Innovations in Wastewater Treatment: Liquid Gated Membranes

A team from the University of Waterloo and Northeastern University have collaborated with Wyss Institute to find a biological solution for wastewater filtration and further innovations in wastewater treatment.

Conducted at Harvard University, the study wanted to compare the effectiveness of a standard filter and a liquid-gated membrane filter in terms of pressure requirements and fouling tendencies.

Normally, compound water mixtures such as that found in wastewater are passed through a standard filter with pores that are just large enough to let water molecules pass. This filters out larger particulate matter from passing through resulting in cleaner water.

However, there is a large amount of pressure needed to push the water through the pores in the standard filter and there is a high propensity for particles to clog up these pores over a short period of time. This entails frequent filter washing or replacement which, along with the energy needed to produce the appropriate pressures for filtration, makes water treatment very costly.

Liquid-gated membranes, on the other hand, offer two benefits: higher efficiency and nearly three times longer before it clogs up. Less pressure is required to push the water through the filter compared to conventional membranes. This could significantly cut energy costs and lower emissions when filtering municipal and industrial wastewater. Liquid-gated membranes were inspired by nature where liquid-filled pores control the movement of liquids, gases, and particles in an energy efficient manner. A similar analogy could be found in the stomata of plants, which allows gases to pass through and act as reversible gates that fill and seal the pores.

The research team tested the liquid-gated membranes on a suspension of bentonite clay too closely resemble wastewater produced in drilling activities in the oil and gas industry. The filter membranes were infused with perfluoropolyether, a liquid lubricant, and then placed under pressure to push the water out. They monitored the performance of this setup and compared it with a standard filtration system. The untreated filters clogged at a much faster rate than the liquid-gated membrane making the latter a better solution.

The liquid-gated membranes reduced the amount of nanoclay accumulated by as much as 60% and required 16% less pressure to initiate filtration. The study determined that this would make for less frequent backwashing, a reduced use of cleaning chemicals, and less energy requirements.

Harvard University co-author Joanna Aizenberg is enthusiastic that the novel approach will harnesses dynamic and responsive control over a highly sensitive and reversible gating mechanism. The team foresees many useful applications of this technique including industries as diverse as food and beverage processing, biopharmaceutical manufacturing, textiles, paper, pulp, chemical, and petrochemicals. They plan to move forward with larger-scale pilot studies with industry partners and gain comprehensive insight into the commercial viability of liquid gated membranes.

If you are a municipality in Ontario and in need of a biosolids management solution, please feel free to contact us at 1 (877) 479-1388.

Sources:
https://wyss.harvard.edu/filtering-liquids-with-liquids/
https://www.designnews.com

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