$5.$The maximum permissible limit of arsenic in drinking water according to WHO standards is:

a$)0\mathrm{.}01$ mg$/$L

b$)0\mathrm{.}05$ mg$/$L

c$)0\mathrm{.}1$ mg$/$L

d$)0\mathrm{.}5$ mg$/$L

What is the primary method used for the removal of fluoride from drinking water?

a$)$ Reverse osmosis

b$)$ Distillation

c$)$ Lime treatment

d$)$ Coagulation

Which of the following is NOT a common treatment step in the conventional water treatment process?

a$)$ Filtration

b$)$ Disinfection

c$)$ Adsorption

d$)$ Flocculation

The removal of hardness from water is typically achieved by:

a$)$ Coagulation

b$)$ Ion exchange

c$)$ Sedimentation

d$)$ Reverse osmosis