Treatment Plant Operator Exam Study Guide Answers

What causes the pH to decrease during the overnight portion of the diurnal cycle? The answer to the question is B, respiration. The diurnal cycle is the change of night to day to night. During the daylight hours, the algae undergo photosynthesis and produce oxygen while taking in carbon dioxide. The causes the pH to increase. The inverse is also true: during the night the algae undergo respiration, consuming the oxygen and producing carbon dioxide. This causes the pH to decrease. The lack of oxygen and lowered pH levels may mean the lagoon can be in an upset condition during the