What is the primary cause of turbidity in wastewater?

Turbidity in wastewater primarily results from finely divided suspended material. These suspended solids can include various organic and inorganic matter such as silt, clay, and bio-material, which contribute to the cloudiness or haziness observed in water. This turbidity is significant because it affects light penetration, which can impair the growth of aquatic plants and disrupt the photosynthesis process.

While color, dissolved calcium, and hardness can play a role in the overall quality of wastewater, they do not directly cause turbidity in the same way that finely divided suspended material does. Color may be influenced by dissolved organic matter or other substances, but it does not account for the physical obstruction of light that defines turbidity. Dissolved calcium often relates to water hardness rather than turbidity itself, and hardness typically refers to the concentration of calcium and magnesium ions in water, affecting the overall chemistry but not specifically contributing to turbidity. Therefore, the presence of finely divided suspended material is the most accurate answer regarding the primary cause of turbidity in wastewater.