DO, BOD and COD: What is the Difference? JMS

Organic matter, the number of microorganisms, and the amount of oxygen that is dissolved in water all have major connections to one another. For their metabolism, aerobic microbes need the presence of oxygen. • BOD and COD measurements are taken to determine the pollution level of wastewater.

The plants which treat wastewater from the commercial operations measure COD. BOD refers to the biochemical oxygen demand, which measures the amount of dissolved oxygen (DO) required by aerobic organisms to break down organic material present in a given water sample at a given temperature and specified time. Since BOD is a biochemical process, it is not a precise quantitative test. But, BOD is a widely used test method, indicating the organic quality of water.

BOD Vs COD What Is BOD What Is COD

This temperature may be significantly different from the temperature of the natural environment of the water being tested. Conclusion

CHEMetrics offers a comprehensive line of USEPA-accepted COD vials. K-7350S is for low range measurements (0-150 ppm) while K-7360S is for high range measurements (0-1,500 ppm).

A substance that absorbs carbon dioxide (typically lithium hydroxide) is added in the container above the sample level. The sample is stored in conditions identical to the dilution method. Oxygen is consumed and, as ammonia oxidation is inhibited, carbon dioxide is released. The total amount of gas, and thus the pressure, decreases because carbon dioxide is absorbed. From the drop of pressure, the sensor electronics computes and displays the consumed quantity of oxygen. Winkler published the methodology of a simple, accurate and direct dissolved oxygen analytical procedure in 1888,.[10] Since that time, the analysis of dissolved oxygen levels for water has been key to the determination of surface water.

Related Differences:

• Whereas COD is the amount of oxygen required for the chemical oxidation of total organic matter in water. The BOD test has a minimum time requirement of five days, and as a result, it cannot be used effectively in the management of treatment operations. The chemical oxygen demand test is an alternative method for determining the level of organic matter in either natural or treated water. Therefore, they extract energy from organic materials using dissolved oxygen. As a result, the biological oxygen demand refers to the quantity of dissolved oxygen that aerobic organisms need to decompose organic molecules and receive the energy necessary for their metabolism. Difference between Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) Biochemical oxygen demand (BOD) is the amount of oxygen microorganisms require to break down organic materials.

• The good news is these two units are equal and thus are interchangeable!
• BOD of wastewater effluents is used to indicate the short-term impact on the oxygen levels of the receiving water.
• This is important because the organic content in wastewater needs to be reduced before the wastewater is discharged.
• A COD test measures all organic carbon with the exception of certain
  aromatics (benzene, toluene, phenol, etc.) which are not completely oxidized
  in the reaction.
• BOD & Suspended Solids (SS) 300 mg/I, which is usual for package sewage treatment systems, COD is not always stated as part of the discharge license.

The dilution water blank is used to confirm the quality of the dilution water that is used to dilute the other samples. This is necessary because impurities in the dilution water may cause significant alterations in the results. The GGA control is a standardized solution to determine the quality of the seed, where its recommended BOD5 concentration is 198 mg/L ± 30.5 mg/L. For measurement of carbonaceous BOD (cBOD), a nitrification inhibitor is added after the dilution water has been added to the sample. The inhibitor hinders the oxidation of ammonia nitrogen, which supplies the nitrogenous BOD (nBOD). When performing the BOD5 test, it is conventional practice to measure only cBOD because nitrogenous demand does not reflect the oxygen demand from organic matter.

Significance of BOD and COD

Not what you immediately think of when you see the word organic, but that’s what it means. If the oxygen levels in our air changed, it would be a big issue. Log in to TheConstructor to ask questions, answer people’s questions, write articles & connect with other people. Join TheConstructor to ask questions, answer questions, write articles, and connect with other people.

Measures both biodegradable and non-biodegradable organic substances. One is the initial depletion of oxygen and the second is the final depletion after five days. This method is limited to the measurement of the oxygen consumption due only to carbonaceous oxidation. The BOD is used in measuring waste loadings to treatment plants and in evaluating the BOD-removal efficiency of such treatment systems. Based on the strength of BOD and COD present, the domestic wastewater can be classified as weak, medium, strong and very strong as shown in table-2 below.

Difference Between BOD and COD (Based on certain parameters)

The sample is then subjected to ultra-violet (UV) radiation, which
reacts with the oxidant and breaks down all remaining carbon bonds in the
sample to release CO2. The CO2 released from both the
acid reaction and the UV radiation represents all the carbon (TC) released
from the sample. Sorting through these different measurements that all have to do with oxygen content, or potential consumption can be difficult.

• A closed water sample is incubated with a strong oxidizer such as potassium dichromate (K2Cr207) in combination with boiling sulfuric acid (H2SO4) at a specific temperature for a specified period of time. Although wastewater analytical tests are often separated into categories, it is important to understand that these tests are not independent of each other (Figure 1). In other words, a contaminant identified by one test in one category can also be identified in another test in a separate category. bod vs cod For example, the organics in a wastewater sample represented by BOD will also be represented in the spectrum of solids, either as suspended (TSS) or dissolved (TDS) particulates. For most people a complete understanding of the standard methods required to accurately complete critical wastewater analytical tests is not necessary. Its SI units is milligrams per liter (mg/l) COD or chemical oxygen demand is the total measurement of all chemical (organics and inorganics) in the water/wastewater.

What is the optimum DO concentration for aquatic organisms?

Long story short, the dog’s going to the bathroom in this field, and water running over it when it rained, added a certain amount of biological material to the outfall. They built a berm before the pen, channeled the water around, and avoided the dog’s bathroom, and the BOD went way down. Well, it turned out the guard dogs were kept in a pen that had a grassy depression. Well, this grassy depression was a natural gully that led to another channel which fed directly into the stormwater outfall.

• Chemical oxygen demand is similar to biochemical oxygen demand in that they are both used to calculate the oxygen demand of a water sample.
• This oxidation process converts the organic matter into carbon dioxide and water.
• BOD, or Biochemical Oxygen Demand, is a measure of the amount of oxygen required by microorganisms to degrade organic matter in water.
• COD and BOD tests are important because they help in the determination of the amount of waste in wastewater.

Understanding these key differences helps in selecting the appropriate method for water quality assessment and regulatory compliance. BOD is the abbreviation of biochemical oxygen demand, which defines the amount of dissolved oxygen used by aerobic organisms to break down organic material present in a given water sample. BOD is done by incubating a sealed water sample for five days and measuring the loss of oxygen in it. BOD serves as an important indicator of the organic pollution level in water bodies. High BOD values indicate the presence of substantial amounts of biodegradable organic substances, such as sewage, agricultural runoff, or industrial wastewater, which can deplete dissolved oxygen levels.

Therefore, there has been a significant movement towards combined sensor systems that can monitor parameters and use them, in real-time, to provide a reading of BOD that is of laboratory quality. It is usually seeded with the type of
bacteria found in municipal plants. The types of bacteria needed in
papermills or refineries usually differ in species from the standard
procedures method. The hard to degrade organics found in some of these
systems also may take longer than 5 days to break down, so a BOD test will
give an inaccurate measurement of the amount of pollution that may be
present in a waste stream. Organic
matter content is typically measured as total organic carbon and dissolved
organic carbon, which are essential components of the carbon cycle.

Biochemical oxygen demand

Since COD is based on a chemical process testing for it will only take a few hours. COD testing typically involves digestion of the water sample in a sealed vial with potassium dichromate and sulfuric acid at 150oC for 2 hours. The chemical oxygen demand (COD) is a measure of water and wastewater quality.

This analysis is performed using 300 mL incubation bottles in which buffered dilution water is dosed with seed microorganisms and stored for 5 days in the dark room at 20 °C to prevent DO production via photosynthesis. The bottles have traditionally been made of glass, which required cleaning and rinsing between samples. A SM 5210B approved, disposable, plastic BOD bottle is available which eliminates this step. In addition to the various dilutions of BOD samples, this procedure requires dilution water blanks, glucose glutamic acid (GGA) controls, and seed controls.

COD is the oxygen demand that is consumed by both inorganic and organic matter present in the wastewater sample. The chemical oxygen demand is expressed as the mass of oxygen consumed over the volume of the solution. The measurement of COD involves the chemical oxidation of organic compounds in a water sample using strong oxidizing agents, such as potassium dichromate (K₂Cr₂O₇) or potassium permanganate (KMnO₄).

In environmental chemistry, there does seem to be a correlation between COD and BOD, so sometimes one is used as an indicator of both of them. So, just like COD, this is a methodology of determining a degree of pollution in your runoff. Now we aren’t talking about controlling population here, I’ll let you talk to a biologist to cover that matter, we’re talking about the breaking down, or decay of matter, which our stormwater runoff can contribute to. I took chemistry in college and graduate school, but I don’t profess to be a chemist.