Utilização de ostra e macroalga como biofiltro para efluentes de cultivo de camarão marinho

Abstract

The efficiency of an integrated treatment system to improve the water quality from shrimp pond was assessed laboratory-scale by using sedimentation, oyster filtration and macroalgal absorption (trial 1), and the evaluation of oysters and macroalgae densities in effluent treatment of autotrophic and heterotrophic shrimp culture systems (trial 2). Native species of oyster (Crassostrea rhizophorae) and macroalgae (Gracilaria sp.) were selected due to their local availability and aquaculture potential in northeastern Brazil. In trial 1, the effluent water was left to settle for 24 h without aeration (first phase) and in the next two phases (oyster and macroalgae) the effluent water was drained into experimental units (and control) for 24h each with aeration. In trial 2, three densities of oyster (0.2, 0.4 and 0.8 oyster.L-1) and macroalgae (2.0, 4.0 and 8.0 g.L-1) were assessed during 48 h to treat effluent water (24 h for each phase). Chemical and physical variables were measured during experiments periods (0 to 72 h for trial 1 and 0 to 48 h for tria 2). Variations in the concentration of chlorophyll a, pheophytin, total phosphorus, total phosphate, orthophosphate, total ammonia, nitrate, nitrite, total suspended solids, organic suspended solids and inorganic suspended solids showed that the two biological filters reduced significantly the concentration of the different pollutants in the shrimp effluent, however oyster and macroalgae densities should be more studied.