Production Optimisation of a Land-Based Trout Farm and the Reduction of its Environmental Effects

Abstract

In this study, certain water quality parameters (water temperature, dissolved oxygen (DO), pH, total inorganic nitrogen (TIN), phosphate (PO4), nitrite (NO2), nitrate (NO3), ammonium (NH4), and (BOD5) in the effluents and the efficiency of the treatment systems for eliminating wastes at a commercial trout farm with a capacity of 10 tons/year in Izmir (Kemalpasa) were examined. The DO, temperature, pH, TIN, PO4, NO2, NO3, and BOD5 measured, were different in the outlet waters when compared with the inlet waters (p<0.05). The settling basin did not reduce the TIN and PO4, on the contrary, it caused an increase in the nitrogen (N) up to 19.9% and phosphorus (P) up to 20.30%, while the wetlands reduced the N, P, and BOD 5 up to 53.2%, 58.2%, and 36.5%, respectively (p<0.05). According to the chemical and biological methods, the averages of the TIN and P loads for one tone of cultured trout without treatment were estimated to be were 80 kg and 7 kg, respectively. The annual TIN load of this trout farm was estimated to be 21.3 kg while the TP load was 2.9 kg for one tone of cultured trout when the treatment efficiency was taken into account. The microbiological analyses conducted with the effluent waters showed that the rate of aerobic mesophilic bacteria was found to be high in the summer but low in the winter. It was also detected that the coliform group bacteria were present in the environment in the summer while their occurence was with-in standards in the winter. Interactions of the 9 water quality parameters were identified through the linear regression analysis in order to reduce the environmental effects of the facility DO= 28.296 – (0.248 × BOD 5 ) – (2.948 × pH) + (0.189 × temperature) + (0.851 × inlet water) + (0.163 × winter) (R2=0.912). According to this model, the DO values were increased by the temperature, inlet water and the winter season while reduced by the BOD5 and pH. The dissolved oxygen content in the wetland outlet water was measured as being high because of the nutrient and temperature rises which boosted photosyntesis. It was concluded that using mechanical settling methods were inadequate to minimise the nutrients released into the receiving water body so wetlands should be constructed in such a way as to receive the flow of effluents from the trout farms. As a result the quality of water used by the facility has no adverse impact on the aquaculture and environmental ecosystem.