Influence of bioremediation on the growth and survival of Cyprinus carpio var koi using aquaculture waste water
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Date
2015
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Fisheries College and Research Institute, Thoothukudi, Tamil Nadu Fisheries University
Abstract
Aquaculture generates quantum of wastes in the form of residual food, faecal matter, metabolites byproducts leading to self-pond pollution. Discharge of these waste water into the environment will lead to environment degradation and also huge expenses on water exchange. A number of commercial microbial products including live bacterial inocula, enzyme preparation are being promoted for use in improving water quality in aquaculture ponds. The present study was an attempt to know the effect of using a mixed microbial consortia in the form of a commercial probiotic (Bacillus subtilis, Nitrosomonas, Nitrobacter and Rhodobacter) at various concentration (0.25 g/m3, 0.5 g/ m3 and 1g/ m3) to know its ability to remove the nitrogenous compounds Phosphate-P, BOD and COD from the aquaculture waste water and making it fit for rearing of Cyprinus carpio var koi. The initial physico-chemical parameters of aquaculture waste water collected from the farm revealed that it was not fit for rearing of fishes.
Laboratory study of the microbial inoculum applied demonstrated a greater rate of removal of nitrogenous compounds, phosphate-P, BOD, COD and an increase in the dissolved oxygen concentration. The total heterotrophic bacterial count showed that the microbial consortium was well established in the system and involved in the mineralization and nitrification process .Significant impact of the removal of nutrients and organic matter due to the application of probiotics was observed. The TAN value of 0.915mg/l was reduced to 0.074 mg/l by the 9th day in T-3 (@ 1g/m3) whereas in control (without probiotic) it was reduced only to 0.655 mg/l.There was a significant increase in the dissolved oxygen concentration in T-3 when compared to other treatment tanks and control. Probiotics added at the same concentration in the treated bioremediated rearing system also had a significant impact. Limited aeration was provided to all the experimental tanks to maintain an optimum dissolved oxygen concentration level. All the physico-chemical parameters were within the permissible limit. The growth parameters of koi carps such as total length, body weight, specific growth rate and survival rate of control and various treatment tanks were observed. The maximum length obtained in T-3 was 65.1 ± 1.159 mm and 5.279 ± 0.128 g at the end of the culture period. At the same time the koi carps in control reached a maximum length of 44.8 ± 0.628 mm and 2.89 ± 0.162 g at the end of culture period. The mean length gain, weight gain and specific growth rate was comparatively better in T-3 when compared with control and other treatments. Survival rate of koi carp (97.25%) registered in T-3 was higher than T-1, T-2 and control tank (90.5%). The study proved that the probiotics (Bacillus subtilis, Nitrosomonas, Nitrobacter and Rhodobacter) used at a concentration of 1 g/m3 were instrumental in improving the water quality, by reducing the nitrogenous species and organic matter by nitirification and mineralization process and thereby improved the growth and survival of koi carps The novel thought behind this study is that aquaculture waste water instead of discharging into the open system can be reused again after bioremediation.
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