Water Analysis – pH Determination

The pH test is an important preliminary test. Small changes in pH (0.3 units or even less) are usually associated with relatively large changes in other water qualities.
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The pH test is an important preliminary test. (see pH) Small changes in pH (0.3 units or even less) are usually associated with relatively large changes in other water qualities. Most natural waters will have pH values from pH 5.0 to pH 8.5. the acidic, freshly fallen rain water may have a pH value of 5.5 to 6.0. If it reacts with soils and minerals containing weak alkaline materials, the hydrogen ion concentration will decrease. The water may become slightly alkaline with a pH of 8.0-8.5. Waters more acid than 5.0 and more alkaline than 8.5 to 9.0 should be viewed with suspicion. Sudden changes in pH values serve as warning signals that water quality may be adversely affected through the introduction of contaminates.

pH of water samples can be determined in the field or the samples can be collected and pH determined later. Since most aquatic systems have a pH in the midrange of pH scale, an indicator with a pH from 5-9 may be adequate. However, a wide range indicator is often the best to start with.

Place a small amount of the water sample in a test tube or other container. Add one or two drops of indicator to the sample. After 30 seconds compare the color of the water/indicator solution to the color chart provided with the indicator. Read the pH of the sample from the chart. Indicator paper can also be used.

pH Scale

pH values of some common substances

14.0

 

13.5

household lye

12.6

bleach

12.0

 

11.5

ammonia

11.0

 

10.2

milk of magnesia

10.0

 

9.3

borax

9.0

 

8.4

baking soda

8.0

sea water

7.4

blood

7.0

distilled water

6.7

milk

6.2

corn

6.0

 

5.0

boric acid

4.2

orange juice

4.0

 

3.0

 

2.8

vinegar

2.2

lemon juice

2.0

 

1.0

 

0.3

battery acid

0.0

 

 

pH value

times acidity or alkalinity exceeds that of pure water (7.0)

Acidic 0

10,000,000

1

1,000,000

2

100,000

3

10,000

4

1,000

5

100

6

10

Neutral 7

1

8

10

9

100

10

1,000

11

10,000

12

100,000

13

1,000,000

Alkaline 14

10,000,000

Acid——————–Neutral——————–Alkaline

0–1–2–3–4–5–6–7–8–9–10–11–12–13–14

Bacteria

1.0 – 13.0

Plants (algae or rooted)

6.5 – 12.0

Carp, sucker, catfish, some insects

6.0 – 9.0

Bass, Crappie

6.5 – 8.5

Snails, clams, mussels

7.0 – 9.0

Most animals (trout, mayfly, stone fly, caddis fly)

6.5 – 7.5

Water Analysis – Color, TSS, TDS

Color is an indication of the amounts of dissolved and suspended materials present in water. Total suspended solids (TSS) gives a measure of the turbidity of the water. Total dissolved solids gives a measure of the nutrient material dissolved in the water are indicators of productivity.

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Water Analysis – Temperature

Water temperature must be taken in the field. Temperature should be sampled at various depths using a recording Celsius thermometer. Location of temperature reading also needs to be considered, edge, middle, inlet, etc.

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