Laboratory methods for the measurement of water pollution:
Help to check the water quality and measure water pollution 

                                                                               Photo/Unsplash 

Water is a basic need in our lives. Without water, life can’t be imagined. When we discuss the quality of water, there is talk about how to measure the quality and purity of the water. 

How will the existing parameters check the quality of the water?

The organic matter in the water, especially sewage, is regarded as biologically active if the bacteria can oxidize it. So, biologically active organic matter is important. 

Water pollution is everywhere due to various human activities. Water quality is essential for life, and its measurement involves assessing various parameters to determine pollution levels. Key laboratory methods for measuring water pollution include:

Commonly used laboratory methods are :

1. Biochemical Oxygen Demand ( BOD)
2. Chemical Oxygen Demand ( COD)
3. Total Organic Carbon (TOC)
4. Theoretical Oxygen Demand ( ThOD)

Biochemical Oxygen Demand (BOD)

1. The BOD parameter helps measure organic pollution in sewage and surface water.
2. It helps to measure the DO( Dissolved Oxygen) in water.
3. BOD indicates the amount of organic matter present in the sewage.
4. The nuisance potential of swage can be measured with the help of the BOD parameter.
5. It helps measure the biodegradable organic matter present in the water.
6. The results we get after the incubation period of 5 days.

Chemical Oxygen Demand ( COD)

1. Chemical Oxygen Demand (COD) refers to the oxygen equivalents of organic matter that can be oxidized using chemical oxidizing agents.
2. COD usually uses the strongest chemical oxidizing agent known as potassium dichromate in an acidic medium, required in the presence of a catalyst. 
3. The result we get after 3 hours.
4. COD oxidizes more organic compounds than BOD; hence, COD values are higher than BOD values.

Total Organic Carbon (TOC)

1. Total Organic Compound measurement is done when the total concentration of organic matter is very low.
2. It can be determined by oxidizing organic carbon in the presence of a catalyst to carbon dioxide.

Theoretical Oxygen Demand (ThOD)

1. The organic matter in sewage is primarily composed of carbohydrates, proteins, fats, and products of their decomposition. The theoretical Oxygen Demand (ThOD) refers to the calculated amount of oxygen required to completely oxidize a compound to its final oxidation products, such as carbon dioxide, water, and ammonia.
2. ThOD is a theoretical value that can be calculated, while Chemical Oxygen Demand (COD) and Biochemical Oxygen Demand (BOD) are measured experimentally.
3. The chemical formulas of the organic matter present in individual compounds make it possible to calculate ThOD easily.
4. THOD is a theoretical maximum, while COD measures the oxygen demand required for both biodegradable and non-biodegradable organic matter. On the other hand, BOD measures the oxygen used by microorganisms during the degradation of biodegradable organic matter.
5. THOD represents the theoretical upper limit for the oxygen demand of a compound, whereas COD and BOD are experimental measurements that reflect actual oxygen consumption under specific conditions.

Comparison of Laboratory Methods for Measuring Water Pollution:

Biochemical Oxygen Demand (BOD)	Chemical Oxygen Demand (COD)	Total Organic Carbon (TOC)	Theoretical Oxygen Demand (ThOD)
Measures organic pollution in sewage and surface water. It indicates dissolved oxygen levels and the amount of biodegradable organic matter. Results are obtained after a 5-day incubation period.	Measures oxygen equivalents of organic matter using strong chemical oxidants like potassium dichromate. Usually provides results in 3 hours and measures more compounds than BOD, leading to higher values.	Assesses low concentrations of organic matter by oxidizing it to carbon dioxide.	Refers to the calculated oxygen needed to completely oxidize organic matter. Represents a theoretical maximum, whereas COD and BOD are experimental measurements.

 Overall, these methods help quantify water pollution resulting from human activities.