Unit: 1
There are several methods for measuring organic pollutants in wastewater, including:
Chemical oxygen demand (COD): This method measures the amount of oxygen consumed by the organic compounds in the wastewater during a chemical oxidation process.
Biochemical oxygen demand (BOD): This method measures the amount of oxygen consumed by microorganisms as they break down the organic compounds in the wastewater.
Total organic carbon (TOC): This method measures the total amount of carbon in the organic compounds present in the wastewater.
Gas chromatography-mass spectrometry (GC-MS): This method separates the organic compounds in the wastewater and then identifies and quantifies them using a mass spectrometer.
High-performance liquid chromatography (HPLC): This method separates and quantifies the organic compounds in the wastewater using a liquid chromatography column.
It's important to note that different methods may be more appropriate depending on the specific pollutants of interest and the desired level of accuracy.
Factors affecting BOD Test :
There are several factors that can affect the results of a biochemical oxygen demand (BOD) test, including:
Temperature: BOD is temperature dependent and the test should be conducted at a temperature of 20 ± 1°C.
Sample size: The sample size should be large enough to provide a representative sample of the wastewater, but not so large that it becomes impractical to conduct the test.
Dilution: The sample should be properly diluted to ensure that the oxygen demand does not exceed the capacity of the test method.
Oxygen content: The initial dissolved oxygen (DO) content of the sample should be measured and reported to provide an accurate BOD measurement.
Microbial population: The microbial population in the sample should be representative of the population in the source wastewater.
Time: The BOD test should be conducted over a period of 5 days, and the oxygen demand should be measured at the beginning and end of the test.
Lighting: The samples should be kept in the dark to prevent algal growth.
Preservation : If there is a delay in testing, preservation should be done by adding sulfuric acid or mercury chloride to prevent the growth of microorganisms.
It's important to maintain consistency and control over these factors in order to obtain accurate and reliable BOD test results.
BOD Equations :
The biochemical oxygen demand (BOD) equation is used to measure the amount of oxygen that is consumed by microorganisms in the process of breaking down organic matter in a body of water. The BOD is typically measured in mg/L and is used as an indicator of the water's quality and its ability to support aquatic life. The BOD equation is typically expressed as:
BOD (mg/L) = (Initial DO (mg/L) - Final DO (mg/L)) / Sample volume (L)
Where:
- DO stands for dissolved oxygen
- Initial DO is the dissolved oxygen level before incubation
- Final DO is the dissolved oxygen level after incubation
- Sample volume is the amount of water used in the BOD test
Methods Of Estimating Bod
There are several methods for estimating Biological Oxygen Demand (BOD) in water samples, including the standard 5-day BOD test, the 3-day BOD test, and the 1-day BOD test. The standard 5-day BOD test involves measuring the initial dissolved oxygen (DO) level in a water sample, incubating the sample at 20°C for 5 days, and then measuring the final DO level. The difference between the initial and final DO levels is used to calculate the BOD.
The 3-day BOD test and 1-day BOD test are variations of the standard test that use shorter incubation times. Additionally, the BOD can also be estimated using mathematical models such as the Stodola formula, which uses water temperature and the dissolved oxygen level to estimate BOD.
Thomas method for BOD measurement :
The Thomas Method is an alternative method for measuring Biological Oxygen Demand (BOD) in water samples. It is a modified version of the standard 5-day BOD test that uses a 2-day incubation period instead of 5 days. The method is similar to the standard BOD test, in that it involves measuring the initial dissolved oxygen (DO) level in a water sample, incubating the sample at 20°C for 2 days, and then measuring the final DO level. The difference between the initial and final DO levels is used to calculate the BOD.
The Thomas Method is intended to be a more rapid and efficient alternative to the standard BOD test, while still providing accurate BOD measurements.
Fujimoto Method For Bod Measurement :
Least square method for BOD Measurement :
The Least Squares Method is a statistical method that can be used to estimate the parameters of a mathematical model. It is not a specific method for measuring Biological Oxygen Demand (BOD) in water samples, but it can be used in conjunction with other BOD measurement methods.
For example, the Least Squares Method can be used to fit a mathematical model, such as the Stodola formula, to a set of BOD data. The Stodola formula is an empirical mathematical model that uses water temperature and the dissolved oxygen level to estimate BOD. By using the Least Squares Method to fit the Stodola formula to a set of BOD data, the parameters of the model can be estimated with a high degree of accuracy.
In general, the Least Squares Method is a powerful tool for fitting mathematical models to data, but it would be used as a complement for the BOD measurement methods, not as a standalone method.
Biological v/s Physicochemical analysis :
Biological and physicochemical analysis are two different types of methods used to analyze water samples.
Biological analysis involves assessing the presence and abundance of living organisms in water samples. This type of analysis can include identifying and counting the types of microorganisms present, such as bacteria and algae, as well as assessing the overall health and diversity of aquatic ecosystems. This can be done through methods such as microscopy, DNA sequencing and other molecular biology techniques.
Physicochemical analysis, on the other hand, involves analyzing the chemical and physical properties of water samples. This can include measuring parameters such as pH, temperature, dissolved oxygen, turbidity, and the presence of various dissolved and suspended compounds. The most common used methods are colorimetry, spectrophotometry, titration, and ion chromatography.
Both types of analysis are important for assessing the overall quality and health of a water body. Biological analysis can provide information about the presence and abundance of aquatic life, while physicochemical analysis can provide information about the physical and chemical conditions that affect the survival and growth of aquatic organisms.
The main difference between biological and physicochemical analysis is the type of information they provide about water samples.
Biological analysis focuses on assessing the presence and abundance of living organisms in water samples, including microorganisms such as bacteria and algae, as well as larger aquatic organisms. It provides information about the overall health and diversity of aquatic ecosystems.
Physicochemical analysis, on the other hand, focuses on analyzing the chemical and physical properties of water samples, such as pH, temperature, dissolved oxygen, turbidity, and the presence of various dissolved and suspended compounds. It provides information about the physical and chemical conditions of the water that can affect the survival and growth of aquatic organisms.
Both types of analysis are important for assessing the overall quality and health of a water body. Biological analysis gives information about the presence and abundance of aquatic life, while physicochemical analysis gives information about the physical and chemical conditions that can affect aquatic life. Together, they can provide a comprehensive understanding of the water body, which is necessary for making informed decisions about its management and protection.
Disclaimer : this is not a class note or assignment answer this is my nots Which i make from other sources
.jpg)
0 Comments