The project goal was to develop and fabricate a bentonite clay membrane (cheap and readily available) and a precipitator unit with either tubular ceramic or clay membranes to provide a water treatment system that would process produced water into reusable water, reducing current disposal costs by as much as 90%.

Program
This project was selected in response to DOE's Oil Exploration and Production solicitation DE-PS26-01NT41048, focus area Effective Environmental Protection. The goal of the program was to reduce compliance costs and improve environmental performance by providing lower-cost technologies, and/or provide sound scientific basis for cost-effective, risk-based regulatory decisions.

New Mexico Institute of Mining and Technology
Socorro, NM

Disposal of large amounts of produced water is expensive for the oil and gas industry and potentially dangerous to the environment. RO has been shown in some studies to be potentially feasible for decontamination of produced waters, but costs would be prohibitive and existing technology inadequate. Researchers proposed to develop an inexpensive RO membrane that needs little or no pretreatment, which would make RO desalination more cost-effective.

Project Results
Researchers developed some promising synthetic clay membranes, although the original betonite membranes did not prove successful for salt rejection. The new membranes developed are being tested further for potential use in gas separation.

Benefits
The development of a modified reverse osmosis (RO) system such as that proposed by the project would be a significant breakthrough in the field of water treatment by decreasing operating costs through the use of a cheap membrane such as the proposed bentonite clay membrane. Potential uses of the treated and purified water would be significant.

Project Summary
The project covered the following tasks:

• Task I: Bench-scale testing and prototype developing. Bench-scale experiments on clay and ceramic membranes were to lead to numerical design criteria for membranes to be used to develop a prototype of a modified RO system.
• Task II: Field demonstration of trailer-mounted RO unit consisting of a prefilter, one or more RO modules, and a tubular membrane precipitation unit. The originally proposed Task II could not be delivered due to failure of salt rejection rates using compacted bentonite membranes.
• New Task II: The bench-scale test with the presence of organics, continued development of the spiral-wound module, and development of the fluidized bioreactor module to simultaneously remove organic and salt (tested with a ceramic or clay membrane), which will be utilized in removing bacteria. Several good results were obtained:
  • Synthetic bentonite membranes were developed whose Na+ rejection rate was com-prable to the compacted membranes tested in the first part of this project. However, their permability to water was significantly higher than that of the compacted thick membranes, which made them unsuitable for steady salt rejection during operations. Fortunately, they are very well adapted to test gas/gas separations.
  • Synthetic zeolite membranes. Unlike the bentonite clay membranes, the zeolite mem-branes maintained stability and high salt rejection rate even for a highly saline solution. Actual produced brines from gas and oil fields then were tested. Preliminary results were favorable for salt rejection and showed that the dissolved organics-mainly hydrocarbons-did not affect the salt rejection (though rejection of organics was inconclusive).
  • Methane conversion. An -alumina-supported Pt-Co/Na Y catalytic zeolite membrane was developed and demonstrated for overcoming the two-step limitation of nonoxidation meth-ane (CH4) conversion to higher hydrocarbons (C2+) and hydrogen (H2).

The project is complete. A new project, Treating Coalbed Methane Produced Water for Beneficial Use by MFI Zeolite Membranes (DE-FC26-04NT15548), carries on the studies begun in this project. The new project will develop a new technology of reverse osmosis through molecular sieve zeolite membranes to efficiently treat for beneficial use coalbed natural gas produced water with high total dissolved solids. The project will include extensive fundamental investigation of the RO mechanisms on zeolite membranes. The understanding gained will be used to improve zeolite membranes, and finally, to subject these improved membranes to long-term (>1,500 hours) RO operation to study their stability and to collect experimental data for technical and economic evaluations of the new technology.

$916,000

$285,642 (24% of total)

NETL - John Ford (john.ford@netl.doe.gov or 918-699-2061)
NMIMT - Robert Lee (prrc@prrc.nmy.edu or 505-835-5142)

Publications
Lee, R., and Dong, J., Modified Reverse Osmosis System for Treatment of Produced Waters, final technical progress report, September 1, 2000-February 28, 2004, U.S. DOE, Contract No. DE-FC26-00BC15326, June 2004.

Li, L., Dong, J., and Lee, R., Preparation of ?-alumina-supported mesoporous bentonite mem-branes for reverse osmosis desalination of aqueous solutions, J. Colloid and Interface Sci., 273 (2004) 540-546.

Li, L., Dong, J., Nenoff, T., and Lee, R.: Reverse osmosis of ionic aqueous solutions on a MFI zeolite membrane, Desalination, Nov. 5, 2004, V. 170, No. 3, pp. 209-316.

Li, L., Dong, J., Nenoff, T., and Lee, R., Desalination by Reverse Osmosis Using MFI Zeolite Membranes, J. Membrane Sci., Nov. 1, 2004, V. 243, No.1-2, pp. 401-404.