Efluente de parboilização do arroz: biorremediação e produção de biomassa

Abstract

Rice parboilization is a hydrothermal process that demands high volume of water, generating effluent of high complexity and polluting potential. The development of new treatment methods is necessary, considering the limitations of current techniques in the treatment of this effluent. The objective of this work was evaluate the bioremediation potential and biomass production in the effluent of rice parboilization (PE), using as microbiological agents the Saccharomyces cerevisiae yeast and microalga Chlorella spp., isolated from the pond after tertiary treatment. Physicochemical parameters were evaluated: phosphorus (P), total nitrogen (TKN) and chemical oxygen demand (COD); and microbiological parameters: cell viability and biomass. Cultures with S. cerevisiae were carried out in baffled flasks of 1 L, 180 rpm, 28 ºC and pH 5.5, and presented 17.28% of phosphorus removal, 74% NTK, 55% COD, 1.79 x 109 CFU.mL-1 of cell viability and 1.52 g.L-1 of biomass in 48 h. The application of S. cerevisiae in the reduction of physicochemical parameters is a low-cost alternative to assist in the treatment and reduction of PE complexity with the generation of biomass of wide applicability as a co-product. The cultures with microalgae Chlorella spp. were realized with 2000 lux, pH 7 and 28 ºC, and showed maximum removals of 82.48% of COD and 92.96% of TKN, generating 3.1 g.L-1 of biomass after 18 days of cultivation. P concentrations oscillate but there was no removal during cultivation. Nevertheless, these results suggest that the application of microalga Chlorella spp. is an alternative to reduce the concentrations of COD and TKN in the PE with generation of commercially biomass. The absence of supplementation and suitability of the medium, besides the simplicity of cultivation and monitoring, highlighted the potential of the microorganisms used in the treatment of PE, generating 1.52 g.L-1 of S. cerevisiae and 3.1 g.L-1 of Chlorella spp. and removal rates sufficient to match the PE to regulated levels or reduce the complexity of the effluent that is routed to effluent treatment station. Further studies will be performed using S. cerevisiae and Chlorella spp. on a larger scale and level of parameter control in order to optimize removals, model the treatment process and increase biomass.