Biological Oxygen Demand.docx

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Biological Oxygen Demand (BOD) is one of the most common measures of pollutant organic material in water a low BOD is an indicator of good quality water, while a high BOD indicates polluted water Dissolved oxygen (DO) is consumed by bacteria when large amounts of organic matter from sewage or other discharges are present in the water DO is the actual amount of oxygen available in dissolved form in the water When the DO drops below a certain level, the life forms in that water are unable to continue at a normal rate. Chemical Oxygen Demand is the total measurement of all chemicals in the water that can be oxidized

Oxygen-Demanding Waste • Organic matter decays – Degraded by bacteria – Bacteria use up oxygen – Oxygen concentration goes to 0 • Kills fish • Foul odors

-Oxidation is gain of oxygen

Nutrients • You can work hard to remove all of the organic matter from sewage, but plant nutrients are still left • Plants in lakes and streams take nutrients and recreate the organic matter • Process called EUTROPHICATION

Is Eutrophication Bad? • Good – if you want to produce food from the water – Some fish grow better • Bad – if you want to use the lake for recreation – Causes tastes and odors – Degrades water for recreational use

Eutrophication presents as one of the most serious ecological problems of open water sources such as lakes, oceans and reservoirs. It is characterized by dense algal and plant growth owing to the enrichment by phosphorus and nitrogen nutrients needed for photosynthesis. EFFECTS •

Threatens the survival of fish and other aquatic life forms

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Deterioration of water quality and limits access to safe drinking water Poisoning and impact on human health Endangers fishing Degradation of recreational opportunities