Advancements in Water Ultrafiltration Technology

Advancements in Water Ultrafiltration Technology

Strained water resources across the world necessitate innovative ways for power plants to more efficiently use, and reuse, the water that is available. At the U.S. Department of Energy’s Argonne National Laboratory, researchers working on materials for water-energy systems have developed a suite of membrane technologies that tackle this issue at the molecular level.

Water that is used for power plants often must undergo ultrafiltration as part of its pretreatment process. The membranes used for this process are typically designed to filter particulates of about 1 nanometer (nm) to 50 nm in size. These could be anything from colloids and larger organic molecules like proteins, to viruses and bacteria, all of which can lead to problems down the line as the water makes its way through the power plant.

The membranes typically used for ultrafiltration offer considerable durability against poor water quality, are compact, and do not require the use of chemicals to clean the water. All filters, however, must address two serious problems: fouling and energy-efficiency challenges.

Fouling is the physical blocking up of the filter, much like bits of food getting caught in a kitchen sink drain. Ultrafiltration membranes prevent fouling further downstream within a power plant, but the membranes themselves inevitably become fouled. This limits the lifetime of the membrane, as the pores within it are blocked, eventually requiring the membrane to be removed and cleaned, or replaced altogether, costing valuable time and resources.

The smaller the pores get, the more energy it takes to push water through them. Commercial membranes used for ultrafiltration do not have uniform pore sizes either. There is a gamut of pore sizes within any given membrane. In order to ensure that a power plant is filtering out the necessary particulates, one has to use a membrane with a smaller average pore size than the smallest substance one is trying to filter out. The smaller pore sizes then dramatically increase the energy required to push water through the membranes.

Membrane Improvements

At Argonne, scientists have developed several membrane technologies to address these exact issues, focusing on the interface between the water and the ultrafiltration membrane. They have developed technologies for both passively and actively addressing fouling, as well as technologies for improving the energy efficiency of ultrafiltration membranes.

1. Seth Darling is director of the Institute for Molecular Engineering at Argonne and the Advanced Materials for Energy-Water Systems Center. He said “Innovating these technologies for the recycling and reuse of water is a boon for all future uses of water.” Courtesy: Argonne National Laboratory

“We’ve been able to both manipulate the material of the membrane, so things are less likely to adhere to them, and degrade what does manage to adhere,” said Seth Darling (Figure 1), director of the Institute for Molecular Engineering at Argonne (IME@Argonne) and the Advanced Materials for Energy-Water Systems Center (AMEWS), one of the U.S. Department of Energy’s Energy Frontier Research Centers.

Using atomic layer deposition (ALD), a process commonly used to coat microprocessors and other circuitry components, researchers have successfully applied different coatings to ultrafiltration membranes that directly address the issue of fouling.