Research Interest

My major research interest is membrane technology for water desalination, reclamation, and reuse. Membrane process is an emerging and the most promising technology for seawater desalination and advanced water purification nowadays and possibly in the foreseeable future. One of the widely used membrane processes, reverse osmosis (RO) can produce high quality water from the nontraditional water sources (seawater, brackish water, and treated wastewater) with a competitive edge to most conventional treatment processes. Studies also show that RO membranes can be a good barrier for the emerging organic pollutants, such as DBPs (disinfection by products) and EDCs (endocrine disrupting chemicals).

I have been working in this field for 20 years and the research projects that I have conducted cover a wide scope of membrane technology, including fundamental theories of crossflow membrane processes, fouling characterization and mitigation, process optimization and energy reduction. I will continue to do research in the field of membrane desalination in my academic career. At this moment and in a near future, I will focus my research efforts in following 4 areas.

1. Membrane Fouling Characterization and Mitigation

Membrane fouling is one of the most serious problems or obstacles for more effective use of the technology in water desalination and purification. The cost to control membrane fouling is a major component of the total cost of desalination. The measures for membrane fouling control include pretreatment, membrane cleaning, and membrane replacement. My research plan in this area will start with the development of a more effective method to characterize the type and strength of fouling of the feedwater. For this purpose, the local water sources that can be current or potential feed water to RO processes will be tested on the batch- and/or pilot-scale RO devices for fouling characterization, which means the determination of the fouling rate and foulant identification. Then various pre-treatment methods will be tested and evaluated for their effectiveness in fouling mitigation. Theoretical development of this research program also includes the advanced modeling and simulation methods for fouling development under given operating conditions (feed water quality, average permeate flux, process recovery, and pretreatment options). With the help of theoretical modeling tools, most effective and economic fouling control strategy can be development.

2. Process Optimization and Energy Reduction of RO Desalination

RO desalination is an energy intensive process. Energy consumption contributes a major portion of the total cost of water desalination and can reach as high as more than 50% of the total cost of RO processes. Since the emergence of the technology in 1960s, there have been consistent efforts to reduce energy consumption in RO desalination in order to make it a more affordable means of water supply. However, energy consumption still remains as the largest cost component in RO seawater desalination and offers the greatest potential for further cost reduction. In this research area, I will first study the energy usage in the most widely used RO membrane configuration: 6-8 membrane elements are placed in series in long pressure

vessels, and pressure vessels are arranged in multi-stage of Christmas-tree structure. Mathematical model will be developed for RO systems of such configurations. Then the mathematical model will be used in the process optimization to minimize the energy consumption or the total cost of RO desalination. Furthermore, new configurations of the RO desalination systems (e.g., short pressure vessels or parallel membrane elements arrangement) will be investigated to improve the energy efficiency in water desalination.

3.Membrane Desalination for Small-scale Applications

There is a need for small-scale desalination systems (200 m3/d or smaller) for seawater and brackish groundwater to supply communities and settlements scattered in the vast rural areas, where fresh water resources are either unavailable or have been fully allocated. Conventional RO technology cannot adequately serve the need for small-scale desalination because the lower recovery and lower energy efficiency typically associated with small-scale RO systems lead to much higher cost per treated water volume than large-scale desalination. The fundamental reason for the low recovery and low energy efficiency of small-scale RO systems is the insufficient number of membrane elements to be to form the structures that are commonly used in the large-scale RO systems to optimize the recovery and minimize energy. My research plan in this area is to study an innovative RO configuration that is featured with a parallel arrangement of membrane elements coupled with closed concentration circulation. The so-called closed circuit desalination RO (CCDRO) system completely eliminates energy waste associated with concentrate discharge because the concentrate stream is unpressurized at discharge. With the closed concentrate circulation, the CCDRO can achieve high water recoveries that are no longer dependent on the number of membrane elements. These two features of he CCDRO systems can significantly improve the overall performance, and especially energy efficiency, of small-scale RO desalinations. The tradeoff between the high recovery/high energy efficiency and more expensive RO system will be investigated and assessed for different scenarios.

4. Wastewater Reclamation and Reuse

Wastewater can be an important and reliable water source in the arid and semiarid regions with the appropriate technology. Due the high levels of impurities are often found in the wastewater, a single membrane process alone is usually insufficient either technically or economically to treat the wastewater up to the standards for reclamation and reuse. The integrated membrane processes (e.g., membrane bioreactor + RO membrane) may provide a better solution than the conventional treatment technologies for of wastewater reclamation and reuse. The reclaimed water can be used for industrial water and groundwater recharge and save the fresh water for potable use. The cost analysis of wastewater reclamation as compared to the cost of increased new desalination capacity can be an interesting topic to study.