Explanation:

BOD (Biochemical Oxygen Demand) is a measure of the amount of oxygen required by microorganisms to decompose organic matter in water. It is an important parameter in wastewater treatment and pollution control. The ultimate BOD is the total amount of oxygen required to completely oxidize the organic matter in wastewater.

Temperature has a significant effect on the rate of organic matter decomposition and hence on the BOD. However, the ultimate BOD value of a waste remains the same at all temperatures. This is because ultimate BOD is a measure of the total amount of organic matter in the waste, which does not change with temperature.

Effects of temperature on BOD:

- Increases with temperature: The rate of organic matter decomposition increases with temperature. This means that the BOD value of a waste will increase as the temperature increases. However, this is not the same as the ultimate BOD value.
- Decreases with temperature: At very low temperatures, the rate of organic matter decomposition is very slow, and hence the BOD value may decrease. However, this is not a significant factor in wastewater treatment as the temperature is usually within a range that supports microbial activity.
- Doubles with every 10C rise in temperature: This is known as the Q10 rule, which states that the rate of a chemical reaction doubles for every 10C rise in temperature. However, this rule is not applicable to the ultimate BOD value.

Conclusion:

In conclusion, the ultimate BOD value of a waste remains the same at all temperatures as it is a measure of the total amount of organic matter in the waste, which does not change with temperature. However, the rate of organic matter decomposition and hence the BOD value may vary with temperature.