Avaliação da eficiência de SCOBY de kombucha na coagulação e adsorção em tratamento de efluente

Abstract

Currently, population and industrial growth has increased the generation of effluents which, when disposed of without proper treatment, compromise water quality. Among these effluents, those from the textile industry stand out due to the presence of synthetic dyes, such as methylene blue, which are difficult to degrade and have potential toxicity to ecosystems. This work aimed to evaluate the use of kombucha SCOBY as a coagulant and adsorbent for methylene blue. Kombucha was prepared from the infusion of green tea with sucrose to form the SCOBY, which was used in its natural state in the tests. Coagulation and sedimentation tests were performed in a Jar Test, while adsorption was performed in a Shaker at 25 ºC. The SCOBY was characterized in terms of pH (3.5), ash content (~0.32%) and SEM (Scanning Electron Microscopy). Coagulation diagrams were constructed and analyses of chemical oxygen demand (COD), apparent color, turbidity, and alkalinity were performed. Turbidity removal was best achieved at an acidic coagulation pH (3.7–4.0) and with 36.5 g SCOBY L⁻¹ at sedimentation velocity 3 (VS3) for 21 min. Under optimal coagulation conditions, COD removal (~40%) was observed; however, the SCOBY itself contributed to an increase in COD compared to the raw effluent. In adsorption studies with methylene blue, the point of zero charge was pH 5.00, and a maximum removal of 69% occurred in 24 h with 5 g of SCOBY 25 mL⁻¹ in a 10 mg dye L⁻¹ solution. The isotherms better fit the Freundlich model (R²=0.91) than the Langmuir model (R²=0.87), indicating that the process preferentially occurred on a heterogeneous surface, with the possibility of multilayer formation. Thus, SCOBY demonstrated potential for adsorbing methylene blue dye in purified water and as a possible effluent coagulant.