New water filtration membranes worth the investment

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“New Water Filtration Membranes Worth the Investment”

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High-performance water filtration systems — needed to reduce water scarcity — can also reduce cost and energy consumption, a new analysis led by Northwestern University finds.

In the new study, researchers performed a high-level analysis of membrane filtration systems to assess the cost, energy consumption, and greenhouse gas emissions associated with desalination and wastewater treatment. The researchers specifically examined antifouling membranes, a high-performance filtration system that resists the build-up of pollutants.

Although fouling-resistant membranes may cost more to purchase, they cost less over their lifetime than cheaper, non-fouling-resistant membranes, which require frequent cleaning and need to be replaced more often. In fact, researchers found that municipal wastewater facilities can spend 43% more on antifouling membranes for wastewater treatment and up to three times more on antifouling membranes for desalination—and still maintain their baseline costs. of operation.

As aging infrastructure and climate change stress water supplies, many municipalities and researchers are exploring processes, including desalination and wastewater treatment, that can increase water availability from less conventional water sources, such as brackish water. Investing in antifouling membranes upfront can help reduce the costs of these typically expensive treatment systems.

“With increasing water scarcity, technologies like desalination are becoming more important than ever,” said Northwestern’s Jennifer Dunn, who led the work. “But there is always a trade-off between engineering performance and cost. A filtration system can have amazing performance, but if the cost is too high, then people will not use the technology. We hope that our modeling and analysis can help guide research and development.”

The study was published on August 15 in the journal ACS ES&T Engineering. It marks the first internationally published study co-authored by the US-Israel Cooperative Water-Energy Research Center (CoWERC), a global consortium of research institutions, water utilities and private companies exploring new solutions to critical challenges in the energy nexus – water. .

Dunn is an associate professor of chemical and biological engineering at Northwestern’s McCormick School of Engineering and director of the Center for Engineering Sustainability and Resilience. Sabyasachi Das and Margaret O’Connell, both members of Dunn’s lab, are co-first authors on the paper.

In membrane filtration systems, a membrane acts as a physical barrier between drinking water and contaminants. The pumps push the water through the membrane, which is filled with pores of micro, nano or even smaller sizes. The membrane traps fine particles while allowing water to flow through the pores.

Fouling occurs when contaminants accumulate on the surface of the membrane, blocking the pores. When a membrane experiences fouling, higher pressures are needed to pump the water. Eventually, however, fouling becomes so extensive that the membrane must be cleaned or even replaced entirely. The energy and costs associated with increasing water pressure, cleaning and replacement can increase the operating costs of a treatment facility.

In contrast, antifouling membranes have specialized surface chemicals that prevent the accumulation of contaminants. This leads to reduced cleaning frequency and an overall extended life of the membrane. In the study, researchers found that increased membrane life was the most influential factor in reducing operating costs.

“The whole desalination process revolves around this membrane,” Dunn said. “Anything we can do to improve membrane life or reduce cleaning costs will help lower the cost of clean water.”

Dunn hopes this study will help policy makers, decision makers and water treatment plant operators understand that water treatment facilities can tolerate the cost of using more expensive, higher performance membranes. This is especially true for desalination plants, 65% of which already use membrane-based filtration systems.

“There is a payoff in terms of reduced energy consumption and reduced frequency of purchasing new membranes,” Dunn said. “If we want to build more desalination plants to reduce water scarcity, we want to do it in a way that doesn’t increase energy consumption. Everything is interconnected.”

Reference: Das S, O’Connell MG, Xu H, et al. Evaluation of advances in antifouling membranes to improve process economics and sustainability of water treatment. ACS EST Eng. 2022. doi: 10.1021/acsestengg.2c00184

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