Q1: The clarigesters are

ANS:D - circular Imhoff double storey tanks without bottom hoppers.

The clarigesters are circular Imhoff double tanks with bottom hoppers. Clarigesters are a type of sewage treatment unit used for primary sedimentation and sludge digestion. They are designed based on the principles of the Imhoff tank, which consists of two compartments: an upper sedimentation chamber and a lower sludge digestion chamber. The sedimentation chamber allows settleable solids to settle, while the sludge digestion chamber facilitates the decomposition of organic matter through anaerobic digestion. In clarigesters, these two chambers are arranged in a circular configuration with bottom hoppers. The circular design allows for efficient settling of solids and digestion of sludge within a compact footprint. The bottom hoppers aid in the collection and removal of settled solids and digested sludge from the tanks. Therefore, clarigesters are circular Imhoff double tanks with bottom hoppers.