ANS:E - All the above.

1. Turbidity is more in strong sewage: Turbidity refers to the cloudiness or haziness of a fluid caused by suspended solids, such as particles of soil, organic matter, and microorganisms. Strong sewage, which typically contains a higher concentration of suspended solids and organic matter, may indeed exhibit higher turbidity compared to diluted or weaker sewage. The presence of more suspended solids can increase the scattering and absorption of light, leading to increased turbidity.
2. The black color indicates septic sewage: Septic sewage refers to sewage that has undergone anaerobic decomposition, leading to the production of foul-smelling gases, such as hydrogen sulfide, and the breakdown of organic matter into darker compounds. While septic sewage may indeed exhibit a darker color due to the presence of decomposed organic matter and other substances, the color alone is not a definitive indicator of septicity. Septic sewage is more accurately characterized by its foul odor and composition rather than its color.
3. The fresh sewage is practically odorless: Fresh sewage, particularly when it has not undergone significant decomposition, tends to have a relatively mild or neutral odor. Odor in sewage develops over time as organic matter decomposes, releasing volatile compounds and foul-smelling gases. Fresh sewage, especially when it is newly generated and has not been exposed to prolonged anaerobic conditions, may indeed be practically odorless or have a minimal odor associated with its organic composition.
4. The sewage emits offensive odors after four hours: Offensive odors in sewage typically develop over time as organic matter decomposes, especially under anaerobic conditions where oxygen is limited. The timeline of four hours mentioned here is arbitrary and may not universally apply to all sewage conditions. The onset of offensive odors can vary depending on factors such as temperature, organic content, and microbial activity. However, in general, sewage can emit offensive odors as decomposition progresses, particularly in stagnant or poorly aerated conditions.