Community Environment Monitoring

Testing for Phosphorus

Phosphorus is a nutrient required for plant and algal growth. Too much of it in water causes considerable problems, particularly the toxic algal blooms which are becoming more common in our rivers and lakes, especially in late summer when flows are low and water temperatures high.

Otho-phosphorus is the portion that is readily and immediately available for reaction.
A great deal more phosphorus may be adsorbed onto the surface of particles in the water, not reactive immediately, but liable to be released if suitable conditions of acidity and temperature are encountered.
Total phosphorus can be measured by boiling a sample in acid for a half hour and then carrying out the same test as for ortho-phosphorus.

My test kit is one supplied by WaterWatch, (Merck, Aquaquant, part number 1.14445.0001)
This kit contains several small dropper bottles of dilute acid and one bottle of powder. 20ml of sample is placed in each of two glass bottle about 1.5 cm diameter and 11 cm deep. The chemicals are added to one of these and the resultant colour compared by sliding the supplied colour card beneath the two bottles.

High turbidity makes this sort of colour comparison difficult. Filtering can be required when turbidity is high. This can add considerably to the time taken up by the test.

Links

To be added.
Last updated, JP, Design Productivity, 7/6/2001