연구원들이 하수 담수화 과정에서 정밀여과를 할 때 토양의 유기체적 문제로부터 발생하는 ‘추가적인 역삼투 멤브레인 오염 메커니즘’을 발견했다. 

이스라엘과 독일 과학자들의 합동 연구는 멤브레인 생물반응장치에 있는 역삼투 멤브레인에서 형성된 유기막이 RO 멤브레인 내의 유동을 줄일 수 있지만, 미생물에 의해 분비된 큰 분자에 의한 유동 절감은 전환될 수 있다는 사실을 밝혀냈다.

연구원들은 UF 침투에 의한 영구적인 손상이 멤브레인 폴리아미드에서의 붓기를 가라앉히는 과정에서 발생했으며, 붓기 효과(swelling effect)는 멤브레인을 통한 물의 수송에 결정적인 요인이라고 밝혔다.

그들은 깨끗한 멤브레인과 EPS로 오염된 멤브레인을 사용하면서 pH값이 6에서 8로 전환되고, 다시 6으로 돌아왔을 때 역삼투 침투 유동에서 양면의 기회를 봤다고 말했다.

 

 

 

Researchers have uncovered "an additional reverse osmosis (RO) membrane fouling mechanism" arising from organic matter from soil present in ultrafiltration (UF) permeate during wastewater desalination.

 

 The study by scientists in Israel and Germany found that organic films that form on RO membranes in a membrane bioreactor from organic material in UF permeate irreversibly reduce flux in the RO membrane, But flux reduction by large molecules secreted by microorganisms - extracellular polymeric substances (EPS) - can be reversed.

 

They proposed that the permanent damage inflicted by UF permeate arose from its arrest of the swelling in the membrane polyamide which the researchers had measured. The swelling effect is crucial to water transport through the membrane, the researchers said.

 

The scientists ran parallel, fouling experiments with UF permeate and EPS in an RO plate-and-frame unit. They saw reversible changes in the RO permeate flux as pH values were altered from 6 to 8 and back to 6 using pristine and fouled membranes with EPS.

 

On putting UF permeate-fouled membranes throughout he same pH variation the scientists found "irreversible flux decline" in the RO. The pH change, they said, promoted interaction between the UF permeate organic matter and the membrane to reduce further membrane permeability. They concluded that substances originating in soil were binding irreversibly with the membrane surface: "More studies need to be carried out to analyse the effects of humic substances, abundant in the UF permeate fouling layer, that irreversibly interact with the polyamide surface.

 

They found that the film deposited from UF permeate enhanced the attachment of bacteria, but had no effect on EPS adsorption.

 

The swelling changes and film build-up were measured using quartz crystal microbalance with dissipation - a technique that uses shifts in resonant frequency caused by changes in the mass of the membrane.
The work was published in the Journal of Membrane Science.

 

[출처 = Desalination & Water Reuse / 2014년 10월 14일]