Grantee Research Project Results
Final Report: Solar-Energy-Combined Desalination Systems
EPA Grant Number: SU840147Title: Solar-Energy-Combined Desalination Systems
Investigators: Kim, Seokjhin , Lampert, David , McIlroy, Dave , Aichele, Clint , Ritchie, Liesel , Mahmodi, Diako , Austin, Aaron , Bias, Alex
Institution: Oklahoma State University
EPA Project Officer: Page, Angela
Project Period: November 2, 2020 through November 1, 2021
Project Amount: $25,000
RFA: P3 Awards: A National Student Design Competition Focusing on People, Prosperity and the Planet (2020) RFA Text | Recipients Lists
Research Category: P3 Awards , P3 Challenge Area - Safe and Sustainable Water Resources
Objective:
The Water for 2060 Act specifically recommends increasing the usage of marginal quality waters. Some of the main potential sources of marginal quality waters are brackish and saline aquifers, which we refer to collectively as brackish groundwater. Brackish groundwater (BGW), with total dissolved solids (TDS) concentrations between 1,000 mg/L and 10,000 mg/L, in the mid-continent represents a vast resource that could be used as an alternative source of water during droughts. The petroleum industry has become increasingly interested in the use of brackish groundwater for hydraulic fracturing operations, recognizing that it is politically expedient to preserve and protect fresh water resources for agriculture and public supply. The Blaine, Garber-Wellington, and Rush Springs aquifers, which are located in the Western and Central portions of the state where irrigation demand is high, are currently of limited value due to their brackish nature. They could be used for public supply, rural water systems, and agriculture during periods of drought in Western Oklahoma if economical treatment technologies were available for desalination.
Future economic development in the Southern Great Plains to meet demands for energy and agriculture will require new sources of water. Brackish groundwater could be a valuable resource for the energy and agricultural sectors during periods of limited water availability, if more economical approaches to improve water quality existed. There is a critical need for new methods to treat this alternative water supply. Addressing this need will require a comprehensive, multidisciplinary approach. The excessive salinity of brackish groundwater makes its reuse a particularly complex technical challenge. However, brackish groundwater could augment freshwater supplies during droughts if technologies could be developed for treatment to levels needed for irrigation. Brackish groundwaters have arguably more potential for reuse due to their lower salinity, although desalination costs are currently too high to justify their use for irrigation.
Treatment of brackish groundwater typically requires a series of pretreatment (e.g., flocculation, cartridge filtration, settling, backwashing, and chemical treatment) and post-treatment processes to the TDS level and RO membrane fouling. As a pretreatment step, thermal processes (using heat to evaporate water) can be effective, but they are capital intensive and require high energy costs to heat air. Solar evaporation can be the most economically suitable and cost-efficient approach to minimize high operating costs. As a post-treatment step to remove organic substances including volatile organic compounds (VOCs), numerous studies have been performed on applications of polymeric membranes for water treatment applications. Ceramic membranes offer a chemically robust treatment option by reducing replacement and cleaning costs relative to current polymer membrane technology. Very little is known about systematic approaches using ceramic membrane-based water treatment to achieve high water permeability and high organics rejection of brackish groundwater treatment. There is a clear need for further characterization of the efficacy of ceramic membranes for brackish groundwater treatment. In this research, as an innovative desalination process, energy-efficient solar-energy-combined desalination systems for treating brackish groundwater will be proposed.
The treatment of brackish groundwater presents a complex engineering problem as its composition is dependent upon local geology and requires removal of many classes of contaminants including suspended solids, naturally occurring radioactive material (NORM), dissolved solids, and hydrocarbons. The team proposes to combine a thermal desalination system with a solar energy collector as an alternative to fossil fuels. The overall goal of the proposed research is to develop novel, energy-efficient solar-energy-combined desalination systems for treating brackish groundwater to levels suitable for reuse. The primary research objectives of the proposed investigation are to:
1. Design chemical pretreatment process
2. Develop solar evaporation and condensation system
3. Synthesize ceramic membranes for organics rejection
4. Investigate public attitudes toward water reuse
Summary/Accomplishments (Outputs/Outcomes):
With the support of the EPA Phase I grant, we developed a dead-end filtration system for removing oil components from brackish groundwater. The pristine α-alumina tubular membrane with active surface area 0.162 cm2 was utilized for treating a synthetic brackish water. Synthesized brackish water was processed in the dead-end system to measure the flux, TOC and TDS. With applied pressure of 15 psi pressure, the flux through the system was measured to be 443.5 liter/m2/h (LMH). Based on this result, we plan to modify the α-alumina tubular membrane by dip-coating method. By modifying the pristine α-alumina membrane, we expect to endow it with anti-fouling properties, as well as adjust the membrane pore size to prohibit the passage of organics while enabling the passage of water molecules.
Second, we developed a high-efficiency solar evaporator system that removes solids and significantly reduces the salinity to a level that meets all EPA requirements for agricultural uses. The design criteria for the evaporator was that it be energy passive and maximize throughput. To achieve this objective, we integrated a high surface area coating consisting of 1D nanostructures (nanosprings) with a solar collector. The high surface area coating is a multipurpose coating. Our setup consists of a simple bulb housing to heat the system, where the metal parts are painted black to maximize infrared absorption from the light source, maximize energy absorption, which subsequently preheats the water before entering the evaporation zone.
To increase the evaporation rate of the solar evaporator the surface is coated with a layer of unique one-dimensional nanostructures called nanosprings. The silica nanosprings (NS) were grown on a ceramic cylinder via a modified vapor-liquid-solid method, where a detailed explanation of the process can be found in references. The NS coated cylinder is then coated with Graphite from the University of Idaho TAR (GUITAR) via atmospheric chemical vapor deposition (APCVD). GUITAR conformally coats the NS and is useful for heat retention and efficiency in the system without adding any complexity or hindrance to the process. Due to the high surface area and natural hydropholicity of NS, they are a great candidate for desalination of water. For the evaporator used in this study, the nanosprings were grown on a solid alumina cylinder and subsequently coated with GUITAR. SEM of the high surface area showed that NS chemically bound to the surface. The cylinder is secured in a glass tube with inputs and outputs on either end. Synthetic brackish water is gravity feed into the system, is evaporated and collected and its salinity tested. This system is unique in the simplicity of its design, ease of use, and having a relatively short processing time (< 2 hours per batch).
We applied 15 psi pressure to the dead-end membrane filtration system, which produced a flux of 443.5 LMH. At each step, we measured TOC and TDS before and after filtration. TOC and TDS were reduced after passing through the dead-end system by 53.9% and 0.92%, respectively. TDS was reduced by 99% after passing through the solar evaporator. The elemental compositions of the synthetic brackish water before and after using the combined filtration system are given in Table 2. The results showed no significant rejection observed after using the pristine α-alumina membrane for salt components rejection, which was expected due to larger membrane pore size (~200 nm) than salts. The major reason for using the dead-end filtration system is oil component rejection. Furthermore, after using the solar evaporation system, we could remove salt components to a level that meets all the EPA requirments for reuse, especially for agricultural purposes.
This unique technology is expected to produce an energy-saving and cost-effective solar-energy-combined desalination system for treating brackish groundwater to levels suitable for reuse. These promising results provide advancements in the technical knowledge needed to enhance the sustainability of human society on the planet. The results of our collaborative study provide important insight into the efficacy of solar evaporation and ceramic membranes for brackish groundwater management.
In addition, a business plan to developing a nano-filter polymeric membrane for environmentally cleaning targeted wastewater streams has been developed. The team (Aperion Solutions) won the $6,000 3rd place in the High Growth Graduate Division at the Love’s Entrepreneur’s Cup, 2021.
Conclusions:
The EPA Phase I study aimed to develop Solar-Energy-Combined Desalination Systems for small communities that need improved water supplies, was successfully performed, and the objectives accomplished. We ran the synthetic brackish water in the dead-end filtration-solar evaporator system. At each step, we measured TOC and TDS to evaluate the combined filtration system and evaluate its oil and salt rejection performance. TOC and TDS were successfully reduced. The results showed significant oil rejection observed with the pristine α-alumina membrane and substantial reduction in salt components after the solar evaporator.
It is important to develop water supply networks, especially in small municipalities, rural areas, tribal communities, and at the same time to improve the quality of marginal water that would be very useful across the planet. Since energy and water systems are inherently interconnected, the sustainability of each of these vital resources cannot be assessed independently. Increasing the energy efficiency will reduce the carbon footprint of desalination and help preserve the integrity of the planet’s resources for future generations of people. The EPA Phase I project results will be used to improve the performance of desalination infrastructure by optimizing the solar evaporation system and thereby increase prosperity.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 2 publications | 2 publications in selected types | All 2 journal articles |
---|
Type | Citation | ||
---|---|---|---|
|
Mahmodi G, Ronte A, Dangwal S, Wagle P, Echeverria E, Sengupta B, Vatanpour V, McIlroy D, Ramsey J, Kim S. Improving antifouling property of alumina microfiltration membranes by using atomic layer deposition technique for produced water treatment. DESALINATION 2022;523(115400). |
SU840147 (Final) |
Exit |
|
Mahmodi G, Bafti R, Boroujeni N, Pradhan S, Danwal S, Sengupta B, Vatanpour V, Sorci M, Fathizadeh M, Bikkina P, Belfort G, Yu M, Kim S. Improving cellulose acetate mixed matrix membranes by incorporating hydrophilic MIL-101(Cr)-NH2 nanoparticles for treating dye/salt solution. CHEMICAL ENGINEERING JOURNAL 2023;477(146736) |
SU840147 (Final) R835441 (Final) R835872 (Final) |
Exit |
Supplemental Keywords:
produced water, chemical pretreatment, ceramic membrane, solar evaporator, treatment technologies, energy efficiency, sustainable water managementThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.