Membrane Processes For Wastewater Treatment Research Articles

APPLICATION OF ECONOMIC EVALUATION OF MEMBRANE TECHNOLOGIES FOR WASTEWATER TREATMENT

In the face of water scarcity, the world seeks to explore all available options to reduce overexploitation and so limited freshwater resources. One of the most reliable available water resources is wastewater. As the world's population grows, so do industrial, agricultural, and domestic activities, which produce large amounts of such water that can be treated and reused.
 Sewage treatment processes have been somewhat successful in wastewater treatment, but many are high-tech and cost-effective. Membrane technology has become a favorite choice for the reclamation of water from various wastewater streams for reuse.
 Organic membranes are made of synthetic organic polymers. Pressure membranes are mainly produced for separation processes (microfiltration, ultrafiltration, nanofiltration and reverse osmosis) from synthetic organic polymers. These include polyethylene (PE), polytetrafluoroethylene (PTFE), polypropylene and cellulose acetate. In addition, membranes are made of materials such as ceramics, metals, zeolites or silica. They are chemically and thermally stable and are widely used for industrial purposes such as hydrogen separation, ultrafiltration and microfiltration.
 Pressure-controlled membrane technologies are the most widely used membrane processes in wastewater treatment, from previous contamination followed by additional treatment. These processes are based on microfiltration (MF), ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO). They are necessary but costly
 The choice of wastewater treatment option is based on comparative economic efficiency. The main ways to determine such efficiency are: pairwise comparison of options and determine the minimum of the reduced costs of the compared options. Pairwise comparison of options is carried out by determining the coefficients of comparative economic efficiency and payback periods of additional capital investments.

Electrochemically self-cleanable carbon nanotube interlayered membrane for enhanced forward osmosis in wastewater treatment

Forward osmosis (FO) is considered as a promising alternative to pressure-driven membrane processes for wastewater treatment due to its relatively low-energy operation and better fouling resistance, but biofouling still occurs during long-time operation. The electrochemical cleaning strategy is effective for membrane fouling control, but has been seldom applied to FO processes so far due to unsatisfactory performance. Here, we fabricated a carbon nanotube-interlayered thin-film composite membrane with high electric conductivity, water permeability and self-cleaning ability to favor FO operation. By taking advantage of the electro-generated oxidative species in situ, especially the reactive chlorine species generated from locally-accumulated chlorine ions, the deposited bacterial cells and extracellular polymeric substances on membrane surface were efficiently removed to sustain the membrane operation. Applying 2.5 V voltage to the fouled membrane for 30 min restored 85% of its original water flux, and remained stable performance in three operating cycles. Overall, our work provides an efficient electrochemical cleaning strategy for FO membrane fouling control, which may further promote the application of FO wastewater treatment technologies.

Fouling Characteristics of MF membrane operated for separation of nitrocellulose from wastewater.

Membrane processes for wastewater treatment have become one of the emerging technologies, which affords a fast development through the past few decades. This study investigated the occurrence of fouling membrane and its composition factors and its effect on membrane performance. In this study, a project pilot scale forward the opposition to cluster transport from one side to the other side of membrane is eventual of the membrane and due to the coat of material on the membrane surface and into the membrane. Effect of severalparameters including trans-membrane compressing (pressure), crossflow velocity, and organic matteron microfiltration (MF) membrane fouling are investigated. The results show that theorganic material existing in the actual wastewater NC30 does not induce foulingin 0.14µm MF membrane with NC fines.

Innovative technologies in municipal wastewater treatment plants in Sweden to improve Baltic Sea water quality

The article presents new trends in the treatment of municipal wastewater in Sweden caused by the constantly increasing requirements for discharging pollutants into Baltic Sea waters. The development of new technologies for nitrogen removal, pharmaceutical residues removal and the possibility of using membrane processes in wastewater treatment is presented. The state of research on innovative wastewater treatment processes at the level of pilot-scale tests and their implementation in full technical scale has been described. These technologies can allow the application of new, economical and environmentally friendly wastewater treatment processes based on biological, chemical and physical methods. Swedish wastewater treatment plants are preparing to meet the new conditions required for discharged wastewater with a value of 6 mg N/L for total nitrogen and 0.2 mg P/L for total phosphorus. This requires large investments in the reconstruction of municipal wastewater treatment plants and the introduction of new treatment processes.

Axial-Flexural Interaction of Square FRP Tube Columns In-Filled with Ultra-High Performance Concrete

Membrane fouling leads to increased expenses in the processes in which they are implemented, and this is especially problematic in wastewater treatments. Therefore, fouling minimization and control represents the key to make those processes feasible. In the present paper, a review on the results of fouling control by the critical and threshold flux theories, focusing on olive mill wastewater coming from Spain (OMW-S) and Italy (OMW-I), is briefly covered. In first place, adequate fouling inhibition methods should be designed upstream the membrane operation, in order to make the downstream membrane processes for wastewater treatment technically and economically feasible. The followed strategy allows the operation of the membranes system in a controlled framework that permits the stable operation of the plant. Moreover, the calculated membrane area upon the adoption of feed control (FC) resulted in a requirement for the OMW-S stream of 74.2 and 50.3 m2 for the UF and NF membranes, respectively, whilst 113.1 and 49.7 m2 would be required for the treatment of the OMW-I stream. This also minimizes the membrane plant design, avoiding the common over-dimension wrongly estimated by engineers in order to guarantee sufficient operating autonomy to conduct the process that makes it unfeasible

A step forward to a more efficient wastewater treatment by membrane surface modification via polymerizable bicontinuous microemulsion

An innovative hydrophilic and anti-fouling coating material for application in membrane technology for wastewater treatment has been developed by polymerization of a polymerizable bicontinuous microemulsion (PBM) and used for surface modification of a commercial flat polyethersulfone (PES) membrane. The novel nanostructured coating has been produced using acryloyloxyundecyltriethylammonium bromide (AUTEAB) as a co-polymerizable surfactant, obtained through a synthetic method characterized by a lower cost and a higher reproducibility compared to other known polymerizable surfactants. The novel composite membranes have been characterized and compared with the uncoated PES membranes. Coated membranes resulted in a smoother surface and a higher hydrophilicity with respect to the uncoated ones, and showed a particular nano-size channel-like morphology making them highly resistant to the fouling phenomenon. The covalent anchorage of the surfactant on the membrane surface ensured the embedment of the molecule in the polymeric matrix avoiding its leaching and also leading the coated membranes to have significant antimicrobial activity, which is very important for reducing the biofouling phenomenon.All these aspects make the tailored coating material an ideal and efficient coating for modifications of commercial membrane surfaces, to be used in membrane processes in wastewater treatment.

Integrated membrane process for wastewater treatment from production of instant tea powders

This study investigated an integrated process to treat the wastewater from an instant tea powder factory. The wastewater was pretreated by combination of coagulation–flocculation. Polyaluminum ferric chloride (PAFC) was used as the coagulating agent. The optimum operating conditions with respect to contaminant removal were determined to be pH5, 20°C and 800mg/L of PAFC, with polyacrylamide (PAM) as coagulant aid at a dosage of 20mg/L. The discharged water from the coagulation–flocculation was treated with ceramic UF membranes. It was found that interactions between the molecules of PAFC and organic foulants reduced the membrane fouling and improved the removal efficiencies effectively. The permeate flux of UF membrane was almost three times higher than typical flux obtained without pretreatment. In the subsequent NF process, the removal efficiencies of turbidity, COD and TOC were all higher than 99.9%, and the TSS wasn't detected in the permeate. The effects of cleaning methods on permeate flux were also investigated. It was found out that 0.5wt.% NaClO flushing produced the highest flux recovery ratio of 99% and showed good reproducibility. This study showed the feasibility of applying coagulation–flocculation, UF and NF in the treatment of instant tea powder factory wastewater.

Impacts of NF concentrate recirculation on membrane performance in an integrated MBR and NF membrane process for wastewater treatment

As water shortages are increasing, the need for sustainable water treatment and the reuse of water is essential. Water reuse from wastewater can be accomplished in a membrane bioreactor (MBR) in the secondary activated sludge stage of a wastewater treatment plant. To remove viruses, dissolved organics and inorganics still present in the MBR permeate, nanofiltration (NF) can be applied. Nevertheless, the major drawback of nanofiltration membranes is the production of a concentrate stream that cannot be discharged to the environment. In this research we investigate the concept of a combined MBR and NF system with NF concentrate recirculation back to the MBR to produce reusable water in a sustainable way. Long-term continuous operation (1 year) shows that the NF permeate quality is not impacted by the recirculation. Fouling on the NF membrane is mostly the result of inorganics, while organics (e.g. humic acids) do not have a major impact on NF fouling. In fact, the flux of the NF was enhanced by the presence of humic acids due to recirculation. However, the MBR showed increased fouling and consequently more frequent membrane cleaning. The results presented show that the continuous production of reusable water from wastewater in a combined MBR and NF process with NF concentrate recirculation can be successful.

Oxidation of organics in retentates from reverse osmosis wastewater reuse facilities

The use of membrane processes for wastewater treatment and reuse is rapidly expanding. Organic, inorganic, and biological constituents are effectively removed by reverse osmosis (RO) membrane processes, but concentrate in membrane retentates Disposal of membrane concentrates is a growing concern. Applying advanced oxidation processes (AOPs) to RO retentate is logical because extensive treatment and energy inputs were expended to concentrate the organics, and it is cheaper to treat smaller flowstreams. AOPs (e.g., UV irradiation in the presence of titanium dioxide; UV/TiO 2) can remove a high percentage of organic matter from RO retentates. The combination of AOPs and a simple biological system (e.g., sand filter) can remove higher levels of organic matter at lower UV dosages because AOPs produce biologically degradable material (e.g., organic acids) that have low hydroxyl radical rate constants, meaning that their oxidation, rather than that of the primary organic matter in the RO retentate, dictates the required UV energy inputs. At the highest applied UV dose (10 kWh m −3), the dissolved organic carbon (DOC) in the RO retentate decreased from ∼40 to 8 mg L −1, of which approximately 6 mg L −1 were readily biologically degradable. Therefore, after combined UV treatment and biodegradation, the final DOC concentration was 2 mg L −1, representing a 91% removal. These results suggest that UV/TiO 2 plus biodegradation of RO retentates is feasible and would significantly reduce the organic pollutant loading into the environment from wastewater reuse facilities.

Pollutants removal and simulation model of combined membrane process for wastewater treatment and reuse in submarine cabin for long voyage

A laboratory scale test was conducted in a combined membrane process (CMP) with a capacity of 2.91 m3/d for 240 d to treat the mixed wastewater of humidity condensate, hygiene wastewater and urine in submarine cabin during prolonged voyage. Removal performance of chemical oxygen demand (COD), ammonia nitrogen (NH(4+)-N), turbidity and anionic surfactants (LAS) was investigated under different conditions. It was observed that the effluent COD, NH(4+)-N, turbidity and LAS flocculated in ranges of 0.19-0.85 mg/L, 0.03-0.18 mg/L, 0.0-0.15 NTU and 0.0-0.05 mg/L, respectively in spite of considerable fluctuation in corresponding influent of 2120-5350 mg/L, 79.5-129.3 mg/L, 110-181.1NTU and 4.9-5.4 mg/L. The effluent quality of the CMP could meet the requirements of mechanical water and hygiene water according to the class I water quality standards in China (GB3838-2002). The removal rates of COD, NH(4+)-N, turbidity and LAS removed in the MBR were more than 90%, which indicated that biodegradation is indispensable and plays a major role in the wastewater treatment and reuse. A model, built on the back propagation neural network (BPNN) theory, was developed for the simulation of CMP and produced high reliability. The average error of COD and NH(4+)-N was 5.14% and 6.20%, respectively, and the root mean squared error of turbidity and LAS was 2.76% and 1.41%, respectively. The results indicated that the model well fitted the laboratory data, and was able to simulate the removal of COD, NH(4+)-N, turbidity and LAS. It also suggested that the model proposed could reflect and manage the operation of CMP for the treatment of the mixed wastewaters in submarine.

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

AbstractPossibilities 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 %).

Industrial wastewater treatment by means of membrane techniques

Industrial wastewater treatment by means of membrane techniques The importance of membrane processes in wastewater treatment is continuously growing. Membranes can be used for the separation of liquids, dissolved or suspended solids or solutes in the colloid form. The main features of membrane processes application for the treatment of spent solutions are possibilities of removal or recovery of valuable or harmful components as well as the possibility of closing water systems what reduce fresh water consumption. Very often the use of membrane processes allow to purify wastewater to a degree difficult to achieve by conventional techniques. The possibility of an application of pressure driven techniques such as ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO) for oily wastewater treatment, has been presented. The studies on the two-stage treatment of bilge water combining UF and RO or NF have demonstrated a high effectiveness of purification. NF could also be applied to recover glycols from spent coolant liquids. The utilization of membrane distillation for saline wastewater concentration or for the treatment of spent metal pickling solutions was demonstrated. The potential application of a hybrid process combining photocatalytic degradation of organic matter with membrane separation for the treatment of wastewaters from textile industry has been shown.

A novel application of an anaerobic membrane process in wastewater treatment

The applications of membrane processes in anaerobic biological wastewater treatment still have some limitations due to severe membrane scaling and fouling, although they have been proven to achieve superior COD removal and biomass retention. An innovative anaerobic membrane process for wastewater treatment was conducted to control the membrane scaling problems. The process comprises an anaerobic reactor, an aerobic reactor, and a membrane separation tank. Anaerobic sludge from a full-scale UASB reactor treating food wastewater was inoculated to anaerobic and aerobic reactor to purify synthetic wastewater consisting of glucose and sodium acetate. The anaerobic reactor was operated in a sludge bed type without three-phase separator. The aerobic reactor can eliminate residual organics from the anaerobic reactor effluent using facultative microorganisms. To provide solid-liquid separation, hollow fiber ultrafiltration module was submerged in the separation tank. The results clearly show that the anaerobic membrane process combined methanogenic and aerobic COD reduction is a stable system. No fatal scaling was found after two months of operation even without chemical cleaning for the membrane. It was also found that inorganic precipitates formed in the aerobic reactor were reduced due to CO2 stripping in aerobic reactor. Another important finding was that the inorganic precipitates were entrapped into facultative aerobes floc. The ash/SS ratio of aerobes floc increased from 0.17 to 0.55 after 50 days of operation, which confirms this phenomenon. Based on our investigation, the new process can control scaling effectively to extend the membrane application in anaerobic treatment.

Removal of endocrine disrupting compounds with membrane processes in wastewater treatment and reuse

Endocrine disrupting compounds can affect the hormone system in organisms and are the subject of environmental and human health concerns. The effluents of wastewater treatment plants contribute to the emission of estrogenically active substances into the environment. Membrane technology, which is an advanced wastewater treatment option, is the subject of this research. The removal techniques under investigation are membrane bioreactors, reverse osmosis, and nanofiltration. Eleven different nanofiltration membranes were tested in the laboratory set-up. The observed retention of NP and BPA ranged between 70% and 100%. The contact angle is an indicator for the hydrophobicity of a membrane, whose influence on the permeability and retention of NP was evident. Regarding the retention of BPA no dependency on the contact angle was observed. Results of the investigation of a full-scale landfill leachate treatment plant indicate a bisphenol A (BPA) removal of more than 98% with membrane bioreactors and reverse osmosis. The mass balance indicates that biological degradation is the most important removal process in the membrane bioreactor configuration.

Optimal design of membrane processes for wastewater treatment and metal recovery

Different continuous operating modes of a nondispersive solvent extraction (NDSX) process with membrane modules of hollow fibre for wastewater treatment and metal recovery are evaluated. Cocurrent and countercurrent flow of aqueous and organic phases in the membrane modules with alternative product extraction locations for the removal and recovery of hexavalent chromium from wastewater are studied. The design of NDSX process in a countercurrent continuous operation is addressed for the first time in this work and the improvement achieved is reported. The membrane area required in the countercurrent operation is reduced significantly compared with the cocurrent operation, requiring also less investment in pumps and pumping cost leading to the minimum total cost. Thus a significant improvement in the design of this new and cleaner technology is presented.

A review of pressure‐driven membrane processes in wastewater treatment and drinking water production

AbstractIn pressure‐driven membrane processes (reverse osmosis, nanofiltration, ultrafiltration, and microfiltration) a pressure exerted on the solution at one side of the membrane serves as a driving force to separate it into a permeate and a retentate. The permeate is usually pure water, whereas the retentate is a concentrated solution that must be disposed of or treated by other methods. Membranes may be polymeric, organo‐mineral, ceramic, or metallic, and filtration techniques differ in pore size, from dense (no pores) to porous membranes. Depending on the type of technique, salts, small organic molecules, macromolecules, or particles can be retained, and the applied pressure will differ. This paper reviews the principles behind the different techniques, the types of membranes used, rejection mechanisms, and process modeling. Applications of pressure‐driven membrane processes are also considered, including reverse osmosis and nanofiltration for the treatment of wastewater from landfills and composting plants, nanofiltration in the textile industry, and ultrafiltration and microfiltration in drinking water production and wastewater treatment.Lastly, the paper discusses recent developments, including techniques to prevent membrane fouling by modifications affecting surface roughness or hydrophilicity/hydrophobicity, or by cleaning the membranes, and methods for treating or disposing of the retentate.