What it is
Biochemical oxygen demand (BOD) measures the oxygen consumed by micro-organisms as they digest the organic matter in a sample over five days at 20 °C. The “+ATU” in the method name means a chemical is added to stop nitrifying bacteria from using oxygen too, so the result reflects carbon-based pollution only. The higher the BOD, the more work a sewage works or a river has to do to deal with the discharge.
Where it comes from
Anything organic raises BOD: food and drink residues, milk, blood, sugars, starches, oils and fats, yeast, process wash-down water, and detergents. Food and beverage manufacturing, dairies, breweries, abattoirs and commercial laundries typically produce high-BOD effluent. Domestic sewage is usually in the low hundreds of mg/l; strong food-industry effluent can be many times that.
Why it matters
BOD is an environmental and commercial measure rather than a health one. In a river, high BOD strips out dissolved oxygen and kills fish and invertebrates. In the sewer, it is the main driver of your trade effluent charges under the Mogden formula, and exceeding your consent limit can mean a notice, a prosecution or the consent being withdrawn.
What can be done about it
Start by keeping product out of the drain: catch spills, dry-sweep before wash-down, and collect first rinses separately. Beyond that, balancing tanks, fat and grease interceptors, dissolved-air flotation and biological pre-treatment each bring BOD down by a different route. A Pozzani engineer can review your process and consent together and advise which gives the quickest return.
Information last reviewed 6 October 2026 by Pozzani Pure Water.