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Biochemical Oxygen Demand vs Chemical Oxygen Demand

bod vs cod

BOD and COD are two measurements which describe the demand of DO by bacteria in the water. BOD refers to the biochemical oxygen demand bod vs cod and COD is the chemical oxygen demand. BOD and COD are essential parameters in assessing water quality and organic pollution levels.

  • COD or Chemical Oxygen Demand is the total measurement of all chemicals
    in the water that can be oxidized.
  • Sewage was
    dumped in a river and it took five days for it to reach the ocean, hence the
    five-day incubation requirement in the BOD method.
  • It oxidises pollutants completely into CO2 and H2O, unlike in BOD.
  • As an added bonus, the BOD of polluted water is often greater than that of clean water.
  • Well, this grassy depression was a natural gully that led to another channel which fed directly into the stormwater outfall.

For industrial samples, COD may be the only feasible test because of the
presence of bacterial inhibitors or other chemical interferences, which
would interfere with a BOD determination. COD testing also gives the fast
measurements required in many treatment systems for informed decisions
regarding process control adjustments. Many industrial and municipal
laboratories find that parallel COD and BOD testing is beneficial because
the COD test can be used to target a specific BOD range. The need for
multiple BOD dilutions is minimized or eliminated. Almost all wastewater treatment plants are required to measure one of these three
items as a measure of the pollution value in the water. In my role working with the JMS Eco-AIR (Low Profile Cascade Aerator) at wastewater treatment plants, I have the opportunity to speak with operators about the quality of processed wastewater leaving their plants.

Difference between BOD and COD-

COD stands for ‘Chemical Oxygen Demand’ where BOD stands for Biochemical Oxygen Demand. Today, I am going to discuss the difference between BOD and COD in a detailed manner with its definitions and explanation. (2)WET OXIDATION- Persulfate oxidation / NDIR Method
There are two types of this method, persulfate oxidation supported with UV
(Ultraviolet) irradiation activation and heated persulfate oxidation. Is using a security service for protection against online attacks. • BOD refers to the biochemical demand for oxygen and COD is the chemical demand for oxygen. COD & BOD might sound like a mystifying thing from your NPDES permit, but it’s really pretty simple.

bod vs cod

Extensive observation of the COD and BOD levels on the same wastewater has shown that the COD to BOD ratio of a particular wastewater will remain constant over time. BOD is defined as the amount of oxygen demanded by the
micro-organisms in the sewage for the decomposition of bio-degradable matter
under aerobic condition. This is the most commonly used parameter to determine
the strength of municipal or organic quality of the water. It requires samples
injection by syringe into a high temperature furnace with a platinum or
cobalt catalyst. This process oxidizes all of the carbon materials present
to CO2. This value will be affected by the number of nutrients and the rate of enzymatic processes, hence testing at a certain temperature and for a specific amount of time is required.

This new
methodology can be used for the same applications where the traditional TOC
methods have been employed. • BOD is determined by incubating a sealed water sample for five days and measuring the loss of oxygen from the beginning of the test. Measure of oxygen equivalent required for chemical oxidation of both biodegradable and non-biodegradable organic matter.


The Winkler method is still one of only two analytical techniques used to calibrate oxygen electrode meters; the other procedure is based on oxygen solubility at saturation as per Henry’s law. To determine COD, the sample water is taken in a closed container and incubated with a strong oxidant like potassium dichromate with H₂SO4 under standard conditions of temperature and time. This is the only method that enables determining the organic load in heavy toxic sewage. There are two completely different tests-a C-BOD test and a BOD test.

bod vs cod

However, concentration isn’t the whole story since it does not tell how much (i.e., mass or weight) of a substance is going down the drain? COD Provides a comprehensive assessment of the overall organic pollution load and aids in designing treatment processes and pollution control strategies. Provides a comprehensive assessment of the overall organic pollution load and aids in designing treatment processes and pollution control strategies. Used to assess the level of organic pollution, microbial activity, and treatment efficiency. This general standard should be prescribed either by Statute or by order of the Central Authority, and should be subject to modifications by that Authority after an interval of not less than ten years. Total
organic carbon is a good parameter to measure and actually a more accurate
indication of some of the pollutants that cause the most problems than a BOD

BOD (biochemical oxygen demand)

Each measurement, however, represents its own unique quantitative measure of a key system variable. The dissolved oxygen content (DO) of a sample is measured in milligrams per liter, or parts per million. This measurement indicates the actual amount of free oxygen dissolved in water and is an important requirement to support aquatic life in our streams and rivers. It can also be expressed in percent saturation (which is the maximum amount of oxygen that can be dissolved in water depending on altitude and temperature). Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) are the primary techniques used to determine the amount of organic matter present in a given water sample. Although these two approaches are somewhat distinct from one another, they are often combined to determine the amount of nonbiodegradable organic materials present in wastewater.

A physical walk-through is conducted, process flow diagrams are examined, previous design criteria are examined and current standard operating procedures are evaluated along with data logs. These articles, the information therein and their other contents are for information purposes only. All views and/or recommendations are those of the concerned author personally and made purely for information purposes. Nothing contained in the articles should be construed as business, legal, tax, accounting, investment or other advice or as an advertisement or promotion of any project or developer or locality. BOD isn’t a particularly reliable test but is used to evaluate water’s organic quality. • The respiration and the decomposition of the organisms remove oxygen from the system and the photosynthetic organisms, the aeration and the flow of the flow return the oxygen to the water.

Biological Oxygen Demand (BOD)-

Since oxygen is required to convert all organic carbon to CO2 and H2O, COD measures how much oxygen is present. In addition to its role in the breakdown of organic materials, chemical oxygen demand also plays a role in oxidising inorganic compounds (ammonia and nitrite). • This measures the amount of dissolved oxygen (DO) required by aerobic organisms to decompose the organic material present in a given water sample at a specified temperature and specified time.

Nitrification is inhibited so that only the oxidation of COD occurs. COD is usually a measurement of chemicals and the test is simple and easy
to perform with the right equipment and can be done in 2 hours. BOD usually
takes 5 days and TOC used to require large expensive pieces of equipment
that could measure the sample in minutes, but was cost prohibitive. There
are now test in tube kits that utilize COD digesters to run a test similar
to a COD test method available to run a quick, simple and inexpensive TOC
test. The Biochemical Oxygen Demand (BOD) and the Chemical Oxygen Demand (COD) tests are the main methods used in the determination of the concentration of organic matter in a sample of water.

• COD measurements are usually made with samples of waste water or natural water, which are contaminated by domestic and industrial waste. Wastewater generated by commercial, industrial and institutional facilities is typically referred to as “high-strength” compared to typical household wastewater. Table 1 shows the typical concentrations (mg/L) of organics found in untreated domestic wastewater. This table can be used to understand how non-sanitary process wastewater compares to typical domestic wastewater. At the same time, population and production increases have increased water use, creating a corresponding rise in wastewater quantity. This increased water use and process wastewater generation requires more efficient removal of by-products and pollutants that allows for effluent discharge within established environmental regulatory limits.

Learn what to do if your stormwater sample results exceed limits or benchmarks in New York under a SPDES stormwater permit. Running an industrial operation in New York (city, county, or state) all… When you place organic chemicals or biological matter into water, it will eventually break down.

The BOD value is most commonly expressed in milligrams of oxygen consumed per liter of sample during 5 days of incubation at 20 °C and is often used as a robust surrogate of the degree of organic pollution of water. BOD measures how much dissolved oxygen (DO) is consumed by microorganisms to decompose organic matter under aerobic conditions. Since BOD is a measurement based on a biological process, testing for it can take a few days. Incubate a sealed water sample at 20oC for five days, followed by measuring the difference in oxygen content before and after incubation. To measure oxygen demand, biochemical oxygen demand (BOD) relies on
bacteria to oxidize readily available organic matter during a five-day
incubation period.

BOD measurement in challenging water times Envirotech Online – International Environmental Technology

BOD measurement in challenging water times Envirotech Online.

Posted: Tue, 11 Apr 2023 07:00:00 GMT [source]

• Which measures the amount of OD required for the decomposition of organic matter and the oxidation of inorganic chemicals such as ammonia and nitrite. • One is the initial DO and the second is the final DO after five days. The BOD is expressed in milligrams of oxygen consumed per liter of the sample for five days (BOD5) of incubation at 20 ° C. Although COD should be considered an independent test from BOD, and will generate a higher concentration reading than BOD for a particular wastewater sample, it is generally accepted that COD and BOD share an empirical relationship.

NPDES permits for our wastewater treatment plants have specifications for all three variables, DO, BOD and COD and frequent measurements are required. Temperature, total dissolved solids and the chemical characteristics of the plant discharge are also measured and provide an indicator of the affect that discharged wastewater will have on the receiving environment. BOD is a measure of the amount of dissolved oxygen (DO) consumed by microorganisms while they decompose organic matter in water.

It helps identify the presence of pollutants that may not be readily biodegradable and could persist in the environment. Monitoring COD aids in evaluating the efficiency of wastewater treatment processes and determining the need for additional treatment or pollution control measures. Oxygen demand measurements are used to estimate water pollution levels entering and leaving wastewater treatment and industrial facilities. Particularly close attention is paid to effluents as high oxygen demand levels indicate a danger to aquatic life.

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