Iranian Journal of Chemical Engineering (IJChE)

Abstract The optimization of membrane bioreactor (MBR) equipped with a submerged flat-sheet polyethersulfone (PES) membrane for the wastewater treatment from dairy processing facilities was investigated. The effects of key parameters such as the hydraulic retention time (HRT, from 8 to 16 hr), mixed liquor suspended solids (MLSS, 3000 to 9000
mg/L), and rate of aeration (Qair: 1 and 2 L/min) on COD removal efficiency were systematically investigated. Through the response surface method (RSM), the maximum the COD removal efficiency of 92.67% was obtained under the optimal conditions of HRT: 13.83 hr, MLSS: 7239.84 mg/L, and Qair: 1.75 L/min. The statistical analysis identified MLSS as the most influential factor in the COD removal efficiency, accounting for 30% of the variation, followed by HRT with
16%, and the rate of aeration showing the least impact of 8%. A notable reduction in the UV absorbance of wastewater between 200 and 500 nm, after treatment using MBR under optimal conditions, signified successful targeting of toxic or colored pollutants. Finally, a mechanism for the wastewater treatment in MBRs, which included the biological degradation, adsorption on the surface of biomass and membrane, and separation through membrane filtration, was proposed.

Abstract The membrane bioreactor (MBR) is a combination of biological and membrane systems. It utilizes advanced technologies in the treatment of various types of wastewater, having unique advantages such as the high-quality effluent and improved efficiency. The primary limiting factor for the utilization of this bioreactor  is the  membrane fouling phenomenon, which increases operational costs. In this study, four membrane bioreactors were used, with the first MBR (R1) serving as the control bioreactor. In the second MBR (R2), an adsorption process was employed, while in the third (R3) and fourth MBR (R4), in addition to the adsorption process, the electrochemical process was applied with voltages of two and one volts respectively. For the four bioreactors, the percentages of the Chemical Oxygen Demand (COD) were recorded as 86%, 91.2%, 90.7%, and 95.3% respectively. The levels of the total Extracellular Polymeric Substances (EPS) in R1, R2, R3, and R4 were about 260, 155, 177, and 98 mg/gVSS respectively. The R4 exhibited significantly lower EPS (98 mg/gVSS) compared to R1 (260 mg/gVSS), possibly due to the adsorption of EPS by nanoparticles and its subsequent removal during the electrochemical process. The role of voltage was evident in R3, where the higher voltage (2V) resulted in the less removal of EPS (155 mg/gVSS) compared to the same in R4 (98 mg/gVSS). The study found that the values of the Soluble Microbial Products (SMP) for R4, R3, R2, and R1 were about 15, 65, 55 and 139 mg/L respectively. Particularly in the most effective MBR, R4, where the addition of the zeolite adsorbent alongside metal ions demonstrated the best performance in the removal of SMP.

Abstract The membrane bioreactor (MBR) is a  treatment bioreactor of urban and industrial wastewaters. The advantages of the MBR technology encompass high-quality effluents, less space requirements, and high-speed startups. This study aims to investigate the fouling phenomenon in the flour industry sewage treatment. The pilot has been designed and constructed in line with the research concerning the industrial wastewater treatment. After the adaptation of microorganisms, physical and chemical tests such as chemical oxygen demands (COD), turbidity and total suspended solids (TSS), extracellular polymeric substances (EPS), and soluble microbial products (SMP) were conducted during the process. The concentration of mixed liquor suspended solids (MLSS) in the membrane bioreactor ranged between 5000 and 8500 mg/L. Hydraulic retention times (HRTs) were fixed at 4, 8, and 16 h. Three types of resistance were considered via measuring the leakage current and transmembrane pressure (TMP). Accordingly, the total resistance rates for HRTs of 4, 8, and 16h were 22.5×10¹⁰, 21.3×10¹⁰, and 20.4×10¹⁰ m^-1 respectively. Considering the average organic loading rate (OLR) in three HRTs of 4, 8, and 16 h (8.84, 5.13, and 2.84 kg the COD/m³×day respectively), the daily feed was provided to the bioreactor, and the removal efficiency of COD was assessed. An average removal of 95 % was achieved in the whole process. In this method, the input turbidity of the effluent has been increased to 187 NTU and, then, reduced to less than 3 NTU. It was also observed that EPS, SMP, and the extracted carbohydrates played more vital roles in the membrane biofouling than the extracted proteins.

Abstract Membrane technology is one of the few non-pollutant choices when selecting a treatment process. A membrane with suitable pore size can remove almost all pollutants without using any chemicals. In this research, chromium, zinc and lead were removed from synthetic wastewater by a membrane bioreactor. The results showed that by using a membrane bioreactor, the COD removal efficiency was increased in all conditions in comparison with that of an activated sludge process system. According to the test results, in the case of having heavy metals; Chromium with a concentration below 50 mg/l , the removal efficiency was shown to be about 95% and at these concentrations, chromium has no toxic effect on micro-organisms. However, the Activated Sludge Process showed poor removal efficiency in the case of having zinc. But when ASP was used in conjunction with the membrane, the removal efficiency was increased to 76%. Membrane showed an improvement of efficiency from 44% to 65% in the case of having 50 mg/ l of lead.