When organic matter such as coffee bean mucilage enters a waterway as pollution, a great many microorganisms in the water are usually waiting to feed on it. And of course, more food supports more microorganisms. Such organisms rely on the presence of oxygen in the water for their metabolism. Biochemical oxygen demand (BOD) is a measure of the amount of dissolved oxygen (DO) needed for organisms to break down organic material (such as coffee bean mucilage) present in a given water sample.