Abstract
The concern in mitigating the negative impact generated by the discharge of nutrients in the receiving water body is a challenge for the sustainable development of Brazilian fish farms. Thus, the purpose of this study was to evaluate the water quality and environmental impact caused by trout farming system effluent with focus on discharge of phosphorus. Sampling was performed on a weekly basis in triplicate from September to November 2010. Sample sites were distributed according to the water flow: upstream from trout farming system, water supply, effluent, artificial wetland, mixing zone and downstream (60 m from effluent). In the field, pH, conductivity, dissolved oxygen, water temperature and turbidity were measured. In laboratory, nitrogen and phosphorus series, chlorophyll a, total solids suspended and their organic and inorganic fractions were analyzed. For the good growth of trout in production system, the abiotic factors described in the water quality monitoring demonstrated acceptable values. Environmentally, after passing through the production system and artificial wetland, there was an increase in concentrations of total phosphorus, total nitrogen, orthophosphate, ammonium, chlorophyll a, total solids suspended and their organic and inorganic fractions (P
Highlights
Brazil is situated in a region of tropical and subtropical climates, trout has been adapted well in the mountainous regions where temperatures are lower, close to 22 ̊C in the hottest month and for at least four months is greater than 10 ̊C [1]
Significant variations among sites were found in conductivity (H = 57.71; P < 0.001), dissolved oxygen (H = 82.98; P < 0.001), water temperature (H = 14.20; P = 0.014), total phosphorus (H = 161.54; P < 0.001), total nitrogen (H = 18.45; P = 0.002), orthophosphate (H = 133.55; P < 0.001), ammonium (H = 65.16; P < 0.001), nitrite (H = 11.84; P = 0.037), chlorophyll a (H = 52.31; P < 0.001), total solids suspended (H = 96.07; P < 0.001), total suspended solids (TSS) organic (H = 45.38; P < 0.001) and TSS inorganic (H = 81.03; P < 0.001) (Table 1)
The turbidity values were below 10 NTU at all sites and the nitrate values were below 0.10 μg/L
Summary
Brazil is situated in a region of tropical and subtropical climates, trout has been adapted well in the mountainous regions where temperatures are lower, close to 22 ̊C in the hottest month and for at least four months is greater than 10 ̊C [1]. In these areas, the rivers are small, with an insufficient flow for the deployment of large trout farming systems [2]. The feed produced in Brazil uses waste of fish, with low levels of protein and high ash contents. Depending on the characteristics of the raw material, the feed contains a large amount of mineral material from the bones and scales [8]
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