Why is biological oxygen demand important

Inversely, low BOD means less oxygen is being removed from water, so water is generally purer. Cold water retains oxygen better than warmer water, so in summer months, dissolved oxygen is usually lower from the start. The Water Education Foundation is a nonprofit, tax-exempt, c 3 organization, federal tax ID Header link June 22, Read more. Header link September 15, Header link November 3, Header link May 15, Water Education Foundation.

Aquapedia background September 7, All projects must have been in the design or construction phase over the last 18 months. Industrial Top Projects. What is Aeration for Wastewater Treatment?

By Cristina Tuser. What is biological oxygen demand? What is Biological Oxygen Demand? Current Issue. October Latest Articles. Not looking for biochemical or biological oxygen demand? Read instead about chemical oxygen demand COD. At beginning of the cycle, algae and other producers in the water take up inorganic nutrients and use them in the process of building up their organic tissues.

Consumers like fish and other aquatic animals eat some of the producers, and the nutrients move up the food chain. When these organisms die, bacteria decompose the organic compounds and release into the water inorganic nutrients such as nitrate , phosphate , calcium , and others.

Some of these nutrients end up at downstream or in sediments, but most of them recycle again and again. Most of the bacteria in the aquatic water column are aerobic. That means that they use oxygen to perform their metabolic activities of decomposition.

Remember that we learned in other related exercises that under normal conditions, dissolved oxygen exists in very low concentrations. Natural levels of oxygen in aquatic systems are always somewhat depleted by normal levels of aerobic bacterial activity.

In most cases, if dissolved oxygen concentrations drop below 5 parts per million ppm , fish will be unable to live for very long. All clean water species such as trout or salmon will die well above this level and even low oxygen fish such as catfish and carp will be at risk below 5 ppm. When abnormally high levels of aerobic bacterial activity take place, however, the level of dissolved oxygen can drop dramatically.

Under what kind of circumstances does such change happen?