The tolerance limit of BOD (Biochemical Oxygen Demand) of sewage to be disposed of on land is 500 ppm. BOD is a measure of the amount of oxygen required by microorganisms to decompose the organic matter present in sewage. It is an important parameter to assess the pollution level of sewage and its impact on the environment.

- What is BOD?
BOD is a measure of the amount of dissolved oxygen consumed by microorganisms while decomposing organic matter in water. It is an indicator of the organic pollution level in water bodies and wastewater. Higher BOD values indicate higher levels of organic pollutants in the water.

- Importance of BOD in sewage disposal
When sewage is disposed of on land, it can seep into the soil and potentially contaminate groundwater sources. The BOD of sewage determines the organic pollution level and the potential impact on the environment. If the BOD is too high, it indicates a high concentration of organic pollutants that can deplete the oxygen levels in the receiving water bodies and harm aquatic life.

- Tolerance limit of BOD in sewage disposal on land
The tolerance limit of BOD in sewage disposal on land is set at 500 ppm. This means that the BOD of the sewage should not exceed 500 ppm to minimize the environmental impact. If the BOD exceeds this limit, it indicates a high concentration of organic pollutants that can degrade the water quality and harm the ecosystem.

- Significance of the tolerance limit
The tolerance limit is set to ensure that the disposal of sewage on land does not cause excessive pollution and harm to the environment. By adhering to the tolerance limit, the concentration of organic pollutants in the sewage is controlled, reducing the risk of contamination of groundwater sources and water bodies.

- Regulatory compliance
Regulatory bodies and environmental agencies enforce the tolerance limit of BOD in sewage disposal on land. Industries, municipalities, and other wastewater generating sources are required to treat their sewage to meet the prescribed BOD limits before disposing of it on land.

- Monitoring and treatment
Monitoring the BOD levels in sewage is essential to ensure compliance with the tolerance limit. Treatment processes such as biological treatment, chemical treatment, and filtration can be employed to reduce the BOD levels in sewage before disposal.

In conclusion, the tolerance limit of BOD in sewage disposal on land is 500 ppm. This limit is set to control the organic pollution levels and minimize the environmental impact of sewage disposal. Compliance with this limit is crucial to protect groundwater sources and water bodies from contamination.