Long-term operation of a domestic wastewater treatment plant with membrane filtration

Possibilities of membrane technology and the use of membrane processes in wastewater treatment were investigated. The main focus was the monitoring of the starting phase of a domestic wastewater treatment plant. Experimental part of the study was realized at the municipal wastewater treatment plant (WWTP) Devínska Nová Ves — Bratislava during the period from February 2005 to September 2006. The system was stable without any external chemical treatment of the membrane modules and the permeate quality was very high. Observed decrease of COD and BOD₅ values ranged between 91 % and 98 %. The process of nitrification was very successful considering its high efficiency (> 95 %). Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Reverse osmosis filtration for space mission wastewater: membrane properties and operating conditions

Reverse osmosis (RO) is a compact process that has potential for the removal of ionic and organic pollutants for recycling space mission wastewater. Seven candidate RO membranes were compared using a batch stirred cell to determine the membrane flux and the solute rejection for synthetic space mission wastewaters. Even though the urea molecule is larger than ions such as Na+, Cl-, and NH4+, the rejection of urea is lower. This indicates that the chemical interaction between solutes and the membrane is more important than the size exclusion effect. Low pressure reverse osmosis (LPRO) membranes appear to be most desirable because of their high permeate flux and rejection. Solute rejection is dependent on the shear rate, indicating the importance of concentration polarization. A simple transport model based on the solution-diffusion model incorporating concentration polarization is used to interpret the experimental results and predict rejection over a range of operating conditions. Grant numbers: NAG 9-1053.     

Secondary membranes for flux optimization in membrane filtration of biologic suspensions

We employ in situ deposited secondary membranes of yeast (SMYs) to optimize permeate flux during microfiltration and ultrafiltration of protein solutions. The deposited secondary membrane was periodically removed by backflushing, and a new cake layer was deposited at the start of the next cycle. The effects of backflushing time, backflushing strength, wall shear rate, and amount of secondary membrane deposited on the permeate flux were examined. Secondary membranes were found to increase the permeate fluxin microfiltration by severalfold. Protein transmission was also enhanced owing to the presence of the secondary membrane, and the amount of protein recovered was more than twice that obtained during filtration of protein-only solutions under othewise identical conditions. In ultrafiltration, the flux enhancement owing to the secondary membrane was only 50% or less. In addition, the flux for ultrafiltration was relatively insensitive to changes in the concentration of yeast used during deposition of SMY and to the backflushing strength used to periodically remove the secondary membrane.     

Retraction Note to: Microenvironment characterization for a novel biocompatible hybrid carbon-silicon material

<正>Retraction to:Science in China Series B:Chemistry,2009,52:1120-1127doi:10.1007/s11426-009-0149-1This article has been retracted at the request of the authors because major parts of the work were previously published in     

Retraction Note to: High Coercivity Induced in Nickel Ferrite Nanoparticles by Mechanical Milling

Journal of Structural Chemistry - This article has been retracted. Please see the Retraction Notice for more detail: https://doi.org/10.1134/S0022476622080194     

Plasmid DNA processing for gene therapy and vaccination: Studies on the membrane sterilisation filtration step

Membrane filtration through 0.2 μm pores is typically the last operation in the production of pharmaceutical grade plasmid DNA. The membrane sterilisation of purified DNA solutions containing plasmids and bacterial artificial chromosomes (BAC) is investigated in this paper. A linear relationship between total DNA transmission and vector size was observed when filtering through 0.2 μm polyvinylidene difluoride (PVDF) membranes. The percentage of DNA transmission assessed spectrophotometrically varied from 98 to 13% for vector sizes ranging from 6 to 116 kb. There was no significant change in transmission during filtration when controlled flux was increased from 0.1 to 2.3 mL/min cm² or DNA concentration changed from 25 to 100 μg/mL. For vectors ≥20 kb; (i) the level of backbone breakage increased with molecular weight, flux and number of filtration passes; (ii) consecutive filtration experiments indicated that greater DNA loss occurred during the first pass of filtration; and (iii) the use of polyethersulfone (PES) membranes with asymmetrical pores improved DNA transmission and decreased DNA damage. The addition of 150 mM NaCl in the formulation buffer improved filtration transmission by 47 and 11% for the 72 and 116 kb vectors, respectively. Complexation with polyethylenimine (PEI) and a lipid–integrin binding peptide (LI) complex did not improve product transmission.     

Characteristics of bio-diatomite dynamic membrane process for municipal wastewater treatment

The characteristics of bio-diatomite dynamic membrane (BDDM) process in municipal wastewater treatment were investigated with a laboratory-scale continuous-flow device. Experimental results indicate that the BDDM reactor was highly effective in removal of COD, NH₄-N and TN, and exhibited the advantages of good retention capacity for suspended solids (SS), short precoating time, high filtration flux, and easy backwash. In the precoating stage, a retention time of 25 min could reduce the effluent SS to non-detectable level. The filtration resistance of BDDM was composed of thickness-increase resistance and compaction resistance. At a low flux, microbial adhesion occurred on the interface between the BDDM and the stainless steel support mesh, which negatively impacted the system operation and backwash. However, microbial adhesion could be effectively minimized by increasing the filtration flux.     

Post-synthesis modification of polyethersulfone membrane by grafting hyperbranched polyethylene glycol for oily wastewater treatment

Research on Chemical Intermediates - The main goal of this study is to modify the polyethersulfone membrane by the grafting hyperbranched polyethylene glycol (HB-PEG) via a two-step grafting...     

Retraction Note to: Recent advancement in production of liquid biofuels from renewable resources: a review

Research on Chemical Intermediates - The authors have retracted this article [1] because it contains significant overlap with an article previously published by Nigam and Singh [2]. The authors...     

Microfiltration performance of regenerated cellulose membrane prepared at low temperature for wastewater treatment

A series of regenerated cellulose membranes with pore diameters ranging from 21 to 52 nm have been prepared by dissolving cellulose in 5 wt% LiOH/12 wt% urea aqueous solution re-cooled to −12 °C. The influences of cellulose concentration on the structure, pore size, and the mechanical properties of the membrane were studied by using Wide angle X-ray diffraction, scanning electron micrography and tensile testing. Their pore size, water permeability, equilibrium-swelling ratio and fouling behaviors of the cellulose membranes were characterized. The water-soluble synthetic and natural polymers as organic matter were used to evaluate the microfiltration performance of the regenerated cellulose membrane for wastewater treatment in aqueous system. The results revealed that the organic matter with molecular weight more than 20 kDa effected significantly on the membrane pore density, and reducing factor a _2, whereas that having molecular weight less than 20 kDa exhibited a little influence on the membrane pore size reducing factor a ₁. Furthermore, a simple model to illustrate of microfiltration process of the RC membrane for wastewater treatment was proposed.     

Activated carbon membrane for water treatments: Application to decolorization of coke furnace wastewater

An activated carbon membrane to be used in water treatments was developed and the decolorization of the coke furnace wastewater was successfully demonstrated as a model case. The activated carbon membrane was prepared by carbonizing poly-vinydenchloride (PVdC) and poly-vinylalcohol (PVA) microspheres aggregating on and within a ceramic pipe. The membrane developed in this work was suspected to have a bidispersed structure, which made it possible to play the roles of both a porous membrane having the molecular weight cut-off of about 10,000 and an activated carbon bed where the dissolved organics with low molecular weight could be adsorbed. The activated carbon membrane developed in this work appears to be useful for compact water treatment processes.     

Monte Carlo simulation of colloidal membrane filtration: principal issues for modeling

The principal issues involved in developing a Monte Carlo simulation model of colloidal membrane filtration are investigated in this study. An important object for modeling is the physical dynamics responsible for causing particle deposition and accumulation when encountering an open system with continuous outflow. A periodic boundary condition offers a solution to the problem by recirculating continuous flow back through the system. Scaling to full physical dimensions will allow for release of the model from flawed assumptions such as constant cake layer volume fraction and thickness throughout the system. Furthermore, rigorous modeling on a precise scale extends the model to account for random particle collisions with acute accuracy. A major finding of this study proves that forces within the colloidal filtration system are summed and transferred cumulatively through the inter-particle interactions. The force summation and transfer phenomenon only realizes its true value when the model is scaled to full dimensions. The overall strategy for model development, therefore, entails three stages: first, rigorous modeling on a microscopic scale; next, comprehensive inclusion of relevant physical dynamics; and finally, scaling to full physical dimensions.     

Comparison between filtrations at fixed transmembrane pressure and fixed permeate flux: application to a membrane bioreactor used for wastewater treatment

Membrane bioreactors for wastewater treatment must operate for long periods without chemical cleaning. This paper investigates the critical flux concept introduced by Field et al. as a means for achieving this goal. Experiments were conducted on a membrane bioreactor containing 600 l of activated sludge, equipped with a 0.25 m² ceramic membrane and located in Compiegne wastewater treatment plant. Hydraulic retention time was set at 24 h and sludge retention time at 60 days, so that suspended solids concentration stabilises at 10 g/l. We conducted two series of tests: at fixed transmembrane pressure (TMP) and at fixed permeate flux, set by a volumetric pump on the permeate. In both cases, velocity was varied from 1 to 5 m/s. In fixed flux tests, the flux was increased by 10 l/h m² increments and the TMP was observed to rise moderately first and then stabilise in about 15 min until a critical value of the flux is reached. Above this critical flux, the TMP rises rapidly and does not stabilise, as in dead-end filtration. The critical flux was found to increase approximately linearly with velocity, reaching about 115 l/h m² at 4 m/s. These data were reproducible at various dates between 30 and 120 days of continuous operation of the bioreactor and permit to know at which flux a membrane bioreactor must be operated. Comparison of constant pressure and constant flux tests under same conditions showed that the critical flux is almost identical to the limiting or pressure independent flux obtained in constant pressure. More generally, constant flux procedure below the critical flux avoids overfouling of the membrane in the initial stage and is more advantageous for membrane bioreactor operation.     

Retraction Note to: Thermodynamic study on the interaction of cyanide ion and jack bean urease at different temperatures

Journal of Thermal Analysis and Calorimetry -     

Low-pressure membrane filtration of secondary effluent in water reuse: Pre-treatment for fouling reduction

Fouling in the low-pressure membrane filtration of secondary effluent for water reuse can be severe due to the complex nature of the components in the water. Pre-filtration, coagulation and anion exchange resin were investigated as pre-treatments for reducing fouling of microfiltration (MF) and ultrafiltration (UF) membranes in the treatment of activated sludge-lagoon effluent. The key fouling components were determined using several analytical techniques to detect differences in the organic components between the feed and permeate.Pre-filtration (1.5 μm) enhanced the permeate flux for MF by removing particulates, but had little effect for UF. Marked flux improvement was obtained by coagulation pre-treatment at 5 mg L⁻¹ Al³⁺ with internal membrane fouling being substantially alleviated. Anion exchange resin removed >50% of effluent organic matter but did not improve the flux or reduce irreversible membrane fouling. These results, together with detailed organic compositional analyses, showed that the very high-molecular weight organic materials (40–70 kDa) comprised of hydrophilic components such as soluble microbial products, and protein-like extracellular matter were the major cause of membrane fouling.     

Parametric study for the treatment of tannery dye wastewater by electro-oxidation

Degradation of tannery effluents is a difficult operation because of their intricate chemical structures. Most of the conventional approaches are becoming ineffective because of the wide variation in the composition of tannery effluent. Dyes from the wastewater is also dangerous, as the wastewater has negative impact on the health of human being, plants and aquatic animals. For the first time once through continuous approach was employed for the removal of Acid yellow 110 tannery dye in electro-oxidation process on Mix Metal Oxide of ruthenium and iridium on titanium sheet electrode. The effects of pH, time (t) and current (i) on % color removal and energy consumed were investigated in a batch setup and found the optimum condition with the help of RSM design. The values of the responses Y₁ and Y₂ were found to be 93.08% and 1.07 kWh/m³ respectively at the optimum condition. Toxicity Bioassay analysis, GC-MS analysis and the kinetic study were performed at optimum condition. At the flow rates of 10–40 ml/min once through continuous experiments was conducted to found the feasibility of the process at pilot scale or industrial scale application.     

Performance of a bench-scale membrane pilot plant for the upgrading of biogas in a wastewater treatment plant

A bench-scale membrane pilot plant for upgrading biogas generated at a municipal wastewater treatment plant was constructed and operated for extended periods of time. The raw biogas was available at 45–60 psia (3.1–4.1 bar) and contained 62.6 mol% CH₄, the balance being mainly CO₂ and a large number of organic impurities. The operation of the pilot plant was tested with two identical hollow-fiber modules for periods of over 1000 h (41 days) with each module. One of the hollow-fiber modules was tested at an average pressure of about 525 psia (36 bar) and at stage-cuts of 0.34–0.41, and the other module at about 423 psia (29 bar) and at stage-cuts of 0.36–0.39. The flow rates of the biogas feed were 30–36 ft³/h (2.4×10⁻⁴–2.8×10⁻⁴ m³/s) and 21–24 ft³/h (1.7×10⁻⁴–1.9×10⁻⁴ m³/s), respectively. The CH₄ concentration in the retentate stream (the upgraded biogas) was raised in these tests to 92–95 mol% CH₄. The performance of the pilot plant was stable over the entire test periods. An even higher CH₄ concentration of 97 mol% was reached in short-term tests at a stage-cut of 0.46. The raw biogas had to be pretreated to prevent the condensation of organic impurities which tended to dissolve the hollow fibers. Upgraded biogas containing over 90 mol% CH₄ produced in a large-scale membrane separation plant could be used for the generation of electricity. At the same time, the permeate (waste) stream would contain over 15 mol% CH₄ and could be used for heating applications.     

Photo-fenton degradation of phenol red catalyzed by inorganic additives: A technique for wastewater treatment

Oxidation by photo-Fenton like reaction is an economically feasible process for degradation of a variety of hazardous pollutants in wastewater from dyeing and printing industries. In present study, the progress of the reaction has been monitored spectrophotometrically. An effort has been made to observe the effect of various inorganic additives like sodium thiosulfate and potassium bromate. The effect of variation of different parameters such as pH, concentrations of dye, Fe³⁺ ion and additives, amount of H₂O₂, and light intensity on the rate of photodegradation was also observed. A tentative mechanism for the reaction has been proposed.