Nitrogen (N) and phosphorus (P) are important waste products of fish farms. N is excreted mainly through the fish gills as ammonia, which represents 75% to over 85% concentration may reach high levels in wastewater coming from rearing tanks causing environmental impact in sheltered coastal areas.Microscreen or sedimentation tanks can reduce nutrient load contained in the particulate matter (PM) and clarifythewastewater (Cripps and Bergheim,2000). Nevertheless, the high water turnover in intensive landbased facilities makes sedimentation tanks inefficient and the microscreen use difficult and expensive because of the frequent maintenance required (Hennessy, 1991). Moreover, mechanical treatment methods are not able to reduce dissolved nutrient loads. So, the use of systems which reduce both suspended and dissolved nutrients should be an important aim to make intensive aquaculture environmentally compatible.
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