal Regulations, Texas
Water Code, and Texas Administrative Code into permit
conditions specific to a particular facility’s
operations.103
When the TCEQ
Wastewater Permits Section drafts a particular
facility’s permit, the most influential source of
regulations are the Texas Surface Water Quality
Standards (“TSWQS”) contained in Chapter 307 of Title 30
of the Texas Administrative Code [22,23]
The specific
TSWQS that would be most relevant to the permitting of a
seawater desalination facility would be aesthetics,
temperature, salinity and toxicity.105
A TPDES permit
will typically contain limitations on the amount of
pollutants that can be discharged, with those
limitations based on technology-based standards or water
quality based standards.106
Technology-based
standards are traditionally organized by EPA-classified
categories of industries. However, EPA has not yet
created an industrial category for desalination, so
there are no industry-wide technology-based standards.
Therefore, effluent limits in a TPDES permit for a
seawater desalination facility will be subject to
separate issues.
The Ground Water Protection Council (http://www.gwpc.org0
and its advisors are addressing this issue. Recently
Veil [43] stated “In previous informal discussions with
several state underground injection control (UIC)
agencies and EPA’s UIC program staff, four possible
injection scenarios were identified, and the regulators
offered opinions on how injected concentrate might be
regulated (Table 6). The scenarios include two types of
source water (brackish ground water and produced water)
and two injection strategies (inject for enhanced oil
recovery or inject for disposal).
Table 6. Injection
Well Class for Concentrate Injection under Different
Scenarios
|
Source of Raw Water |
Injected for Enhanced Recovery |
Injected for Disposal |
|
Produced Water |
Class II |
Class II |
|
Brackish/Saline Ground Water |
Class II |
Not determined – regulators need additional data |
The
agency representatives indicated that if the source
water is produced water, disposal of the resulting
concentrate could be made to a Class II well regardless
of the injection strategy. They also noted that if
brackish water concentrate is injected for enhanced oil
recovery, the resulting well will also be a Class II
well. However, they did not concur on the fourth
combination – brackish ground water as source water and
disposal of the concentrate via injection. Some of the
regulators suggested that they would need to know the
chemical constituents present in the concentrate and
their levels. Based on that information, they might
require Class I or Class V wells or pursue some other
option.”
Source water quality is of great concern, particularly
when the end use will be potable. Any system providing
drinking water to more than 25 people must meet
restrictions on the amount of pollutants allowed in the
drinking water system. Due to the concern regarding
contaminants that exist in the source water, as well as
potential precipitation, fouling, and scaling of the
membranes, a study conducted for the Nueces River
Authority suggested source waters high in salt content
be tested for 27 different parameters prior to the
planning of a treatment facility [24].
Because the rules regarding this type of water source
are not clearly defined, regulatory staff suggested
that, once a project is defined, an official letter be
sent to the State to inquire about all relevant
regulations and permits necessary.
