Overview :
Aquaculture activities which result in the pollution of ground and surface waters include the use of commercial feeds, accumulation of fish faeces, and decomposition of dead fish. The wastes in aquaculture farms is due to residual food and faecal matter, metabolic by-product, residues of biocides and bio stats, fertilizer derived wastes and wastes produced during moulting and collapsing algal blooms. Also, the disturbance of sediment by fish resulting in the vertical mixing of sediment into the water column, excessive use of chemicals results in pollution Indiscriminate disposal of fish waste such as scales, offal, and dead fish also contribute to water pollution. The resulting effects are high concentrations of organic matter, phosphorus, and nitrogen which negatively impact the rearing water and lower dissolved oxygen (DO) levels due to the decomposition of organic substances leading to stressand increased susceptibility to diseases, suitable environment for the proliferation of pathogenic microbes, and eventually mortality of cultured species.
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Fish utilize the nitrogen component of digested proteins, the amino group (NH2) to build new proteins. However,
when they utilize the proteins for energy, they cannot metabolize the nitrogen, and the amino group is split off as ammonia gas.
Ammonia is toxic, and it reduces the ability of the haemoglobin in the blood to hold oxygen. Additionally, ammonia damages the gill structure further
impairing the fish in getting oxygen. Ammonia gas solubilizes readily in water to form ammonium ion.
Zeofreshcan be applied to shrimp ponds to bind Hydrogen Sulphide, Sulphur dioxide and the carbonate form of Ammonia as soon as they are liberated
from the Decomposing Excreta, Feed and Dead Algae in the Pond Bottom. This Binding Action creates a Healthy Pond Bottom and
Favourable Water Quality for the Disease Free Growth of the Prawns and Fish.
The use of Multibacter (probiotic and enzyme) for the remediation of aquaculture wastewater to improve the water quality also confer on the cultured
fish other benefits. Immunostimulation resulting in resistance against pathogens, direct inhibition of pathogenic microbes, provision of nutrient and enzymes,
and improved feed utilization and growth are other benefits of probiotics.
Ammonification, nitrification, and denitrification are part of the processes involved in the nitrogen cycle. The initial form of nitrogen from the death of
plants, animals or their waste products is organic. This organic nitrogen is converted to ammonium (NH+4) and ammonia (NH3) by fungi or bacteria,
including Bacillus species in a process called ammonification. The ammonium is converted to nitrites (NO−2) and then to nitrates (NO−3) mainly by Nitrosomonas
and Nitrobacter species respectively in a process called nitrification. This is then followed by the conversion of nitrate to nitrogen gas (N2) (denitrification),
thus removing bioavailable nitrogen and returning it to the atmosphere.Bacillus remove the different forms of nitrogen from aquaculture wastewater. The removal of
large organic compounds reduces water turbidity.
