BOD, COD or TOC? A comparison of approaches and applications
Wastewater analysis is crucial from an environmental and public health standpoint, while it is also important to identify and understand contamination levels when it comes to legal standards and regulations.
How is wastewater analysed?
Once a sample that has been deemed to accurately reflect the wastewater over time has been taken, it can undergo a number of different assessments, including analysis of its physical nature (temperature, colour, odour), as well as a review of its chemical qualities.
These can include Total Organic Carbon (TOC), Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD).
What is BOD and COD?
Chemical Oxygen Demand is the process of measuring what chemicals within the water sample can be oxidised, indicating how much pollution is also present. Biochemical Oxygen Demand, meanwhile, measures how much oxygen needs to be dissolved for microorganisms to decompose organic matter in water.
What is Total Organic Carbon?
Total Organic Carbon (TOC) is a way for companies to know whether the water they use is of a clean enough quality to be used in their industry.
By measuring the amount of organic compounds in water samples, companies across a range of industries – such as pharmaceutical and environmental businesses, as well as drinking water suppliers and electronics manufacturing companies – can use TOC applications to assess their water purification levels. By analysing the levels of carbon, hydrogen, oxygen, nitrogen and sulphur, TOC analysis can also ascertain whether your systems are decontaminating your water effectively.
Why measure BOD and COD?
Through the assessment of BOD, we can gain a stronger understanding of organic pollution and what it does to the environment. High levels of BOD in rivers and lakes, for instance, can bring about a reduction in oxygen, which can have a negative impact on the ecosystem.
With COD analysis, we can determine what effect an effluent is having on the body of water it is discharged into. This also allows us to assess the quality of the water.
Why measure Total Organic Carbon?
There are several key reasons why you should monitor TOC on your site:
Environmental Health: Your employees’ health and the ecosystems surrounding your site can be harmed with the amount of pollution you produce. Regular assessments of TOC help identify high levels of organic compounds.
Water Quality: Effective water processes within your industry are imperative when it comes to water purification. If water is contaminated, it can lead to safety issues for your company, your staff and your customers.
Industrial Safety: Monitoring TOC efficiently, effectively and regularly can put a stop to dangerous organic compounds being released into the environment.
Legislation Compliance: Frequent analysis and subsequent control of TOC ensures your company continues to adheres to legislation regarding environmental and health issues.
Which approach do you use: BOD, COD or TOC?
Choosing the most effective or impactful analysis approach between BOD, COD and TOC can be difficult. It can also depend on what you are assessing, as each method has been designed for specific research.
For instance, while BOD provides an evaluation of how efficient biological treatment processes in a wastewater treatment plants, it can also take 5 days for results to come back. COD, however, can offer more immediate analysis, with results returning in 10 minutes, however the process can also include the use of hazardous substances. TOC, meanwhile, provides an accurate measurement of a wastewater sample’s total organic carbon, but, because of the use of expensive equipment, the process can be costly.