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Lab Activities: Determination of Physical, Chemical and Biological Characteristics of Water and Wastewater

Water quality testing is an essential laboratory activity in environmental science and civil engineering. By analyzing the physical, chemical, and biological characteristics of water and wastewater, students and researchers can understand the level of pollution and determine whether water is safe for use.

In this laboratory activity, we examine different parameters such as temperature, turbidity, pH, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD), and microbial contamination.

Aim of the Experiment

To determine the physical, chemical, and biological characteristics of water and wastewater samples in order to evaluate water quality and environmental impact.

Apparatus and Materials Required

  • Thermometer
  • Turbidity meter (Nephelometer)
  • pH meter or pH strips
  • Dissolved Oxygen (DO) bottle
  • Incubator
  • Burette and pipette
  • Chemical reagents for BOD and COD tests
  • Microscope
  • Clean water sample bottles

1. Determination of Physical Characteristics

Temperature

Temperature influences chemical reactions and biological processes in water. High temperatures can reduce dissolved oxygen levels and affect aquatic life.

Procedure:
  1. Collect the water sample in a clean container.
  2. Insert a thermometer into the sample.
  3. Wait until the reading stabilizes.
  4. Record the temperature.

Result: Temperature = ____ °C

Turbidity

Turbidity indicates the presence of suspended particles such as silt, clay, organic matter, and microorganisms.

Procedure:
  1. Switch on and calibrate the turbidity meter.
  2. Pour the water sample into the turbidity tube or cuvette.
  3. Place it in the turbidity meter.
  4. Record the turbidity value.

Result: Turbidity = ____ NTU

Colour and Odour

Colour and smell provide an initial indication of possible contamination in water or wastewater.

Procedure:
  1. Take the water sample in a transparent glass container.
  2. Observe the colour against a white background.
  3. Carefully smell the sample to detect any unusual odour.

Observation:

  • Colour: ______
  • Odour: ______

2. Determination of Chemical Characteristics

pH Test

The pH value shows whether water is acidic, neutral, or alkaline. Safe drinking water usually has a pH between 6.5 and 8.5.

Procedure:
  1. Calibrate the pH meter.
  2. Dip the electrode into the water sample.
  3. Allow the reading to stabilize.
  4. Record the pH value.

Result: pH = ____

Dissolved Oxygen (DO)

Dissolved oxygen is important for aquatic organisms and indicates the health of a water body.

Procedure (Winkler Method):
  1. Fill the DO bottle completely with the water sample.
  2. Add manganese sulphate solution.
  3. Add alkaline iodide reagent.
  4. Add sulfuric acid and mix.
  5. Titrate with sodium thiosulphate using starch indicator.

Result: DO = ____ mg/L

Biochemical Oxygen Demand (BOD)

BOD measures the amount of oxygen required by microorganisms to decompose organic matter present in water.

Procedure:
  1. Measure the initial dissolved oxygen level.
  2. Incubate the water sample at 20°C for 5 days.
  3. Measure the final dissolved oxygen level.
  4. Calculate the BOD value.

Formula:

BOD = Initial DO − Final DO

Result: BOD = ____ mg/L

Chemical Oxygen Demand (COD)

COD measures the oxygen required to chemically oxidize organic compounds in water.

Procedure:
  1. Add potassium dichromate and sulfuric acid to the sample.
  2. Heat the mixture in a COD digester.
  3. Titrate with ferrous ammonium sulfate.
  4. Calculate the COD value.

Result: COD = ____ mg/L

3. Determination of Biological Characteristics

Total Coliform Test

Coliform bacteria are indicators of microbial contamination in water.

Procedure (MPN Method):
  1. Inoculate lactose broth tubes with water samples.
  2. Incubate at 37°C for 24–48 hours.
  3. Check for gas formation in Durham tubes.
  4. Use the MPN table to estimate coliform count.

Result: Total Coliform = ____ MPN/100 mL

Microscopic Examination

Microscopic analysis helps identify microorganisms such as bacteria, algae, and protozoa present in wastewater.

Procedure:
  1. Place a drop of the sample on a microscope slide.
  2. Cover with a coverslip.
  3. Observe under a microscope.
  4. Record the observed microorganisms.

Observation: ______

Conclusion

This laboratory activity helps determine the physical, chemical, and biological properties of water and wastewater. These parameters are important for evaluating water quality, identifying pollution levels, and ensuring safe water management.

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