Q1: In normal conditions, the period for sludge digestion, is

ANS:C - 30 days

In wastewater treatment processes, sludge digestion is a biological process where organic solids present in the sludge are broken down by microorganisms in an oxygen-depleted environment. The digestion process reduces the volume of sludge, stabilizes organic matter, and produces biogas, which can be used as an energy source. The period for sludge digestion, also known as the retention time, can vary depending on factors such as temperature, sludge characteristics, and the specific digestion process used (e.g., aerobic digestion, anaerobic digestion). However, in typical wastewater treatment plants, the period for sludge digestion is commonly in the range of:

• 20 to 30 days

This period allows sufficient time for microbial activity to break down organic solids effectively and produce biogas. Shorter digestion periods may not achieve complete stabilization of the sludge, while longer periods may result in reduced efficiency or increased energy consumption. Therefore, in normal conditions, the period for sludge digestion is typically around 20 to 30 days.