Purified Water Test Procedure

i) Appearance

Clear, odorless and colorless liquid.

ii) pH

Transfer 100ml water to a suitable container; add 0.3ml of saturated potassium chloride solution and stirring water, then measure the pH using calibrated pH meter.

iii) Conductivity

Transfer 100ml water to suitable container and immerse electrode then stirring the water, measure the conductivity and Total Dissolved Substances (TDS) using calibrated conductivity meter.

iv) Chloride

To 10ml add 1 ml dilute nitric acid and 0.2ml of silver nitrate test solution. The solution shows no change in appearance for at least 15 minutes.

v) Sulphate

To 10 ml add 0.1 ml dilute hydrochloric acid and add 0.1 ml barium chloride test solution. The solution shows no change in appearance at least 1 hour.

vi) Oxidisable Substance

To 100 ml add 10 ml dilute sulphuric acid, 0.1 ml of 0.02M potassium permanganate solution and boil for 5 minutes. The solution remains faintly pink.

vii) Ammonium

To 20 ml add 1 ml of alkaline potassium tetraiodomercurate solution. After 5 minutes examine the solution down the vertical axis of the tube. The solution is not more intensely colored than a standard solution prepared at the same time by adding 1 ml of alkaline potassium tetraiodomercurate solution to a mixture of 4ml of ammonium standard solution (1 ppm) and 16 ml of ammonium free water.

viii) Calcium and Magnesium

To 100 ml add 2 ml of ammonium chloride buffer pH 10.0, 50 mg of mordent black II triturate and 0.5 ml of 0.01M disodium edetate solution. A pure blue color is produced.

ix) Heavy metals

Heat 200 ml in a glass container on a water bath until the volume is reduced to 20ml. 12 ml of this concentrated solution complies with limit test A. Prepare the standard using 10 ml of lead standard solution (1 ppm).

• a) Test solution: 12 ml of prescribe concentrated solution.
• b) Reference solution: A mixture of 10 ml standard lead solution (1 ppm) and 2 ml prescribe concentrated solution.
• c) Blank solution: A mixture of 10 ml water and 2 ml prescribe concentrated solution.

Procedure: To each solution add 2 ml of buffer solution pH 3.5 R. Mix and add to 0.1ml of sodium sulfide solution. Mixed immediately and examine the solution after 2 minutes. The test is invalid if the reference solution does not show a slight brown color compared to that of blank solution. The substance complies with test if any brown color in the test solution is not more intense than that in the reference solution.

x) Nitrates

Place 5 ml in a test-tube immersed in iced water, add 0.4 ml of a 100 g/l solution of potassium chloride, 0.1 ml of diphenylamine solution and, drop wise with shaking, 5 ml of nitrogen-free sulphuric acid. Transfer the tube to a water-bath at 50°C. After 15 minutes, any blue colour in the solution is not more intense than that in a reference solution prepared at the same time in the same manner using a mixture of 4.5 ml of nitrate-free water and 0.5 ml of nitrate standard solution (2 ppm NO3).

Total Count

Dispense 1ml sample water in 100ml sterilized water and filter through pre-sterilized 0.20µm filter. After completion of filtration transfer filter membrane previously prepared R2A agar plate using sterile forceps. Place the membrane carefully so that air should not be trapped inside the filter. Incubate the plates in upright position at 37ºC for three days. Count the number of colonies formed on the membrane.

Pathogens

Dispense 100ml sample water (for each pathogen) and filter through pre-sterilized 0.20µm filter. After completion of filtration transfer filter membrane previously prepared respective selective media agar plate using sterile forceps. Place the membrane carefully so that air should not be trapped inside the filter. Incubate the plates in upright position at 37ºC for three days. Observe the colonies formed on the membrane.