Reducing nitrate levels in water with denitrifying bacteria
The materials required for the experiment:
- 2000 milliliters of water from an algae-rich pond
- 1 plastic container with 2 liter capacity
- 15ml of Nitrobacter
- 15ml of Nitrosomonas bacteria
- 6 beakers
- 1 measuring cylinder
- 1 syringe
- 1 roll of plastic wrap
- 1 nitrate test kit
1. For this experiment, the independent variable is the introduction of denitrifying bacteria. The dependent variable is the concentration of nitrate in the water. This is determined by testing the water using the nitrate test kit. The constants (control variables) are the size of the water sample, the amount of the denitrifying bacteria present in each water sample and the temperature of the environment, which will remain at room temperature.
2. Label each of the beakers Bacteria 1, Bacteria 2, Bacteria 3, None 1, None 2 and None 3. Measure and pour about 300ml of pond water into each of the 6 beakers.
3. Using the nitrate test kit, measure the level of nitrate in the water samples in each beaker. Record the measurments in a table, as shown below.
4. Using a syringe, add 5ml of the Nitrobacter bacteria and another 5ml of Nitrosomonas bacteria is to each of the 3 beakers labeled as Bacteria 1, Bacteria 2 and Bacteria 3.
5. Cover all 6 beakers using the plastic wrap. Once a week for the next 3 weeks, open the plastic cover to obtain a water sample and measure the nitrate levels in each beaker. Record the measurements in a table, as shown below.