different filtration methods
TRANSCRIPT
DIFFERENT
FILTRATION
METHODS
Vinit Shahdeo
15BIT0335
Digital Assignment Difference between different filtration
methods and finding best method for filtration to remove impurities
Filtration is a process of removing particulate matter from water by forcing the water through a
porous media. This porous media can be natural, like sand, gravel and clay, or it can be a
membrane wall made of various materials. Sometimes, large particles are settled before
filtration; this is called sedimentation. The size of materials that can be removed during
filtration depends upon the size of the pores of the filter. Filtration is a separation process used in
the pretreatment of water to remove from it suspended particles, bacteria, other impurities and
pollutants. Various filtration processes have been developed through the ages to produce water
with specific qualities. Media filtration is normally employed in the removal of particles greater
than > 2 μm. For separation of fine particles in the range of 0.1 to 0.01 μm microfiltration (MF)
and ultrafiltration (UF) membrane processes are employed. The media filtrations, MF and UF are
true filtration processes used in the removal of particles according to their size and are not
effective in removal of hardness or other ionic forms of impurities. The removal of the latter two
forms of impurities is best done by the use of nanofiltration (NF) and/or reverse osmosis (RO)
membrane processes. Various forms of membrane processes, such as MF, UF, and NF filtration,
which proved to be excellent alternatives to media filtration in cleaning contaminants from
drinking water can be utilized effectively in the pretreatment of RO and SWRO. Recently it was
established that NF pretreatment can be used effectively in cleaning feed to seawater desalination
plants from fouling and biofouling constituents (suspended particles and bacteria), in removal of
scale-forming hardness ions (Ca++, Mg++, SO4 + and HCO3 - ) as well as in lowering of feed
TDS, and as a result allows for the improvement of seawater desalination 'plants' performance by
raising their production and water recovery ratio as well as improving their water quality.
Different methods of filtration
1. Microfiltration
2. Ultrafiltration
3. Nanofiltration
4. Reverse Osmosis
A microfiltration filter has a pore size around 0.1micron, so when water undergoes
microfiltration, many microorganisms are removed, but viruses remain in the water.
Microfiltration is a pressure-driven process in which a membrane is applied to separate particles
from an aqueous solution. Microfiltration is defined as the filtration of a suspension with
colloidal or other fine particles having a linear dimension of roughly 0.02 μm to 10 μm. Typical
operating pressure for microfiltration is relatively low, lying between 0.02 MPa and 0.5 MPa.
Applications
1. It is used in Fat/Microbial Removal and Casein/Whey Fractionation.
2. It is used for gelatin and wine clarification.
3. It is used in corn wet milling
4. Plant Extract Clarification
5. It is used for wastewater treatment in industries
6. Clarification of Fermentation Broths
7. It is used for beverage sterilization
Ultrafiltration Ultrafiltration (UF) is basically a pressure-driven separation process governed by a screening
principle and dependent on particle size. UF membranes have pore size between 1 nm to 100nm,
thus allowing retention of compound with a molecular weight of 300 -500 Dalton. For complete
removal of viruses, ultrafiltration is required. The pores of ultrafiltration membranes can remove
particles of 0.001 – 0.1 µm from fluids. Ultra filtration can also be applied for pre-treatment of
water for nanofiltration or Reverse Osmosis.
Pre-treatment of water is very important when these filtration techniques are applied, because
membrane fouling can easily disturb the purification process. Pre-treatment is not only important
for nanofiltration and Reverse Osmosis processes, but also for the above-mentioned
microfiltration and ultrafiltration processes. A pre-treatment needs to be determined as soon as
the composition of the wastewater is known.
Applications of UF
1. It is used for enzyme recovery.
2. It is used in Cheese manufacture.
3. It is used for removal of pathogens from milk.
4. It is used in waste water treatment.
5. It is used for filtration of effluent from paper pulp mill.
6. It is used for fruit juice concentration and clarification.
7. It is used in dialysis and other blood treatments.
8. It is used in laboratory grade manufacturing.
9. It is used for desalting and solvent-exchange of proteins (via diafiltration).
A Nanofiltration filter has a pore size around 0.001 micron. Nanofiltration removes most
organic molecules, nearly all viruses, most of the natural organic matter and a range of salts.
Nanofiltration removes divalent ions, which make water hard, so Nanofiltration is often used to
soften hard water.
Benefits of Nanofiltration
1. It requires lower operating costs.
2. Lower energy costs are required.
3. Lower discharge and less wastewater than reverse osmosis.
4. It reduces total dissolves solids (TDS) content of slightly brackish water.
5. It reduces reduction of pesticides and VOCs (Org. chemicals)
6. Reduction of heavy metals.
7. Reduction color, tannins and sulfates.
8. It softens hard water.
9. No salts are used in the process.
10. The pH of water after nanofiltration is typically non aggressive.
When two solutions of unequal concentrations are separated by a Semipermeable membrane,
solvent will flow from lower conc. to higher conc. This phenomenon can be reversed applying
hydrostatic pressure on the concentrated side and this is called Reverse Osmosis. The water
gets forced through the semipermeable membrane leaving behind the dissolved solids.
Semipermiable membrane is membrane which selectively doesn’t permit the passage of
dissolved solute particles.
Reverse osmosis filters have a pore size around 0.0001 micron. After water
passes through a reverse osmosis filter, it is essentially pure water. In addition to removing all
organic molecules and viruses, reverse osmosis also removes most minerals that are present in
the water. Reverse osmosis removes monovalent ions, which means that it desalinates the water.
About the method:
In reverse osmosis, the two solutions are separated by a semi-permeable membrane, and pressure
is applied to reverse the natural flow of the water. This forces the water to move from the more
concentrated solution to the weaker. Thus, the contaminants end up on one side of the semi-
permeable membrane and the pure water is on the other side. In this process, pressure is applied
to the impure water to force its pure water out through the semipermeable membrane, leaving
behind the dissolved solids (both ionic as well as non-ionic)
Advantages of Reverse Osmosis
1. Reverse Osmosis possesses a distinct advantage in removing ionic as well as non-ionic,
colloidal and high molecular wt. organic matter.
2. It removes colloidal silica which is not removed by demineralization.
3. The maintenance cost is almost entirely on only the replacement cost of membranes.
The life of membrane is high i.e. 2 years.
4. The membrane can be replaced within few minutes thereby providing nearly
uninterrupted water supply.
5. It has very low capital cost and high reliability.
COMPARISON BETWEEN THE METHODS
1. What do these processes remove?
Ultrafiltration removes bacteria, protozoa and some viruses from the water. Nanofiltration
removes these microbes, as well as most natural organic matter and some natural minerals,
especially divalent ions which cause hard water. Nanofiltration, however, does not remove
dissolved compounds. Reverse osmosis removes turbidity, including microbes and virtually
all dissolved substances. However, while reverse osmosis removes many harmful minerals,
such as salt and lead, it also removes some healthy minerals, such as calcium and
magnesium. This is why water that is treated by reverse osmosis benefits by going through a
magnesium and calcium mineral bed. This adds calcium and magnesium to the water, while
also increasing the pH and decreasing the corrosive potential of the water. Corrosive water
may leach lead and copper from distribution systems and household water pipes.
2. What are the advantages of using microfiltration, ultrafiltration, nanofiltration or
reverse osmosis to treat water?
All three of these membrane filtration processes are effective methods of treating water
that cannot be treated using conventional treatment methods. Reverse osmosis, in
particular, has been responsible for ending several nearly decade long Boil Water
Advisories. For example, in 2003, a reverse osmosis system, together with a biological
treatment process, was set up to successfully treat drinking water for the Yellow Quill
First Nation, which had been on a Boil Water Advisory since 1995. The water in the First
Nations community, which is located in Saskatchewan, contained high levels of organic
matter, iron, manganese, ammonium and arsenic, to name a few. Besides the obvious
benefit of providing safe drinking water to a community which had been under a Boil
Water Advisory for approximately nine years, the reverse osmosis system (together with
the biological treatment) allowed the community to treat their water using small
quantities of chemicals.
3. What are the disadvantages of using microfiltration, ultrafiltration, Nanofiltration
or reverse osmosis to treat water?
Compared with the benefits of using membrane filtration to treat water, there are very
few disadvantages. If conventional water treatment processes can effectively treat the
water, then constructing a reverse osmosis water treatment facility would be an
unnecessary cost. But for the First Nations communities that have been on Boil Water
Advisories for many years, a reverse osmosis treatment system can be a valuable
investment that can provide safe drinking water for the residents. Reverse osmosis
removes a number of healthy minerals from water, in addition to the harmful minerals
and particles. The removal of these minerals, including calcium and magnesium, can
actually make water unhealthy, especially for people with inadequate diets and people
who live in hot climates, as water can provide these necessary minerals. The addition of
calcium and magnesium, as described above, can resolve these concerns.
Diagram to demonstrate the comparison
Reverse Osmosis is the best method for
the Purification of Water
1. It improves the taste, odour and appearance of Water more than any other filtration
methods.
2. It is highly effective purification process among all the purification methods.
3. It consumes no energy.
4. It is very convenient.
5. It removes all the pollutants. It doesn’t collect any of them.
6. It gives purified water at very low production cost.
7. Due to low capital cost, simplicity, low operating cost and high reliability it is best water
purification method.
Conclusion The principle of micro filtration and ultrafiltration is physical separation. The extent to which
dissolved solids, turbidity and microorganisms are removed is determined by the size of the
pores in the membranes. Substances that are larger than the pores in the membranes are fully
removed. Substances that are smaller than the pores of the membranes are partially removed,
depending on the construction of a refuse layer on the membrane.
Micro filtration and ultrafiltration are pressure-dependent processes, which remove dissolved
solids and other substances from water to a lesser extent than nanofiltration and Reverse
Osmosis. Reverse Osmosis is the best purification method
.
Submitted By:-
Name- Vinit Shahdeo
Reg. No- 15BIT0335
