Course Content
Introduction to Environmental Chemistry
Environmental chemistry is the study of the chemical and biochemical phenomena that occur in nature. It involves the understanding of how the uncontaminated environment works, and which naturally occurring chemicals are present, in what concentrations and with what effects. Environmental chemistry; is the study of sources, reactions, transport, effects and fate of chemical species in water, soil and air environment as well as their effects on human health and natural environment
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Introduction
Origin of the solar System
Cosmology; is the branch of astronomy involving the study of the of the universe and the solar system. Cosmo-chemistry ;( chemical cosmology); is the study of chemical composition of the matter in the universe and the process that led to those compositions The solar system is made up of the sun (a star) with nine planets orbiting around it. These planets together with all the other heavenly bodies moving around or between individual planet form members of the solar system. Other heavenly body include; asteroids, comets, meteors, meteorites and satellites such as moon. The solar system does not include other stars .
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Origin of The Universe and Solar System
Solutions
Solutions are defined as homogeneous mixtures that are mixed so thoroughly that neither component can be observed independently of the other. The major component of the solution is called solvent, and the minor component(s) are called solute.
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Introduction
Solubility of Solutions
Solubility Product
Solution Concentrations
Chemical Equilibria
Chemical equilibrium in the environment refers to the state where the rates of forward and reverse reactions of a chemical reaction reach a balance. In this state, the concentrations of reactants and products remain constant over time, although the reactions continue to occur.
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Introduction
The Concept of Equilibrium
Relation Between Chemical Kinetics and Chemical Equilibrium
Factors Affecting Chemical Equilibrium
Laws of Chemical Equilibria
Phase Interactions
Phase interactions in solutions refer to the behavior and changes that occur when two or more substances (solutes and solvents) mix together to form a homogeneous mixture. These interactions are related to the different phases of matter, such as solids, liquids, and gases, and how they interact and transform during the process of solution formation.
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Introduction
 Phase interactions
Colligative Properties of Solutions
COLLIGATIVE PROPERTIES OF SOLUTIONS Colligative properties are physical properties of solutions that depend on the concentration of solute particles, rather than the specific identity of the solute. The four colligative properties that can be exhibited by a solution are: 1.Boiling point elevation 2.Freezing point depression 3.Relative lowering of vapour pressure 4.Osmotic pressure
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Introduction
Colligative Properties Examples
Introduction To Organic Chemistry
Organic chemistry is the study of carbon containing compounds and their properties. This includes the great majority of chemical compounds on the planet, but some substances such as carbonates and oxides of carbon are considered to be inorganic substances even though they contain carbon.
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Introduction
The IUPAC Naming (nomenclature) 
Alkyl halides, Alkenes and Alkynes
Alcohols , Ethers, Aldehydes and Ketones
Carboxylic Acids, Esters and Amines
Simple Organic Molecules in the Environment
Soil Chemistry and Pollution
soil
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Introduction to Soil Chemistry
Chemical Characteristics of Soil
Biological Characteristics of Soil
Physical Characteristics of Soil
Soil Salinity, Conductivity and Ion Exchange Capacity
Soil Pollution
Water Chemistry and Polution
Water Chemistry
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Water and the Environment
Water Chemistry
Characteristics and Properties of Water
Portable water 
Water pollution
Water Quality Analysis
Biological Oxygen Demand (BOD)
Chemical Oxygen Demand (COD)
Air Quality and Pollution
Air Quality and Pollution
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Air Quality
Testing Air Quality
Biodegradation
Biodegradation
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Biodegradation
Mechanisms of Biodegradation 
Role of Microorganisms in Biodegradation
BioGeoChemical Cycles
BiogeoChemical Cycles
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Biogeochemical cycles
The Water Cycle
The Carbon Cycle
The Nitrogen Cycle
The Phosphorus Cycle
The Sulfur Cycle
Introduction To Environmental Chemistry
About Lesson

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Biological Oxygen Demand (BOD)

Biological Oxygen Demand (BOD) is a measure of the amount of dissolved oxygen required by microorganisms to decompose organic matter in water. It is an important parameter used to assess the level of organic pollution in water bodies, particularly in freshwater systems.

When organic substances, such as sewage, agricultural runoff, or industrial effluents, are discharged into water bodies, microorganisms begin to break down and consume these organic materials as a food source. This decomposition process consumes oxygen from the water. BOD measures the rate at which oxygen is depleted by the microbial activity, indicating the level of organic pollution present.

BOD is typically expressed in milligrams of oxygen consumed per liter of water (mg/L) over a specified incubation period, often 5 days. This duration is known as the 5-day BOD (BOD5). The test involves collecting a water sample in a sealed bottle and incubating it under controlled conditions, usually at a temperature of 20°C. At the end of the incubation period, the dissolved oxygen concentration in the sample is measured and compared to the initial dissolved oxygen concentration. The difference between the initial and final concentrations represents the amount of oxygen consumed by the microorganisms during the incubation period.

A high BOD value indicates a greater amount of organic pollution in the water, as it requires more oxygen for decomposition. This can have significant implications for aquatic life, as reduced oxygen levels can lead to hypoxia (low oxygen) or anoxia (absence of oxygen), negatively impacting fish and other organisms.

BOD is an important parameter in assessing the effectiveness of wastewater treatment processes and the impact of discharges on receiving water bodies. Regulatory authorities often set limits on BOD levels to protect water quality and ensure the health of aquatic ecosystems.

It is worth noting that BOD is a measure of the oxygen demand associated with biologically decomposable organic matter and may not reflect the presence of specific contaminants or pollutants. Other parameters, such as chemical oxygen demand (COD), may be used in conjunction with BOD to provide a more comprehensive assessment of water quality.

Procedure for BOD testing

BOD (Biological Oxygen Demand) testing is a procedure used to measure the amount of dissolved oxygen consumed by microorganisms during the biological decomposition of organic matter in water. The BOD test typically follows these steps:

  1. Sample Collection: Collect a representative water sample from the water body or wastewater source that needs to be tested for BOD. It is important to handle and store the sample properly to avoid contamination or changes in oxygen levels.

  2. Initial Dissolved Oxygen Measurement: Measure the dissolved oxygen (DO) concentration in the water sample at the start of the test using a dissolved oxygen meter or probe. This provides the initial DO value (DOi) for comparison with the final DO value after incubation.

  3. Incubation: Pour a specific volume of the water sample (typically 300 mL to 500 mL) into a BOD bottle (also called an incubation bottle). The bottle is then tightly sealed with a stopper to prevent the exchange of gases with the surrounding air.

  4. Incubation Conditions: The BOD bottles are placed in a temperature-controlled incubator set at a standard temperature of 20°C. This temperature allows for consistent and comparable results.

  5. Incubation Period: The incubation period for BOD testing is usually 5 days (referred to as BOD5). However, in some cases, shorter periods like 3 or 7 days may be used based on specific requirements or regulations.

  6. Final Dissolved Oxygen Measurement: After the incubation period, remove the BOD bottle from the incubator and measure the dissolved oxygen concentration again using the same dissolved oxygen meter or probe. This provides the final DO value (DOf).

  7. Calculation: Calculate the BOD value using the formula: BOD = (DOi – DOf) x Dilution Factor

    The dilution factor accounts for any dilution or adjustments made to the original sample during the test. It is important to note that BOD is typically reported in units of mg/L or ppm (parts per million).

  8. Quality Control: Include appropriate quality control measures, such as running blank samples (consisting of distilled water) and control samples (with known BOD values), to validate the accuracy and precision of the BOD test results.

BOD testing is essential for assessing the organic pollution level in water bodies, monitoring wastewater treatment processes, and ensuring compliance with regulatory standards. Following standardized procedures and maintaining proper laboratory practices are crucial to obtain reliable and accurate BOD measurements.


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