How to reduce chemical oxygen demand (COD) in wastewater?
Chemical Oxygen Demand or COD is a measurement of the oxygen required to oxidize soluble and particulate organic matter in water. COD can be measured in rapidly or in real-time with Real Tech’s COD instruments to improve wastewater process control and plant efficiency. HOW TO MEASURE COD IN REAL-TIME
What is Cod water quality?
Nov 01, 2018 · COD in wastewater refers to the amount of oxygen required to degrade all oxidizable compounds in a measured sample of effluent. You can find the COD value in wastewater by carrying out a COD test. COD Test
What is bod in wastewater?
Mar 14, 2020 · Chemical Oxygen Demand (COD) in Wastewater Information: Properties: Chemical Oxygen Demand (COD) is a parameter of water quality used to determine the concentration of organic matter in a water supply.1 COD represents the amount of oxygen needed to allow a strong oxidant to oxidise all the organic matter in the sample.
What is cod treatment?
Chemical oxygen demand (COD) is the amount of dissolved oxygen that must be present in water to oxidize chemical organic materials, like petroleum. COD is used to gauge the short-term impact wastewater effluents will have on the oxygen levels of receiving waters. COD versus BOD
What is BOD and COD in waste water treatment?
The biochemical oxygen demand (BOD) represents the amount of dissolved oxygen (DO) consumed by biological organisms when they decompose organic matter in water. The chemical oxygen demand (COD) is the amount of oxygen consumed when the water sample is chemically oxidised.
What COD means?
1.2 Chemical Oxygen Demand. COD is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution, which in SI units is milligrams per liter (mg/L).
What is COD in water testing?
The Chemical Oxygen Demand (COD) of water is a measure of the amount of oxygen that is consumed by reactions with chemicals in the water. Generally, a COD test is used to measure the amount of organic pollutants in a water body as an indicator of water quality.
Why is it important to determine COD in wastewater treatment?
In wastewater treatment, the Chemical Oxygen Demand (COD) is an important measurement for the amount of oxygen that is required to break down pollutants (organic substances) in water. The chemical oxygen demand can be measured using different methods, direct or indirect.Aug 11, 2017
What if COD is high in water?
Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen (DO) levels. A reduction in DO can lead to anaerobic conditions, which is deleterious to higher aquatic life forms.
What causes high COD in water?
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.Mar 14, 2020
How do you test for COD waste water?
What test methods are typically used to determine COD at water and wastewater laboratories? The most common test method is the colorimetric analysis after oxidizing the COD with acid and using indicator compounds, such as hexavalent dichromate.
How do you test for COD?
COD is measured via a laboratory assay in which a sample is incubated with a strong chemical oxidant for a specified time interval and at constant temperature (usually 2 h at 150°C). The most commonly used oxidant is potassium dichromate, which is used in combination with boiling sulphuric acid.
How long does a COD test take?
2-3 hoursCOD is expressed in mg/L, which indicates the mass of oxygen consumed per liter of solution. The COD test only requires 2-3 hours, while the Biochemical (or Biological) Oxygen Demand (BOD) test requires 5 days. It measures all organic contaminants, including those that are not biodegradable.
Does aeration reduce COD?
This process is done in two main ways, namely aeration and anaerobic. In the aeration process, COD reduceed by making the bacteria can break down organic compounds in water. These bacteria are called heterotrophic bacteria break down organic compounds due to the use of oxygen.Dec 9, 2015
How can COD be removed from water?
One way to reduce COD in water is to use coagulants and flocculants to bind sludge together. Once they are bound into big enough masses that they can be easily filtered out and deposited into a sedimentation tank for removal. This method does however rely on the use of chemicals, and requires high reoccurring cost.
Why is COD higher than BOD?
The COD test uses a chemical (potassium dichromate in a 50% sulfuric acid solution) that “oxidizes” both organic (predominate) and inorganic substances in a wastewater sample, which results in a higher COD concentration than BOD concentration for the same wastewater sample since only organic compounds are consumed ...
How to reduce COD in wastewater?
There are various proven methods for COD reduction in wastewater management. Two of the most common techniques for COD wastewater removal are: 1 Wastewater separation (coagulation and flocculation) 2 COD removal by microbial action.
What is the best way to remove COD from sewage?
Another efficient technique for COD removal is to introduce bacteria or microorganisms that break down organic compounds present in the wastewater. Microbes in sewage treatment can be aerobic or anaerobic.
Why is chemical oxygen demand important in wastewater treatment?
A key benefit of knowing the chemical oxygen demand in wastewater treatment is that it helps industrial and municipal clients determine the best method for treatment and the most effective structure for their wastewater treatment facility.
What does high oxygen demand mean in water?
High chemical oxygen demand in water indicates greater levels of oxidizable organic matter and consequently, a lower amount of Dissolved Oxygen (DO). Critical DO depletion due to organic contamination can kill off aquatic life forms.
What is the chemical oxygen demand?
What Is Chemical Oxygen Demand? Chemical Oxygen Demand (COD) is the amount of oxygen required to oxidize all soluble and insoluble organic compounds present in a volume of water. COD value is usually expressed in milligrams per liter of water (mg/L).
How long does it take to get a COD test?
The common technique uses COD vials for measurement and results are typically achieved within 2 – 3 hours.
Is anaerobic COD removal good for wastewater?
It is a highly beneficial method because the biofuel generated from the process can be utilized as an alternative energy source for power, heating, and drying applications. Anaerobic COD removal is suitable for wastewater with COD > 2000 mg/L.
What is COD in water?
Chemical Oxygen Demand (COD) is a parameter of water quality used to determine the concentration of organic matter in a water supply.1 COD represents the amount of oxygen needed to allow a strong oxidant to oxidise all the organic matter in the sample. However, the strong oxidants used in COD tests do not discriminate between inorganic and organic compounds; some inorganics will be oxidised while some organics will remain intact.2 Despite its inability to measure the absolute organic carbon concentration perfectly, COD is often sufficient for wastewater treatment applications. These tests also only take a matter of hours rather than days ( Biological Oxygen Demand, or BOD, levels take around five days to measure) and generally provide enough information about water quality to be useful in wastewater treatment. In addition, COD can be used in toxic wastes that would otherwise kill the bacteria used in BOD testing.2
What to do if COD is elevated in wastewater?
Action: If COD is elevated in wastewater, treatment methods such as aerobic and anaerobic biological treatment, filtration, coagulation and flocculation should be used to remove organic and inorganic material.
Why does COD increase in water?
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.
Why is it important to monitor COD?
It is important to monitor COD because it reflects the level of pollution and contamination present in a water sample. In wastewater treatment, organic compounds can react with chlorine-containing disinfectants in the final steps of treatment to form THM’s. This is a major problem due to the carcinogenic nature of THM’s.
How long does it take to measure BOD?
These tests also only take a matter of hours rather than days ( Biological Oxygen Demand, or BOD, levels take around five days to measure) and generally provide enough information about water quality to be useful in wastewater treatment.
What is COD in water?
Chemical oxygen demand (COD) is the amount of dissolved oxygen that must be present in water to oxidize chemical organic materials, like petroleum. COD is used to gauge the short-term impact wastewater effluents will have on the oxygen levels of receiving waters.
When is it necessary to measure BOD or COD in the influent water?
For compliance, it’s necessary to measure BOD or COD in the influent water as it enters the plant, before mechanical screening processes and at the end of the treatment at the discharge point.
How is wastewater treated?
Municipal and Industrial Wastewater Treatment 1 Primary Treatment:#N#Clarifiers, or sedimentation basins, slow the flow of the wastewater to allow suspended solids to settle. Surface skimmers collect any floating fats, oils and greases. With the use of this mechanical and physical means, approximately 30% of organic matter is removed from the wastewater and is routed to the solids management area of the plant. 2 Secondary Treatment:#N#This process uses living organisms to aid in reducing organics. In the aeration basin, bacteria and microorganisms convert biodegradable organic matter to carbon dioxide and water. With this conversion, organics are reduced, thereby reducing oxygen demand. 3 Discharge Limits:#N#Discharge limits vary from plant to plant depending on the characteristics of the receiving water, effects on aquatic life, recreational uses and other factors. Discharge permits may stipulate a specific maximum concentration for BOD or COD, or a percent removal. Some plants require achieving as much as 90% removal of oxygen demand.
What is the difference between COD and BOD?
COD describes the amount of oxygen required to chemically break down pollutants, while BOD indicates the amount of oxygen required to breakdown organic pollutants biologically with microorganisms.
What happens when wastewater is discharged into the environment?
When treated wastewater is discharged into the environment, it can introduce pollution in the form of organic content to receiving waters. High levels of wastewater COD indicate concentrations of organics that can deplete dissolved oxygen in the water, leading to negative environmental and regulatory consequences.
What is surface skimming?
Surface skimmers collect any floating fats, oils and greases. With the use of this mechanical and physical means, approximately 30% of organic matter is removed from the wastewater and is routed to the solids management area of the plant.
Is there a correlation between COD and BOD?
There is a correlation between COD and BOD, however, it must be experimentally established before using one parameter to express another. Usually COD analysis (which is a much faster and more accurate method) is used to estimate BOD using the established correlation.
How much COD is removed from wastewater?
How to reduce COD in wastewater. Primary and secondary treatments remove around 75-85% COD, but the hard-to-treat COD remains. Typically, legislation for COD discharge is from below 120 mg/L in the EU to below 50 mg/L in China and therefore in order to meet regulatory standards, additional treatment is often required.
What is the purpose of a COD test?
A COD test can be used to decipher the level of organics in water. Regulators enforce limits on the maximum amount of COD allowed in wastewater before it enters the environment and the local utility provider stipulates levels for effluent going ...
Is COD a biodegradable substance?
COD can be split into two types – non-biodegradable and biodegradable.
Can Nyex treated wastewater be reused?
Because of the lack of dosing chemicals in the process, Nyex™ treated wastewater can also be safely reclaimed and reused for other purposes within the business, saving money and addressing high water demands in times of shrinking supplies.
What are the sources of COD in stormwater?
Sources of COD in stormwater are varied. However, soluble organic compounds are most likely to contribute to escalated COD concentrations. Residual food waste from bottles and cans, antifreeze, emulsified oils are all high in COD and are common sources of COD for industrial stormwater.
What happens when COD levels are low?
Low (generally under 3 mg/L) dissolved oxygen, or “hypoxia,” causes reduced cell functioning, disrupts circulatory fluid balance in aquatic species and can result in death of individual organisms. [iii] as well as large “dead zones”. [iv] Hypoxic water can also release pollutants stored in sediment. [v]
Is COD a constituent of interest?
Although COD measures more than organic constituents, the organic fraction usually predominates and is the constituent of interest. [vii] Chemical oxygen demand was developed as an alternative to the more lengthy BOD analysis. Sources of COD in stormwater are varied.
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 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.
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 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 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 ...
How to reduce COD in water?
One way to reduce COD in water is to use coagulants and flocculants to bind sludge together. Once they are bound into big enough masses that they can be easily filtered out and deposited into a sedimentation tank for removal. This method does however rely on the use of chemicals, and requires high reoccurring cost.
Why is COD important?
COD is an extremely important element of water quality. It helps to assess the effect that wastewater will have on the environment that it’s being released into. When the COD levels are higher , there is a greater demand for oxygen. This means that there is likely more oxidizable organic material in water with high COD levels.
What is the purpose of a moving bed bio reactor?
The bacteria can treat and stabilize the wastewater without the use of chemicals. Moving Bed Bio Reactors utilize this bacteria process in order to clean wastewater.
Is low concentration of oxygen harmful?
A Low concentration of Dissolved Oxygen is harmful life forms which oxygen to live. Therefore it’s best to reduce COD levels, thus increasing DO concentrations, in wastewater before releasing it. How to Reduce COD in Wastewater. Luckily, there are several ways to reduce COD.
Can bacteria reduce COD?
It is also possible to use biology to reduce COD and thus promote BO levels. More specifically, utilizing certain types of bacteria can reduce COD.
Is there oxidizable organic matter in water?
This means that there is likely more oxidizable organic material in water with high COD levels. This also means that there are reduced Dissolved Oxygen (DO) concentrations in wastewater with high COD levels. A Low concentration of Dissolved Oxygen is harmful life forms which oxygen to live. Therefore it’s best to reduce COD levels, thus increasing ...
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 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.
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 ...
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.
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 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 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.
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.
