Biotechnology and Bioinformatics (1+1)

6.1.2.Effect of aquaculture wastewaters

The major impact on the receiving water bodies are

· eutrophication,

· silting,

· oxygen depletion and

· toxicity of ammonia and sulfide.

· High organic load increases the oxygen demand in water bodies. This eventually reduces dissolved oxygen levels in aquaculture systems.

The urine and faeces from the aquatic animals can cause

· high content of ammonia nitrogen and

· an increase of BOD (biochemical oxygen demand).

· Ammonia is the main nitrogenous waste that is produced by fish via metabolism and is excreted across the gills.

· Nitrite is a naturally occurring intermediate product of the nitrification process.

· The nitrate ion (NO3^–) is the most oxidized form of nitrogen in nature and is relatively non-toxic to fishes. However, when nitrate concentrations become excessive and other essential nutrient factors are present, eutrophication and associated algal blooms can become a serious environmental problem.

· Excess nitrogen and phosphorous content lead to eutrophication and algal bloom, especially of toxic species produced by high levels of nutrients. This can cause environmental hazards including mortality of fish and severely reducing water quality.