Processes, technology and equipment employed to purify the water
There are various processes employed to purify the water and various combinations
of the processes mentioned below are incorporated to ensure that final composition
of the product confirms to latest BIS norms.
Desalination
Desalination
is defined as the removal of dissolved salts from various waters – brackish,
sea, etc. Desalination can be performed by several processes including two-membrane
process, namely reverse osmosis and electrodialysis. The other membrane process,
which can be employed for partial desalination, include ultrafiltration and nanofiltration.
Reverse
Osmosis
RO membranes are effective
in removing constituents and are efficient in removing TDS in any feedwater up
to 40,000 ppm (i.e. sea water.)
Osmosis is
natural bio-chemical process that affects the movement or diffusion of water molecules
through a semi-permeable membrane towards a solution that has high TDS, and it
is induced by osmotic pressure. RO is accomplished by forcing water molecules
under pressure through a semi-permeable membrane out of solution that has high
TDS. The feedwater on the inlet side becomes brine and water that passes through
– permeates, becomes the product water.
RO
membrane can be distinguished from other membranes based on pore size, which is
around 0.0005 microns. The pore size of RO membrane is small, that it functions
primarily by diffusion instead of filtration or adsorption.
Nanofiltration (NF)
NF is effective
in removing divalent ions (i.e. calcium and magnesium), larger monovalent ions
(i.e. sulphate), high molecular weight organic molecules, and colour. NF membranes
are efficient in softening feedwater below 1,000 mg/l TDS. These membranes provide
significant rejection of hardness caused by dissolved calcium and magnesium. The
pore size of NF membranes range between 0.0007 to 0.01 microns. (Taylor, 1989,
18)
Ultrafiltlration
(UF)
UF is effective in removing
high molecular weight proteins, bacteria and viruses. Rejection of monovalent
and divalent ions are considerably less than RO and NF. UF membrane pores are
smaller than MF but greater than NF, and range between 0.001 to 0.1 microns. The
primary mechanism of constituent removal is filtration, however, some salts are
transported across the semi-permeable membranes by diffusion.
Microfiltration
(MF)
MF is effective in removing
suspended solids of all types and larger colloids. These generally filter out
suspended constituents in feedwater.
Ultra
Violet Unit (UV)
Thorough research
in last few years have given lot of confidence to water treatment professionals
in terms of its effectiveness in microbiological treatment.
 |
UV is a band of invisible light in the electromagnetic
spectrum, in the range of 200-400 nm wavelengths, having germicidal effectiveness,
which penetrates the microbial cell membrane to destroy the DNA molecule thus
preventing cell replication. |
 |
UV is used to provide Bacterial Disinfection
in water. As UV does not change the Physical or Chemical characteristics in water
& does not have any residual properties left in treated water, it is widely
used to disinfect the water for micro biological contamination. |
The U.S. Public Health Service requires
that UV disinfection equipment have a minimum UV dosage of 16000 uW sec/cm2 (microwatt
seconds per square centimeter).
Recommended
maximum concentration levels in Ultra Violet unit
Turbidity
: 5 NTU [ Nephelometric turbidity unit ]
Suspended
Solids : 10mg/Litre
Colour : None
pH : 6.5 to 8.5
Ozonation
through Ozonator
What
is Ozone?
Ozone, triatomic Oxygen is
colourless, unstable & reactive gas with a acrid odour. It is strongest available
sanitizer and decomposes back to oxygen without leaving any tresses and makes
preferred choice for disinfection. Since it is a very reactive Disinfecting agent,
& 3000 times more effective than any other known disinfectents, It destroys
any Bacteria, Viruses, Cysts and Pathogens in a shortest possible time when it
comes into contact with water .
Ozone
Production
Ozone generation involves
splitting of an Oxygen molecule into two highly unstable Oxygen atoms. These unstable
Oxygen atoms combine with other Oxygen molecule to ultimately produce Ozone.
Dry
air or Oxygen is passed through the Ozone cell consisting of two electrodes kept
at a high potential with a dielectrics in between them. The Corona discharge formed
in the gap energizes the Oxygen molecules, thereby converting a portion of Oxygen
into Ozone. As Ozone is highly unstable & cannot be stored is produced at
site where it is required.

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