The presence of high BOD may indicate faecal contamination or increases in particulate and dissolved organic carbon from non-human and animal sources that can restrict water use and development, necessitate expensive treatment and impair ecosystem health. Human ill health due to water quality problems can reduce work capability and affect children’s growth and education. High levels of oxygen consumption pose a threat to a variety of aquatic organisms, including fish. It helps to identify communities where wastewater treatment action is required to protect the ecosystem. Untreated or insufficiently treated wastewater can result in increased nutrient levels, high levels of organic matter and hazardous substances, posing threats to aquatic ecosystems and human health. It can be calculated separately for different terrestrial ecological regions.