Which of the following is an organic impurity in sewage?

Human faeces

The correct answer is option 2. Human faeces.

An organic impurity in sewage is Human faeces.

Human faeces contain organic matter, as they are composed of undigested food, bacteria, and other organic substances. In sewage treatment, the removal and treatment of organic impurities, including human waste, are crucial to prevent environmental pollution and ensure the safe disposal of wastewater.