Performance and microbial community analysis in an anaerobic hybrid baffled reactor treating dairy wastewater

Anaerobic dairy waste treatment requires effective control to avoid long-chain fatty acid (LCFA) inhibitory effects on anaerobic microorganisms, especially methanogens. The hybrid anaerobic baffled reactor (HABR) can provide system stability, but more needs to be done to understand how the microbial communities underpinning the HABR compartments behave and respond. Thus, this study aimed to examine the HABR's microbial community correlating its performance when subjected to an increase in organic loading rate (OLR) during simulated dairy wastewater treatment. Besides the elevation in OLR, the system could maintain a high COD removal efficiency, nearly to 91\%, and elevate the methane production to 53\%. Almost all of the organic matter removal occurred mainly in C1 and C2 compartments. The genera Methanosaeta, an acetoclastic methanogen, and Methanobacterium, a hydrogenotrophic methanogen, were the HABR's dominant species. The most representative phylum found was Bacteroidetes (12--28\%), Firmicutes (3--20\%), Chloroflexi (4--26\%), and Proteobacteria (4--14\\%). Species capable of syntrophic partnership with methanogens were also identified, belonging to the family of Syntrophomonadaceae and Syntrophaceae. Microorganisms able to perform the AD process as HA73, VadinCA02, T78, Longilinea, Clostridium, and Syntrophomonas were present in the HABR.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior – CAPES Finance Code 001 and process no. 23038.009805/2012–39