Biochemical Oxygen Demand

Biochemical Oxygen Demand (BOD)

The amount of dissolved oxygen needed by biological organisms in water to break down material, expressed in mg O2/L.

Sources of BOD

Natural sources include bogs, swamps, leaves, and vegetation; human sources include pulp and paper mills, meat-packing plants, food processing industries, and wastewater treatment plants.

Five-day BOD test (BOD5)

The standard incubation period for measuring BOD, conducted for 5 days at 20 °C.

Ultimate BOD

The complete biochemical oxidation of organic matter in a water sample, typically considered to take twenty days.

Winkler Method

A method for determining BOD that uses titration and involves three bottles for measuring dissolved oxygen.

Algal effect

An error in BOD measurements where algae artificially lower the BOD results.

Chemical Oxygen Demand (COD)

A measure similar to BOD, determined using a strong oxidizing agent and reflects the amount of oxygen that would be consumed.

Dilution method

One of the three commonly used tests for measuring BOD.

Compounds in water that are biodegradable

Almost anything can be biodegradable if the right organism is present and it is accessible to them.

Dissolved oxygen

The amount of oxygen dissolved in water, necessary for the survival of aquatic life.

Nitrification effect

An error where the presence of nitrifying bacteria increases BOD measurements artificially by converting ammonia to nitrate.

BOD bottle

A special bottle used for collecting samples for BOD analysis, which must not be aerated during collection.

Chlorine's impact on BOD

Chlorine can artificially lower the BOD results by killing bacteria needed for the decomposition process.

Recovery Zone

The area in a stream where conditions are returning to maintaining a high quality stream environment after pollution.

Pollution zone

The area impacted by pollution where low oxygen concentrations restrict life to species that tolerate poor conditions.

Threshold for maximum COD

The maximum COD value typically measured is 800 mg/L.

Total Organic Carbon (TOC)

A technique used to assess water quality by measuring the total amount of organic matter, impacting drinking water and creating disinfection byproducts.