Water filtration membranes reduce costs, energy

A Northwestern University study has found that high-performing water filtration systems can significantly reduce energy costs and consumption. 

Northwestern researchers performed a high-level analysis of membrane filtration systems to evaluate 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 accumulation of contaminants. 

Although foul-resistant membranes cost more money upon initial purchase, the study found that they cost less over their lifetimes than cheaper, non-foul-resistant membranes, which require frequent cleaning and must be replaced more often. 

The researchers estimate that municipal wastewater facilities spend up to 43 per cent more on antifouling membranes for wastewater treatment and up to three times more on antifouling membranes for desalination — and still maintain their baseline operating costs.

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 resources, such as brackish water. Investing in antifouling membranes upfront could help drive down the costs of these typically expensive treatment systems.

Lead Researcher, Associate Professor Jennifer Dunn, said, “With increasing water scarcity, technologies like desalination are becoming more important than ever. 

“But there are always tradeoffs between engineering performance and cost. A filtration system might have amazing performance, but if the cost is too high, then people won’t adopt the technology. We’re hoping that our modelling and analysis can help guide research and development.”

Northwestern’s research is the first internationally co-authored, published study from the U.S.-Israel Collaborative Water-Energy Research Center (CoWERC), a global consortium of research institutions, water utilities and private companies that explores new solutions to critical challenges at the energy-water nexus.

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

Fouling occurs when contaminants accumulate on the membrane’s surface, clogging the pores. When a membrane experiences fouling, higher pressures are needed to pump the water through. 

Eventually, however, fouling becomes so extensive that the membrane must be cleared or even fully replaced. The energy and costs associated with increased water pressure, cleaning and replacement can increase a treatment facility’s operating costs.

By contrast, antifouling membranes have specialised surface chemistries that prevent contaminants from accumulating. This leads to decreased frequency of cleaning and an overall extended lifetime of the membrane. In the study, the researchers found that increasing the membrane’s lifetime was the most influential factor in reducing operating expenses. 

“The entire process of desalination revolves around this membrane,” Ms Dunn said. 

“Anything we can do to improve the membrane’s lifetime or reduce cleaning costs will help reduce the cost of clean water.”

Ms Dunn said she hopes this study will help policymakers, decision-makers and water treatment plant operators realise that water treatment facilities can tolerate the cost of using more expensive, higher-performing membranes. This is particularly true for desalination plants, 65 per cent of which already use membrane-based filtration systems.

“There is a payback in terms of reduced energy consumption and reduced frequency of buying new membranes,” Ms 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. It’s all interconnected.”

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