The correct answer is A. 100 to 500.
Sewage is a mixture of wastewater from homes and businesses, as well as stormwater runoff. It contains a variety of solids, including organic matter, inorganic matter, and pathogens. The concentration of solids in sewage can vary depending on the source of the wastewater and the treatment that it has received.
In general, the concentration of solids in sewage is between 100 and 500 milligrams per liter (mg/L). However, the concentration can be much higher in some cases, such as when there is a lot of stormwater runoff.
The solids in sewage can cause a number of problems, including:
- Odor: The organic matter in sewage can decompose and produce unpleasant odors.
- Clogging: The solids in sewage can clog pipes and other infrastructure.
- Disease: The pathogens in sewage can cause diseases such as cholera, typhoid, and dysentery.
To reduce the problems caused by solids in sewage, it is important to treat sewage properly. Treatment methods include primary treatment, secondary treatment, and tertiary treatment.
Primary treatment removes large solids, such as grit and sand, from sewage. Secondary treatment removes dissolved organic matter and some pathogens from sewage. Tertiary treatment removes additional pollutants, such as nutrients and heavy metals, from sewage.
Proper sewage treatment is essential to protect public health and the environment.