ارزيابي آب خاكستري و اثرات تجمعي زيست محيطي مزارع پرورش ماهي

Fish farming is a key activity in the food supply chain. However, discharging multiple pollutants from aquaculture into water sources can lead to decreasing water quality for human health (drinking and sanitation) and biodiversity. For example, the phenomenon of eutrophication is an environmental consequence that can be intensified by fish farm effluents. Releasing excessive nitrogen and phosphorus polluting compounds to the surface water can consequently affect the aquatic, terrestrial and even marine ecosystems downstream. This issue is especially important in Iran, where aquaculture is an active industry in the upstream of rivers where their appropriate management can directly affect the supply chain of water and food. In this study, by eva‎luating the water quality of the influent and effluent of trout farms in some regions inside Iran, and comparing the results with studied examples available in other countries, GWF of trout farms is calculated as a net added pollution load and is used as an auxiliary index in LCA. Finally, by the application of midpoint-endpoint coefficients of life cycle assessment (LCA), the cumulative environmental impacts of this industry is estimated quantitatively. This approach employs combined water quality and environmental impacts of wastewater to make a base for accounting the food environmental footprint (FEF) index, as a state-of-the-art index under food-environment nexus. For this purpose, the available data on the water quality of trout farms in Iran was compared with similar cases in several countries around the world, and the Grey Water Footprint (GWF) was calculated. The results showed that the GWF of trout in Iran and other countries is more affected by total suspended solids (TSS) and ammonium (NH4) pollutants, respectively, and its average is 17400 and 14700 m3/ton. Moreover, estimations through life cycle impact assessment (LCIA) with the coefficients of the ReCiPe model (2016) showed that the reduction in clean water access downstream has the highest impact comparatively, and the average cumulative environmental impacts for farms in Iranand other countries are equal to 1.40E+04 and 7.10E+03. It shows that the cumulative environmental impacts of Iranian samples are on average 2 times greater than farms in other countries. Reviews also showed that the constructed wetland, as a wastewater treatment system, can remove more than 80% of TSS, BOD and NH4 and 60% of total nitrogen (TN) and total phosphorus (TP). Accordingly, it can be expected that these units can be properly used in fish farming wastewater treatment, where the GWF and the total environmental impacts would be reduced by 85.5% and 57%, respectively. The sensitivity analysis results also showed that changing the ReCiPe main approach in damage estimation and the maximum allowable concentration of pollutants have the greatest effect on the final results. The FEF index for trout farms is 0.024, which verifies the sustainability of trout production (<1). The value of this index is still sustainable even without the use of wastewater treatment systems and is equal to 0.194. FEF means that for saving one personʹs life from hunger, only 0.194 lives would be damaged by the environmental pollution from this activity in the long term. Therefore, this research showed that using the combined method of GWF-LCIA and FEF index can provide decision makers with a more comprehensive and quantitative framework for environmental comparison of food products.

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