Trout farm effluents: Characterization and impact on the receiving streams

• Type: Article in International Scientific Journal
• Date: 1997

Authors

Rui Boaventura (Author) FEUP; Pedro, AM (Author) Other; Coimbra, J (Author) Other; Lencastre, E (Author) Other

Journal

Title: Environmental Pollution

Vol. 95 No. 3

Pages: 379-387

ISSN: 0269-7491

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 46 Citations

Scopus - 47 Citations

Other information

Authenticus ID: P-001-CCC

DOI: 10.1016/s0269-7491(96)00117-0

Abstract (EN): Effluents from three rainbow trout (Oncorhyncus mykiss) farms located in Northern Portugal were characterized and their impact on the receiving streams was evaluated. Mean fish productions in the studied fish farms were 15, 55 and 500 t of trout per year, respectively. The feeding water was abstracted from Fornelo, Inha and Coura Rivers, at flow rates ranging from 1.2 (15 t year(-1) fish farm) to 4.8 litre s(-1) per ton annual fish production (500 t year(-1) fish farm). As the water flows through the farms, net variations in the chemical characteristics were observed: a mean reduction in the dissolved oxygen (DO) concentration between 0.7 and 2.4 mg litre(-1); mean increases between 1.9 and 3.2 mg CaCO3 litre(-1) for total alkalinity, between 0.9 and 14 mg litre(-1) for BOD5, between 0.27 and 1.46 mg litre(-1) for ammonia nitrogen (NH4-N), between 0.060 and 0.579 mg litre(-1) for soluble phosphorus (PO4-P) and less than 16 mg litre(-1) for suspended solids; variations in the pH value and nitrate nitrogen concentration were not statistically significant (p < 0.05). At the 500 t year(-1) fish farm it was also possible to defect net increases of total hardness (3.2 mg CaCO3 litre(-1)), electric conductivity (19 mS cm(-1)) and permanganate value (3.6 mgO(2) litre(-1)). At the other farms net variations in these parameters were not significant. Net mass flow variations reported to the annual fish production are presented. The DO mass flow decreased, on average, between 255 and 549 g t(-1) of fish per day. The mean daily BOD5 increase ranged from 353 to 1510 g t(-1) of fish. The corresponding ranges for the other parameters were 105-157 g t(-1) for NH4-N, 24-62 g t(-1) for PO4-P, 348-1035 g CaCO3 t(-1) for total alkalinity and 224x10(6)-506x10(6) t(-1) for mesophilic bacteria. Daily net variations of suspended solids, total hardness, electric conductivity and permanganate were below 1753 g t(-1), 342 g CaCO3 t(-1), 2081 mS cm t(-1) and 392 gO(2) t(-1), respectively. Longitudinal concentration profiles for the most relevant parameters show the impact of the effluent discharges on the physico-chemical and bacteriological river water quality downstream from the trout farms. Analyzing the situations from a purely chemical point of view, the polluted stretches were 3, 5 and 12 km long downstream from the effluent discharges, respectively. The microbiological contamination extended over longer distances. (C) 1997 Elsevier Science Ltd.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 9