Water Quality and Pollution

The Ganges river basin is one of the most fertile and densely populated regions in the world that covers an area of 1,80,000 $km^2$. The river flows through 29 cities with population over 100,000; 23 cities with population between 50,000 and 100,000, and about 48 towns. 

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. The BOD measures the amount of oxygen consumed by biochemical oxidation of waste contaminants. The total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion is called as the ultimate BOD. The BOD is universally adopted as a measure of relative pollution effect.

Biochemical oxygen demand is a measure of the quantity of oxygen used by microorganisms (e.g., aerobic bacteria) in the oxidation of organic matter. Natural sources of organic matter include plant decay and leaf fall. However, plant growth and decay may be unnaturally accelerated when nutrients and sunlight are overly abundant due to human influence. Urban runoff carries pet wastes from streets and sidewalks, nutrients from lawn fertilizers; leaves, grass clippings, and paper from residential areas, which increase oxygen demand. Oxygen consumed in the decomposition process reduces other aquatic organisms of the oxygen they need to live. If dissolved oxygen concentrations drop below 5 parts per million (ppm), fish will be unable to live for very long. This can occur in the form of organic pollution for sources such as domestic sewage, septic tank leakage, and fertilizer runoff, or could be in the form of inorganics from domestic or industrial sources. 

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. 

Biological oxygen demand (BOD) is one of the most common measures of pollutant organic material in water. BOD indicates the amount of putrescible organic matter present in water. Therefore, a low BOD is an indicator of good quality water, while a high BOD indicates polluted water. The BOD test serves an important function in stream pollution-control activities.

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic microorganisms to break down organic material present in a given water sample at certain temperature over a specific period of time. Thus, the correct answer is option C.

BOD is abbreviated form of biological oxygen demand. It is the amount of oxygen required by microbes to break down the organic matter present in a certain volume of a sample of water. The amount of BOD in the water is a measure of a number of organic pollutants in the water.

Biochemical Oxygen Demand (BOD) measures the amount of oxygen required by aerobic microorganisms to decompose organic matter. High BOD indicates a high concentration of organic pollutants in the water.

Chemical Oxygen Demand (COD) measures the total amount of oxygen required to chemically oxidize all organic matter, whereas BOD only measures biodegradable organic matter. Therefore, COD is almost always higher than BOD.

Biological Oxygen Demand is a measurement of the amount of dissolved oxygen that is used by aerobic microorganisms when decomposing organic matter in water.  It is expressed in milligrams of oxygen consumed per liter of the sample during 5 days of incubation at 20°C and is used to determine the degree of organic pollution of water. Hence when a huge amount of carbon dioxide is added BOD will not be affected. Thus, the correct answer is option C.

Algal blooms lead to excessive organic matter. As this matter decomposes, aerobic bacteria consume dissolved oxygen, leading to a decrease in O2 levels and an increase in BOD, which harms aquatic life.

BOD or Biochemical oxygen demand is the amount of dissolved oxygen which is required by the aerobic organisms during the decomposition of organic matter. The BOD is measured at a specific temperature and specific period of time. BOD value is represented in the form of oxygen which is consumed per litre of the sample used for testing. The sample is tested before and after 5 days of incubation at 20 °C. The value describes the amount of organic material present in the contaminated or waste water. 

Water pollution can be identified by testing its PH level and Biological Oxygen Demand (BOD)  Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, aquifers and groundwater). This form of environmental degradation occurs when pollutants are directly or indirectly discharged into water bodies without adequate treatment to remove harmful compounds. Acid rains, dumping of chemicals into the water by individuals, industries, and communities.; steam from coal mine drainage etc affect the pH of the water in its reservoir. Thus by testing the pH of water, on the scale from 1 to 14, the pollution in water can be identified.  Biochemical oxygen demand is a measure of the quantity of oxygen used by microorganisms (e.g., aerobic bacteria)  in the oxidation of organic matter. This value varies with the amount of pollution in water hence pollution can be determined by BOD.

Sewage is waste water having food residue, animal and human excreta, detergent, discharges from industrial and commercial establishments. Degree of impurity of water due to organic matter is measured in terms of BOD or biochemical oxygen demand. BOD is the oxygen in milligrams required for 5 days in one litre of water at 20 degree centigrade for the micro organisms to metabolise organic wastes. If the water, is polluted with sewage and other organic wastes, the BOD will increase.