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Membrane fouling control
Water shortage is a serious issue in current human generation. Purifying water to be reused for mankind is at utmost importance. Membrane filtration poses as a valuable method of choice for separating literally any substances from water, ranging from micro-sized particles to even ions, depending on the type of membrane process used. During membrane filtration, substances that are larger than the size of the pores of membrane gets stuck on the surface of the membrane, only allowing water to pass through.
Pollutants such as microalgae, dissolved organic matters (DOM), sand and clay are easily filtered according membrane types. As most of the target pollutants are easily removed by stacking on the surface of membrane, the stacked pollutants work as a physical barrier, degrading the filtration efficiency. This leads to the most notorious phenomenon in membrane filtration, known as membrane fouling. Membrane fouling increases as the membrane filtration proceeds, and ultimately blocks all the pores on the membrane, even blocking the water passage.
Therefore, it is important to control the rate of fouling on membrane surface, either by physical cleaning or chemical dissolving. Chemical agents such as oxidizing agents dissolve the chunk of membrane pollutants to reduce the already-formed membrane fouling layer. However, as chemical agents may affect the quality of filtrated water as well as characteristics of foulants, physical approach or mild chemical approach that does not alter the foulant properties are widely used in field such as water treatment, and juice concentration.
Physical cleaning, in this laboratory, are divided into two categories, one with the prevention of fouling layer, and another with the removal of already-formed fouling layer.
By changing the hydrodynamic condition of water flow, foulants present within the solution can be washed away by high-speed, high-turbulence flow. Spacer and air sparging are one example of causing turbulence on the surface of the membrane. Using orifice-based techniques and other related methods, fouling layer can be controlled, leading to high water filtration efficiency despite thick foulant concentration.
Computational fluid dynamics (CFD), and other mathematical tools are implemented to predict the degree of fouling during membrane filtration. Another way of controlling the fouling is be removing the trapped foulants by generating bubble vis electrochemical way. Fabrication of electro-membrane can enhance the electrical conductivity of membrane, pushing away the foulants when the membrane undergoes hydrogen evolution reaction.
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