The correct answer is: Slightly less than 1.
Sewage is a mixture of water and solid waste. The solid waste in sewage is mostly organic matter, such as food scraps, human waste, and paper products. Organic matter has a specific gravity that is slightly less than 1. Therefore, the specific gravity of sewage is also slightly less than 1.
The specific gravity of a substance is its density relative to the density of water. The density of water is 1 gram per cubic centimeter. The specific gravity of sewage is typically between 0.9 and 1.0. This means that sewage is slightly less dense than water.
The specific gravity of sewage can vary depending on the composition of the sewage. For example, sewage that contains a lot of organic matter will have a lower specific gravity than sewage that contains less organic matter.
The specific gravity of sewage is important because it is used to calculate the amount of sewage that can be treated in a wastewater treatment plant. The specific gravity of sewage also affects the way that sewage flows through pipes and other infrastructure.