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The model describes how dissolved oxygen (DO) decreases in a river or stream along a certain distance by degradation of biochemical oxygen demand (BOD). The equation was derived by H. W. Streeter, a sanitary engineer, and Earle B. Phelps , a consultant for the U.S. Public Health Service , in 1925, based on field data from the Ohio River .
An aquatic system lacking dissolved oxygen (0% saturation) is termed anaerobic, reducing, or anoxic. In water, oxygen levels are approximately 7 ppm or 0.0007% in good quality water, but fluctuate. [5] Many organisms require hypoxic conditions. Oxygen is poisonous to anaerobic bacteria for example. [3]
Decreased levels of dissolved oxygen (DO) is a major contributor to poor water quality. Not only do fish and most other aquatic animals need oxygen, aerobic bacteria help decompose organic matter. When oxygen concentrations become low, anoxic conditions may develop which can decrease the ability of the water body to support life.
Water chemistry in river ecosystems varies depending on which dissolved solutes and gases are present in the water column of the stream. Specifically river water can include, apart from the water itself, [citation needed] dissolved inorganic matter and major ions (calcium, sodium, magnesium, potassium, bicarbonate, sulphide, chloride)
The Citarum River (more correctly called the Tarum River, as the prefix "Ci" simply means "river") (Sundanese: Walungan Citarum) is the longest and largest river in West Java, Indonesia. [3] It is the third longest river in Java, after Bengawan Solo and Brantas. It plays an important role in the life of the people of West Java.
PHS also conducted studies and described pollution problems in several major river systems and the Great Lakes. The PHS studies supported the development of the Streeter–Phelps equation, a water quality modelling tool that is used to predict dissolved oxygen levels in water bodies in response to pollutant loads. [94]: 1063–5
They include: dissolved oxygen and biochemical oxygen demand (BOD), temperature, pH, turbidity, phosphorus, nitrates, total suspended solids, conductivity, alkalinity, and fecal coliform. [6] BOD is perhaps the most widely used metric to assess water quality. [citation needed] Water quality is also closely linked with water quantity issues.
Red circles show the location and size of many dead zones (in 2008). Black dots show dead zones of unknown size. The size and number of marine dead zones—areas where the deep water is so low in dissolved oxygen that sea creatures cannot survive (except for some specialized bacteria)—have grown in the past half-century.