What does the oxygen sag curve explain?
Oxygen sag or the oxygen sag curve refers to the reduction in dissolved oxygen plotted over a distance along a water body from a point at which sewage or other pollutants have been discharged.
What is an oxygen sag curve quizlet?
Oxygen sag curves occur when the oxygen dissolved in the water is depleted. This is caused by the addition of anything which increases the BIOLOGICAL OXYGEN DEMAND such as biological waste and sewage. they are found mostly in slow flowing streams.
What causes an oxygen sag curve?
When pollutants (waste or excess fertilizer) enter the water, BOD and DO levels change, producing the oxygen sag curve. DO and BOD levels create characteristic zones in a stream around the point source of pollution known as the Clean zone, Decomposition Zone, Septic Zone, and Recovery Zone.
What is an oxygen sag curve apes?
We show the SAG of dissolved oxygen in a stream or a river or marine body of water. The SAG point again denotes our lowest level of dissolved oxygen in our water.
Does sag curve short note?
The curve obtained when the concentration of dissolved oxygen in a river into which sewage or some other pollutant has been discharged is plotted against the distance downstream from the sewage outlet (see graph). Samples of water are taken at areas upstream and downstream from the sewage outlet.
Which model is used for DO sag curve?
Sewage – not a pleasant thought! In this section of Fate you use the Streeter-Phelps model to look at the dissolved oxygen (DO) of a stream.
What happens to dissolved oxygen in the recovery zone?
In the recovery zone, the dissolved oxygen increases, and the BOD is reduced because most oxygen demanding organic waste from the input of sewage has decomposed and natural stream processes are replenishing the water with dissolved oxygen.
What is the relationship between dissolved oxygen and biochemical oxygen demand?
BOD directly affects the amount of dissolved oxygen in rivers and streams. The greater the BOD, the more rapidly oxygen is depleted in the stream. This means less oxygen is available to higher forms of aquatic life.
How do you draw an oxygen sag curve?
Oxygen Sag Curve & Streeter-Phelps Equation | Waste Water Engineering
Does sag curve equation?
D0 = deficit at t = 0. Note that both L0 and D0 are the values in the stream after any external waste streams have been mixed in. This equation is known as the DO sag equation (for its distinctive shape) or the Streeter-Phelps equation, after the gentlemen who first published it in 1925.
What is used to describe the lowest point in an oxygen sag curve?
The critical point on the oxygen sag curve is called the critical deficit, Dc. This point (see Figure 1) has the lowest dissolved oxygen content and will determine the impact on living organisms in the stream.
Which of the following equation helps us to plot the oxygen sag curve?
KRT = KR20 (1.016)T-20, where KR20 is the reoxygenation constant at 20oC.
What are 3 factors that influence dissolved oxygen levels?
NATURAL FACTORS INFLUENCING DISSOLVED OXYGEN
- Aquatic life- animals living in water use up dissolved oxygen.
- Elevation- the amount of oxygen in elevation increases.
- Salinity (saltiness)- Salty water holds less oxygen than fresh water.
- Temperature- cold water holds more dissolved oxygen than warm water.
Is dissolved oxygen same as BOD?
BOD, also called biological oxygen demand, is the amount of dissolved oxygen needed (i.e., demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.
What is the difference between oxygen demand and dissolved oxygen?
The amount of dissolved oxygen used up by aerobic microorganisms to decompose the organic matters present in a sample of water is termed Biochemical Oxygen Demand or Biological Oxygen Demand (BOD). BOD and DO are inversely proportional to each other i.e a decline in DO levels reflects a high level of BOD.
What does the minimum point of the DO sag curve indicate?
Which of the following represents the oxygen sag curve in the following figure?
Which of the following represents the oxygen sag curve in the following figure? Explanation: The oxygen sag curve is represented by the red curve. It is also called as an oxygen deficit curve.
What factors decrease and increases dissolved oxygen?
What causes dissolved oxygen to decrease?
Temperature increases, decaying aquatic plants and algae, fertilizers, and weather changes are common causes of low dissolved oxygen in the water.
What causes high BOD in water?
Sources: BOD represents the amount of organic matter in a water supply; therefore, it increases when decaying plants, human or animal waste, and other organic compounds are added to water.
Why is BOD important in water quality?
The BOD is an important parameter for assessing water quality. It deals with the amount of oxygen consumption (mg O2 Lā 1) by aerobic biological organisms to oxidize organic compounds. Sewage with high BOD can cause a decrease in oxygen of receiving waters, which in turn can cause the death of some organism.
What is the relationship between BOD and dissolved oxygen?
What does low BOD indicate?
The dissolved oxygen readings are usually in parts per million (ppm). Higher BOD indicates more oxygen is required, which is less for oxygen-demanding species to feed on, and signifies lower water quality. Inversely, low BOD means less oxygen is being removed from water, so water is generally purer.
What are the three sinks and sources of oxygen in the extended oxygen sag model?
The expanded model is a modification of the traditional model and includes internal sources (reaeration and photosynthesis) and sinks (BOD, background BOD, SOD and respiration) of DO.
What 3 factors influence the amount of dissolved oxygen?
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).