Water treatment technology used for drinking water

water filtration

Water is most essential thing that our body needs after air. Purity of water is crucial for health and living. Industrialisation, Fertilizers, chemicals etc have posed big challenge for obtaining pure water. Drinking water is often obtained after treating impure water.

Water quality can be compromised by the presence of infectious agents, toxic chemicals, and radiological hazards. Impurity in water can be of either physical, chemical or biological.

  • Physical impurity (TDS, TSS, color, odor, taste etc.)

  • Chemical impurity (pH, Hardness, Alkalinity, COD, BOD, pesticides etc.)

  • Microbiological impurity (bacteria, E. coli, coli form, toxicity taste, plate count etc.)

These impurities are treated through various purification process. These are

  • Filtration

  • Reverse Osmosis

  • UV Treatment

  • Distillation System

We will see these process in details.

1. Filtration process

Filtration is a physical process that occurs when liquids, gases, dissolved or suspended matter adhere to the surface of, or in the pores of, an absorbent medium. Filtration filters out such impurities depending on the amount of contaminant, size of the contaminant particle, and the charge of the contaminant particle.

Depending on water supply to be treated, water may be subjected to pretreatment process. Pretreatment before filtration may include the addition of coagulants and powdered activated carbon, adjustments in pH or chlorine concentration levels, and other pretreatment processes in order to protect the filter’s membrane surface.

Depending on filter membrane size, filtration can be divided in three type

1.1 Microfiltration

A microfiltration filter has a pore size of approximately 0.1 micron (pore size ranges vary by filter from 0.05 micron to 5 micron)

Microfiltration has a very high effectiveness in removing protozoa (for example, CryptosporidiumGiardia)

Microfiltration has a moderate effectiveness in removing bacteria (for example, CampylobacterSalmonellaShigellaE. coli)

Microfiltration is not effective in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus)

Microfiltration is not effective in removing chemicals.

1.2 Ultrafiltration

An ultrafiltration filter has a pore size of approximately 0.01 micron (pore size ranges vary by filter from 0.001 micron to 0.05 micron; Molecular Weight Cut Off (MWCO) of 13,000 to 200,000 Daltons). Ultrafiltration filters remove particles based on size, weight, and charge

Ultrafiltration has a very high effectiveness in removing protozoa (for example, CryptosporidiumGiardia)

Ultrafiltration has a very high effectiveness in removing bacteria (for example, CampylobacterSalmonellaShigellaE. coli)

Ultrafiltration has a moderate effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus)

Ultrafiltration has a low effectiveness in removing chemicals.

1.3 NanoFiltration

A nanofiltration filter has a pore size of approximately 0.001 micron (pore size ranges vary by filter from 0.008 micron to 0.01 micron; Molecular Weight Cut Off (MWCO) of 200 to 2000 Daltons); Nanofiltration filters remove particles based on size, weight, and charge;

Nanofiltration has a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);

Nanofiltration has a very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli);

Nanofiltration has a very high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);

Nanofiltration has a moderate effectiveness in removing chemicals.


2. Reverse Osmosis Systems

Reverse Osmosis Systems, also termed as hyperfiltration is a process that reverses the flow of water in a natural process of osmosis so that water passes from a more concentrated solution to a more dilute solution through a semi-permeable membrane.

Pre- and post-filters are often incorporated along with the reverse osmosis membrane itself. A reverse osmosis membrane has a pore size of approximately 0.0001 micron. which is much precise than filtration process.

RO process details

As Water passes through RO Membrane, it removes hazardous chemicals dissolved in water such as pesticides, herbicides, heavy metals, hardness & other salts from water. It is effectively used in treating water with high TDS value compared to any other filtration process.

Reverse Osmosis Systems have a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);

Reverse Osmosis Systems have a very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli);

Reverse Osmosis Systems have a very high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);

Reverse Osmosis Systems will remove common chemical contaminants (metal ions, aqueous salts), including sodium, chloride, copper, chromium, and lead; may reduce arsenic, fluoride, radium, sulfate, calcium, magnesium, potassium, nitrate, and phosphorous.


3. Distillation Systems

Distillation Systems use a process of heating water to the boiling point and then collecting the water vapor as it condenses, leaving many of the contaminants behind.

Distillation Systems have a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);

Distillation Systems have a very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli);

Distillation Systems have a very high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);

Distillation Systems will remove common chemical contaminants, including arsenic, barium, cadmium, chromium, lead, nitrate, sodium, sulfate, and many organic chemicals.


4. Ultraviolet Treatment Systems (with pre-filtration)

Ultraviolet Treatment with pre-filtration is a treatment process that uses ultraviolet light to disinfect water or reduce the amount of bacteria present. A UV Water Purifier with its Ultraviolet Technology disinfects and deactivates bacterias and viruses from the water with ultraviolet rays and is best suited for the areas with low TDS level.

Ultraviolet Treatment Systems have a very high effectiveness in removing protozoa (for example, Cryptosporidium, Giardia);

Ultraviolet Treatment Systems have a very high effectiveness in removing bacteria (for example, Campylobacter, Salmonella, Shigella, E. coli);

Ultraviolet Treatment Systems have a high effectiveness in removing viruses (for example, Enteric, Hepatitis A, Norovirus, Rotavirus);

Ultraviolet Treatment Systems are not effective in removing chemicals.

4.1 UV purifier working

UV purifier uses UV mercury vapor lamps that produce ultraviolet radiation. The UV lamp never contacts the water; it is either housed in a quartz glass sleeve inside the water chamber or mounted external to the water which flows through UV transparent Teflon tubes.

In order to kill microorganisms, the UV rays must actually strike the cell. UV energy penetrates the outer cell membrane, passes through the cell body and disrupts its DNA preventing reproduction.

UV treatment does not alter water chemically; nothing is being added except energy. The sterilized microorganisms are not removed from the water. UV disinfection does not remove dissolved organics, inorganics or particles in the water.


5. Comparison of different purification technique

Tabular comparison for different water purification technique

Water filtration technique

Thus different water purification process serve different purpose. Before choosing which process is suitable for you, first step is to know your water. If you thinks your water needs treatment then must is to find out what are contaminants in your water.

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