Which of the following is a common indicator of water quality in wastewater treatment?

Biochemical Oxygen Demand (BOD) is a critical indicator of water quality in wastewater treatment. It measures the amount of oxygen that microorganisms will consume while decomposing organic matter in water. This is significant because a high BOD level indicates a high level of organic pollution, which can lead to oxygen depletion in water bodies if not adequately treated. Monitoring BOD helps wastewater treatment facilities assess the efficiency of their treatment processes and ensure that the effluent released into the environment does not harm aquatic ecosystems and complies with regulatory standards.

Other indicators, such as chlorine levels, are important but serve different purposes, primarily related to disinfection processes rather than overall organic content and pollution. While heavy metal concentration is also a concern in wastewater treatment, it is more about specific contaminants than general water quality assessment. Carbon content is generally not a direct indicator used to evaluate water quality in wastewater treatment contexts.