What affects BOD?

Sources of BOD include leaves and woody debris; dead plants and animals; animal manure; effluents from pulp and paper mills, wastewater treatment plants, feedlots, and food-processing plants; failing septic systems; and urban stormwater runoff.

What are the factors affecting BOD?

The factors affecting BOD include the type and amount of organic material present, the temperature, the pH, the dissolved oxygen concentration, and also the presence of bacteria.

What causes BOD to increase?

High biochemical oxygen demand can be caused by: high levels of organic pollution, caused usually by poorly treated wastewater; high nitrate levels, which trigger high plant growth.

What affects dissolved oxygen levels in water?

The amount of oxygen that can be dissolved in water depends on several factors, including: water temperature, the amount of dissolved salts present in the water (salinity), and atmospheric pressure (Tables 1 and 2).

What causes a decrease in BOD?

During the secondary treatment of primary effluents, the BOD level decreases because useful microbes consume a major part of the organic matter. Reduction in the organic matter leads to lowering of BOD.

Biochemical Oxygen Demand (BOD): Explained details (Animation)

How is BOD affected by temperature?

The BOD removal rate in the bioreactor increased when the temperature increased from 20 degrees C to 30 degrees C, 40 degrees C, and 50 degrees C, but it decreased when the temperature increased from 50 degrees C to 60 degrees C. Higher temperature enhanced the endogenous respiration of microbes in the bioreactor.

Under what conditions will BOD increase and do decrease?

If there is no organic waste present in the water, there won't be as many bacteria present to decompose it and thus the BOD will tend to be lower and the DO level will tend to be higher.

What are 3 factors that influence dissolved oxygen levels?

Does pH affect dissolved oxygen?

Dissolved oxygen does not directly affect the pH of a solution because there is no physical-chemical connection between the two. There is often some confusion that there is a relationship between DO and pH, as pH is related to the presence of free carbon dioxide (CO2) atoms which contain two oxygen atoms.

How do you control dissolved oxygen in water?

Four common techniques can be used to remove dissolved oxygen (DO) from water, both chemically and mechanically. These techniques include boiling water at 1 atm (atmospheric pressure), boiling water under reduced pressure, nitrogen (N) purging, and sonication under reduced pressure.

Does chlorine affect BOD?

BOD reduction: Chlorine accomplishes BOD reduction by oxidation of organic compounds present in wastewaters. 4. Oxidation of metal ions: Metal ions which are in reduced state are oxidized by chlorine (e.g., ferrous to ferric ion and manganous to manganic ions).

Why does BOD increase with temperature?

The bacteria require oxygen for this process so the demand for oxygen (BOD) is high at this location. Therefore, increased water temperatures will speed up bacterial decomposition and result in higher BOD levels. Temperature also influences the survival of aquatic organisms.

Can chlorine increase BOD?

Chlorine dosages above 10 mg l⁻¹ resulted in increased BOD and COD levels of the effluent, with chlorine dosages above 30 mg l⁻¹ resulted in almost double the original BOD and COD values.

Does rain affect BOD?

The rainfall intensity is one of the major contributors towards the decreasing amount of BOD. As rainy periods are increased, it fills flush the contaminant on the roof, hence decreasing the value of BOD along the rain periods [6].

What causes high BOD and COD?

Sources: COD increases as the concentration of organic material increases. It also increases if inorganic compounds susceptible to oxidation by the oxidant (typically dichromate) are present. Water with high COD typically contains high levels of decaying plant matter, human waste, or industrial effluent.

Does pressure affect dissolved oxygen?

How does pressure affect oxygen solubility? Dissolved oxygen concentration will increase as pressure increases. This is true of both atmospheric and hydrostatic pressures. Water at lower altitudes can hold more DO than water at higher altitudes.

How does temperature affect dissolved oxygen?

Cold water can hold more dissolved oxygen than warm water. In winter and early spring, when the water temperature is low, the dissolved oxygen concentration is high. In summer and fall, when the water temperature is high, the dissolved-oxygen concentration is often lower.

What happens if dissolved oxygen is too low?

When dissolved oxygen becomes too low, fish and other aquatic organisms cannot survive. The colder water is, the more oxygen it can hold. As the water becomes warmer, less oxygen can be dissolved in the water.

How do you increase dissolved oxygen?

Simple aeration or agitation can increase dissolved oxygen enough to prevent problems. Injecting air or, especially, pure oxygen can increase levels as well, but only as high as saturation levels. Paying attention to temperature can also help improve DO, as colder water can hold more oxygen.

What are two situations that reduce the dissolved oxygen content of water?

Temperature: High temperatures reduce the solubility of oxygen in water (i.e., warm water holds less DO than cold water). Nutrients: High nutrients can lead to excessive plant growth, resulting in DO declines due to respiration and decomposition.

What factors affect the rate of oxygen?

The rate of oxygen uptake depends on roughly the second power of the surface area to volume ratio of the erythrocyte, whereas the rate of release is much less dependent on the size and shape of the red cell.

Does pollution increase BOD?

The more organic matter there is (e.g., in sewage and polluted bodies of water), the greater the BOD; and the greater the BOD, the lower the amount of dissolved oxygen available for higher animals such as fishes. The BOD is therefore a reliable gauge of the organic pollution of a body of water.

Is BOD higher during the winter?

The BOD level in the winter (0.64 mg/L) is lower than that of the rainy season (1.97 mg/L); whereas COD (265.33 mg/L in the winter) was much higher than the BOD level that means the sample could be visualized as toxic.

Does BOD depend on time?

The quantity of oxygen for stabilization is taken as a measure of decomposable organic matter. As the rate of exserrtion of BOD depends on time and temperature, ultimate BOD exertion takes very long time.

Why is BOD high in polluted water?

Question: Why is BOD high in polluted water? Answer: The larger the amount of organic pollutants in the water, the more oxygen the bacteria demand, and this oxygen requirement is known as BOD. As a result, the amount of pollution in a body of water is proportional to the BOD.