Two-stage anaerobic fluidized-bed membrane bioreactor treatment of settled domestic wastewater

Abstract

A two-stage anaerobic fluidized-bed membrane bioreactor (SAF-MBR) system was applied for the treatment of primary-settled domestic wastewater that was further pre-treated by either 10 μm filtration or 1 mm screening. While the different pre-treatment options resulted in different influent qualities, the effluent qualities were quite similar. In both cases at a total hydraulic retention time of 2.3 h and 25 °C, chemical oxygen demand and biochemical oxygen demand (BOD5) removals were 84-91% and 92-94%, with effluent concentrations lower than 25 and 7 mg/L, respectively. With a membrane flux of 6-12 L/m(2)/h, trans-membrane pressure remained below 0.2 bar during 310 d of continuous operation without need for membrane chemical cleaning or backwashing. Biosolids production was estimated to be 0.028-0.049 g volatile suspended solids/g BOD5, which is far less than that with comparable aerobic processes. Electrical energy production from combined heat and power utilization of the total methane produced (gaseous and dissolved) was estimated to be more than sufficient for total system operation.

The Performance and Fouling Control of Submerged Hollow Fiber (HF) Systems: A Review

“…Almost as an afterthought, PAC also was recognized as being beneficial for inducing fouling-mitigating shear on the membrane [254][255][256][257]. Because the increased inertia associated with larger-sized particles can lead to more effective scouring, granular activated carbon (GAC), whose mean diameter is an order-of-magnitude larger than that of PAC, has recently gained interest [24,130,[257][258][259][260][261][262][263][264]. Although PAC is more effective than GAC in terms of adsorption capability [257], it has been claimed that GAC is more effective at the higher concentrations encountered in practice and in the longer term [24].…”

“…Extensive tests subsequently have been carried out [24,27,128,130,244,, especially in view of the potentially lower energy cost than that of bubbling [24,204] and suitability for the anaerobic MBR. Effects of treating different types of wastewater [258,259,261,262,276] (e.g., using municipal versus synthetic wastewater [24,258]), trace organics [128,278], membrane type [273] (including effects on membrane integrity [271,272,275]), screen size [259], fluidized media [236,244,279,280] (including size and packing amount [244,267,268,271,275]), operating conditions [260,271] such as temperature [260][261][262], scale [261], design [130,261,264,265,276] (e.g., single (AFMBR) versus two-stage (AFBR-AFMBR) systems [130]), which collectively proved the efficacy of GAC in scouring the membranes. Different embodiments of the AFMBR include single (AFMBR) versus two-stage (AFBR-AFMBR) systems …”

Pilot scale application of anaerobic baffled reactor for biologically enhanced primary treatment of raw municipal wastewater

“…In AnMBRs treating real wastewater at temperatures <20 C, dissolved methane was reported at 40e50% of the total production (Smith et al, 2013). In an anaerobic fluidized bed-fluidized membrane bioreactor 63% of the methane produced was in dissolved phase (Yoo et al, 2012;Bae et al, 2013).…”

“…Yoo et al (2012) estimated a lower total electrical energy potential from methane production at 0.08 kWh/m 3 (based on 33% conversion efficiency) in a two stage anaerobic fluidized bed-membrane bioreactor (SAF-MBR) treating primary clarifier effluent at 25 C. However the theoretical energy demand of the system reduced the net energy generation to 0.04 kWh/m 3 . In a subsequent study with the SAF-MBR, Bae et al (2013) used filtered wastewater (1 mm and 10 mm) at 25 C. Under these conditions the system produced an electrical energy potential of 0.1 kWh/m 3 . The estimated 0.05 kWh/m 3 energy demand of the system (not including filtration) was not satisfied by 0.03 kWh/m 3 potential of the gas phase methane production, but could be satisfied if the dissolved methane were captured.…”

“…Anaerobic reactor configurations that provide long solids residence time (SRT) decoupled from hydraulic residence time (HRT) can compensate for slower kinetics at ambient temperature. Anaerobic secondary treatment at psychrophilic temperature has been demonstrated in membrane bioreactors receiving primary clarifier effluent (Yoo et al, 2012;Bae et al, 2013;Smith et al, 2013). The implementation of anaerobic primary treatment in conjunction with anaerobic secondary treatment can significantly reduce biosolids production and maximize methane production from the wastewater organics.…”