OBJECTIVES
To measure the temperature of a given water sample using a thermometer.
To measure the color of a water sample using a tintometer (colorimeter).
To measure the pH of a water sample using a pH meter.
To measure the turbidity of a water sample using a turbidity meter.
APPARATUS REQUIRED
a. Temperature Measurement:
Calibrated thermometer
250 mL beaker
Burette stand
b. Color Measurement:
Colorimeter (tintometer)
Hazen disc
Glass tubes
Distilled water
c. pH Measurement:
pH meter with electrode
100 mL and 250 mL beakers
pH 4 buffer solution
Deionized water
d. Turbidity Measurement:
Turbidity meter
Sample cells (cuvettes)
Distilled water
Tissue paper
THEORY
a. Temperature
Proper Background:
Temperature quantifies the average kinetic energy of water molecules and influences chemical, biological, and physical processes in aquatic systems. Accurate field measurements prevent alterations during sample transport.
Definition & Principle:
Thermometers operate on thermal expansion:
• A sealed liquid (mercury or alcohol) expands/contracts with temperature changes.
• The displacement is calibrated to a scale (°C or °F).
Significance:
• Affects dissolved oxygen levels, microbial growth, and chemical reaction rates.
• High temperatures (>15°C) accelerate bacterial proliferation.
b. Color
Proper Background:
Color in water indicates dissolved impurities from natural (humic acids, tannins, metals) or anthropogenic (industrial dyes, waste) sources. Pure water is colorless.
Definition & Principle:
• Hazen Scale (Pt-Co): Measures color by comparing the sample to a platinum-cobalt standard.
• 1 Hazen Unit (1ºH): Color produced by 1 mg/L platinum and 0.5 mg/L cobalt chloride in distilled water.
Significance:
• High color (>5ºH) indicates organic pollutants that may form toxic disinfection byproducts (e.g., THMs).
• Aesthetic concerns affect consumer acceptability.
c. pH
Proper Background:
pH measures water’s acidity/alkalinity, influencing corrosion, disinfection, and aquatic life.
Definition & Principle:
• pH = -log[H⁺]
• pH Meter: Measures voltage difference between glass (pH-sensitive) and reference electrodes.
Significance:
• Low pH (<6.5): Corrodes pipes, leaches metals.
• High pH (>8.5): Reduces disinfection efficiency.
• WHO Standard: 6.5-8.5.
d. Turbidity
Proper Background:
Turbidity measures cloudiness caused by suspended particles (clay, algae, microbes).
Definition & Principle:
• Nephelometric Turbidity Unit (NTU): Measures light scattering at 90°.
• 1 NTU = Turbidity from 1 mg/L silica suspension.
Significance:
• High turbidity (>5 NTU) shields pathogens, reduces disinfection efficacy.
• WHO/Nepal NDWQS Limit: ≤5 NTU.
PROCEDURE
1. Temperature Measurement
• 200 mL of the sample was poured into a 250 mL beaker.
• A thermometer was clamped vertically using a burette stand and immersed in the sample.
• The reading was recorded after stabilization (nearest 0.1°C).
2. Color Measurement
• The sample was poured into a clean glass tube.
• A tintometer with Hazen discs was used for visual comparison.
• The color was recorded in Hazen units (ºH).
3. pH Measurement
• The pH meter was calibrated using pH 4 and 7 buffer solutions.
• The electrode was rinsed with deionized water and immersed in the sample.
• The stabilized pH reading was recorded.
4. Turbidity Measurement
• The turbidity meter was calibrated with a 0 NTU standard.
• The sample was gently mixed to suspend particles.
• The cuvette was placed in the meter, and turbidity was recorded in NTU.
CALCULATION
• pH: Direct digital reading from the calibrated meter.
• Turbidity: Meter output in NTU.
• Color: Visual match to Hazen scale.
• Temperature: Direct thermometer reading.
RESULTS & DISCUSSION
| Parameter |
Sample Result |
WHO Guideline |
Nepal NDWQS 2079 |
| Temperature |
25°C |
No limit (note >15°C risk) |
No explicit standard |
| Color |
6.0°H |
Aesthetic concern |
≤5 TCU (exceeded) |
| pH |
7.5 |
6.5-8.5 |
Within range |
| Turbidity |
38 NTU |
Emphasizes removal |
≤5 NTU (exceeded) |
Discussion
• Temperature (25°C): Exceeds microbial safety thresholds; requires cooling or enhanced disinfection.
• Color (6.0°H): Violates Nepal’s limit, indicating organic/chemical contamination.
• pH (7.5): Within safe range; no adjustment needed.
• Turbidity (38 NTU): Far exceeds limits, requiring coagulation-filtration for pathogen removal.
CONCLUSION & CONTROL STRATEGY
1. Temperature (25°C): Use breakpoint chlorination to suppress microbial growth.
2. Color (6.0°H): Apply coagulation (alum/ferric chloride) + activated carbon adsorption.
3. pH (7.5): No treatment needed; recalibrate faulty meter.
4. Turbidity (38 NTU): Implement coagulation, sedimentation, and sand filtration.
PRECAUTIONS
Temperature:
• Use calibrated thermometers.
• Avoid sunlight exposure.
• Stir before reading.
Color:
• Use clean, bubble-free cells.
• Compare against Hazen standards.
pH:
• Calibrate with buffers (pH 4 & 7).
• Rinse electrode between samples.
Turbidity:
• Use scratch-free cuvettes.
• Degas samples to remove bubbles.
