i. Talk about the terms "short circuiting" and "turbulence" in settling tanks under the following headings - causes, effects and design improvements/remedial calculates taken to avoid them.

ii. Talk about the mechanism of coagulation in terms of the electrostatic and van der Waal's forces acting on the colloidal particles. Sketch diagrams to illustrate your answer.

iii. What is aeration used for in drinking water purification? Talk about some methods by which ventilation can be improved to increase gas transfer through the water.