Explain the process of secondary treatment give to the priamry efflueint up to the point it shows significant change in the level of biological oxygen demand (BOD) in it.

Explain the process of secondary treatment given to the primary effluent up to the point it shows significant change in the level of biological oxygen demand (BOD) in it.

Assertion: If BOD level of water in a reservoir is less than 5 ppm it is highly pollution. Reason: High biological oxygen demand means low activity of vacteria in water.

All living cells require energy for various activities. This energy is available by the breakdown of simple carbohydrates either using oxygen or without using oxygen. The graph below represents the blood lactic acid concentration of an athlete during a race of 400 m and shows a peak at point D. Lactic acid production has occurred in the athlete while running in the 400 m race. Which of the following processes explains this event?