Q1: The flow velocity in detritus tanks is

ANS:B - 0.09 m/sec

A flow velocity of 0.09 m/sec means that the sewage or liquid within the detritus tank is moving at a rate of 0.09 meters per second. This velocity indicates how fast the sewage is flowing through the tank. In the context of detritus tanks, this flow velocity is within a typical range often used in wastewater treatment systems. Detritus tanks are designed to allow heavier solids, such as sand, grit, and other inert materials, to settle out from the sewage. The flow velocity needs to be controlled to ensure that these solids settle properly without being carried away by the flow. A flow velocity of 0.09 m/sec is moderate, meaning it's not too fast to disturb the settling process but also not too slow that it causes ineffective settling. It strikes a balance between allowing for efficient separation of solids while maintaining a reasonable flow rate through the tank. Overall, a flow velocity of 0.09 m/sec is suitable for detritus tanks in wastewater treatment systems, as it helps in achieving effective solid-liquid separation.