A dynamic filtration method with a rotating disk was developed for effective microalgal cell harvesting. Firstly, its harvesting performance was investigated for different rotation speeds and disk configurations. Even at high biomass concentrations, increasing the rotation speed effectively helped improve the permeate flux mitigating mainly cell cake formation and to some degree adsorption fouling with the help of high shear stress created on the membrane surface. Cross-flow velocity and shear stress on the membrane surface were significantly higher with the perforated disk than those with the solid disk, which led to a more effective fouling alleviation and higher permeate flux. The performance of the dynamic filtration method developed in this study was compared with other methods of coagulation, electro-flotation, electro-coagulation-flotation, and centrifugation. It turned out to be best suited with desirable features of no biomass loss, high concentration of harvested biomass, and moderate energy consumption. A surface-modified membrane was tested for further reduction of adsorption fouling which could not be effectively removed even under high-shear conditions. The membrane coated by a hydrophilic polymer clearly exhibited an increased hydrophilicity, reduced mean pore size, and neutralized surface charge, which led to a decreased adsorption fouling and consequently an increased permeate flux. An integrated filtration system was newly developed in which the impeller of the circulating centrifugal pump acted as rotating disk also. Such pump-integrated module resulted in a simplified system and a much less energy consumption.
본 연구는 고농도 바이오매스를 생산할 수 있는, 효과적인 분리막 기반의 미세조류 수확기술을 개발하기 위해 회전체 장착형 분리막 여과에 대해 연구하였다. 먼저, 회전체의 회전속도와 구조의 영향에 대해 조사하였다. 회전속도가 증가함에 따라 높은 전단응력에 의해 케익오염이 대부분, 흡착오염이 어느정도 감소되어 고농도의 바이오매스에서도 여과속도가 효과적으로 향상되었다. 구멍이 있는 회전체를 썼을 때 유속과 전단응력이 효과적으로 증가하여 높은 여과속도를 얻었다. 고농도 미세조류 수확에서의 성능을 응집, 전기부양, 전기응집부양, 원심분리와 비교한 결과, 회전체 장착형 분리막 여과만이 적절한 에너지로 바이오매스 손실 없이 고농도 바이오매스 생산이 가능하여 가장 적합하였다. 친수성 고분자를 코팅하여 표면을 개질한 분리막을 활용해 회전체만으로 완전히 제거할 수 없는 흡착오염을 감소시켜 여과속도가 더욱 향상되었다. 유입펌프로 활용 가능한 원심펌프의 임펠러를 회전체와 같이 막오염을 제거할 수 있는 펌프 일체형 시스템을 새롭게 개발하여 에너지 소모량을 저감하였다.
