Question

About water purification:

A. Name 3 water treatment trains and explain them.

Answer 1

1. Ultra filtration: The process is same like reverse osmosis, the hydrostatic pressure is applied to filtration process. The only difference is the membrane pore size. The ultra filter membrane removes very tiny particles such as some viruses, bacteria and many other disease causing agents. The pore size is about 0.1 micron. This is widely used in sea water, sewage water/ muncipal water purification.

2. Nano filtration: A pore size of 0.001 micron to remove nano participles. Nanofiltration is used to remove most of the organic molecules, all viruses, some organic matter, most of the salts and some divalent ions. The water becomes drinkable, odorless and colourless.

3. Reverse osmosis: It is a water purification step where a partial permeable membrane filters the ions, non-essential molecules such as fluoride, salt, chlorine, arsenic etc.. It is widely used to purify sea water to make it drinkable. The mechanism is strong force is applied to the water over the filter membrane which then separates the molecules and passes water through it. The RO membranes are of 3 types: filter membrane: to clear sand particles, sediment membrane: to clear volatile organic compounds and chlorine etc. or semi-permeable membrane it removes the all dissolved solids. The pore size is 0.0001 micron.