oxygendemanding

Oxygen-demanding, in scientific usage, refers to substances, processes, or organisms that require molecular oxygen to function or to release energy via oxidation. In environmental science, the term is commonly applied to biodegradable organic matter and the microorganisms that oxidize it, which consume dissolved oxygen (DO) in the surrounding water.

In aquatic systems, high oxygen demand can reduce available DO and lead to hypoxic or anoxic conditions, harming fish and invertebrates that rely on oxygen. Oxygen demand is influenced by temperature, mixing, and the presence of aerobic microbes; warmer water speeds microbial metabolism and increases demand.

In wastewater treatment and water quality assessment, oxygen-demanding waste includes sewage and biodegradable organics from industry and households. Biochemical Oxygen Demand (BOD) is a standard measure estimating the amount of oxygen consumed by microbes during the breakdown of organic matter, typically over five days (BOD5). Chemical Oxygen Demand (COD) measures the total amount of oxygen required to chemically oxidize both biodegradable and some non-biodegradable organics.

Management aims to minimize oxygen demand before discharge to protect aquatic ecosystems, using pretreatment, aeration, and proper sludge handling to reduce BOD and COD loads. The term is used alongside other indicators of water quality and is contrasted with non-oxygen-demanding or anaerobic processes.