Analysis of Solids Present in Different Media in the Biofloc System: Sedimentation, Correlation, and Regression
Author: Magna dos Santos Silva (Currículo Lattes)
Advisor: Dr. Wilson Wasielesky
Abstract
The Biofloc Technology (BFT) system has been applied in intensive and super-intensive aquaculture as a way to promote more sustainable farming with low water exchange and high productivity. However, the excess of solids generated in this system may cause various problems during cultivation and must be constantly monitored. Nevertheless, the correlation between settleable solids (SS) analyses is not always strong when compared to total suspended solids (TSS) and turbidity. The present study aimed to improve methodologies for settleable solids analysis through the application of different doses of three chemical products in Penaeus vannamei culture media—predominantly photoautotrophic, heterotrophic, and chemoautotrophic—to correlate with TSS and turbidity, in addition to evaluating water quality parameters, microorganism abundance, proximate composition, and shrimp zootechnical performance. The chemical products used to enhance sedimentation in the Imhoff cone were polyaluminum chloride (100%; PA), copper sulfate (19.5%; CS), and aluminum sulfate (100%; AS). This study was divided into two experiments. Experiment I was conducted over 60 days and consisted of two treatments: one predominantly photoautotrophic medium and one predominantly heterotrophic medium. The efficiency of various doses of the chemical products in compacting and sedimenting SS at different TSS ranges was evaluated. The study revealed that polyaluminum chloride and aluminum sulfate showed better performance in terms of correlations and solids compaction at minimal doses, while copper sulfate demonstrated greater efficiency at higher doses. Experiment II lasted 70 days and consisted of three treatments: a predominantly photoautotrophic medium, a predominantly heterotrophic medium, and a predominantly chemoautotrophic medium. Shrimp with an initial average weight of 1.17 g were stocked at a density of 500 shrimp/m³. Water quality parameters, proximate composition, and zootechnical performance remained within acceptable ranges. The results indicated that polyaluminum chloride (100%; PA) and aluminum sulfate (100%; AS) allowed better sedimentation and compaction of solids in the Imhoff cone analyses in photoautotrophic and heterotrophic treatments, showing strong correlations. An exception was the highest dose of aluminum sulfate (100%; AS) in the predominantly heterotrophic medium, which caused solids not to compact in the Imhoff cone, affecting the reading. It is recommended that producers estimate TSS values not only through the cone but also via turbidity, as it is a practical and fast analysis with a very strong correlation observed during the experiment.