Comparison between thermophilic and mesophilic membrane-aerated biofilm reactors- a modeling study

Abstract

Membrane aerated biofilm reactor (MABR), as a novel biological waste treatment technology, has received much attention in recent years, due to its advantages, as compared to conventional biofilm. Considerable amount of research and development of MABR technology were conducted in lab-scale, pilot-scale studies and even full-scale applications for various types of waste treatment and air pollution control. Though many researches have mentioned that operation factors would result in different system performance, few researches are focused on temperature changing impacts. While thermophilic aerated biological treatment already became a hot issue for waste water treatment. Thus, combined with thermophilic aerated biological treatment, the concept of thermophilic membrane-aerated biofilm reactor (ThMABR) is proposed in this research. This concept has a great potential to develop a new type of ultracompact, highly efficient bioreactor for high strength wastewater. In order to prove the high temperature has positive effect on MABR system, a mathematic modeling was established. Mathematical modeling was conducted to investigate the impact of temperature (mesophilic vs. thermophilic) on oxygen and substrate concentration profiles, membrane-biofilm interfacial oxygen concentration, oxygen penetration distance, and oxygen and substrate fluxes into biofilms. In the first part of this thesis, it focuses on a state-of-the-art literature review (2007-present) on the research progress and technology development of the MABR technology. The biological and membrane performances of MABRs for chemical oxygen demand (COD) and nitrogen removal in wastewaters, air pollution control, and modeling studies are systematically reviewed and discussed. However, few articles mentioned the temperature changing effect on MABR system. So in the second part, the concept of thermophilic membrane-aerated biofilm reactor (ThMABR) is proposed. This concept combines the advantages and overcomes the disadvantages of conventional MABR and thermophilic aerobic biological treatment, and has a great potential to develop a new type of ultra-compact, highly efficient bioreactor for high strength wastewater and waste gas treatments. Mathematical modeling was conducted to investigate the impact of temperature (mesophilic vs. thermophilic) on oxygen and substrate concentration profiles, membrane-biofilm interfacial oxygen concentration, oxygen penetration distance, and oxygen and substrate fluxes into biofilms. The general trend of oxygen transfer and substrate flux into biofilm between ThMABR and MMABR was verified by the experimental results in the literature. The results from modeling studies indicate that the ThMABR has significant advantages over the conventional mesophilic MABR in terms of improved oxygen and pollutant flux into biofilms and biodegradation rates and an optimal biofilm thickness exists for maximum oxygen and substrate fluxes into biofilm.