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Advanced Wastewater Treatment :
Advanced wastewater treatment is required to remove hazardous Nitrogen and
Phosphorous. Most of the widely used processes in the present day are
Reverse Osmosis (RO), Ion Exchange and Redox method, they are discussed
in brief :
Reverse Osmosis (RO) :
Reverse osmosis devices use pressure to force contaminated water against a
semi permeable membrane, which acts as a filter, allowing the water to be
pushed through its pores, but restricting the passage of larger molecules that
are removed.
Ion Exchange :
Ion exchange is a device wherein toxic ions in the waste water can be removed
by using a special resin which reacts with toxic ion in the solution like heavy
metals and are removed.
Reduction - Oxidation (Redox) :
Redox signifies a chemical process whereby reduction and oxidation takes place
in the same reaction. For example hexavalent chromium which is toxic can be
converted to trivalent chromium following the way when sulphur dioxide (SO
2
)
is used as a reducing agent. This process is used for chromium plating.
3SO
2
+ 3H
2
O 3H
2
SO
3
2CrO
3
+ 3H
2
SO
3
Cr
2
(SO
4
)
3
+ 3H
2
O
Wastes that include chromium (hexavalent), mercury, lead, silver can be
removed by redox method. Most organics, cynamides, bezene, phenol, arsenic,
iron and manganese can also be removed from the waste water.
