A Study Of The Conductive Membrane Electrode And Its Function In Integrated System In MBR/MFC

In past decades, membrane bioreactor (MBR) process, which integrates a filtration membrane with a bioreactor, has gained worldwide attention and popularity due to its high treatment efficiency, low sludge production, and good effluent quality. However, there are still some problems to be solved before its more widespread application, such as high costs of membrane materials, severe membrane fouling and high energy consumption for aeration.Microbial fuel cells (MFCs) have emerged as a promising technology to recover energy from wastewater. Exciting progress has been made in MFC and electricity generation over the past decade. However, for wastewater treatment, MFCs usually have poor effluent quality and low treatment efficiency because of their limited biomass retention, which necessitates a further treatment with additional operational costs. It has been hypothesized that a combined MBR/MFC system might offer an attractive option. The operation of MBR may overcome the drawbacks of MFC by improving biomass retention and chemical oxygen demand (COD) removal efficiency, while MFC may generate power to partially offset the energy demand for aeration and filtration in MBR and lower the overall oxygen consumption for COD removal.In this paper, a simple MBR-MFC system is developed for wastewater treatment and energy recovery without using any noble metal. A low cost, conductive polyester filter cloth, modified by in-situ formed PANi (polyaniline)-phytic acid (PA) is tested as cathode or anode in MBR-MFC system. Electrically conductive membranes were prepared by coating graphene (Gr) and polyaniline (PANi) doped with phytic acid (PA) on polyester filter cloth. The Gr/PANi-PA modified membrane had a good conductivity and an excellent antifouling property, its electric resistance was93%lower than the PANi-HA (doped with hydrochloric acid) modified membrane and13%lower than the PANi-PA modified membrane. The antifouling performances of the modified conductive membranes were compared in EMBR (MBR, membrane bioreactor attached with a0.2V/cm electric field), tested by a short time filtration of a yeast suspension solution. The result indicated that the membrane with a higher conductivity had better antifouling property, smaller slopes in its t/V-V curves (adopting the classical cake filtration model, a suitable description for the membrane fouling process). The short-term cumulative permeate volume from the Gr/PANi-PA modified membrane was increased by -58%after applying0.2V/cm electric field, while it was only-10%for PANi-PA modified membrane.In MBR-MFC system, when a low cost, conductive polyester filter cloth, modified by in-situ formed PANi (polyaniline)-phytic acid (PA) was tested as cathode, a maximum power density (44.80mW/m2) was obtained, using500Ω external resistor and graphite granule as the anode. Further, replacing graphite granule anode with the modified membrane, power density at13.02mW/m2was obtained with inoculated S. oneidensis MR-1(Shewanella oneidensis MR-1). And the COD removal efficiencies can reach95%in the integrated system. This suggests that the PANi-PA modified membrane is applicable as anode and cathode in MBR-MFC system for the wastewater treatment and energy recovery.