Análise da formação de biofilmes bacterianos em carvão ativado do endocarpo de Orbignya phalerata (babaçu) impregnado com prata

Abstract

Activated carbon is used in water filters, however, it is susceptible to the formation of microbial biofilms on its surface. When adhered to the surface of the activated carbon, biofilms can prematurely saturate the filter and dislodge during the filtration process, contaminating the filtered water. An industrial alternative to avoid the contamination of water by means of microorganisms is the impregnation of activated carbon with silver, since it has bacteriostatic activity and may inhibit the formation of biofilms. In this context, the objective was to impregnate silver in activated carbon of the Orbignya phalerata Babaçu endocarp, to quantify and characterize the carbon samples, to evaluate the formation of mixed biofilms of Escherichia coli ATCC 8739 and Pseudomonas aeruginosa ATCC 9027 on the activated carbon surface, to evaluate the silver leaching and verify the inhibitory activity of the metal in the formation of mixed biofilms. The methodology applied for silver impregnation was carried out by heating with stirring until complete dryness, followed by calcination in muffle. The characterizations followed the methods of the American Society of Testing and Materials. The analysis of formation and inhibition of the biofilm, together with the leaching of the metals were carried out in fixed bed filter medium. The results of metal quantification in the samples were: 0.0180%, 0.0218% and 0.0453% silver by mass. The characterization of the samples showed that the activated carbon had a high adsorptive capacity, which was not affected by the impregnation of the metals. The bulk concentration of silver leached into the water remained within the standards required by ABNT NBR 16098/2012 and Ordinance 2914/2011 regarding the concentration of metal present in the filtered water demonstrating that the process of impregnation of activated carbon with silver did not alter the quality filtered water. The mixed biofilm formation of Escherichia coli and Pseudomonas aeruginosa occurred in the samples of non-impregnated activated carbon, while for impregnated activated carbon samples there was complete inhibition of the biofilm growth by Escherichia coli and concentration-dependent reduction for Pseudomonas aeruginosa, arriving at complete inactivation. Under the experimental conditions used, silver impregnated with activated carbon inhibited the formation of mixed biofilms, presenting as highly effective metal in bacterial inactivation. Therefore, the use of silver at lower concentrations than those used commercially (0.08%) showed inactivation properties of mixed microbial biofilms, without compromising drinking water, showing its application as a filter medium in domestic water filters and industrial alternative for possible savings of resources.