Parametric study and process modeling for metronidazole removal by rhombic dodecahedron ZIF-67 crystals.

Metronidazole (MNZ) is an extensively used antibiotic against bacterial infections for humans and farm animals. Prevention of antibiotics discharge is essential to prevent adverse environmental and health impacts. A member of metal-organic frameworks, zeolite imidazole framework-67 with cobalt sulfate precursor (ZIF-67-SO4) and exceptional physio-chemical properties was prepared via room temperature precipitation to adsorb MNZ. The study framework was designed by Box-Behnken Design to evaluate the effect of pH, ZIF-67-SO4 dose, and contact time on adsorption efficiency. The polynomial model fitted the adsorption system indicated the optimal condition for 97% MNZ removal occurs at pH = 7, adsorbent dosage = 1 g/L, and mixing time = 60 min. The model also revealed that the removal increased with contact time and decreased at strong pH. Equilibrium and kinetic study also indicated the adsorption of MNZ followed the intra-particle diffusion model and the Langmuir isotherm model with a qmax = 63.03 mg/g. The insignificant loss in removal efficacy in use-reuse adsorption cycles reflected the practical viability of ZIF-67-SO4.

Using acidic-modified bentonite for anaerobically digested sludge conditioning and dewatering.

In this study, the acidic-modified bentonite (AMB) was developed to enhance conditioning and dewatering processes of anaerobically digested sludge (ADS) for the first time and its performance was compared with inorganic salts, e.g. FeCl3, AlCl3, Al2(SO4)3 and Fe2(SO4)3. AMB structural changes were investigated employing XRD, XRF, FT-IR and specific surface area tests. AMB reduced the specific resistance to filterability (SRF), capillary suction time (CST) and time to filter (TTF) of the sludge by 95.8%, 90.4% and 80.8%, respectively. Moreover, it reduced the sludge compressibility and increased filtration yield significantly. Also, sludge conditioning with the AMB resulted in a significant increase in the sludge particles size and formation of denser and stronger flocs. In order to evaluate the related sludge conditioning mechanism, zeta potential, bound water, extracellular polymeric substances (EPS) and XRF tests were conducted. It was determined that AMB acts as physical and chemical conditioner. Dewatering of conditioned sludge with AMB utilizing a filter press resulted in the sludge with 41% dry solids (DS). In addition, the economic survey showed that the cost of conditioning by using AMB is $ 33.79 USD/t DS. In general, it can be concluded that AMB has an effective performance in conditioning and dewatering of anaerobically digested sludge and is economically affordable in comparison to common polymers.

Employing Electrochemical-Fenton process for conditioning and dewatering of anaerobically digested sludge: A novel approach.

In this study, for the first time, the occurrence mechanism of anaerobically digested sludge conditioning for dewatering process based on Electrochemical-Fenton technology was investigated and the optimum condition has been determined to employ a lab-scale reactor. Due to the results of current studies using electrochemical and Fenton methods, a comparative economic-technical investigation has been provided accordingly. The results showed that under optimum operational condition by utilizing Electrochemical-Fenton process e.g. H2O2 = 25 mg/g DS (dry solid), Fe2+ = 15 mg/g DS, retention time = 20 min, electrolysis voltage = 11 V, the specific resistance to filterability (SRF) and time to filter (TTF) parameters reduction equal to 93.8% and 75.9% respectively. The occurrence mechanism of the sludge conditioning was determined by evaluation of extracellular polymeric substances (EPS), particle size distribution, zeta potential and bound water tests. The dry solids concentration of the conditioned sludge by Electrochemical-Fenton process was increased from 2.3% to 41% by dewatering employing filter press system. Furthermore, the estimated cost of conditioning using this method is 41.82 USD$/t DS, which is less than other investigated methods e.g. traditional Fenton process. It can be concluded that the results reached in this comprehensive and comparative study could be a suitable basis for further investigations regarding utilization of novel electrochemical advanced oxidation technologies for efficient sludge conditioning and dewatering purposes.

Application of peroxymonosulfate-ozone advanced oxidation process for simultaneous waste-activated sludge stabilization and dewatering purposes: A comparative study.

In this study, the efficiency of the Peroxymonosulfate-ozone (PMS+O3) advanced oxidation process in lab scale by the aim of stabilization and dewatering the biological excess sludge was investigated and the results were compared with persulfate-ozone (PS+O3), hydrogen peroxide-ozone (H2O2+O3) and ozonation (O3) processes. The results show that the PMS+O3 is more effective than other mentioned procedures. Therefore, under optimized conditions (pH = 11, PMS/O3 = 0.06 and Dose O3 = 12.5 mmol), VS (Volatile solids) and fecal coliforms reduced respectively 42% and 89% after 60 min and the stabilized sludge in term of pathogen reduction requirements was class B. Furthermore, time to filter (TTF) of sludge decreased 70% relative to the raw sludge. In order to demonstrate the dewatering conditions' improvement, the variations of particle size distribution, extracellular polymeric substances (EPS) and zeta potential were evaluated. Overall, the results show that the PMS+O3 has the capability of stabilizing and dewatering the sludge simultaneously.

Characterization and Antibiofouling Performance Investigation of Hydrophobic Silver Nanocomposite Membranes: A Comparative Study.

Biofouling is one of the drawbacks restricting the industrial applications of membranes. In this study, different thicknesses of silver nanoparticles with proper adhesion were deposited on poly(vinylidenefluoride) (PVDF) and polyethersulfone (PES) surfaces by physical vapor deposition (PVD). The crystalline and structural properties of modified and pure membranes were investigated by carrying out X-ray diffraction (XRD) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Scanning electron microscope (SEM) and atomic force microscopy (AFM) analyses were employed to examine the surface morphology and the bacteria anti-adhesion property of the membranes. The morphology measurements confirmed that even though after silver grafting the surface became more hydrophobic, the homogeneity increased and the flux reduction decreased after coating. Moreover a comparison between PVDF and PES revealed that CFU (colony forming units) reduced 64.5% on PVDF surface and 31.1% on PES surface after modification. In conclusion, PVD improved the performance of the membrane antibiofouling, and it is more promising to be used for PVDF rather than PES.

Optimizing stabilization of waste-activated sludge using Fered-Fenton process and artificial neural network modeling (KSOFM, MLP).

Sludge management is a fundamental activity in accordance with wastewater treatment aims. Sludge stabilization is always considered as a significant step of wastewater sludge handling. There has been a progressive development observed in the approach to the novel solutions in this regard. In this research, based on own initially experimental results in lab-scale regarding Fered-Fenton processes in view of organic loading (volatile-suspended solids, VSS) removal efficiency, a combination of both methods towards proper improving of excess biological sludge stabilization was investigated. Firstly, VSS removal efficiency has been experimentally studied in lab-scale under different operational conditions taking into consideration pH [Fe(2+)]/[H2O2], detention time [H2O2], and current density parameters. Therefore, the correlations of the same parameters have been determined by utilizing Kohonen self-organizing feature maps (KSOFM). In addition, multi-layer perceptron (MLP) has been employed afterwards for a comprehensive evaluation of investigating parameters correlation and prediction aims. The findings indicated that the best proportion of iron to hydrogen peroxide and the optimum pH were 0.58 and 3.1, respectively. Furthermore, maximum retention time about 6 h with a hydrogen peroxide concentration of 1,568 mg/l and a current density of 650-750 mA results to the optimum VSS removal (efficiency equals to 81 %). The performance of KSOFM and MLP models is found to be magnificent, with correlation ranging (R) from 0.873 to 0.998 for the process simulation and prediction. Finally, it can be concluded that the Fered-Fenton reactor is a suitable efficient process to reduce considerably sludge organic load and mathematical modeling tools as artificial neural networks are impressive methods of process simulation and prediction accordingly.