Environmental Engineering Water Resources Water Quality Para

Environmental Engineering: Water Resources

Water Quality Parameter: pH

Water Quality Contaminant: Lead

For Parameter:

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1. What media(s) should be sampled?

2. Describe any existing field methods.

3. Describe the analytical or instrumental methods.

4. Describe sampling methods.

5. What type of vessel and preservation techniques must be used?

6. How long can the sample be kept?

7. What calibration techniques or internal quality controls need to be included?

Solution

For Parameter pH:

1) pH of samples should be measured in-situ i.e., at the site only, but for some media like well water or when access to a lake or river is very difficult, in this cases media should be sampled and measured immediately after the sample is obtained.

2.) Existing Field Methods: pH can be measured by indicator papers like Litmus paper. Red litmus paper turns to blue in alkaline medium and Blue litmus paper turns to red in acidic medium from this method we can find out whether water is acidic or basic. We can measure approximate pH of water by using universal Indicator which gives different colors for different indicators. For example Phenolphthalein 8.6 to 10.2, Methyl orange 4.4 to 6.0 by using this type of indicators and colour matching discs we can findapproximatepHof water.

3.) Analytical and Instrumental methods:

Different instrumental methods are a)  Hydrogen-Electrode Method b) Quinhydron-Electrode Method c) Antimony-Electrode Method d) Glass-Electrode Method e) Semiconductor sensor methods

In all these methods the principle of measuring pH is same, which consists of a sensing electrode and a reference electrode connected to an electric circuit which measures the voltage and finally it displays pH of sample.

4.) Samples can be collected at different depths and if we are collecting samples from borewell we should runout the water for at least 3 minutes and then we collect that sample water. Samples should be collected in airtight bottles and bottle should be washed with the sample water to prevent any contamination of sample from any liquids present in that bottle.