Chapter 4 Practical 1
Determine water quality of a given location using rapid pollution monitoring kits
Aim:
To determine the physicochemical and biological quality of a water sample collected from a local water body (e.g., river, lake, pond) using a rapid water pollution monitoring kit and to assess its suitability for different uses based on the obtained parameters.
Principle:
Water quality is a measure of the physical, chemical, and biological characteristics of water relative to the requirements of its intended use (e.g., drinking, bathing, irrigation). Rapid monitoring kits provide a quick, on-field method for semi-quantitative analysis of key pollution indicators. These kits are based on colorimetric and titrimetric principles, where a specific reagent reacts with the target pollutant to produce a color change. The intensity of the color is then compared to a standard chart to determine the concentration.
Key parameters tested often include:
Physicochemical:
pH: Measures acidity or alkalinity. Crucial for aquatic life and chemical processes.
Turbidity: Measures cloudiness caused suspended particles. Affects light penetration and aesthetics.
Dissolved Oxygen (DO): Essential for aquatic organisms. Low DO indicates pollution.
Total Dissolved Solids (TDS): Measures inorganic salts and organic matter. High TDS affects taste and utility.
Nitrates & Phosphates: Key nutrients; high levels cause eutrophication (algal blooms).
Chemical:
Free Chlorine: indicates disinfection level in treated water.
Hardness (Ca²⁺ & Mg²⁺ ions): caused by dissolved calcium and magnesium salts.
Biological:
Most Probable Number (MPN) or Presence/Absence tests for Total Coliforms and E. coli, which are indicators of fecal contamination and the potential presence of pathogenic organisms.
Materials Required:
Rapid Water Testing Kit: (e.g., from brands like Systronics, Lovibond, or a standard JAL-TARA kit).
Water Sample: Collected in a clean, sterile 1L plastic bottle from a predetermined location (e.g., local pond, river, tap source).
Apparatus: Beakers (100 ml, 250 ml), measuring cylinder, glass rod, droppers, thermometer, stopwatch.
Distilled Water: For rinsing apparatus and as a blank.
Notebook and Pen: For recording observations.
Procedure:
Step 1: Sample Collection
Select the sampling site (e.g., midpoint of a pond, upstream/downstream of a discharge point).
Rinse the sample bottle three times with the water to be sampled.
Collect the water sample, label it with date, time, and location, and store it in a cool, dark place if not testing immediately (ideally test within 6 hours).
Step 2: Testing Physicochemical Parameters (Follow kit manual precisely)
pH:
Dip a pH strip into the water sample.
Wait for 30 seconds and compare the color change with the standard chart provided.
Record the value.
Turbidity (NTU):
Fill the provided tube with the water sample up to the mark.
Place the tube in the turbidity meter or hold it against the turbidity chart.
Record the value in NTU (Nephelometric Turbidity Units).
Total Dissolved Solids (TDS):
Dip the TDS meter probe into the water sample.
Wait for the reading to stabilize and record the value in mg/L.
Nitrate (NO₃⁻) and Phosphate (PO₄³⁻):
Take a known volume of water (e.g., 10 ml) in a test tube.
Add the reagent powder/pillow or liquid as per the kit instructions.
Shake well and wait for the specified time for color development.
Compare the color with the standard chart to estimate the concentration in mg/L.
Total Hardness:
Titrate the water sample against the reagent (e.g., EDTA solution) until the color changes from wine red to blue.
Note the volume of titrant used and calculate hardness in mg/L as per the kit formula.
Step 3: Testing for Biological Contamination (Presence/Absence Test)
Coliform Test:
Aseptically add the water sample to a prepared culture vial containing a nutrient medium.
Incubate the vial at a specified temperature (e.g., 35°C) for 24-48 hours.
Observe for a color change (e.g., from purple to yellow) and/or gas production in a small inner tube (Durham tube). A positive result indicates the presence of coliform bacteria.
Step 4: Data Recording and Analysis
Record all observations in a structured table.
Compare the obtained values with standard permissible limits for drinking water (e.g., as per WHO or Bureau of Indian Standards - BIS IS 10500).
Observations:
Table 1: Water Quality Analysis of Sample from [Location Name] on [Date]
| Parameter | Observations & Method | Result Obtained | Permissible Limit (BIS IS 10500 for Drinking Water) | Remarks |
|---|---|---|---|---|
| Temperature | Measured using thermometer | 28 °C | - | Ambient condition |
| pH | Color change on pH strip | 7.8 | 6.5 - 8.5 | Within Limit (Slightly alkaline) |
| Turbidity | Visual comparison with chart | 18 NTU | 1 NTU (5 NTU max) | Polluted (Highly turbid) |
| TDS | Digital meter reading | 850 mg/L | 500 mg/L (2000 mg/L max) | Beyond Limit |
| Nitrate (NO₃⁻) | Colorimetric analysis | 45 mg/L | 45 mg/L | At Maximum Limit |
| Total Hardness | Titration with EDTA | 320 mg/L as CaCO₃ | 200 mg/L (600 mg/L max) | Beyond Desirable Limit |
| Coliform Bacteria | Presence/Absence test | Color change to yellow, gas observed | Absent in 100 ml | Polluted (Positive result) |
Result:
The analysis of the water sample from [Location Name] revealed that it is unsuitable for drinking purposes without extensive treatment. Key parameters of concern are:
High Turbidity (18 NTU): Indicating a high load of suspended particles.
High TDS (850 mg/L): Indicating dissolved inorganic salts are beyond the desirable limit.
High Nitrate level (45 mg/L): At the maximum permissible limit, often due to agricultural runoff or sewage.
Presence of Coliform Bacteria: Confirming fecal contamination, making the water a potential health hazard.
The pH and hardness, while beyond desirable limits, are within the maximum allowable limits.
Discussion:
Sources of Pollution: The high nitrate level and presence of coliforms strongly suggest contamination from sewage discharge or agricultural runoff (from fertilizers and animal waste). High turbidity could be due to soil erosion or organic matter.
Impact on Human Health:
Nitrates: Can cause methemoglobinemia ("blue baby syndrome") in infants.
Coliforms: Indicate the potential presence of pathogenic bacteria, viruses, and protozoa that can cause diseases like cholera, typhoid, and dysentery. This directly links to the syllabus topic of "Impacts on environment, human health, and welfare".
Impact on Aquatic Ecosystem:
High nutrients (nitrates) can lead to eutrophication, causing algal blooms that deplete dissolved oxygen and harm aquatic life.
High TDS and turbidity can affect the gill function of fish and block sunlight for aquatic plants.
Limitations of Rapid Kits: While excellent for field screening, these kits provide semi-quantitative results. For regulatory purposes, more precise analytical methods like spectrophotometry or atomic absorption spectroscopy are used in laboratories.
Environmental Justice: The quality of water available to communities is a fundamental aspect of environmental justice. Marginalized communities often have limited access to clean water, forcing them to use such contaminated sources, leading to health disparities.
Conclusion:
This practical demonstrated the application of rapid water testing kits as an effective tool for the preliminary assessment of water quality. The results clearly indicated that the sampled water body is polluted with microbial and chemical contaminants, primarily from anthropogenic activities like sewage disposal and agriculture. This makes it a potential risk to both public health and the aquatic ecosystem. Regular monitoring using such kits is crucial for identifying pollution hotspots, raising public awareness, and prompting action from concerned authorities to restore water quality, as envisioned in initiatives like the Jal Jeevan Mission and the Water (Prevention and Control of Pollution) Act, 1974.
Viva Voce Questions:
Why is pH an important parameter to test in water?
pH affects the solubility and toxicity of chemicals and heavy metals in water. Most aquatic life thrives in a specific pH range (6.5-8.5). Highly acidic or alkaline water can be corrosive and harmful to both organisms and plumbing infrastructure.
What is the significance of testing for coliform bacteria instead of direct pathogens?
Testing for all specific pathogens is difficult and expensive. Coliform bacteria (especially E. coli) are found in the intestines of warm-blooded animals and are therefore a reliable indicator organism. Their presence signals that fecal contamination has occurred and that pathogens might be present.
What does a high TDS value indicate about the water's history?
High TDS indicates that the water has been in contact with soluble rocks and minerals (e.g., limestone, gypsum). It can also be elevated by industrial effluent, sewage, and agricultural runoff. It affects the taste of water and can cause scaling in pipes and boilers.
How is the 'Hardness' of water related to human health?
Moderately hard water contributes to dietary calcium and magnesium requirements. However, very hard water can cause scale formation in pipes and appliances, reducing their efficiency. It also reduces the lathering of soap, leading to higher consumption.
What is the next step if a water source is found to be contaminated with coliforms?
The water should be immediately declared unsafe for drinking without treatment. The next steps involve Boiling (rolling boil for 1 minute) or Chlorination to disinfect it. The finding should also be reported to local health or water authorities for investigation into the source of contamination.
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