Membrane Filtration is a technology consisting of a membrane barrier with tiny pores that will allow the passage of water and dissolved substances (such as salt and sugar) but prevent the passage of particulates, including bacteria, protozoa, and virus.
Membrane Filtration is a mature, well established technology, which is commonly used in water treatment applications. It offers a number of technological advantages including:
- Robust barrier against bacteria and protozoa regardless of fluctuations in the feedwater
- Can handle high amounts of particulates
- High quality filtered water
- Easy to add instrumentation that allows monitoring of system performance from anywhere in the world.
Characteristics that are considered negatives include:
- Very high capital cost compared with conventional technologies such as sand filtration for applications with relatively low amounts of particulates
- High operating costs, especially when factoring in replacement membranes. Membranes will last 7 to 10 years.
- Susceptible to “fouling” on some water sources. This adds risk to operation, and can be difficult to quantify this risk.
Membrane Filtration is a general way of describing a couple of different types of membrane. It can be broken down into Microfiltration and Ultrafiltration.
Microfiltration has pore size of around 0.1 micron (one ten-thousandth of a millimetre). This means it will remove most particulates including bacteria and protozoa. Very tiny particulates including viruses and colloidal silica are not well removed.
Ultrafiltration has a smaller pore size of around 0.01 micron. This means it will also remove colloids, viruses, and proteins.
Neither of these will remove dissolved substances such as salts and organics