Phosphates
Testing Parameters
Phosphates are found in nature in low levels. Like nitrates, phosphates are also used in fertilizers to help stimulate plant growth. However, in conjunction with heavy nitrates, a body of water may undergo eutrophication a process where a body of water becomes overly rich in organic and inorganic nutrients. This causes excessive algal growth until these nutrients are depleted. As the algae begin to die off, the decomposition process robs the water of oxygen. Phosphates can be measured using a chemical test, measured in parts per million (mg/L).
Testing Procedures
There are two possible tests for phosphates. One is the mid-range indicator, the other is the low-range indicator test. On your first trip in the field, use the mid-range test first to get an idea of what levels are common in your area.
Gloves and goggles must be used when performing this test.
Mid-range test:
- Fill test tube to the 10 ml mark with sample water.
- Use the 1.0 ml pipette to add 1.0 ml of Phosphate Acid Reagent.
- Cap and mix. If you fill the pipette over the 1.0 ml line, squeeze out the phosphate acid reagent until it is right on the 1.0 ml line. Be sure to squeeze it into the wastewater bucket.
- Use the 0.1 g spoon to add 0.1 g of Phosphate Reducing Reagent.
- Cap and mix until dissolved.
- Wait five minutes for the color to develop.
- Insert test tube into Octet Comparator and hold up to a steady light.
- Match the colors and record the reading. If your sample color is between two colors on the comparator, mark "less than". Write in the higher number.
- Divide your reading by three and record as mg/L phosphates on the data sheet.
Low-range test:
- Fill test tube to the 10 ml mark with sample water.
- Use the 1.0 ml pipette to add 1.0 ml of Phosphate Acid Reagent.
- Cap and mix. If you fill the pipette over the 1.0 ml line, squeeze out the phosphate acid reagent until it is right on the 1.0 ml line. Be sure to squeeze it into the wastewater bucket.
- Use the 0.1 g spoon to add 0.1 g of Phosphate Reducing Reagent. Cap and mix until dissolved. Wait five minutes for the color to develop.
- Insert test tube into Axial Reader and compare. If your sample color is between two colors on the comparator, record the average of the two values.
- Divide by 3 and record as mg/L phosphate.
Axial Reader set-up:
- Place Axial Reader on the tabletop with the open side facing the operator.
- Insert the Octet Comparator in the open slot so that the numbers are facing the operator. The bottom of the comparator should be even with the bottom of the Axial Reader.
- Fill three test tubes to the mark with water. Treat one test tube as the instructions indicate, using the others as blanks.
- Insert the ampoule of water in the square hole on the left side of the Octet Comparator.
- Insert the treated sample into the Axial Reader holder directly behind the water ampoule.
- Insert the two untreated test tubes into the Axial Reader on the sides of the treated sample.
- Slide the Octet Comparator down until the top is even with the top of the Axial Reader
- Hold the comparator against light to match the colors of the water sample and the comparator.
- If the colors on the first line do not match, slide the Octet Comparator up and compare the sample against the bottom row.
- If the sample is still too dark, move the water ampoule, treated sample and blank samples over to the next row.