Wastewater treatment requires continuous monitoring of pollutants, therefore, analyses criteria for this type of water have been established, i.e., temperature, fats and oils, sedimentable solids, pH, conductivity, inorganic ions concentration, etc. Organic matter determination represents one of the most significant challenges since it includes all carbonaceous compounds and some other elements, such as hydrogen, oxygen, and nitrogen. Nevertheless, currently the Total Organic Carbon (TOC) (Federation W. E., & APH Association [26] – 5310) analysis is being extensively more used than the other two [93]. The COD is the oxygen equivalent of the amount of potassium dichromate consumed during the complete oxidation of organic matter in an acidified water sample during two-hour of boiling in a reflux apparatus to avoid loss of water by evaporation. The COD is a quicker method of estimating the oxygen demand of a sample. Furthermore, COD test utilizes a strong oxidizing reagent to oxidize materials in water while BOD test does not use a chemical reagent instead it allows microorganisms to act on the organic matter.

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 bod vs cod also measured and provide an indicator of the affect that discharged wastewater will have on the receiving environment. BOD refers to the amount of oxygen consumed by microorganisms to decompose organic matter in water under aerobic conditions.

Typical values

These optical properties are used for the final determination of residual hexavalent chromium or of the Cr3+ formed for COD determination (Table 5.3). The choice of wavelengths (and obviously of the oxidant concentration) depends on the COD range. The final determination of COD at 610 (600) or 440 (435) nm is widely used, with filter photometers for commercial tube test methods. However, some problems in reading can exist in the case of suspended solids present in industrial samples, for example, or, more often, in the case of precipitation occurring during COD test.

BOD is commonly treated by biological methods, such as adding bacteria and providing favourable conditions to break down the organic matter quickly. Sewage treatment plants commonly use return activated sludge (RAS) as a bacteria source to treat organics in the water. The analysis of BOD5 methods shows there is unification in the systems, which allows them to be performed in situ or, in the best of cases, with an online identification of the results.

DO, BOD and COD: What is the Difference?

Methods focusing on the detection system have not yet been fully developed, as their only function is to make the final response more sensitive. Therefore, most do not directly modify the standard method; their applications aim to obtain the answer so that it can be more quickly detected and established, in some cases on online systems. Of course, wastewater generated by commercial, industrial, or institutional facilities often has higher BOD and COD levels compared to domestic wastewater. Thus both BOD and COD are indicators of the amount of organic pollution in a water body. Along with the potassium dichromate in 50% sulfuric acid solution, pre-prepared COD vials also contain silver sulfate as a catalyst and mercuric sulfate to eliminate chloride interference. Thus, COD vials are considered hazardous waste and must be handled and disposed of in an approved manner.

• For more water quality indicators and related monitoring equipment for wastewater treatment, please see this article water quality sensors for water treatmet.
• Clean TeQ Water provides tertiary treatment of wastewater, polishing nutrients or improving water quality once the majority of COD and BOD has been removed.
• Are you willing to understand the difference between biochemical oxygen demand (bod) and chemical oxygen demand (cod)?
• In a BOD test, only biologically reactive carbon is oxidized while in a COD test, all organic matter is converted to carbon dioxide.

This table can be used to understand how non-sanitary process wastewater compares to typical domestic wastewater. Are you willing to understand the difference between biochemical oxygen demand (bod) and chemical oxygen demand (cod)? If yes, this guide will help you understand terminologies like accounts receivable, accounts payable, etc. It requires samples injection by syringe into a high temperature furnace with a platinum or cobalt catalyst.

Polargraphic method

Besides, BOD value in polluted water is normally higher than the fresh water. High BOD can be a result due to domestic sewage, petroleum residues and wastes of animals and crops. There is a significant relationship among organic matter, microbial population and dissolved oxygen content in water. Hence, they use dissolved oxygen and convert organic matter into energy. Moreover, they utilize the provided energy from organic food, for their further metabolic reactions and especially for their reproduction.

Most of the studies reviewed focus on the use of microorganisms or biological systems, which can ascertain BOD in less than 1 day. They also focus on using equipment that could increase the sensitivity of the measurement of biodegradable organic matter. Being TOC a sensitive technique, it is challenging to accomplish a significant change in the methodology; this way, the applied modifications focus on different possibilities to detect the carbon present in the sample. Until recently, real-time monitoring of BOD was unattainable owing to its complex nature. 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. The purpose of the BOD is to provide an estimate of the amount of dissolved oxygen that will be required to oxidize the BOD load in a wastewater discharged into a receiving water body.

Structural Analysis Simplified: Understanding Load Paths and Forces

Also, costs are reduced while obtaining statistically comparable results. The BOD5 test is limited in some applications such as industrial wastewaters, which often contain heavy metal ions, cyanides, and other substances toxic to microorganisms. When microorganisms become poisoned by toxic substances, they are unable to oxidize waste, in which case the BOD5 test becomes an ineffective measure of organic pollution.