COMPATIBILITY OF RICE HUSK AS A CARRIER MEDIUM FOR BACILLUS SP. IN AN ACTIVATED SLUDGE PROTOTYPE FOR DOMESTIC SEWAGE TREATMENT

Vollständiger Abstract

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Sanitation in Brazil still shows significant gaps in coverage and operational efficiency, which encourages the search for inputs capable of enhancing the performance of wastewater treatment plants. Among these inputs are granular bioremediators, whose formulation relies on food-grade cereals – mainly wheat bran – as the carrier medium for microorganisms, accounting for roughly 70% of the product cost. This article assesses the compatibility of rice husk, an abundant and low-cost agro-industrial residue, as a carrier medium for Bacillus sp. in an activated sludge prototype operated as a sequencing batch reactor. The material was ground, sieved, heat-treated and submitted to tests of moisture, density, dispersion in liquid media, mesophilic plate count, pathogen control and stability, in accordance with ANVISA resolution RDC 679/2022. Three treatment scenarios were then compared over nine batches: commercial bioadditive, rice husk-based bioadditive and no additive at all. Rice husk limited to 425 µm dispersed better than wheat bran and met every microbiological requirement after heat treatment at 100 °C for 60 minutes. Mean chemical oxygen demand removal efficiencies were 84.28%, 81.47% and 57.82%, respectively. A non-inferiority test confirmed, within a 1% margin, that the proposed product is not inferior to the commercial one.