Evaluating the Performance of Anaerobic Baffled Reactor in Treating Municipal Wastewater

Abstract

The anaerobic baffled reactor (ABR) is widely recognized as a cost- effective solution for decentralized municipal wastewater treatment, however

its application is often constrained by long hydraulic retention time (HRT) required to support the slower growth rate of anaerobic microorganisms. This study explored two enhanced configurations of the ABR - the carrier anaerobic baffled reactor (CABR), incorporating pieces of polyvinyl chloride (PVC) corrugated pipe as carrier media, and the sponge anaerobic baffled reactor (SABR), utilizing polyurethane sponge sheets. These configurations were designed to improve biomass retention, enhance microbial activity, and optimize treatment performance while reducing HRT requirement. In the first study, the CABR operated under mesophilic conditions (35±1°C) and evaluated at HRTs ranging from 24 to 4 hours, consistently outperformed the conventional ABR. At HRTs between 24 and 8 hours, the CABR achieved organic removal efficiencies of 81- 88%, compared to 68-73% for the ABR. Notably, at an HRT of 6 hours, the CABR maintained an organics removal efficiency over 80%, whereas the ABR efficiency declined significantly to 59%, demonstrating a 36% performance variation. In the second study treatment performance of SABR was evaluated and compared with that of CABR. Results revealed that both configurations sustained COD removal efficiencies exceeding 80% in shortening the HRT from 18 to 8 hours. However, at an HRT of 6 hours, the CABR outperformed the SABR, maintaining a removal efficiency of over 80%, while the SABR efficiency dropped to 63%.

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In another study, the SABR was tested with real municipal wastewater under mesophilic conditions at HRTs of 18, 12, 8, and 6 hours. The reactor achieved removal efficiencies of 96% for total suspended solids (TSS), 79% for COD, 60% for total nitrogen (TN), and 53% for total phosphorus (TP). Except for TP, all other parameters met the effluent discharge standards at an optimal HRT of 8 hours. Microbial community analysis of sludge from the SABR identified eight major bacterial species, including a novel Ralstonia strain with 96.07% nucleotide identity to known species, indicating potential taxonomic novelty. The microbial community was analyzed using 16S rRNA gene sequencing, which provided insights into the dominant bacterial populations present in the system. The findings underscore the effectiveness of CABR and SABR as efficient, space-saving solutions for decentralized wastewater treatment in warm climates. Furthermore, the identification of a novel bacterial strain highlights the importance of integrating microbial studies to enhance reactor design and performance, contributing valuable insights into anaerobic treatment processes and future research.