Low Pressure Reverse Osmosis Membrane Research Articles

Application of Low-Pressure Reverse Osmosis Membranes for Drinking Water Softening

Application of Low-Pressure Reverse Osmosis Membranes for Drinking Water Softening

Research of phosphate removal from water on reverse osmotic filters

Eutrophication of natural water bodies caused by an excess of biogenic substances is one of the global environmental problems of modern times. Usually, phosphorus is a limiting biogenic element, the concentration of which determines the intensity of eutrophication processes in water bodies. Therefore, it is important to develop methods aimed at preventing excessive amounts of phosphates from entering the environment. To remove phosphates from water, typically used biological degradation technologies, which usually proceed very slowly and depend on the conditions under which the process takes place. Also, Biogenic elements can be removed by using ion exchange, reverse osmosis, and chemical methods. However, the disposal of concentrated solutions becomes an issue with these methods. Baromembrane purification methods, particularly reverse osmosis, are becoming increasingly important in the field of water treatment and purification and are essential in creating efficient and low-waste complex technologies for water purification from biogenic compounds. The study investigated the processes of removing orthophosphates from distilled and artesian water using a low-pressure reverse osmosis membrane Filmtec TW30-1812-50. The dependence of membrane productivity and selectivity on the concentration of phosphates and the degree of permeate rejection was determined. Was found that residual concentrations of phosphates in the permeate increase with the increase in the degree of permeate rejection. The lowest residual concentrations of phosphates were observed at the initial concentration of up to 10 mg/dm3. The highest residual phosphate concentrations were observed at initial concentrations above 900 mg/dm3. At the same time, the membrane productivity constantly decreased with increasing feed concentration and degree of permeate recovery due to the increased osmotic pressure on the membrane. The selectivity of the membrane was highest at an initial concentration of up to 10 mg/dm3 and slightly decreased at a rejection rate of 20-50% for initial phosphate concentrations of 100-900 mg/dm3. At the maximum degree of permeate rejection (90%), the selectivity of the membrane reached 97-99 % and decreased with an increase in phosphate concentrations, which is due to a change in the pH of the medium, hydrolysis of phosphates, hydration of ions, and concentration polarization. The membrane selectivity for phosphates in solutions in artesian water was slightly lower (95-99 %), which was due to the competing influence of chlorides, sulfates, and bicarbonates, as well as a decrease in the pH of the solution to 7.52-7.67, which promotes the hydrolysis of o-phosphates.

ВИЗНАЧЕННЯ ЕФЕКТИВНОСТІ ВИЛУЧЕННЯ СУЛЬФАТІВ НА ЗВОРОТНООСМОТИЧНІЙ МЕМБРАНІ НИЗЬКОГО ТИСКУ

The dependence of the efficiency of the low-pressure reverse osmosis membrane Filmtec TW30-1812-50 on the initial concentrations of sodium sulfate in the range of 10-650 mg/dm3 at permeate recovery rates of 1-90 % using a pressure of 4 atm was determined. The effect of increasing the permeate recovery rate on selectivity, membrane performance, and the in-crease in the sulfate content of concentrates was determined. It is shown that the concentration of sulfates in permeate depends on their initial concentration in solutions and increases both with an increase in the initial concentration and with an increase in the degree of permeate extraction. The latter factor is quite significant at initial sulfate concentrations of 650 mg/dm3. The membrane performance increases with decreasing salt content in water and decreases with increasing permeate removal rate, which leads to an increase in salt concentration in the pre-membrane space. The selectivity of the membrane for sulfates is 94.9-99.3 % and increases with increasing concentration of sodium sulfate solutions in solutions, despite a certain increase in salt concentrations in permeates. It is shown that as the degree of permeate selection increases, the selectivity for solutions with low initial sulfate concentrations increases. A FFP-based process modeling was performed to determine the sulfate con-centration in the permeate and concentrate at any initial sulfate concentration in a certain range. It was found that the con-centrate solutions are stable in the entire range of concentrations used with an increase in the degree of permeate recovery from 10 to 90 %. Based on the research results, a method for determining the capacity of the plant and the osmotic and oper-ating pressures based on the salt concentration and the set pressure in the system was proposed. From the data obtained, it can be concluded that the permissible level of mineralization at which the use of low-pressure reverse osmosis membranes is ad-visable.

Feasibility of Poly (Vinyl Alcohol)/Poly (Diallyldimethylammonium Chloride) Polymeric Network Hydrogel as Draw Solute for Forward Osmosis Process.

Forward osmosis (FO) has been identified as an emerging technology for the concentration and crystallization of aqueous solutions at low temperatures. However, the application of the FO process has been limited due to the unavailability of a suitable draw solute. An ideal draw solute should be able to generate high osmotic pressure and must be easily regenerated with less reverse solute flux (RSF). Recently, hydrogels have attracted attention as a draw solution due to their high capacity to absorb water and low RSF. This study explores a poly (vinyl alcohol)/ poly (diallyldimethylammonium chloride) (PVA-polyDADMAC) polymeric network hydrogel as a draw solute in forward osmosis. A low-pressure reverse osmosis (RO) membrane was used in the FO process to study the performance of the hydrogel prepared in this study as a draw solution. The robust and straightforward gel synthesis method provides an extensive-scale application. The results indicate that incorporating cationic polyelectrolyte poly (diallyldimethylammonium chloride) into the polymeric network increases swelling capacity and osmotic pressure, thereby resulting in an average water flux of the PVA-polyDADMAC hydrogel (0.97 L m-2 h-1) that was 7.47 times higher than the PVA hydrogel during a 6 h FO process against a 5000 mg L-1 NaCl solution (as a feed solution). The effect of polymer and cross-linker composition on swelling capacity was studied to optimize the synthesized hydrogel composition. At 50 °C, the hydrogel releases nearly >70% of the water absorbed during the FO process at room temperatures, and water flux can be recovered by up to 86.6% of the initial flux after 12 hydrogel (draw solute) regenerations. Furthermore, this study suggests that incorporating cationic polyelectrolytes into the polymeric network enhances FO performances and lowers the actual energy requirements for (draw solute) regeneration. This study represents a significant step toward the commercial implementation of a hydrogel-driven FO system for the concentration of liquid-food extract.

Tradeoff between micropollutant abatement and bromate formation during ozonation of concentrates from nanofiltration and reverse osmosis processes

Water treatment with nanofiltration (NF) or reverse osmosis (RO) membranes results in a purified permeate and a retentate, where solutes are concentrated and have to be properly managed and discharged. To date, little is known on how the selection of a semi-permeable dense membrane impacts the dissolved organic matter in the concentrate and what the consequences are for micropollutant (MP) abatement and bromate formation during concentrate treatment with ozone. Laboratory ozonation experiments were performed with standardized concentrates produced by three membranes (two NFs and one low-pressure reverse osmosis (LPRO) membrane) from three water sources (two river waters and one lake water). The concentrates were standardized by adjustment of pH and concentrations of dissolved organic carbon, total inorganic carbon, selected micropollutants (MP) with a low to high ozone reactivity and bromide to exclude factors which are known to impact ozonation. NF membranes had a lower retention of bromide and MPs than the LPRO membrane, and if the permeate quality of the NF membrane meets the requirements, the selection of this membrane type is beneficial due to the lower bromate formation risks upon concentrate ozonation. The bromate formation was typically higher in standardized concentrates of LPRO than of NF membranes, but the tradeoff between MP abatement and bromate formation upon ozonation of the standardized concentrates was not affected by the membrane type. Furthermore, there was no difference for the different source waters. Overall, ozonation of concentrates is only feasible for abatement of MPs with a high to moderate ozone reactivity with limited bromate formation. Differences in the DOM composition between NF and LPRO membrane concentrates are less relevant than retention of MPs and bromide by the membrane and the required ozone dose to meet a treatment target.

Low-pressure reverse osmosis membrane made of cellulose nanofiber and carbon nanotube polyamide nano-nanocomposite for high purity water production

Cellulose nanofiber (CNF) and multiwall carbon nanotube (CNT) nanocomposite polyamide membranes were synthesized and used in a low-pressure reverse osmosis (RO) system. Incorporating CNT and CNF into the polyamide structure (PA-CNT/CNF) allows the homogenous dispersion within the polymeric matrix, increasing its hydrophobic character and surface oxygen functionalities while reducing its surface roughness when compared to plain polyamide (PA), PA-CNT, and PA-CNF membranes. The resultant nanocomposite was tested at 0.75 MPa and sodium chloride salt concentration of 500 ppm resulting in a rejection of 99.47 % and water permeability of 1.65 m3/m2day. The rejection and permeation performance is highly competitive compared with commercial RO membranes. A 2in spiral module built with the PA-CNT/CNF membrane and tested for SiO2, NaCl, and CaCl2 rejection showed a reduction in its permeability of 24.9 % after 100 h of operations, while the commercials showed a decrease of 49.42 %. The present RO membrane module achieved a calcium rejection of 97.5 % and a boron rejection of 50.4 %. The 2in PA-CNT/CNF spiral module was tested in a two-step RO filtration system for high pure water (HPW) production and compared with a TW30 module with NSF certification. The PA-CNT/CNF module revealed a permeability reduction of 9.07% after 30 h operation, while TW30 had a reduction of 20.3%, which is about twice the durability. Molecular dynamics simulation showed that the CNF increased water hydration and boron diffusion on the membrane while CNT increased charge transfer to the PA structure. This polymeric nanocomposite has potential use in producing high purity water for brackish water or wastewater reuse for applications in the emerging semiconductor or pharmacology industry.

Electrocoagulation pretreatment of pulp and paper wastewater for low pressure reverse osmosis membrane fouling control.

Low pressure reverse osmosis (LPRO) has been increasingly used in advanced treatment of pulp and paper wastewater (PPWW) for the purpose of water reuse. However, membrane fouling is a major problem encountered by full-scale RO systems due to the organic and inorganic contents of the feedwater. Electrocoagulation (EC) as an effective treatment for foulants removal can be applied in pre-filtration. Therefore, the LPRO membrane fouling mechanism and the membrane fouling control performance by EC treatment were investigated in this study. EC pretreatment could reduce the membrane fouling and improve the membrane flux by 31%, by effectively removing and/or decomposing the organic pollutants in PPWW. Fluorescent spectrometry analyses of the feedwater and the permeate revealed that humic acid-like and fulvic acid-like organics in PPWW were the major foulants for the LPRO membranes. Fourier transformation infrared spectrometry results confirmed that the organic foulants contained benzoic rings and carboxylic groups, which were typical for organic substances. EC effectively removed organic pollutants containing functional groups such as carboxylic acid COH out-of-plane bending, olefin (trans), and NH3+ symmetrical angle-changing. Moreover, the extended Derjaguin-Landau-Verwey-Overbeek model suggested that the membrane filtered 30-min EC-treated PPWW had the strong repulsion force to foulants due to the higher cohesion energy (12.1mJ/m2) and the lower critical load, which theoretically explained the reason of EC pretreatment on membrane fouling control.

Micropollutant abatement with UV/H2O2 oxidation or low-pressure reverse osmosis? A comparative life cycle assessment for drinking water production

Micropollutants (MP) are undesired in drinking water. Advanced oxidation processes (AOP) or low-pressure reverse osmosis membrane filtrations (LPRO) can be used to remove them during the water purification process. For a specific case, two treatment scenarios were compared with a life cycle assessment (LCA), using three impact assessment methods (Ecological Scarcity 2013, ILCD 2011, EDIP 2003). Scenario 1 (AOP-based) was a UV/H2O2 oxidation with a subsequent granular activated carbon (GAC) filter to remove excess H2O2 before soil infiltration. Scenario 2 (LPRO-based) was a side-stream treatment with an ultrafiltration (UF) and low-pressure reverse osmosis (LPRO) filtration before soil infiltration and the LPRO retentate was treated with O3/H2O2 and subsequent granular activated carbon (GAC) filter before discharge back into Rhine. Sensitivity analyses were performed on the relevant contributors to evaluate the robustness of the results. LCA results showed that in the base-line scenario (electricity from renewable energy sources) the LPRO-based treatment had notably fewer environmental impacts than the AOP-based treatment, which was confirmed with three impact assessment methods. Key contributors to the impacts were mostly operating resources, i.e., electricity, H2O2, liquid O2 for ozone generation and GAC, but also construction resources in the LPRO process. The electrical energy source was decisive for the results: with a share of renewable energy sources <80%, the AOP-based treatment was the better option due to its lower specific energy demand. The optimization of treatment conditions, such as lower H2O2 concentration at an increased UV fluence; different H2O2:O3 molar ratios; or extended GAC utilization time could influence the environmental impact within a range of ±10–30%. Environmental benefits, i.e. the reduction of potential hazardous effects of 21 MPs, were determined with EDIP 2003 and USEtox for both treatment scenarios. The estimated benefits were negligible in comparison to the environmental burden caused by the treatments, thus would not be justified from a global LCA impact-benefit perspective. However, because of several uncertainties and lack of data, the inclusion of treatment benefits in LCAs for drinking water purification requires further research.

Hollow-Fiber RO Membranes Fabricated via Adsorption of Low-Charge Poly(vinyl alcohol) Copolymers

We report a new type of alkaline-stable hollow-fiber reverse osmosis (RO) membrane with an outside-in configuration that was established via adsorption of positively charged poly(vinyl alcohol) copolymers containing a small amount of quaternary ammonium moieties. Anionic sulfonated poly(arylene ether sulfone nitrile) hollow-fiber membranes were utilized as a substrate upon which the cationic copolymer layer was self-organized via electrostatic interaction. While the adsorption of the low-charge copolymer on the membrane support proceeded in a Layer-by-Layer (LbL) fashion, it was found that the adsorbed amount by one immersion step was enough to form a defect-free separation layer with a thickness of around 20 nm after cross-linking of vinyl alcohol units with glutaraldehyde. The resultant hollow-fiber membrane showed excellent desalination performances (NaCl rejection of 98.3% at 5 bar and 1500 mg/L), which is comparable with commercial low-pressure polyamide RO membranes, as well as good alkaline resistance. The separation performance could be restored by repeating the LbL treatment after alkaline degradation. Such features of LbL membranes may contribute to extending RO membrane lifetimes.

Impact of the Recovery on Concentrating Acetic Acid with Low-Pressure Reverse-Osmosis Membranes.

This work deals with the optimization of the concentration of volatile fatty acids (VFAs) using low-pressure reverse osmosis (LPRO) membranes. Membrane filtration of a synthetic solution simulating the product of biomass hydrolysis was performed. Experiments were run on two flat-sheet XLE membranes under 22 and 25 bar in continuous operation mode. Separation efficiency was evaluated for different recoveries. A correlation between the osmotic pressure of the concentrate and the parameter Rc, representative of the separation efficiency, was found. Under the conditions of the present study and taking into consideration the rejection properties of the applied membrane, a recovery of 33% and 44% is recommendable to maximize the ratio between the concentration of acetate in the concentrate and permeate and thus increase the total reclaim of acetic acid.

Reverse osmosis treatment of condensate from ammonium nitrate production: Insights into membrane performance

Ammonium nitrate is an important fertilizer and industrial explosive. The production of ammonium nitrate entails the generation of a large volume of condensate laden with nitrogen that must be treated before environment discharge. Results in this study show that through appropriate membrane selection, over 90% rejection of ammonium nitrate can be achieved by reverse osmosis (RO) filtration. Using RO (which is highly compact and efficient) to enrich ammonium nitrate in the condensate would significantly reduce the size of the evaporation separator for ammonia recovery. The results also highlight the importance of membrane selection for this application. Results reported here suggest that a low pressure RO membrane (e.g. ESPA2) is more suitable for the dilute condensate while a high pressure RO membrane (e.g. SW30) is recommended for the concentrated condensate to ensure adequate ammonia and nitrate rejection. Ammonia and nitrate rejections were dependent on key operating parameters including applied pressure (or water flux), temperature, feed solution pH, and initial ammonium nitrate concentration in the condensate. The impact of operating conditions on ammonia and nitrate rejections was more profound for low pressure (thus high flux) than high pressure RO membrane. An extended filtration experiment shows no evidence of membrane fouling. Results from this study are useful to the integration of a compact RO system to ammonium nitrate manufacturing for pollution prevention and improving product yield.

Treatment of municipal waste landfill leachate with low pressure reverse osmosis and nanofiltration membranes

Two different approaches to treat municipal landfill leachate with reverse osmosis membranes are evaluated and discussed. Possibilities are evaluated to radically reduce concentrate flow by a value that does not exceed 0,5-1 % of initial feed water flow to withdraw all rejected impurities together with dewatered sludge. Experimental procedure is developed and described to evaluate reduction of membrane flux and rejection during leachate treatment and recovery increase. Results of experimental investigations are presented that enable us to determine main characteristics of membrane process such as: membrane flux, ammonia rejection, membrane types, number of stages, and recovery. Experimental relationships are obtained to determine the required membrane recovery values that correspond to ammonia concentration in the feed water to meet required regulation values in the product water.

Probing and relating the morphology, structure and performance evolution of low pressure RO membranes under chlorine exposure

The polyamide layer of reverse osmosis (RO) membrane is susceptible to chlorination degradation. Guidelines for validation and integrity monitoring of the low pressure RO (LERO) membrane morphology and performance upon chlorination is still rarely reported. In this study, we selected three commercial LERO membranes (i.e., LP, ULP and LCLE) to study their structure and separation performance change for exposing to chlorine under both pressurized and static chlorination conditions, with different active chlorine concentrations and pH. At the pressurized testing, the membrane water flux increased at the initial stage due to the decrease of water passage restriction by the destroy of the hydrogen bond in the polyamide, and then the water flux sharply decreased and gradually leveled off, which should be resulted from the destroy of chemical structure of polyamide and membrane compaction under high pressure. The salt rejection slightly changed, presumably due to the combination of tightening effect, compactness and defect plugging by foulants. As for the static chlorination test, active chlorine concentration and chlorination time were not unequivocalness at the same chlorination intensity. Higher active chlorine concentration could cause more serious chlorination degradation. Based on the water flux change at neutral pH and under static chlorination conditions, a flux reduction equation with active chlorine concentration was fitted by y = axb (1＜x＜1000), which could help us to predict the water flux under a specific chlorine concentration and time.

Treatment of Effluent of Upflow Anaerobic Sludge Blanket Bioreactor for Water Reuse

The low-pressure reverse osmosis (LPRO) process is a recent development of reverse osmosis (RO) technology for the reduction in RO energy consumption and operation cost. The goal of this study was to investigate the performance of LPRO processes for the treatment and reuse of effluent discharged from brewery upflow anaerobic sludge blanket bioreactors (UASB). In this study, three different commercially available LPRO membranes were tested to evaluate the water quality that can be achieved under different operational and pretreatment conditions. It was found that the filtration performance and the effluent quality of the LPRO membranes can be considerably affected by the operation conditions and the selection of the pretreatment processes. The ultrafiltration (UF) pretreatment and the control of the operation pressure were found to be essential for mitigating LPRO membrane fouling, which could be caused by Ca2+ associated precipitates and organic gelation, in the treatment of the brewery UASB effluent. Water quality analyses showed that an integrated process of the UASB + UF + LPRO could achieve an effluent quality characterized by concentrations of 10.4–12.5 mg/L of chemical oxygen demand (COD), 1.8–2.1 mg/L of total nitrogen (TN), 1.3–1.8 mg/L of ammonia nitrogen (NH3-N) and 0.8–1.2 mg/L of total phosphorus (TP). The effluent quality and the LPRO performance could be further improved by adding a granular activated carbon (GAC) adsorption process between the UF and LPRO processes, which reduced the concentration of COD to 7–10 mg/L and those of TN, TP, NH3-N to below 1 mg/L. For the treatment of the UASB effluent tested in this study, the UF, UF + GAC (retention time 4 hrs), UF + LPRO, and UF + GAC + LPRO, respectively, achieved overall COD removal efficiencies of 89.6–93.7%, 94.5–96.7%, 99.3–99.1% and 99.3–99.4%; TN removal efficiencies of 73.0–78.2%, 89.2–97.2%, 97.1–98.2% and 94.3–99.7%; and TP removal efficiencies of 29.3–46.2%, 77.0–95.4%, 95.9–97.6z% and 98.0–98.3%. This study showed that both UASB + UF + LPRO and UASB + UF + GAC + LPRO are effective treatment processes for treating brewery wastewater toward reuse water quality standards set by the United States Environmental Protection Agency (US EPA). Therefore, the results of this study would help to answer whether a LPRO can treat the brewery UASB effluent to meet the requirements of wastewater reuse standards.

Removal of Trace Organic Contaminants by Parallel Operation of Reverse Osmosis and Granular Activated Carbon for Drinking Water Treatment.

In response to increasingly stringent restrictions for drinking water quality, a parallel operation of two common technologies, low-pressure reverse osmosis (LPRO) and activated carbon filtration (ACF), was investigated in a comprehensive five-month pilot study for the removal of 32 typical trace organic contaminants (TrOCs) from Rhine bank filtrates employing a semi- technical plant. TrOCs have been divided into three groups: polyfluorinated aliphatic compounds; pharmaceuticals, pesticides and metabolites; in addition to volatiles, nitrosamines and aminopolycarboxylic acids, which were also examined. The net pressure behavior, normalized salt passage and rejection of TrOCs by LPRO were investigated and compared with ACF operation. In addition, autopsies from the leading and last membrane modules were performed using adenosine triphosphate (ATP), total organic carbon (TOC), ICP-OES and SEM-EDX techniques. Generally, rather stable LPRO membrane performance with limited membrane fouling was observed. TrOCs with a molecular weight of ≥ 150 Da were completely retained by LPRO, while the rejection of di- and trichloro compounds improved as the filtration progressed. ACF also showed significant removal for most of the TrOCs, but without desalination. Accordingly, the ACF and LPRO can be operated in parallel such that the LPRO permeate and the ACF-treated bypass can be mixed to produce drinking water with adjustable hardness and significantly reduced TrOCs.

Operational strategies for brackish water desalination plants in island regions of South Korea

Based on the operational data from the Korea Water Resources Corporation (K-water), this study aimed to reduce the operation and maintenance (O&M) costs for 20 brackish water desalination plants in the island regions of South Korea. In addition, brackish water reverse osmosis (BWRO) and low-pressure reverse osmosis (LPRO) membranes were compared and evaluated in terms of reduction in specific energy consumption (SEC) for an island brackish water desalination plant. The high labor costs and plant breakdown accounted for most of the operating losses with low operation rates (less than 60% in 19 plants) and low water flow rates (less than 90% in 15 plants). Thus, in order to reduce the O&M costs of island region desalination plants, it was essential to optimize the plant design while increasing the operation and water flow rates. In particular, installation of the LPRO membrane has shown potential for SEC improvement (approximately 16%) due to high pressure pump optimization and high recovery. These operational strategies for island region desalination plants are applicable alternatives in terms of reduction in O&M costs and SEC.

Desalination of high salinity brackish water by an NF-RO hybrid system

Desalination of brackish water is an important approach to overcoming freshwater shortage. 85% of brackish water contains 1–10 g/L of salt; however, most work on brackish water desalination targets at low salinity (1–5 g/L) brackish water. This work looks into membrane desalination processes suitable for high salinity brackish water. Feed waters with a high-concentration (≥10 g/L) of NaCl or mixed NaCl/MgSO4 salts were considered, and the desalination performance of representative commercial nanofiltration membranes (VNF2 and ESNA1) and low-pressure reverse osmosis membranes (ULP100, LP100, and ESPA1) were evaluated. It was revealed that the desalination process can be operated at a pressure below 1.6 MPa, and the combination of ULP100-VNF2 arranged in series was a good option for production of freshwater from the high-salinity brackish water.

Prediction of rejection properties and performance of nanofiltration membranes based on scaling prognosis in drinking water treatment

Reverse osmosis (RO) and nanofiltration (NF) are widespread for drinking water production from underground water sources; these techniques are used to reduce hardness, iron, fluoride, ammonium, strontium, nitrate, pesticides etc. At the same time, with high efficiency of removing iron, hardness, fluoride, ammonium from source water, nanofiltration membranes are much less exposed to the risk of calcium carbonate precipitation than the traditionally used low-pressure RO membranes. Usually it is important to predict the rejection properties of membranes not only at the launch time of RO/NF unit, but during all operation period and gradual membrane fouling/scaling. The article presents experimental data on determining membrane selectivity (nanofiltration membrane OPMN-K, Russia) for iron. fluoride and ammonium depending on the TDS, water hardness and the amount of calcium carbonate precipitate in the membrane module. Operational guidance has been developed that allow to determine the costs of chemicals for the operation of NF installations depending on the source water quality and membrane type. The above calculations show that the use of nanofiltration membranes instead of reverse osmosis can significantly reduce the cost of operating groundwater treatment facilities.

Role of nanofiltration or reverse osmosis integrated to ultrafiltration-anaerobic membrane bioreactor treating vinasse for the conservation of water and nutrients in the ethanol industry

Sugarcane vinasse is the byproduct of ethanol production and, in many places, its final disposition has been its application in cane fields through fertigation. However, the incorrect practice of this technique can result in soil acidification, increase of salinity, and contamination of groundwater. Appropriate technologies and treatment processes can enable the recovery of byproducts from sugarcane vinasse, such as water, nutrients and energy. Thus, this study studied the integration of nanofiltration (NF) and reverse osmosis (RO), to ultrafiltration (UF) and two-stage anaerobic membrane bioreactor (2S-AnMBR) treatment aiming at the recovery of energy, nutrients (NF/RO concentrate) and water (NF/RO permeate). Seven types of commercial nanofiltration (NF) / reverse osmosis (RO) membranes were evaluated. The 2S-AnMBR reduced the vinasse organic matter and potentially produced 4.9 Nm3 of CH4 m−3 of vinasse that can be used for energy purposes. The low-pressure RO membrane stood out among the membranes investigated in this study, demonstrating a good performance in terms of pollutants retention, fouling potential and specific energy consumption (SEC), with an optimal recovery rate value below 40 % at 12 bar of operation. The final RO treatment was a viable alternative to generate water for industrial reuse, allowing the production of 3.2–4.8 m3 of treated water per m3 of ethanol produced. Besides, the retentate produced by RO had an organic carbon concentration 9 times lower compared to raw vinasse, which reduces the impact during soil disposal and associated CO2 generation.

A new technique to purify biologically treated wastewater by reverse osmosis: utilization of concentrate

Introduction. Possibilities to purify municipal wastewater using reverse osmosis membrane techniques are investigated aimed at production of quality water for industrial use or meeting regulations for surface water sources discharge. A new eveloped tools to utilize concentrate effluents by reducing its flow by a value that does not exceed 0.5–1.0 per cent of initial feed water flow and it’s withdrawal of all rejected impurities together with dewatered sludge as a sludge moisture. Objectives: development of reverse osmosis techniques to purify wastewater after biological treatment; evaluation of possibilities to radically reduce concentrate flow to withdraw it together with activated sludge as it’s moisture. &#x0D; Materials and methods. Experimental research is conducted to develop membrane operational modes during wastewater treatment. Experimental procedure is developed and described to evaluate reduction of membrane rejection of dissolved impurities and product flow decrease during experimental wastewater treatment and concentrate utilization test run. &#x0D; Results. The basic equations are derived that enable us to determine: the required concentrate flow value that corresponds to concentration values of COD and suspended solids values in the feed water; the required values of membrane recoveries that correspond to ammonia concentration in the feed water to meet required regulation values in the product water. The tools to evaluate membrane area and a number of membrane modules are developed and described. Optimum values of the working pressure are evaluated as well as other economic parameters are presented to compare the developed techniques with biological treatment.&#x0D; Conclusions. To reach the required ammonia concentration in product water, double stage treatment of feed water with low-pressure reverse osmosis membranes is required. Influence of dissolved organics defined as COD, on membrane performance. The optimum value of working pressure is determined which is 7.5–8 Bars.