Iranian Journal of Chemical Engineering (IJChE)

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 The biosorption of Cd(II) ions from aqueous solutions by dried activated sludge was investigated as a function of initial pH, initial cadmium ion concentration, adsorbent mass, adsorbent particle size and temperature. Biosorption experiments were performed using activated sludge of the systems of wastewater refining of milk factory. The results showed that increasing the initial pH from 2 to 5.5 and the adsorbent mass from 0.5g to 2g increased the removal efficiency from 11% to 68% and 68% to 79% respectively. Increasing the adsorbent particle sizes from smaller than 0.063mm to greater than 0.5mm and the initial cadmium ion concentration from 15ppm to 120ppm decreased the removal efficiency from 77% to 67% and 80% to 54% respectively. The equilibrium data fitted both the Langmuir and Freundlich adsorption models, but the Freundlich isotherm was found to fit the experimental data slightly better than the Langmuir isotherm. The characteristic parameters for each isotherm have been determined. Maximum adsorption capacity (q 0) was calculated at different temperatures (303, 318, and 333 K) 1.283, 1.581 and 1.726 mg/g, respectively. The dimensionless separation factor (RL) showed that the activated sludge of milk factory can be used for the removal of cadmium ions from aqueous solutions. The results (n, RL) represented good and favorable adsorption. Therefore, the activated sludge could remove Cd(II) ions effectively from aqueous solution.

Abstract This investigation was designed to evaluate the effects of bioaugmentation on maintaining the system stability under shock loading conditions, standardizing the effluent, and improving the sludge settlement. In this study, phenol was chosen as a model of mono-aromatic compounds which are found commonly in many industrial wastewaters, especially petroleum refineries and the petrochemical industry in Iran. Impacts of bioaugmentation with the best isolated microorganism on the system performance facing sudden toxic shock were investigated after acclimatizing the system with phenol, isolating the phenol degrading microorganisms, and selecting the best phenol degrading strain. Results indicated that this method was improved the efficiency of the system under shock loading from 30% to 94% and SVI from 333 ml/g to 80 ml/g. The effluent was standardized after bioaugmentation at a minimum HRTs of 10, 10, 12 and 24 h, respectively, and at influent COD of 800, 1000, 1500 and 2000 mg/l. The system efficiency and SVI were located in an average range of 99.4-99.9% and 50-71 ml/g, respectively, and the sludge growth was good, even under high organic loading rates after bioaugmentation. In conclusion, bioaugmentation could be used as an effective and efficient method to improve a CAS process facing sudden toxic pollutant shock loading.