Microfiltration Ultrafiltration Research Articles

DETERMINATION OF RECYCLE WATER TECHNOLOGY FOR WASTEWATER TREATMENT AT UNIVERSITAS PERTAMINA AREA WITH ANALYTICAL HIRACHY PROCESS (AHP)

<p><em>The wastewater treatment plant (</em><em>WWTP</em><em>) at the </em><em>Universitas Pertamina</em><em> </em><em>area </em><em>is one of the campus's efforts to reduce the environmental impact of wastewater production. The processed WWTP can be processed into ready-to-drink water as an effort to reduce plastic waste. This plastic waste is usually produced by the consumption of mineral water products. The availability of ready-to-drink water in the campus complex is expected to increase the interest of campus residents to use tumblers and reduce the generation of plastic waste as well as university proactive efforts. The purpose of this study was to analyze the units needed to process WWTP effluent into ready-to-drink water by looking at various alternatives. This study uses the analytical hierarchy process (AHP) in determining the best alternative. The units required for each alternative are equalization tub, slow sand filter, and disinfection. Meanwhile, for processing, there are three alternatives, namely microfiltration (MF), ultrafiltration (UF), and combined microfiltration – ultra-filtration (MF-UF). The selection of these alternatives was adjusted to the criteria of cost, required membrane area, flux recovery after backwashing, and the effectiveness of total coliform removal. MF filtration technology is the largest weight, which is 0.381. Where the use of MF in the </em><em>Universitas Pertamina</em><em> </em><em>area</em><em> is cheaper and requires better area than UF and MF-UF technology.</em></p>

Fouling process and anti-fouling mechanisms of dynamic membrane assisted by photocatalytic oxidation under sub-critical fluxes

Membrane fouling is often considered as a hindrance for the application of microfiltration/ultrafiltration (MF/UF) for drinking water production. A novel process of photocatalytic membrane reactor/dynamic membrane (PMR/DM), operating in a continuous mode under sub-critical flux, was proposed for the mitigation of membrane fouling caused by humic acids (HAs) in water. The mechanism of membrane fouling alleviation with synergistic photocatalytic oxidation and dynamic layer isolating effect was comprehensively investigated from the characterization of foulant evolution responsible for the reversible and irreversible fouling. The results showed that the PMR/DM utilized photocatalytic oxidation to enhance the porosity and hydrophilicity of the fouling layer by converting the high molecular weight (MW) and hydrophobic HA molecules with carboxylic functional groups and aromatic structures into low-MW hydrophilic or transphilic fractions, including tryptophan-like or fulvic-like substances. The fouling layer formed in the PMR/DM by combination of photocatalytic oxidation and DM running at a sub-critical flux of 100 L·h−1·m−2, was more hydrophilic and more porous, resulting in the lowest trans-membrane pressure (TMP) growth rates, as compared to the processes of ceramic membrane (CM), DM and PMR/CM. Meanwhile, the dynamic layer prevented the foulants, particularly the high-MW hydrophobic fractions, from contacting the primary membrane, which enabled the membrane permeability to be restored easily.

Investigation of Algal Biotoxin Removal during SWRO Desalination through a Materials Flow Analysis

The operation of seawater reverse osmosis (SWRO) desalination facilities has become challenged by the increasing frequency and severity of harmful algal blooms (HABs). The efficiency of algal toxins removal during SWRO and pretreatment processes has critical human health implications. Therefore, a probabilistic materials flow analysis (pMFA) was developed to predict the removal of algal toxins in source water by various pretreatment configurations and operations during SWRO desalination. The results demonstrated that an appreciable quantity of toxins exists in the SWRO permeate (ng/L–µg/L levels), the backwash of pretreatment, and final brine rejects (µg/L–mg/L levels). Varying the pretreatment train configuration resulted in statistically significant differences in toxin removals, where higher removal efficiencies were evidenced in systems employing microfiltration/ultrafiltration (MF/UF) over granular media filtration (GMF). However, this performance depended on operational practices including coagulant addition and transmembrane pressures of MF/UF systems. Acute human health risks during lifetime exposure to algal toxins from ingestion of desalinated water were benign, with margins of safety ranging from 100 to 4000. This study highlights the importance of pretreatment steps during SWRO operation in the removal of algal toxins for managing marine HABs.

Microfiltration/ultrafiltration polyamide-6 membranes for copper removal from aqueous solutions

Microfiltration/ultrafiltration (MF/UF) Adsorptive polyamide-6 (PA-6) membranes were prepared using wet phase inversion process. The prepared PA-6 membranes are characterized by scanning electron microscopy (SEM), porosity and swelling degree. In this study, the membranes performance has examined by adsorptive removal of copper ions from aqueous solutions in a batch adsorption mode. The PA-6/H2O membranes display sponge like and highly porous structures, with porosities of 41-73%. Under the conditions examined, the adsorption experiments have showed that the PA-6/H2O membranes had a good adsorption capacity (up to 120-280 mg/g at the initial copper ion concentration (C0) = 680 mg/L, pH7), fast adsorption rates and short adsorption equilibrium times (less than 1.5-2 hrs) for copper ions. The fast adsorption in this study may be attributed to the high porosities and large pore sizes of the PA-6/H2O membranes, which have facilitated the transport of copper ions to the adsorption. The results obtained from the study illustrated that the copper ions which have adsorbed on the polyamide membranes can be effectively desorbed in an Ethylene dinitrilotetra acetic acid Di sodium salt (Na2 EDTA) solution from initial concentration (up to 92% desorption efficiency) and the PA-6 membranes can be reused almost without loss of the adsorption capacity for copper ions. The results obtained from the study suggested that the PA-6/H2O membranes can be effectively applied for the adsorptive removal of copper ions from aqueous solutions.

Fluorescent-conjugated MS2 as surrogates for viruses during drinking water treatment

Microfiltration/ultrafiltration (MF/UF) membranes and ultraviolet (UV) light disinfection serve as attractive alternative technologies to aid utilities in complying with both the LT2ESWTR and Stage 2 D/DBP. However, both technologies are limited in their ability to remove viruses and at the same time there is a lack of methods to accurately demonstrate virus removal in full-scale settings. In evaluating the efficacy of MF/UF membranes and UV disinfection systems for virus removal, appropriate surrogates are therefore required. In most cases, various surrogates are used to evaluate the removal performances of individual treatment technologies. This henceforth limits its application when multiple treatment systems are evaluated in series. In view of this, fluorescent-conjugated MS2 and F8781 microspheres were evaluated as possible surrogates for virus removal by integrated coagulation-MF/UF filtration-UV disinfection. At 5 mg Al3+/L, the highest removal of MS2-Sypro was observed, followed by MS2-AMCA, and F8781 during the coagulation-flocculation stage. During MF and UF filtration, dye surrogates provided an underestimate of virus removal except for F8781, which had a considerably smaller particle size than other surrogates. Nevertheless, MS2-SR could accurately represent AD5 during low pressure (LP) UV irradiation but MS2-AMCA existed as a more accurate representation of AD5 as compared to F8781 microspheres during medium pressure (MP) UV irradiation. MS2-SR and MS2-AMCA are therefore preferred surrogates for an integrated filtration-UV disinfection system for LP and MP UV, respectively.

Performance of reverse osmosis (RO) for water recovery from permeates of membrane bio-reactor (MBR)

In this study, permeate from a hollow fiber polyethylene (PE) membrane bio-reactor (MBR) system treating synthetic agricultural wastewater was fed into a cellulose acetate brackish water reverse osmosis (BWRO30 2540) membrane system; three different trans-membranes pressures (TMPs) of 1000, 2500, and 4000 kPa were selected to evaluate the system performance in terms of general operating parameters as well as the removal of chosen important potential fouling water quality parameters. The results showed that highest corrected permeate flux rate was at a TMP of 2500 kPa, whereas lowest recorded at a TMP of 4000 kPa. Similar situation prevailed in water recovery rate. But temperature corrected specific fluxes decreased as the applied TMPs increased. In all selected TMPs, more than 96% of salinity was removed. Permeate from MBR as feed to reverse osmosis required frequent chemical cleaning than the microfiltration/ultrafiltration (MF/UF) permeates and granular media filter (GMF) filtered in order to maintain the required rate of product water. One of the reasons for this frequent chemical cleaning is due to higher total organic carbon as well as total nitrogen (TN) in the MBR permeate. This result needs to be further evaluated through field trials.

Separation Properties of Wastewater Containing O/W Emulsion Using Ceramic Microfiltration/Ultrafiltration (MF/UF) Membranes.

Washing systems using water soluble detergent are used in electrical and mechanical industries and the wastewater containing O/W emulsion are discharged from these systems. Membrane filtration has large potential for the efficient separation of O/W emulsion for reuses of treated water and detergent. The separation properties of O/W emulsions by cross-flow microfiltration and ultrafiltration were studied with ceramic MF and UF membranes. The effects of pore size; applied pressure; cross-flow velocity; and detergent concentration on rejection of O/W emulsion and flux were systematically studied. At the condition achieving complete separation of O/W emulsion the pressure-independent flux was observed and this flux behavior was explained by gel-polarization model. The O/W emulsion tended to permeate through the membrane at the conditions of larger pore size; higher emulsion concentration; and higher pressure. The O/W emulsion could permeate the membrane pore structure by destruction or deformation. These results imply the stability of O/W emulsion in the gel-layer formed on membrane surface play an important role in the separation properties. The O/W emulsion was concentrated by batch cross-flow concentration filtration and the flux decline during the concentration filtration was explained by the gel- polarization model.

Application of ceramic membranes for seawater reverse osmosis (SWRO) pre-treatment

Abstract Low-pressure (microfiltration/ultrafiltration (MF/UF)) membranes are being increasingly used as pre-treatment, prior to seawater reverse osmosis (SWRO). The objective of pre-treatment before reverse osmosis (RO) membranes is to remove undesirable and particulate fouling materials (algae, suspended and colloidal particles). Also, a pre-treatment barrier reduces organics and provides better feed water quality for RO membranes. MF and UF pre-treatment prior to SWRO provides Low Silt Density Index (SDI) values recommended for RO operation. Ceramic membranes are more attractive as they made of more chemically resistant materials, which allow for more stable operation and aggressive backwashing (BW) and cleaning. A pilot plant with a monolith ceramic MF membrane (0.1 μm pore size) from METAWATER was used to carry out the study. Red Sea water pumped from a distance of 700 m offshore from Thuwal (Kingdom of Saudi Arabia) was used as feed water. The pilot plant was operated automatically at constant flux of 150 LMH that involved BW, air flushing and forward flushing at the end of filtration cycle. Seawater permeates were used for hydraulic BW, while sodium hypochlorite, citric acid and sodium hydroxide were used for chemical cleaning (CIP) to restore the membrane permeability after use. Filtration cycles of 2.5 h were adopted for initial experiments. Aggressive BW flux of 1,800 LMH for 15 s, air flushing of 4 bars for 10 s and forward flushing of 300 LMH for 40 s were applied for regular membrane hydraulic cleaning. The increase of membrane resistances over time was monitored. Further studies were also performed by using Anopore ceramic membranes AAO100 (pore sizes of 0.1 μm) using a constant pressure bench-scale set-up. The feed water and permeate were analysed using an SDI unit, flow cytometre (FCM) and liquid chromatography with organic carbon detection (LC–OCD). The results showed that ceramic membrane filtration reduced the SDI15 of seawater from 6.1 to 2.1 which conform to the requirement of SDI < 3 needed for SWRO feed. The removal of bacteria corresponded to 3.7 log removal, while turbidity improved from 0.6 NTU (feed) to 0.05 NTU (permeate). However, ceramic membranes showed low recovery after BW and significant increase of trans-membrane pressure (TMP) during operation with the membrane alone, without coagulation. This increase of TMP can be related to the presence of sticky polysaccharide-like material called transparent exopolymers particles (TEP) that are known to be in abundance in seawater and contribute to organic fouling and eventually bio fouling. TEP showed resistance and stickiness on the membrane surface (AAO100) even after aggressive BW. This may be responsible for the low flux recovery observed after BW in both bench-scale and pilot experiments. To improve membrane filtration, coagulation was performed by using iron III chloride. Continuous addition of iron III chloride (4 mg/L Fe) through inline coagulation showed almost complete control of irreversible fouling and reduces reversible fouling after 30 h of operation, based on 2.5 h intervals of filtration cycle. Also, biopolymers removal improved to 51–71%, with improved removal at low pH, while for stabilization of flux, a dose of 1 mg/L Fe3+ was sufficient. Reduction of high molecular weight Natural organic matters (NOM) is essential for controlling or reducing irreversible fouling. Therefore, coagulation is recommended for smooth operation of ceramic membranes and for provision of low-fouling feed water, prior to SWRO membranes.

ChemInform Abstract: Wastewater Polishing Using Membrane Technology: A Review of Existing Installations

AbstractReview: 28 refs.

Wastewater polishing using membrane technology: a review of existing installations

The use of membrane technology for municipal wastewater reuse is growing in importance worldwide as water becomes increasingly scarce. A review of nine membrane technology-based water reuse plants from across the world has been conducted to provide an insight into the trends in design and operation of these plants, and elucidate the impact of key water quality and other determinants. Data reveal a number of common elements, such as the design flux for the reverse osmosis membrane, as well as a number of other trends. The microfiltration/ultrafiltration (MF/UF) backwash interval appears to correlate better with feed water temperature than turbidity or total suspended solids, whereas chemical cleaning requirements are more dependent on plant operating parameters and water quality. There is some indication that the MF/UF pore size influences the filtrate turbidity (and silt density index) and so downstream reverse osmosis fouling and cleaning. Finally, specific energy demand (SED) values vary widely, from 0.8 to 2.3 kWh m−3 permeate. Whilst the SED for the MF/UF process follows the flux, the overall energy demand shows no apparent dependence on the dissolved solids concentration or other feed water quality determinants. This range of energy demand amounts to 25–70% of the energy demand for seawater desalination.

Using Neural Networks to Predict Treatment Process Performance

This article discusses the application of a simple artificial neural network (ANN) model to predict microfiltration/ultrafiltration (MF/UF) performance with reasonable accuracy using data typically gathered online in an MF/UF facility. By developing a site‐specific ANN model, operators of MF/UF facilities could predict the performance of critical parameters such as transmembrane pressure (TMP) and plan accordingly. For instance, when the model predicts a higher rate of fouling based on feedwater quality, operating conditions could be modified to reduce the rate of increase of TMP, thereby reducing the required cleaning frequency of MF/UF systems.

Application of Vibratory System to Improve the Critical Flux in Submerged Hollow Fiber MF Process

Submerged hollow fiber membrane system is widely used in water and wastewater treatment plants. One of the major problems of the microfiltration/ultrafiltration (MF/UF) process is membrane fouling. Few techniques have been developed to reduce membrane fouling and increase critical flux of the filtration process. In this study, membrane vibration was applied to improve the critical flux in a submerged hollow fiber MF system. A bench scale unit was especially built for this purpose and different vibrating speed was tested. The effect of the feed concentration and vibrating speed on the critical flux measurement were investigated. The critical flux was measured at different vibrating speeds varied from 0–500 oscillation per minute (opm) (5.83 Hz). The lowest critical flux was 15 L·m−2·h−1 when no membrane vibration was used and then increased gradually from 27 to 56 L·m−2·h−1 when the vibrating speed increased from 100 to 500 opm (8.35 Hz). A sharp drop in the critical flux was noticed when the concentration of feed suspension doubled from 5 g/L to 10 g/L. However, the increase in the critical flux was insignificant at higher feed concentration even when a high membrane vibrating speed was applied. This signifies that there is a limit for flux improvement in a vibratory system which is strongly dependent on the feed concentration.

Ultrafiltration as direct pre-treatment of seawater – a case study

Reverse osmosis (RO) and nanofiltration (NF) processes gain more and more interest in the desalination market. Recently, seawater reverse osmosis (SWRO) has become more widespread, using relatively large plants, whilst NF is being applied before thermal desalination, as an advanced treatment for increased efficiency of thermal processes. A proper and reliable seawater treatment before RO and NF, capable to retain suspended solids that cause fast fouling and plugging of sensitive spiral wound membrane modules, is a key to success of desalination processes. Reliability, high and constant quality of permeate, regardless of changes in seawater characteristics, are major advantages of microfiltration/ultrafiltration (MF/UF) over conventional pre-treatment, allowing a stable and high performance of RO and NF processes. This experimental work evaluates performance of two different UF, hollowfibre membrane modules, when fed directly with raw seawater taken from the industrial harbour of Genoa. The study reports the performance of nanofiltration process fed with UF permeate versus the performance of NF fed with raw seawater.

Optimizing inline coagulation to reduce chemical consumption in MF/UF systems

Microfiltration/ultrafiltration (MF/UF) systems preceded by inline coagulation pretreatment are characterized by a high consumption of chemicals. For chemical consumption to be reduced, process conditions for inline coagulation (dose, pH, mixing, flocculation and temperature) should be optimized. In order to establish the optimum conditions for inline coagulation with different types of coagulants, their behaviour under different coagulation conditions needs to be understood. This study aimed at elaborating the behaviour of polyaluminium chloride (PACl) under different conditions of dose, pH, mixing (G) and flocculation (Gt) in the absence of turbidity and with low organic matter content. Tap water, filtered through a 0.1 µm PVDF filter was used as model water. Flocculated solutions were filtered in dead-end mode using an Amicon unstirred cell device. The specific cake resistance was quantified by measuring the modified fouling index (MFI) at a constant pressure of 1 bar and at 20°C. For low coagulant dos...

Colloidal fouling of RO membranes following MF/UF in the reclamation of municipal wastewater

Major municipal wastewater reclamation plants in California, USA, Singapore, and many built or planned for other regions of the world use the high pathogen reduction properties of microfiltration/ultrafiltration (MF/UF) membranes followed by reverse osmosis (RO) membranes. Operational experiences in these plants suggest that while MF and UF membranes encounter pore and cake fouling by colloidal particles (0.1 micron down to molecular sizes, ie. nanoparticles), a significant fraction of the smaller colloidal particles pass through the MF and UF membranes, and end up on RO membranes as cake-layer foulants. Autopsies, foulant analyses and cleaning studies performed on fouled RO membranes from the plants and pilot plants showed that colloidal natural organic matter, colloidal calcium phosphate and some times colloidal silicates are the main components. These colloidal particles have great affinity towards aggregation with each other. Due to incomplete removal by MF and even UF, fouling of RO membranes downstream becomes measurable by trend-charts of normalized values of permeate flow, differential pressure and salt passage. Normalized permeate flow is the most sensitive, and an early indicator of such fouling. In this paper we will provide some details of our studies and provide literature evidences that support the conclusion that calcium phosphate in foulants originated as nanoparticles in the wastewater.

Scottsdale adsorbs total organic carbon problem

This report discusses a case study where the City of Scottsdale, Arizona, will be impacted by the proposed Stage 2 Disinfectants/Disinfection Byproducts Rule (D/DBPR) in its treatment of Salt River Project (SRP) water. The SRP water is a combination of moderate total organic carbon (TOC) concentrations, high water temperature, and free chlorine which creates high levels of chlorinated disinfection byproducts, especially trihalomethanes. Because chilling the water would be very costly and replacing free chlorine as the distribution system residual disinfectant would present other problems, Scottsdale decided that removal of TOC was the best way to meet the requirements of the Stage 2 D/DBPR. This report discusses the selection of microfiltration/ultrafiltration (MF/UF) followed by granular activated carbon (GAC) as the process configuration at its new Chaparral Water Treatment Plant. To maximize the effectiveness of GAC, the project team also evaluated such factors as type of GAC, contact time, configuration, and replacement frequency.