Which of these acts on clarified water in an aeration tank

The process of removing all large objects from the raw sewage before they damage or clog the pipes of primary treatment is called:

The lighter impurities such as oil and grease that float on the surface of waste water in large sedimentation tanks is called:

The sewage pipes are made up of

Dry sludge is used  as

The process of passing waste water through a sand or grit chamber to allow the setting of sand, grit, stones and broken glass is called:

Sludge is used to obtain

Pick the odd one out of the following.

The suspended impurities dissolved in waste water

Name the disposal method in which solid organic wastes are subjected to combustion so as to convert them into residue and gaseous products: