Pilot-scale reactor for removing VOCs from a biowaste treatment plant: removal performance, degrading microorganisms, and their functional genes

Abstract

The widespread generation and treatment of biowaste contribute to odorous volatile organic compounds (VOCs) emissions and health issues and are a challenge to contemporary society. This study designed equipment that integrated a chemical washing tower (CWT) with a biotrickling filter (BTF) to remove VOCs from a biowaste treatment plant and reduce associated health risks. The total VOC concentrations at the biowaste treatment plant ranged from 700.1 to 1800.0 ppb and aliphatic hydrocarbons and volatile organic sulfur compounds (VOSCs) were the dominant VOCs. The inoculum added to the system contained Bacillus, Burkholderia, and other effective microorganisms. It removed 97.9 % of VOSCs (5 ppm) within 3 days under laboratory conditions. At the pilot scale, the combined CWT-BTF system removed 84.0 % of VOCs, with the BTF unit demonstrating superior performance compared to the CWT. The health risks of some VOCs decreased after purification, although the non-cancer and cancer risks remained above acceptable levels. After inoculation, the dominant microorganisms in the BTF changed from Bacillus, Klebsiella, and Burkholderia pseudomultivoran to Polynucleobacter, Verrucomicrobia, and Planctomycetota, which were primarily involved in energy metabolism pathways. Additionally, Polynucleobacter sp. 16-46-70 was found to be involved in sulfur metabolic pathways. Genes related to sulfur metabolism (cysK, cysJ, and metB) and nitrogen metabolism (gltB, GDH2, nirB, and niT) were involved in VOCs removal in BTF. This study indicates that the CWT-BTF technique at suitable loading rates is an effective method for removing VOCs emitted by biowaste and offers insights into the bacteria and genes that hold potential for enhancing removal efficiency.