Nitrate-rich water containing denitrifying bacteria will exhibit a faster rate of reduction in nitrate levels.

Nitrate contamination

The use of fertilizers to improve soil fertility and enhance plant growth has resulted in the contamination of nitrogen compounds such as ammonia, nitrate and nitride in our rivers, lakes and ocean. During soil erosion or heavy rain, flowing water will wash nitrates into the nearest lakes and rivers. This causes the pollution and contamination of the water.
The presence of nitrates in rivers and lakes encourages the growth of algae in the water. The growth of algae will reduce the levels of dissolved oxygen in the water and this poses a problem for the survival of the fish and other living organisms in the water.

Denitrifying bacteria helps to metabolize nitrogen compounds using enzymes to release nitrogen gas. This is an anaerobic process and will only take place in an environment where there is very little oxygen. It is a common occurrence in deep soil and stagnant water. This process is part of the nitrogen cycle, releasing nitrogen gas back into the atmosphere.

The hypothesis that nitrate-rich water containing denitrifying bacteria will have a faster rate of reduction in nitrate levels has been proven to be true.

The level of nitrate and nitrite in the drinking water is normally regulated for the safety and protection of human health and also for the preservation of the aquatic ecosystem. US drinking water standards require the levels of nitrate to be kept below 10mg/liter and nitrite to be kept below 1.0ml/liter. High levels of nitrate in drinking water are known to affect the ability of blood to carry oxygen and cause the blue baby syndrome in infants.

The experiment may be repeated to check the levels of ammonia and nitrite in water.

The experiment may also be modified to compare the effect of denitrification in water samples from different sources.