Question

Why is grit removal important as a procedure in wastewater plants?If conventional grit removal systems are designed to remove particles larger than 0.210 mm and specific gravity of 2.65, why are particles this size and larger often found downstream? Explain.

In chemical disinfection of drinking water,what is breakpoint chlorination? Explain.

Answer 1

1. Grit Removal is an important procedure in waste water treatment plant. Grit consist of particles heavier than that of organic biodegradable particles. Grit particles are of size larger than 0.210 mm and G= 2.65. These particles are necessary to be removed to avoid abrasion of mechanical equipments, blockage of pipes due to Grit and accumulation in various units where it can hinder other processes.

2. Although conventional Grit removal systems are to be designed for particle size 0.210 mm and G = 2.65 but still particles of this size can be found downstream because Grit Chambers are not performing at 100% efficiency. They operate at about 75 to 95% efficiency. Therefore there can be chances of finding such type of particles in downstream.

3. Chlorination is one of the most efficient methods to disinfect the drinking water. Chlorination is to be added to the water in specific amount. There is a specific need depending upon quality of water above which Chlorine added will increase Chlorine residual only and this point is called Break point chlorination.

Breakpoint chlorination point is a point at which disinfection demand of water sample has been fulfilled and more Chlorine added will add to the residual Chllorine above this point.