Biochemical oxygen demand is an alternative term for biological oxygen demand (BOD): the dissolved oxygen that microorganisms need to oxidise biodegradable matter in water over a standard period. Food plants monitor BOD in effluents from dairies, breweries, and processing lines, since high BOD signals organic pollution that can deplete oxygen in receiving waters and harm aquatic life. Treatment systems are sized around BOD load, and discharge permits set strict BOD limits that factories must meet through screening, biological treatment, and monitoring. Reducing BOD at source, by recovering product from waste streams, saves treatment costs and protects waterways simultaneously.