Published in Scientific Papers. Series "Journal of Young Scientist", Vol. 4
Written by Mihai FRINCU, Corina DUMITRACHE
The aim of this paper was to understand how nitrogen cycle evolving through early experimental aquaponic system due to growth of nitrification bacteria such as Nitrozomonas and Nitrobacter. In this respect, it was design an aquaculture system, with different composition of fish species: Carassius auratus (10 pieces) and Hypostomus plecostomus (2 pieces). After we’ve found that the nitrogen cycle was established, we’ve chosen the suitable plants for the hydroponic system. The fishes were fed by organic meal; it was used a feeding rate ratio for design calculations of (0,6 grams /day) and the feed input was kept relatively constant. The pH was controlled on a daily basis (pH was maintained constant by addition of calcium carbonate) and oxygen dissolved (that has been kept constant by using a proper pump). Nitrogen forms (ammonium - NH4, nitrite - NO2 and nitrate - NO3) were determined on a daily basis as well and in the same time with pH measurement, in order to make correlations between evolution of nitrogen concentrations and nitrification bacteria growths. After 30 days of experiment it was found that ammonium - NH4 concentrations are directly and significantly correlated with nitrite -NO2 concentrations (the Pearson correlation factor is r = 0.74). It means that Nitrosomonas bacteria formed an effective biofilm. After 10 days from initiation of aquaculture experiment we also observed that nitrate concentrations values are correlated with nitrites concentrations values (which demonstrates the Nitrobacter growing). The correlation coefficient is negative (r = - 0.75) because in the absence of plants, the nitrates were accumulated in water. In conclusion, according to experimental data, the ammonium- NH4 and nitrite -NO2 concentrations are stabilized after 30 days, reaching values which are lower than legislation in force imposing.
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