Abstract
This study examines the effect of bentonite and zeolite concentration (0.25–5 g/L) on the membrane fouling of a fully automated, pilot-scale membrane bioreactor (MBR) treating high-strength synthetic municipal wastewater. Reversible fouling was estimated by sludge filterability measurements and irreversible fouling was estimated by the reduction of the carbohydrate fraction of soluble microbial products (SMPc), which are considered to be significant MBR foulants. Both minerals were added to biomass samples (during batch-mode experiments) which were obtained from the system’s aeration tank. Results showed that the optimal bentonite and zeolite concentrations were 3.5–4 g/L and 2.5–3.5 g/L, respectively. Interestingly, above these values, the addition of both minerals increased the examined fouling indices, i.e., the measured filterability times and the SMPc concentration, implying that they might act as foulants at high concentrations. Optical microscopy images of the biomass samples showed that the addition of minerals at the optimal concentrations did not affect significantly filamentous microorganisms, since filament index (FI) was practically unaffected (~2). Finally, regarding the system’s treating performance, it was found that the pilot-scale MBR can operate successfully with high-strength synthetic municipal wastewater, since remarkable behaviour was exhibited in terms of organics (BOD5, COD) and ammonium (NH4+-N) removal (>98%).
Highlights
In recent decades, membrane bioreactor (MBR) technology has been widely used for municipal and industrial wastewater treatment, and for water reuse applications as well
The present study examines the effect of two natural minerals, namely bentonite and zeolite, on membrane fouling of a fully automated pilot-scale MBR treating high-strength synthetic municipal wastewater
Membrane bioreactors have been increasingly employed over the last few years for municipal or industrial wastewater treatment, membrane fouling still prevents their widespread application
Summary
Membrane bioreactor (MBR) technology has been widely used for municipal and industrial wastewater treatment, and for water reuse applications as well. Unlike the conventional activated sludge process (ASP), which employs a gravity-based clarifier (or settling tank) for the biomass separation, membrane bioreactors combine the wastewater biological treatment in the aeration tank with membrane filtration. Membrane fouling still remains the major problem of the MBR technology, preventing its widespread application for full-scale municipal or industrial wastewater treatment. Among a wide range of cutting edge methods (e.g., the addition of coagulants or bio-film carriers, application of electrical field, ultrasound or ozone, quorum quenching, membrane surface modifications, etc.), the use of adsorbents is a novel strategy which has been implemented for membrane fouling control over the last few years [1,2,3,4]. Adsorbents provide a large surface area for the adsorption of materials
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