Performance of pilot-scale membrane aerated biofilm reactors integrated with anoxic nano-biotechnological reactor for domestic wastewater treatment.

Membrane-aerated biofilm reactors (MABRs) have aroused increasing attention due to their excellent performance in treating wastewater, where the membranes behave as bio-carriers for microorganisms and bubbleless air diffusers. The MABR technology has not been fully commercialized due to reactor design and low total nitrogen (TN) removal efficiency at short hydraulic retention times (HRT). In this study, a hybrid system of MABR 1 integrated with an anoxic nano-biotechnological reactor filled with Granulated Nanoscale Oxyhydroxides of Fe (GNOF) media was evaluated to assess the improvement in nitrogen removal performance at 12, 10, and 4 h of HRTs. At the same time, another MABR (MABR 2) was operated individually at 12, 10, 8, 6, 4, and 2 h of HRTs to assess the influence of HRT on nitrogen removal performance. An enhancement in removal performance was reported in the hybrid MABR-GNOF, achieving the highest removal efficiencies of 74.3 ± 3.1% for ammonium nitrogen (NH4+-N), 69.8 ± 2.1% for total nitrogen (TN), and 90.9 ± 1.7% for chemical oxygen demand (COD), at 12 h HRT. The hybrid MABR-GNOF system attained 18% higher nitrogen removal than the MABR-only system at 12 h of HRT. A simultaneous anoxic nitrification-denitrification and COD oxidation might be developed for the removal of COD, NH4+-N, and TN from domestic wastewater by using GNOF as an electron acceptor in the hybrid MABR-GNOF unit. The findings in this study confirmed the possibility of integration of GNOF and MABR on a pilot scale and are promising for the application of this hybrid system on a full scale.

Effects of membrane relaxation rate on performance of pilot-scale membrane aerated biofilm reactors treating domestic wastewater.

The membranes of a Membrane Aerated Biofilm Reactor (MABR) function as bubble-less air diffusers and bio-carriers. Recent bench-scale experiments reported that the shape of membranes influenced the oxygen transfer and utilization rates, which in turn affected the pollutant removal performance of the MABR. In this study, two pilot-scale MABRs using multi-layer hollow fiber membranes with the relaxation rates of 0.1-1.8% (MABR 1) and 1.0-2.8% (MABR 2) were used for the treatment of organics and nitrogen in real medium-strength domestic wastewater. Higher-relaxation-rate membranes have loose and more curved fiber bunch that may allow biofilm to grow more easily and let air diffuse more efficiently. MABR 2 had achieved better performance than MABR 1 at 12- and 6-h Hydraulic Retention Time (HRT), with respectively 0.7-4.3%, 17.7-18.1%, and 5.5-9.0% higher removal efficiencies for Chemical Oxygen Demand (COD), Ammonia Nitrogen (NH4+), and Total Nitrogen (TN). The highest COD, NH4+, and TN removal efficiencies were 94.7%, 81.1%, and 57.1%, respectively, at 12 h HRT in MABR 2. The addition of Polyvinyl Alcohol (PVA) gel beads carrying denitrifying bacteria had enhanced the denitrification in both the reactors. Increments of 5.0-9.0% and 6.6-12.3% were reported for TN removal efficiencies of MABR 1 and 2 combined with PVA gel, sequentially.