Dissolved oxygen, water quality indicator

We use water quality indicators, such as pH, temperature, conductivity (specific conductance), dissolved oxygen, oxidation-reduction potential (ORP), and turbidity, as groundwater well stabilization parameters. Stable values of three consecutive measurements of these parameters are considered an indication of a stabilized well. 

Water is the most abundant solvent on Earth. The amount of oxygen contained in water is called dissolved oxygen (DO). Dissolved oxygen is an indicator of water quality because oxygen is necessary for fish and other aquatic life. Oxygen enters a body of water by photosynthesis of aquatic plants and by transfer of oxygen across the air-water boundary. 

The measurements of water quality parameters (oxidation-reduction potential, pH, temperature, conductivity, dissolved oxygen, and turbidity) and the collection of field screening data with field portable instruments and test kits constitute a substantial portion of field work. Field measurements, such as pH, stand on their own as definitive data used for the calculations of solubility of chemical species and chemical equilibrium in water, whereas others serve as indicators of well stabilization or guide our decision-making in the field. Table 3.8 shows the diversity of field measurement... 

Romanian regimentations about water quality protection show that between the strictly surveyed parameters that can indicate organic pollution degree are chemical oxygen demand (CODMn), dissolved oxygen (DO), and biochemical oxygen demand (BOD). 

It follows that the content of dissolved oxygen is an important indicator of the quality of streams, as one of the first indications of surface water pollution by organic substances is a decrease in the oxygen content downstream from the source of poUution. Oxygen in water is of vital importance for fish, a concentration of 3-4 mg 1 is usually considered to be the lower limit, but this depends on the sensitivity of fish. The salmon-like fish require a concentration of approximately 6 mg... 

The amount of O2 dissolved in water is an important indicator of water quality. Water fully saturated with air at 1 atm and 20 °C contains about 9 ppm of O2. Oxygen... 

The complexity with respect to water quality is reflected in the many types of physical, chemical and biological indicators. Therefore, depending on specific project requirements, information about a wide variation of additional parameters may be required in order to describe the state of and the effect on the water quality. Simple measurements such as temperature, pH, dissolved oxygen, conductivity, conductivity, alkalinity (pH) and ammonia can be made on-site in direct contact with the water source. More complex measurements such as toxic contaminants and the presence of micro organisms may require water sampling followed by an analysis in the laboratory. 

We judge the quality of water by taste, smell, color, and lack of pathogenic organisms or harmful contaminants. Often bad taste, odor, or color indicates contamination. Most of the water we drink has been treated to remove harmful substances and has had chlorine, ozone, or chloramines added to kill bacteria. Ordinary water contains dissolved gases such as oxygen, nitrogen, carbon dioxide, and other atmospheric components, as well as harmless minerals. 

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