Anyone who has studied (and paid attention to) at least secondary biology is familiar with the concept of a membrane, in particular a semi-permeable membrane. Biological living cells are packed in semi-permeable membranes that keep their functions separate from the environment. The semi-permeable aspect only allows certain ions and organic molecules to enter or leave the cell. The membrane can be selective in a passive or active capacity. The UF purification and microfiltration processes use a semi-permeable membrane to separate micropollutants from a water stream. What is the difference between UF purification and microfiltration? We will first explain how semi-permeable membranes work. Below we will explain the differences between the UF and microfiltration membrane treatment processes for water and wastewater treatment.But both fitration systems are used in Industrial Ro plant.
How does a semi-permeable membrane work?:
One of the ways is via active transport across a membrane surface that takes place in different ways. Each of these transports requires the cell to use a certain amount of energy to do this. One way is via transport channels that respectively receive and expel nutrients and metabolic waste. Another is endocytosis in which the cell wall forms something like a pseudo-mouth, which wraps around an external object and then bursts into the cell like a vesicle. The opposite is exocytosis. Internal vesicles fuse with the membrane and its contents are excreted in the surrounding solution. Another way is through passive mechanisms known as diffusion and osmosis. Diffusion is the movement of ions and molecules from high concentration areas to low concentration areas to create a state of equilibrium on both sides of the membrane. While these ions are moving, they create an osmotic pressure difference. Osmosis works opposite diffusion and tries to create a balance by moving a solvent fluid (usually water) to the higher concentration area. The passive diffusion / osmosis process is a mechanism that can easily be replicated on a much larger scale. There are many potential applications for such technology, but in particular its usefulness in water and wastewater treatment. Micro and ultra filtration purification are two of such membrane technologies. They are very similar filtration / separation processes with a difference that each makes ideal for their own specific applications.
Fundamentally similar:
Microfiltration and UF purification are more similar than they differ. As mentioned in the introduction, they are both passive membrane-based separation technologies. These system processes work by applying differential pressure over a semi-permeable membrane and that pressure pushes water and small particles through the membrane pores, while larger solids are retained on the other side. Both of these processes also provide useful pre-treatment steps for reverse osmosis. Membranes need a lot of care, so they can last as long as possible without replacement. Filter pre-treatment reduces concentrations of larger solid particles and reduces the chance of membrane contamination.
The membranes for these microfiltration and UF purification systems are also available in the same configurations. Plate and frame, tubular, hollow fiber and spiral wound are possible options. These different configurations offer their own advantages and disadvantages. There are also different materials that the membranes can consist of, namely polymers and ceramics.
Similar benefits:
- No chemicals
- Constant product quality regardless of the feed quality
- Compact
- Comparable costs:
- Equipment
- tanks, pumps, skids, controls, etc.
- Construction materials
Characterization of water:
What is in the water / waste water determines what must be done to treat it properly. More complex compositions or high concentrations of contaminants will require pre-treatment steps or more energy intensive processes or more resilient membranes to cope with these conditions. Low concentrations and simple contaminating compositions usually require less pre-treatment and therefore lower operational costs.
Flow rates:
- Higher flow rates are associated with higher capital and operational costs
- Schedule
- Needed space
- Installation
- Pre-packaged versus non-assembled systems
- Shipping costs
- Operational costs
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