Q1: The detention period for plain sedimentation water tanks, is usually

ANS:A - 4 to 8 hours

A detention period of 4 to 8 hours for plain sedimentation water tanks is relatively short compared to the typical range of 8 to 16 hours. Here's an explanation of the 4 to 8 hours detention period:

1. Purpose: The detention period in a sedimentation tank is the time required for water to remain still so that suspended particles can settle to the bottom of the tank. The purpose of sedimentation is to remove suspended solids, such as sand, silt, and organic matter, from the water, thus clarifying it before further treatment or distribution.
2. Shorter Timeframe: A detention period of 4 to 8 hours implies that water spends a relatively brief amount of time in the sedimentation tank. During this period, the settling process occurs, but it may not allow sufficient time for all suspended particles to settle completely. As a result, the efficiency of particle removal may be lower compared to longer detention periods.
3. Applicability: Sedimentation tanks with shorter detention periods may be suitable for certain applications where space or operational constraints limit the size or capacity of the treatment facility. They may also be used in situations where the suspended solids concentration in the influent water is relatively low and the desired level of treatment is achievable within the shorter timeframe.
4. Considerations: While a detention period of 4 to 8 hours may be sufficient for some treatment scenarios, it is essential to consider the specific requirements of the water treatment process and the quality standards for the treated water. Inadequate detention time may result in incomplete removal of suspended solids, leading to reduced water quality and potential issues downstream in the treatment process or distribution system.

In summary, a detention period of 4 to 8 hours in plain sedimentation water tanks provides a shorter timeframe for particle settling compared to longer detention periods. While suitable for certain applications, careful consideration of water quality goals and treatment efficiency is necessary when selecting the detention period for sedimentation tanks.