What is BOD and why is it important?
The BOD is an important parameter for assessing water quality. It deals with the amount of oxygen consumption (mg O2 L− 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 BOD in water quality?
Biochemical oxygen demand (BOD) is the amount of dissolved oxygen (DO) 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 causes high BOD in wastewater?
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.Mar 12, 2020
What happens if BOD is high?
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. The consequences of high BOD are the same as those for low dissolved oxygen: aquatic organisms become stressed, suffocate, and die.
What increases BOD water?
Organic loading is occurrence of excess organic matter inside water due to sewage disposal and eutrophication. This leads to an increase in biological oxygen demand (BOD) for putrefaction. Explosive multiplication of alga leads to algal bloom. These conditions result in decrease in dissolved oxygen in water.
Does chlorine reduce 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).
How can I reduce my BOD?
These are the best practices for reducing BOD and TSS that facility managers should know:Focus on removing TSS from wastewater first. ... Get a properly sized EQ tank. ... Control the pH of the waste stream. ... Install a modern plate pack DAF made of stainless steel or plastic. ... Use a regenerative turbine air dissolution pump.More items...•Aug 16, 2018
What happens if BOD is low?
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 is a BOD in wastewater?
Biological Oxygen Demand (BOD) is a chemical procedure for determining the amount of dissolved oxygen needed by microorganisms to break down organic matter.
What is a BOD tank?
BOD - Aeration Tank Process. In a conventional BOD Wastewater Treatment process, microorganisms use oxygen to break down organic compounds. The microorganisms essentially consume the organic matter, but there must be enough oxygen in the water. If there isn’t enough oxygen in the water, the microorganisms will die.
How does a sludge thickener work?
When there is enough wastewater in the sludge thickener, the slurry from the tank is pumped into the Filter Press. The filter press separates the liquids and solids using pressure filtration. Sludge Cake will form between the filter plates, where it can be safely removed and easily discarded. The excess water is returned to the Initial Settling Tank.
How is wastewater collected?
Wastewater is collected in the Initial Settling Tank or the Primary Clarifier . The main function and purpose of the Initial Settling Tank is to make the wastewater homogeneous, and it allows for solids to settle to bottom of the tank forming sludge. The sludge collect is removed and piped over to the Sludge Thickening Tank. While the Setting Tank will remove much of the initial solids, there are organic compounds will not settle, and it will need to be treated in the Aeration Tank or a DAF Clarifier, depending on the specific application.
What is the purpose of diffused air in wastewater?
Diffused Air supplies the aeration tank with an ample amount of oxygen. The organic compounds in the wastewater provide the microorganisms their “food”. Since microorganisms will multiply in the wastewater over time, it is essential to have the correct balance of Oxygen, Organic Matter, and Microorganisms.
Where is the waste activated sludge collected?
The Waste Activated Sludge from the clarifier is collected in the Sludge Thickener. The thickening tank will provide additional solid-liquid separation. Any liquid overflow will be returned to the settling rank. The thickened sludge will be processed by the Filter Press .
Does setting tank remove solids?
While the Setting Tank will remove much of the initial solids, there are organic compounds will not settle, and it will need to be treated in the Aeration Tank or a DAF Clarifier, depending on the specific application.
What is BOD in wastewater?
Industries that discharge wastewater into municipal sanitary sewers or waterways are facing strict regulations on levels of biological or biochemical oxygen demand (BOD). Solid materials in wastewater can consist of organic and/or inorganic materials and organisms.
What is the purpose of a biological oxygen demand test?
Biological Oxygen Demand (BOD) is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic biological organisms “bio-bugs” in a body of water to break down organic material present in a given water sample at a certain temperature over a specific time period. It is not a precise quantitative test, although it is widely used as an indication of the quality of water.
Does ALAR water treatment increase BOD?
ALAR Water Treatment provides these industries with cost effective wastewater equipment solutions in order to help achieve BOD discharge compliance.
What is BOD5 in wastewater?
Typically, municipal wastewater treatment plants will use BOD5 as a measure of the organic concentration into, and through, the wastewater plant. Industrial wastewater systems will more often use COD to measure the organic concentration moving through the treatment plant. In my experience, I see TOC being used much less often (rarely) ...
What is the BOD5 test?
The BOD5 test measures the oxygen consumed by microorganisms as they oxidize (consume or eat) the soluble organic matter in the wastewater. But the BOD5 test is a somewhat unreliable means of determining the amount of organic matter present in water. The test measures only the approximate amount of oxygen that will be required ...
How long does it take to complete the Bod5 test?
Due to the length of time required to complete the BOD5 test (five days), BOD results provide historical data only and do not facilitate rapid water quality assessment for optimal process control. The often highly variable chemical composition ...
What is the purpose of a wastewater test?
The test measures only the approximate amount of oxygen that will be required (absorbed or consumed) by a wastewater when it is exposed to air or oxygen for an extended period of time. Toxic substances in the wastewater inhibit or even prevent bacterial growth and, therefore, oxidation of the organic matter.
How long does it take to test for organics in wastewater?
The often highly variable chemical composition and strength of industrial wastewater requires a much more rapid method for measuring the organic concentration, hence the use of the two hour COD test or, in some plants, the 30 minute TOC analysis.
How much COD is in water?
The COD in industrial water may be 50 – 2,000 mgO 2 /L, although it may reach 5,000, depending on the type of industry. The main difference between BOD and COD is that COD measures all organic material, while BOD only measures organic material which is or can be biologically degraded.
What is COD in water?
COD, the chemical demand for oxygen a source of water has, is the amount of oxygen required to break down organic substances chemically and convert them to CO 2 and H 2 O. It is also expressed in mgO 2 /L, and the higher the COD, the more polluted the water is.
What is the biological demand for oxygen in water?
BOD, the biological demand for oxygen a source of water has, is the amount of oxygen used by microorganisms to break down organic substances. These are usually bacteria (aerobic or anaerobic), yeasts and plankton contained in the water. It is a measure of the degree of contamination and is expressed in mgO 2 /L.
How is Bod5 measured?
It is measured via a delicate and time-consuming biological process, which depends on temperature. The standard measurement is performed at 20°C for 5 days and is called BOD5. The period of 5 days was chosen, as this is the average time it takes a British river to reach the sea. In general terms, the greater the pollution, the higher the BOD.
Is the COD greater than the BOD?
Therefore, for a given water sample, the COD is always greater than the BOD, and the second result (COD), as the complete chemical oxidation of the sample, can be considered to include the first. BOD and COD are related and maintain their relationship for each type of water.
Is the Bod/COD relationship the same for different types of water?
The relationship is not the same for different types of water; however, industrial water of the same type has a similar BOD/COD relationship. By providing more information and being quicker to obtain, the COD is becoming the reference standard in the field.
What is COD in biology?
Chemical Oxygen Demand (COD): COD is defined as the oxygen equivalent of the organic portion of the sample that is susceptible to oxidation by a strong chemical oxidant potassium dichromate K2Cr2O7, Biochemical Oxygen Demand (BOD) is a chemical procedure for determining how fast biological organisms use up oxygen in a body of water.
What is the difference between a Bod and a Cod?
BOD is a measure of, the amount of oxygen that requires for the bacteria to degrade the organic components present in waste water. COD or Chemical Oxygen Demand is the total measurement of all chemicals (organics & in-organics) in the waste water. ther is arelationship between BOD&COD ,COD is higher than that of BOD;
What is the BOD5 method used for?
BOD5 is commonly used to measure natural organic pollution.
What is the purpose of the Biochemical Oxygen Demand?
Biochemical Oxygen Demand (BOD) is a chemical procedure for determining how fast biological organisms use up oxygen in a body of water. It is usually performed over a5-day period at20° Celsius. It is used in water quality management and assessment, ecology and environmental science.
Is a BOD a quantitative test?
BOD is not an accurate quantitative test, although it could be considered as an indication of the quality of a water source. In environmental chemistry, the chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in ...
Is BOD a pollutant?
It is listed as a conventional pollutant . BOD is similar in function to chemical oxygen demand (COD), in that both measure the amount of organic compounds in water. However, COD is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biologically active organic matte.
What is the BOD of water?
Ans. BOD or Biochemical Oxygen Demand is the measure of the amount of oxygen utilized by aerobic microbes to degrade the organic waste present in water. It is calculated over five days at a specific temperature of 20°C.
What is the importance of BOD in sewage treatment?
These are -. BOD finds its primary importance in sewage treatment plants. It gives the respiration rate of sewage, sludge , soil, garbage. It determines the rate of respiration in living beings. Measuring BOD gives the COD or Chemical Oxygen Demand of inorganic substances. It indicates the polluting potential of water.
Why is it important to reduce the biochemical oxygen demand of water bodies before discharging into water bodies?
It is extremely important to reduce the biochemical oxygen demand of water bodies or wastewater before discharging into water bodies because high BOD of water means more and more oxygen is utilized by the aerobic bacteria for breaking down the organic waste in the water. This significantly reduces the available oxygen for the respiration ...
How does pollution affect the BOD of water?
Sources that increase Biological Oxygen Demand of water are both natural and man-made. Pollution is a major contributor to increasing the BOD of water bodies. A good lifestyle is associated with an ample usage of water on a regular basis which results in a lot of wastewater with organic content in it. With increasing industrialization, pollution is increasing manifold. Factories have enormous wastewater being generated. Few industries that have huge quantities of wastewater are paper mills, food processing plants, jute mills, etc. The environmental factors contributing to increasing BOD include surface runoff, floating debris, dead animal and plants, soil erosion, etc. There are few chemicals that affect the BOD of drinking water. One of these is phosphate, which when present in high amount increases the BOD of water.
How is oxygen demand measured in water?
Biochemical Oxygen Demand of a water sample is measured by a Bioassay procedure which measures the oxygen consumed by the bacteria from the decomposition of the organic matter over a period of five days at an incubation temperature of 20°C. BOD is expressed in milligrams per litre of sample water. Although this is not a precise quantitative test, it is widely used as an indication of the polluting potential of water. This test was given by Sawyer and McCarty in the year 1978.
How can the BOD of water be reduced?
The BOD of water can be reduced by reducing pollution. The lesser we contaminate the water bodies lesser is its biochemical oxygen demand levels. There are various treatments done to reduce BOD levels in various wastewaters.
What happens when the BOD of a water body increases?
When BOD of a water body increases significantly, the aquatic life is adversely affected . The oxygen used by aquatic organisms for respiration and metabolism is significantly reduced by the microbes for breaking down of organic waste.
