The correct answer is: C. Both A and B
A comminutor is a machine that shreds or cuts solid waste into small pieces. A shredder is a machine that cuts solid waste into smaller pieces than a comminutor. Both comminutor and shredder can be used to dispense with the use of coarse screens for the disposal of sewage.
Coarse screens are used to remove large objects from sewage, such as rags, paper, and sticks. However, they can also remove small objects, such as sand and grit. This can cause problems in the sewage treatment process, as these small objects can clog pipes and equipment.
Comminutor and shredder can break down these small objects into smaller pieces that can be easily removed from the sewage. This can help to improve the efficiency of the sewage treatment process and reduce the risk of problems.
In addition, comminutor and shredder can also help to reduce the amount of solid waste that needs to be disposed of. This can be beneficial for both environmental and economic reasons.
Therefore, both comminutor and shredder can be used to dispense with the use of coarse screens for the disposal of sewage.