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Dynamic membranes (DMs) formed upon cost-effective mesh filters are considered as convenient alternatives to conventional membranes in membrane bioreactors (MBRs). This novel study investigates how hydrodynamics resulting from aeration rates of 2.5, 5, 10, and 15 L/min and agitation speeds of 100, 200, 300, and 400 rpm affect the sludge particle size, soluble microbial product (SMP), accumulation of sludge upon filter media, fouling propensity, effluent turbidity, and separation properties of DMs. The results conveyed that mixing flow and mixing intensity affect sludge properties considerably as well as DMs formed in the MBR. Despite fouling propensity, sludge mean particle size and dry weight of DMs decreased by increasing aeration rate and agitation speed. Optimum performance in terms of turbidity removal and blue pigment separation was obtained at the aeration rate of 5 L/min and the agitation speed of 300 rpm. In addition, more uniform DMs were formed by the flow pattern created by agitation which improved the performance. The DM formed by the agitation speed of 300 rpm could remove approximately 82% of blue pigments with a mean particle size of 0.9 μm which performs similar to microfiltration. [ABSTRACT FROM AUTHOR]

In this study the effects of Al2O3 nanoparticle concentration were investigated on the membrane structure/performance; the boundary of variations was detected, introduced as Nanoparticle Concentration Threshold (NCTh), and was used for forecasting the field of membrane application. For this purpose, Al2O3 nanoparticles with a size of 70 nm and a concentration between 0 and 0.52 Wt.% were added to the membrane matrix. Loading threshold of Al2O3 nanoparticles was evaluated and the properties of the nanocomposite membrane were compared up and sub the loading threshold. Rheometric analysis, contact angle measurement, SEM images, and filtration experiments showed that concentration threshold of Al2O3 nanoparticles was 0.39 Wt.%. Based on their properties, the antifouling performance of those membranes possessing Al2O3 concentration below the threshold was evaluated in a membrane bioreactor (MBR). [ABSTRACT FROM AUTHOR]

Highlights: [•] To develop formation process of self-forming dynamic membrane on mesh filter. [•] To optimize imposed flux and aeration rate for self-forming dynamic membrane. [•] To evaluate efficiency of dynamic membrane bioreactor in removal of COD and TDS. [•] To investigate the preferable cleaning method for recovery of fouled mesh filter. [•] To characterize dominant chemical matter in dynamic membrane using FTIR analysis. [ABSTRACT FROM AUTHOR]

Abstract: In this study membrane fouling was studied in a novel airlift oxidation ditch membrane bioreactor (AOXMBR) working under various high organic loading rates (OLRs). The results confirmed the high performance of AOXMBR in terms of Chemical Oxygen Demand (COD) removal, even at very high OLRs. The role of the membrane barrier appeared to be significant when the COD in the supernatant was high under such conditions. In addition, the study confirmed the performance of the AOXMBR was better in comparison with the conventional activated sludge as such colloid matters cannot be retained via a simple secondary settling step. Also, on-line viability measurement of the activated sludge illustrated that the fouling increased with a decrease in the viability of the activated sludge. The results showed that the qualitative change of the activated sludge affected the fouling phenomenon. The membrane fouling dynamics analysis pointed out the relationship between cause of the membrane fouling and MBR operating conditions. Adsorption in pores appeared to be the dominant cause when any biofilm or deposit was present on the membrane surface. On the other hand at high OLR in the absence of any deficiency (oxygen deficiency, large pH variations etc.) for the microbial population the biofilm played the dominant role consequent, whereas with drastic decreases of OLRs -due to significant cell lysis – external and reversible deposits appeared as the dominant cause of membrane fouling. [Copyright &y& Elsevier]

The objective of this study was to investigate the effect of salt concentration on performance of a membrane bioreactor (MBR) for treating an olefin plant wastewater. For this purpose, a lab-scale submerged MBR with a flat-sheet ultrafiltration membrane was used for treatment of synthetic wastewater according to oxidation and neutralization unit of olefin plant. The synthetic wastewater was adjusted to have 500 mg/L chemical oxygen demand (COD). Trials on different concentrations of sodium sulfate (Na2SO4) (0-20 000 ppm) in the feed were conducted under aerobic conditions in the MBR. The results showed that increasing the salt concentrations causes an increase in the effluent COD, phenol, and oil concentrations. These results are due to reduction of the membrane filtration efficiency and also decline in the microbial activity that it is indicated by decreasing the sOUR in MBR. But in all the trials, the effluent COD and oil concentration was well within the local discharge limit of 100 and 10 mg/L, respectively. These results indicate that the MBR system is highly efficient for treating the olefin plant wastewater, and although high salt concentrations decreased organic contaminant removal rates in the MBR, the effluent still met the discharge limits for treating the olefin plant wastewater. [ABSTRACT FROM AUTHOR]

Abstract: Treatment of pharmaceutical wastewater is a real challenge for wastewater engineers. In this study, a pilot-scale system including an external loop airlift membrane bioreactor (ELAMBR) was applied for treatment of a synthetic pharmaceutical wastewater. The performance of this system was evaluated in removal of acetaminophen as the main pollutant of a pharmaceutical wastewater. A conventional activated sludge (CAS process) laboratory system was used in parallel with this system to compare both systems in regard to their ability for acetaminophen removal. The performance of the ELAMBR system was monitored for approximately one month to investigate the long-term operational stability of the system and possible effects of solids retention time on the efficiency of removal of acetaminophen. The removal efficiency was significantly higher in the ELAMBR system than the CAS process. 100% of the acetaminophen was removed after 2days in this system. The results also showed that initial concentration of acetaminophen, chemical oxygen demand (COD) and mixed liquid suspended solids (MLSS) are the most effective parameters in removal of a pollutant such as acetaminophen. This study demonstrates the usefulness of ELAMBR system for pharmaceutical wastewater treatment with the advantages such as: (i) simple operation and maintenance, (ii) efficient removal of pharmaceutical pollutant and COD and (iii) low-energy consumption. [Copyright &y& Elsevier]

Abstract: The rising demand for high quality water heightens the need to soften hard and very hard water. In this study, flat sheet polysulfone ultrafiltration membranes were prepared by phase inversion and modified by UV-induced polymerization of acrylic acid in order to prepare nanofiltration membranes for water desalination. Polyethylene glycol of different molecular weights mainly in the range of 1500–4000Da were used in the casting solution and acrylic acid was polymerized on the membrane surface. In this way, a manipulated membrane was prepared with higher pore size and higher surface charge density for improved water softening. The results show that by increasing irradiation time and monomer concentration in the photografting process, pure water flux declines and salt rejection increases. For a membrane photografted for 180min with acrylic acid solution (6wt.%) and PEG-4000 as additive, the rejection of Na2SO4, MgSO4, NaCl and CaCl2 follows a decreasing in order of 100%, 77.9%, 49.9% and 35.9% respectively. The RMS roughness of the prepared membrane is 1.65nm, which is well in the nanofiltration roughness range. Featuring a large pore size and high surface charge density, the developed nanofiltration membranes show a promising capability for water desalination. [Copyright &y& Elsevier]