Removing Dissolved Solids by Filtration Flashcards
What is the main purpose of filtration systems?
To remove larger molecules and particles from liquids
Historically, filtration systems have evolved from removing large objects to filtering fine and micro-particles.
What does membrane filtration use to allow certain ions and molecules to pass?
A semi-permeable membrane
The membrane retains other substances based on filter pore size.
What determines the levels of filtration in membrane filtration?
The size of filter pore
Filtration levels can range from microfiltration to reverse osmosis.
What is the particle size that microfiltration can remove?
Down to about 0.1 micrometres (μm)
This includes yeast cells, small suspended solids, large colloids, and most bacteria.
What is the typical pore size for filters used in sterile filtration?
0.45μm
These filters operate at a pressure of about 0.7-4 bar.
How does ultrafiltration compare to microfiltration in terms of performance?
Ultrafiltration performs 10 times better than microfiltration
It has a filter pore size down to 0.01μm.
What types of substances does ultrafiltration remove?
Most viruses, colloids, and large organics
It does not remove dissolved substances or change water’s chemical characteristics.
What is the pressure range for ultrafiltration systems?
2-7 bar
This pressure is necessary for the operation of ultrafiltration.
What is the pore size for nanofiltration?
Down to 0.001μm or 1 nanometre (nm)
This allows for the removal of most organics and 20-80% of dissolved salts.
What significant changes does nanofiltration cause to water?
De-mineralisation and dealkalisation
This is due to the removal of dissolved salts.
What is the pressure range required to operate a nanofiltration system?
6-10 bar
This significant pressure is necessary for effective operation.
What is the ultimate form of membrane filtration?
Reverse osmosis (RO)
It features incredibly small filter pore sizes for maximum purification.
