Removing Unwanted Substances from Fracking Waste
PART ONE — CONTENT OF WASTEWATER
The composition of wastewater differs dependent upon the fluids used for extraction, but they all have the same types of materials. Three types of cleaning wastewater include removing oil with sponges, removing boron with electrocoagulation and removing salt with Forward Osmosis (FO).
- Managing and cleansing flowback fluids constitute a significant environmental challenge for fracking operations. The waters can vary in salinity, contain a variety of salts, and be laden with oils, sand, and fracking chemicals. This cocktail of contaminants makes treatment options challenging to implement.
- The flowback water from the fracking process is a blend of the numerous additives used for fracking returning to the surface along with the naturally occurring formulation brine. The chemistry of wastewater from fracking varies, and changes in acidity.
- Oil is only a small part of the equation in remediating wastewater from fracking. It is typically high saline, and can have arsenic, zinc, lead or radioactive materials in it.
- According to an expert in the field, there are some modular treatment trains, where you take out one pollutant or several pollutants at a time using different technologies.
- A table from the EPA which breaks down the materials in fracking wastewater is available here.
Current Cleaning Technologies
Removing Oil with Sponges
- Nanoporous absorbents like activated carbon, zeolites, and mesoporous silica can remove organic pollutants from wastewater by adsorption with 90-99% removal efficiency.
- However, because of the clogging of small pores, these materials have a low pollutant uptake, and consume high energy for the release of the adsorbed pollutants. Furthermore, their nanometer-sized pores cannot adsorb micrometer-sized crude oil droplets.
- Because of their larger micrometer-size pores, sponges could allow higher oil uptake and subsequent easy release. While superwetting sponges have been investigated for oil-water separation for applications such as surface oil removal, the use of sponges for oil microdroplet adsorption from wastewater is only recently been researched.
- With the right type of coating, the properties of the sponge surface can be customized for complex crude oil microdroplet adsorption over a wide range of pH conditions.
- A critical challenge for adsorption of crude oil microdroplets is their complex wetting alteration behavior. Crude oil microdroplets adsorb hydrogen or hydroxyl ions from the surrounding water depending on the pH.
- For most solid surfaces, this results in ineffective oil microdroplet attachment at some pH conditions.
- A research team at Imperial College London has developed a coating that alters the sponge’s texture, chemistry, and charge. Among other things, this coating contains particles with hairs that act like tiny fishing rods for oil droplets.
- The coated sponge was put to the test in water with four different levels of acidity, and while it worked at varying speeds, it never took more than three hours to soak up 95 to 99 percent of the oil. The team has also developed a solvent that extracts the oil so that the sponge can be reused.
Removing Boron with Electrocoagulation
- Hydrolyzing metal ions such as aluminum and iron can be employed as coagulants for on-site treatment of oilfield wastewaters since they are highly effective in removing suspended colloids and particles.
- To this end, aluminum electrocoagulation has been shown to well-remove turbidity, and evidence suggests it can also remove boron when it is present in relatively low concentrations.
- Boron has also proved to be successfully removed from a variety of wastewater streams using biosorbents, ion exchange, and precipitation/adsorption.
- These investigations focused mainly on optimizing process parameters to maximize boron removal, including sorption kinetics and thermodynamics, in many instances using synthetic water and generating only limited information on sorption mechanisms.
- It is known that boron adsorption onto iron and aluminum hydroxides during electrocoagulation of different waste streams is endothermic (absorbs heat). It also decreases in the presence of some negatively charged atoms (anions). Associated geometry, conformation, and complexation mechanisms during actual flow back water treatment still need to be established.
- Spectroscopic evidence for trigonal boron uptakes during aluminum electrocoagulation of flowback water has been researched.
- The research team believes that boron removal mechanisms during frack water treatment using the other common coagulant, iron, has not yet been investigated.
- Electrocoagulation is still an emerging and energy-intensive technology that needs additional on-site testing for cost-efficient field implementation.
- On the other hand, conventional chemical coagulation is widely implemented as one of the first steps in most real-world clarification processes. It has proven to remove turbidity from a variety of industrial wastewater streams successfully.
Removing Salt — Forward Osmosis (FO)
- Technologies, such as mechanical vapor compression, reverse osmosis, membrane distillation, and forward osmosis, have all been investigated to desalinate fracking wastewater.
- Mechanical vapor compression and reverse osmosis are energy-intensive processes, and the composition of fracking wastewater creates distinct challenges for membrane distillation (most notably fouling and wetting).
- Forward osmosis has also been proposed to treat fracking wastewater, with possible economic advantages over more conventional processes.
- The primary concept underlying this process is the osmotic transport of water (water flux) through a semi-permeable membrane from a low salinity feed solution to a high salinity draw solution.
- A downstream separator integrated for the recovery of draw solutions is crucial for the successful implementation of the FO process.
- Reverse draw solute flux generates concentration polarization, which is why low water flux is achieved in FO.
- Moreover, in long-term operation, the draw solution will be significantly lost due to reverse draw solute flux.
- This loss of draw solute will require the addition of more draw solute to the draw side to maintain a constant concentration, which will increase the cost of draw solution.
- In the search for effective organic draw solutes for the desalination of highly saline fracking wastewaters via FO, research reports four organic draw solutes (potassium acetate, potassium formate, sodium glycolate and sodium propionate) with high solubility, high osmotic pressure, feasibility for recovery by membrane distillation, and very low specific reverse salt flux.
PART TWO — WASTEWATER REGULATIONS
- The regulations included below for Alaska, Colorado, Louisiana, and North Dakota have been repeated verbatim to ensure accuracy.
- Full regulation concerning technical requirements for oil field waste pits is found primarily in the Alaska Administrative Code, Title 18, Chapter 60, Article 4, as regulated by the Alaska Department of Environmental Conservation (ADEC).
- Additional regulation can be found in the Alaska Administrative Code, Title 20, Chapter 25, Article 1 and Alaska Administrative Code, Title 20, Chapter 25, Article 5, as regulated by the Alaska Oil and Gas Conservation Commission (AOGCC).
- 18 AAC 60.430 details the criteria that must be met in the management of drilling waste. This information includes the submittal of a storage plan that must be submitted and approved by ADEC at least 30 days before the beginning of operations.
- 18 AAC 60.430 details design criteria of storage facilities, which includes:
- Sizing to contain all waste and anticipated precipitation with a minimum of 2’ freeboard.
- Prohibition of leaking.
- Liner material which meets minimum acceptable standards.
- Account for the high water table, surface water, permafrost, and proximity to populations.
- Appropriate closure requirements.
- 18 AAC 60.430 details operating standards, which include analysis of surface water and subsurface thermal monitoring in areas of permafrost.
- 18 AAC 60.430 details closure requirements, which provide for a final site inspection with written notification of inspection, removal of all pumpable fluid, construction of a cap with minimum design requirements, and revegetate cap.
- 18 AAC 60.440 details corrective action plans that ADEC may deem necessary following the closure of the reserve pit.
- 20 AAC 25.025 details the bonding requirements that are necessary for any entity proposing to drill a well. This bonding is required for the issuance of a drilling permit.
- 20 AAC 25.033 details requirements for properties and equipment regarding reserve pits and drilling fluids.
- 20 AAC 25.025 details requirements for construction of reserve pits, including details for an impervious confining surface and preventing hazard to freshwater sources upon closure of operations.
- 20 AAC 25.172 details the removal of all materials and equipment from the site upon cessation of activities and the grading and filling of all pits and the site to a natural state or approved state by the AOGCC.
- Regulations for oil and natural gas exploration and development wastes are regulated by the Colorado Oil and Gas Conservation Commission.
- Regulations can be found in the Rules and Regulations of the Commission, Series 100-1200.
- Financial assurance requirements are detailed in Series 700 of the Rules and Regulations. They include bonding requirements, plugging and abandonment requirements, requirements for centralized waste management facilities, and details for the Oil and Gas Conservation and Environmental Response Fund.
- Exploration and production waste management regulations are found in Series 900 of the Rules and Regulations.
- General pit regulations can be found in Section 902 of the rules and regulations, including minimum freeboard of 2’, prohibition and removal of hydrocarbons from pits, wildlife intrusion protection such as fencing, the prohibition of construction of unlined pits constructed on fill material, and multiple well-use regulations.
- Section 903 specifies that the Commission reserves the right to prior approval of pit design and construction and, in what instances, prior approval is required of the pit operator.
- Section 904 details pit liner requirements, which include the pit types requiring liner, the material to be used in a liner, the minimum thickness of liners, foundations of liners, allowable alternative liner design, and details regarding centralized waste management facility liners.
- Section 905 details requirements for closure of pits, which includes evacuation of materials and proper disposal of pit contents, liner disposal, and reclamation of the pits, per Series 1000 of the rules and regulations.
- Section 906 details the requirements for notification, prevention, and remediation and releases of E&P wastes and produced waters.
- Section 907 details the proper management of E&P wastes, including the storage, handling, transportation, treatment, and disposal of waste, including drilling fluids and produced waters.
- Section 909 details the closure requirements for pits other than drilling pits specified in Section 903, which were special waste pits.
- Regarding tanks, the Rules and Regulations sporadically address regulations regarding tanks throughout Series 900, including the requirements for secondary containment of tanks, repair of leaking tanks, and requirements for the disposal of tank bottoms.
- The regulation concerning technical requirements for oil field waste pits is found primarily in Title 43, Part XIX, Chapter 3 of the Louisiana Administrative Code, namely “Pollution Control — Onsite Storage, Treatment and Disposal of Exploration and Production Waste (E&P Waste) Generated from the Drilling and Production of Oil and Gas Wells (Oilfield Pit Regulations).”
- With limited exception all produced water pits, onshore terminal pits, and washout pits must meet the liner requirements outlined in Rule §307.
- The limited exception includes the permitting by the Louisiana Water Discharge Permit System permit as outlined in §303.K.8 or a maximum threshold of pit size and capacity, as described in section §303.M.
- Rule §307 requires minimum technical design standards for various classifications of pits, defined in the §303 General Requirements section of the rule. These requirements include:
- Minimum liner design specification
- Minimum freeboard requirement
- Operating procedures
- The right, on behalf of the Office of Conservation, Department of Natural Resources, to deem it necessary for any pit to develop a plan to prevent the pollution of a groundwater aquifer or underground source of drinking water. The rule also allows the Office of Conservation to employ drainage and collection requirements, monitoring programs, or other methods of prevention and detection of contamination.
- Certain criteria are met for the closure of pits following the completion of their designated life. Pits may be closed, if approved by the Department of Conservation, by the methods of burial, solidification, onsite land development, or other approved techniques. Part C details the various chemical constituents the waste pit must be tested for before closure.
- Financial Assurance and Security requirements are found in LAC 45, Part XIX, Chapter 1, Rule §104. These requirements include the provision of financial security before issuance of permits, security forms and requirements, and security release criteria.
- LAC 45, Part XIX, Chapter 1, Rule §115 provides the requirements for all exploration and production (E&P) waste fluid storage tanks. Included in these requirements are containment by a dike or retaining wall, placement on an impervious surface if sited in wetlands, and removal of all fire hazards from within the immediate vicinity of the tank battery.
- Regulations concerning technical requirements for waste pits and tanks are found in Title 43, Article 43-02, Chapter43-02-03 of the North Dakota Administrative Code (NDAC), as regulated by the Oil and Gas Division of the North Dakota Industrial Commission.
- 43-02-03-15 details bond conditions required for financial assurance, including bonding requirements before commencement of drilling operations, alternate forms of financial security, and bond amounts and limitations.
- 43-02-03-15 details permitting requirements before any person can commence drilling activities. These requirements include the obtaining of a bond, submittal of an accurate plat showing the location of the drilling activities, the submittal of the proposed mud program, and the provision of any information at the request of the director.
- 43-02-03-19 describes the pit design and storage of muds and fluids in pits in addition to the disposal of waste. This section includes site construction requirements, fencing, and screening of pits, closure of pits, disposal of waste requirements, and special treatment for the waste of shallow wells. This section also identifies prohibited uses and authorized uses for drilling pits, including technical criteria of those pits. This section also includes limited location restriction criteria.
- 43-02-03-30 covers protection against leaks or fires, including specific notification requirements in the event of leakage or fire, and leak and spill cleanup requirements.
- 43-02-03-48 covers the requirements of central production facilities and commingling of production, including the location of all tanks.
- 43-02-03-50 covers requirements for tank cleaning permits and wastes, including the prior approval is not required to remove tank bottom waste for tanks not used for the storage or sale of crude oil.
- 43-02-03-53 describes saltwater handling, including storage and disposal, to avoid pollution of freshwater supplies, including technical requirements for surface facilities such as dike construction requirements and liner and secondary containment requirements.