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Integrating conventional coagulation with novel treatment methods is expected to enhance natural organic matter (NOM) removal in water treatment. The great variability in NOM composition makes it difficult to completely remove from drinking water by any single technique. This chapter discusses NOM removal by integrating coagulation with other treatment processes (ion exchange, oxidation, adsorption, and membrane technology) and hybrid processes combining membrane techniques with other unit processes (coagulation, adsorption, oxidation, and membrane bioreactors).

Abstract Insufficient recycling of a continuously increasing amount of liquid crystal display (LCD) waste leads to the waste of potentially recyclable materials, especially rare and critical indium. Moreover, landfilling of LCD waste increases the potential for environmental risk. This paper describes a recycling process combining membrane filtration unit processes to hydrometallurgical indium recovery process. The LCD panels were crushed and leached with 1 M H2SO4. 97.4% yields on average were obtained, and a novel finding was made about fast kinetics (2 min for the maximum indium yield). Ultrafiltration was used to remove the dissolved organic material from the leachate, which was concentrated with nanofiltration before liquid–liquid extraction for indium purification. The results showed that commercial polymeric membranes removed more than 90% (from over 3000 mg/L to under 200 mg/L) of the dissolved organic compounds, thus potentially significantly diminishing the detriments caused by these compounds in the liquid–liquid extraction step. The concentration of the leachate with nanofiltration enables the use of smaller processing equipment and to save chemicals in the further steps of the process. The indium content in the leachate was more than five times higher after nanofiltration than after leaching (126 mg/L vs. 677 mg/L). In liquid–liquid extraction, the phase separation took place in only 34 s with the membrane-treated leachate, while with the untreated leachate it remained incomplete even after three hours. The purity of indium was increased from 10 to 74%. From the obtained HCl solution, a 95.5% pure indium product with 69.3% yield was obtained by cementation. Graphical Abstract

Only scarce information is available about the abundance of microplastics (MPs) in Nordic lakes. In this study, the occurrence, types, and distribution of MPs were assessed based on the lake water and sediment samples collected from a sub-basin of Lake Saimaa, Finland. The main goal was to estimate the possible effect of the local wastewater treatment plant (WWTP) on the abundance of MPs in different compartments of the recipient lake area. Collected bottom sediment samples were Cs-137 dated and the chronological structure was utilized to relate the concentrations of MPs to their sedimentation years. Raman microspectroscopy was used for the MPs’ identification from both sample matrices. In addition, MPs consisting of polyethylene (PE), polypropylene (PP) and polystyrene (PS) were quantified from lake water samples by pyrolysis-gas chromatography-mass spectrometry to provide a complementary assessment of MPs based on two different analysis methods, which provide different metrics of the abundance of microplastics. MPs concentrations were highest in sediment samples closest to the discharge site of WWTP effluents (4400 ± 620 n/kg dw) compared to other sites. However, such a trend was not found in lake water samples (0.7 ± 0.1 n/L). Overall, microplastic fibers were relatively more abundant in sediment (70%) than in water (40%), and the majority of detected microplastic fibers were identified as polyester. This indicates that a part of textile fibers passing the WWTP processes accumulate in the sediment close to the discharge site. In addition, the abundance of MPs was revealed to have increased slightly during the last 30 years. Highlights • Higher concentrations of microplastics were detected in sediments closer to WWTP. • Polyester fibers were the most common type of plastics near WWTP. • Microplastic pollution has slightly increased from 1990 to 2018.

Although microplastics research has received enormous attention in the last decade, both the research practices and the quality of produced data should still be improved. In this study, the identification process of microplastics with Raman imaging microscope was improved by decreasing the time needed for the analysis. To do that, new features, including terrain mosaic and automatic particle selection, were utilized and various ways of handling the produced microplastics data were implemented and discussed. Furthermore, blank correction of microplastic concentrations was demonstrated and its effects on the recovery of spiked microplastics was assessed with aqueous and solid samples. Six types of microplastics, including fragments and fibers, were spiked in triplicates of ultra-pure water and reference sediment samples. The spiked samples were pretreated by a modified method of the universal enzymatic purification protocol. Microplastics were analyzed with Raman imaging microscope, using terrain mosaic combined with automatic particle selection. The microplastics data were subjected to different identification steps to estimate the potential overestimation and underestimation of microplastics counts. With the complete correction of Raman-based data, the average recovery rates of fragments (77-80%) were higher than fibers (20-33%). The decrease in recovery rates of spiked microplastics (49-57%) were observed when blank correction was applied (28-47%). The impact of the blank correction depended on the polymer, causing exclusion of PE, PET, and PP from sediment samples. For the completely corrected Raman-based data, the average recovery rates of microplastics were higher for water than sediment samples both with and without blank correction. The results demonstrated the impact of blank correction on the microplastics recovery rates. To our knowledge, this is the first study to explore the use of automatic particle selection of Raman imaging microscope for microplastics analysis. Hence, potential drawbacks and advantages of the new features of Raman imaging microscope were explicitly discussed.

Electrodialysis (ED) is a promising emerging electrochemical membrane technology for nutrient concentration and recovery from wastewater. However associated environmental safety aspects have to be assessed before utilizing concentrated nutrient produced by ED, for instance as fertilizer. Municipal wastewaters contain various micropollutants that have the potential of being concentrated during the ED treatment processes. This study quantified the transport of pharmaceuticals during ED nutrient recovery from synthetic centrate wastewater. Specifically, it is evaluated whether pharmaceutical micropollutants are mobile, and therefore able to transport across the cation exchange membranes and concentrate into the ED concentrate product. Results demonstrate that NH4+-N, PO43--P and K+ could be concentrated up to 5 times in the concentrated ED product (3700–4000 mg/L NH4+-N, 21–25 mg/L PO43--P, 990–1040 mg/L K+). Target micropollutants, such as diclofenac, carbamazepine and furosemide were largely retained in the diluent, with less than 8% being transported across to the concentrate product (feed micropollutant concentration 10 or 100 μg/L) based on the final target pharmaceutical amounts in the ED concentrate product (μg). Some transport of micropollutants such as atenolol, metoprolol and hydrochlorothiazide was observed to the concentrate product. For instance a final concentration of 10.3, 9.4 and 8.6 μg/L on average was measured for these pollutants in the final ED concentrate product (final volume ∼1 L) in experiments with a feed water (initial volume 20 L) containing only 10 μg/L of target pharmaceuticals. Transport of pharmaceuticals across the ED membranes was concluded to be dominated mainly by the molecule hydrophobicity/hydrophilicity as well as electrostatic interactions between pharmaceutical molecules and ED membranes. Particularly excluded were those having a negative charge and high hydrophobicity such as diclofenac and ibuprofen. Post-print / Final draft

Herein, to meet the requirement of the stringent sulfur emission and discharge rate standards based on World Health Organization (WHO) and Environmental Protection Agency (EPA), polyamide/titanium dioxide (PA/TiO2) thin film nanocomposite (TFN) membranes were synthesized to remove sulfur compound from sulfur recovery unit (SRU) wastewater. The experiments were designed to appraise the effects of three independent factors including TiO2 nanoparticle concentration, transmembrane pressure (TMP), and operating temperature on membrane performance. Surface physiochemical and morphological properties of the resultant membranes were characterized with analytical techniques. The membrane characterizations revealed that the nanocomposite selective layer was formed on the surface of the substrate and its morphology and surface charge were affected by TiO2 loading. The performance test showed that TFN membrane was highly effective in sulfur removal as the minimum and maximum rejections with this type of membrane in the design space were 92.56% and 99.94%, respectively. In addition, the responses were predicted by the model equations designed via response surface methodology (RSM). Accordingly, the main effects and their interactions were statistically validated by the analysis of variance (ANOVA). In conclusion, the resulting TFN membranes demonstrated not only a very outstanding reduction in sulfur content (more than 97% below the aforementioned global surveillance standards’ level), but also overcame the trade-off effect between permeability and selectivity of the reference TFC membranes.

Nowadays, end-of-life (EoL) reverse osmosis (RO) membranes are considered as waste, hence they are incinerated or discarded in landfills. Due to the environmental problem of disposed membranes, their reuse as nanofiltration (NF) membranes was investigated in this study. At first, the fouling of EoL membrane was cleaned and then the effect of sodium hypochlorite (NaOCl) on removing the polyamide (PA) layer and pure water permeability (PWP) of EoL membranes was investigated. With regard to NaOCl exposure intensities, three groups of EoL membranes with PWP of about 10, 20, and 30 L/(m2h bar) were selected as substrates to convert them to NF membranes by deposition of polyelectrolyte (PE) multilayers. The effects of PE type, substrate permeability, and the charge of outer layer on the performance of the resultant NF membranes were studied. As one of the best results, NF membrane composed of eight bilayers of SC498/KE253 polyelectrolytes on substrates with PWP of 18 L/(m2h bar) had salt water permeability (SWP) of 11 L/(m2h bar) and 94% rejection of MgSO4. Other results are also competitive with commercial NF membranes. The maximum NaCl and MgSO4 rejection of prepared membranes were 92% and 98%, respectively, at a feed pressure of 10 bar. In addition, the stability test showed that the prepared membranes are stable over a long period of filtration.

Thermal drying and consequent incineration of sewage sludge result in an absolute loss of an important macronutrient – nitrogen. To fulfill the growing food demand, humanity relies more on industrial fixation of nitrogen, primarily via the Haber-Bosch process. The present paper examines the nitrogen release during continuous thermal drying of municipal sewage sludge and its consequent recovery for fertilization. Furthermore, the possibility of nitrogen recovery from condensate is assessed. Finally, the study assesses the global warming potential of the proposed nitrogen recovery system and compares it with the baseline system manufacturing fertilizers from industrially fixed nitrogen. The results of the drying experiments showed that 0.73–1.03 g N-NH3 kg−1 total solids of sewage sludge was released to off-gases during its continuous thermal drying under 160 °C, which corresponds to 41–58% of ionized nitrogen content in raw sewage sludge subjected to thermal drying. The global warming potential of the nitrogen recovery was 28% lower compared to that of the commercial fertilizer production of equivalent properties: 4.1 kg CO2-Equiv. kg−1 N versus 5.7 kg CO2-Equiv. kg−1 N. Still, the sensitivity analysis showed that the results might traverse and lead to a higher global warming potential of 6.2 kg CO2-Equiv. during the nitrogen recovery process under certain process parameters.

Conventionally treated municipal wastewaters create environmental challenges due to eutrophication of effluent receiving waters and significant concentrations of micropollutants and other h...

Textile industry produces millions of tons of waste annually, which is predominantly incinerated or landfilled. Cotton textile comprises a quarter of total textile production, and although being renewable, its production is highly chemical- and water-intensive, rising the need for effective waste cotton textile recycling. This study presents an investigation whether it is possible to utilize waste cotton textile as a cellulose source for the fabrication of cellulose membranes. The effect of casting thickness and cellulose concentration on the prepared membranes’ performance was studied. Membranes cast from 2 wt.% casting solutions exhibited the highest permeabilities of 1.11 and 3.09 m3/(m2·s·Pa) for 300- and 150-microns casting thickness, respectively, but poor adhesion stability and low retention. Membranes cast from solutions of higher concentrations (5, 6, and 7 wt.%) resulted in membranes with more stable performance. The permeability values for 300-microns membranes were in the range of 0.27 – 0.39 m3/(m2·s·Pa) and for 150-microns 0.51 – 0.67 m3/(m2·s·Pa). The retention values of these six membranes were relatively close to each other, showing 80 – 92% retention of polyethylene glycol (PEG) 35 kDa. Three most promising membranes (5, 6, and 7 wt.% cast at 150-microns) were additionally characterized, showing negative zeta potential within -23 – -35 mV range at pH 7 and contact angles of very hydrophilic material (14 – 16°). Overall, the results showed that very hydrophilic ultrafiltration membranes having attractive permeability and retention properties can be made from textile waste. 1 m2 of cotton bed linen is enough to produce approximately 20 m2 of cellulose membrane. Publishers version

In this study cellulose-rich membranes were fabricated from untreated and treated hardwood biomass solutions in 1-ethyl-3-methylimidazolium acetate ([Emim][OAc])—dimetylsulfoxide (DMSO) system via wet phase separation. Wood treatment methods aimed to get purified cellulose fraction of wood. Treatment sequence was as followed: deep eutectic solvent pretreatment, sodium chlorite bleaching, and alkaline treatment. Resulted biomass after each treatment step was characterized by chemical composition and crystalline fraction content. Flat-sheet membranes were produced from biomass samples after each treatment step. Characterization of membranes included measurements of pure water permeability and (poly)ethyleneglycol 35 kDa retention, Fourier-transform infrared and Raman spectroscopy, X-ray diffraction measurements and thermogravimetric analysis. The study revealed that it was possible to fabricate membrane from untreated wood as well as from wood biomass after each of treatment steps. The resulted membranes differed in chemical composition and filtration performance. Membrane prepared directly from untreated wood had the highest permeability, the lowest retention; and the most complex chemical composition among others. As treatment steps removed lignin and hemicelluloses from the wood biomass, the corresponding membranes became chemically more homogeneous and showed increased retention and decreased permeability values.

Biotechnologically produced 2,3-butanediol (2,3-BDO) is a potential starting material for industrial bulk chemicals, such as butadiene or methyl ethyl ketone, which are currently produced from fossil feedstocks. So far, the highest 2,3-BDO concentrations have been obtained with risk class 2 microorganisms and pure glucose as substrate. However, as glucose stays in competition to food and feed industries, a lot of effort has been done in the last years finding efficient alternative substrates. Thereby xylose from hydrolysed wood hemicelluloses is a promising substrate for the production of 2,3-BDO. The risk class 1 microorganism Bacillus vallismortis strain was identified as a very promising 2,3-BDO producer. The strain is able to utilize xylose almost in the same manner as glucose. B. vallismortis is less prone to common inhibiting compounds in lignocellulosic extracts/hydrolysates. When using a concentrated hemicellulose fraction from birch wood hydrolysate, which was produced with ultrafiltration and after which the acetate concentration was reduced, a yield of 0.43 g g−1 was achieved and the xylose consumption and the 2,3-BDO production is basically the same as using pure xylose.

Waste biomass (agave bagasse) and native birch wood were used as raw materials for a novel fractionation and derivation process to produce cellulose acetates (CAs). During the first stage of the fractionation process, a significant amount of hemicelluloses and lignin were dissolved from the biomass using a natural deep eutectic solvent (NADES) that consisted of a mixture of choline chloride and lactic acid with the molar ratio of 1:9. Then, the residual solid material was delignified by bleaching it with a mixture of acetic acid and sodium chlorite. The fractionation process generated differently purified pulps (celluloses) which were converted to CAs. The crystallinity index, polymerization degree, chemical composition, and thermal properties of the differently purified pulps and CAs were analyzed to evaluate the efficacy of the acetylation process and to characterize the CAs. The chemical derivation of the differently purified cellulose samples generated CAs with different degrees of substitution (DSs). The more purified the cellulose sample was, the higher its DS was. Moreover, some differences were observed between the acetylation efficiencies of birch and agave bagasse. Typically, cellulose purified from birch by treating it with NADES followed by bleaching was acetylated more completely (DS = 2.94) than that derived from agave bagasse (DS = 2.45). These results revealed that using green solvents, such as NADES, to treat both agave bagasse (waste biomass) and birch wood, allowed pure fractions to be obtained from biomass, and thus, biomass could be valorized into products such as CAs, which present a wide range of applications.

Fouling problems caused by lignin have been limiting the use of membranes in the recovery of value-added materials from biorefinery streams. Fortunately, laccase-based catalytic pretreatments enable modification of lignin to the less fouling form. Because the mechanisms behind the fouling caused by ligneous compounds in wood-based streams are still not deeply understood, the aim of this study was to find out how laccase oxidation affects membrane fouling caused by pressurized hot-water extract. The effect of laccase on the fouling tendency of birch extract was explored both with adsorptive and pressure-driven experiments. The results suggested that laccase treatment increased the molar mass of lignin and improved significantly filtration capacity of commercial polyethersulphone membrane, possibly due to formation of less dense foulant layer during the filtration. Based on FTIR and BET results laccase oxidation decreased both adsorptive and pressure-driven fouling caused by lignin. However, decreases in pure water permeabilities were higher for the samples that were fouled with laccase treated extract. This may have originated from the transformation in the fouling mechanism from the pore narrowing to the pore blocking and could be prevented by the selection of a membrane with a different pore size. Post-print / Final draft

This study investigates the recovery of ammonia from drying fumes during thermal drying of sewage sludge with packed bed acid scrubbers to recover ammonia and to produce ammonium sulfate. The process is modelled for two concentrations, 75 and 100 ppm, and 1000m3/h inlet flowrate of drying fumes containing air and ammonia gas. It results in finding optimal parameters for scale-up of drying fumes during thermal drying of 7700t/a sewage sludge of Lappeenranta city. It is found that a single scrubber, with a 24000 m3/h of inlet gas and an ammonia concentration of 75 ppm, liquid to gas ratio of 1.5, temperature and pH of liquid acid as 100°C and 3 respectively, gives the efficiency of more than 99%, and reduces ammonia concentration in the outlet stream to 0.2 ppm. The capital cost is 290 k€, operating cost is 113k€/a, removal cost with and without revenue of ammonium sulfate is 20 €/t and 18 €/t of sludge. The packed bed acid scrubber would be suitable to remove ammonia in the drying fumes to recover ammonia from the drying fumes, but the initial economic analysis highlights that the production of commercial grade ammonium sulfate fertilizer would be an expensive option.

Membrane fouling in a membrane bioreactor (MBR) is highly influenced by the characteristics of the influent, the mixed liquor microbial community and the operational parameters, all of which are environment specific. Therefore, we studied the dynamics of microbial community during the treatment of real municipal wastewater in a pilotscale anoxic-oxic (A/O) MBR equipped with a gravity-driven membrane filtration system. The MBR was operated at three different solid retention times (SRTs): 25, 40 and 10 days for a total period of 180 days in Nordic environmental conditions. Analysis of microbial community dynamics revealed a high diversity of microbial species at SRT of 40 days, whereas SRT of 25 days was superior with microbial richness. Production of soluble microbial products (SMP) and extracellular polymeric substances (EPS) was found to be intensely connected with the SRT and food to microorganism (F/M) ratio. Relatively longer operational period with the lowest rate of membrane fouling was observed at SRT of 25 days, which was resulted from the superior microbial community, lowest production of SMP and loosely bound EPS as well as the lower filtration resistance of larger sludge flocs. Abundance of quorum quenching (QQ) bacteria and granular floc forming bacterial genera at SRT of 25 days provided relatively lower membrane fouling tendency and larger floc formation, respectively. On the other hand, substantial amount of various surface colonizing and EPS producing bacteria was found at SRT of 10 days, which promoted more rapid membrane fouling compared with the fouling rate seen at other tested SRTs. To sum up, this research provides a realistic insight into the impact of SRT on microbial community dynamics and resulting characteristics of mixed liquor, floc size distribution and membrane fouling for improved MBR operation. (c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Adsorptive fouling, by phenolic compounds, is a serious issue regarding the development and use of membrane based filtration technologies for water purification and wastewater treatment. We have developed a novel, combined, protocol of Raman spectroscopy and surface plasmon resonance (SPR) experiments, along with molecular dynamics (MD) simulation, to study the interaction of vanillin, a model phenolic compound, with the polyethersulfone (PES) surface of a membrane. The adsorption of vanillin to the PES surface was found to be highly pH dependent; the source of this was determined, by MD simulation, to be the stronger interaction with the protonated form of vanillin, predominant at low pH. Vanillin interacts with the PES surface, both through entropy driven, hydrophobic, interactions and, for the case of the protonated form, H-bonding of the hydroxyl group with the sulphur oxygens of the PES molecules. In addition to general insight into the fouling process that can be used to develop new methods to inhibit adsorptive fouling, our results also elucidate the specific interaction of the PES membrane with vanillin that can be used in the development of anti-fouling coatings, based on the structure of vanillin. Post-print / Final draft

The aim of this study was to examine the feasibility of pulsed corona discharge (PCD) oxidation for treatment of the nanofiltration concentrate from a municipal wastewater treatment plant. The concentrate studied contained high concentrations of micropollutants, since it was produced in the two stage nanofiltration process and filtered to a very high volume reduction factor of 300. The goal of the PCD treatment was to decrease the amount of micropollutants and to increase biodegradability of the concentrate. The energy dose (10 kWh/m 3 ) used in the PCD treatment was sufficient to reduce 21% of organic carbon present in the concentrate. However, the PCD treatment degraded efficiently some of the target micropollutants: higher than 92% degradation of diclofenac, carbamazepine, citalopram and furosemide was reached. Degradation rate of the beta-blockers (bisoprolol, sotalol, metoprolol) as well as ketoprofen and N,N-diethyl-meta-toluamide (DEET) was lower: 82, 51, 33, 44 and 50% respectively. The BOD 7 /COD ratio of the NF concentrate was also increased 3.7 times due to the oxidation. Based on a linear regression analysis, molecular weight of the micropollutants, the amount of double bonds in their structure and the hydroxyl radical degradation constant were identified as the determining parameters for the degradation rate of the micropollutant in the PCD oxidation. This lead to a conclusion that presence of hydroxyl radicals was more critical for the degradation of the micropollutants than the presence of ozone under the examined conditions.

Polyelectrolyte multilayer (PEM) membranes were fabricated by using a polycation with a long pendant group in order to prepare loose nanofiltration membranes. Poly(2-methacryloxyethyltrimethylammonium bromide)/poly(styrene sulfonate) multilayer membranes were prepared on the lumen side of polyethersulfone hollow fiber membranes with a dynamic coating method and compared to identically prepared poly(diallyldimethylammonium chloride)/poly(styrene sulfonate) multilayer membranes to observe how the different polycation structures affect membrane properties. Both membranes were evaluated in terms of their water permeability, rejection of MgSO4, rejection of neutral polyethylene glycol model compounds, and stability against sodium hypochlorite at pH 8.0. Poly(2-methacryloxyethyltrimethylammonium bromide)-based membranes with loose nanofiltration properties and high water permeability were successfully fabricated. However, they degraded rapidly under sodium hypochlorite treatment, whereas the poly(diallyldimethylammonium chloride)-based membranes showed no significant degradation until after 50,000 ppm·h of sodium hypochlorite treatment. Despite the rapid degradation of poly(2-methacryloxyethyltrimethylammonium bromide)-based multilayers under the sodium hypochlorite treatment, the results show that choosing polyelectrolytes with appropriate side group structures can be attractive when designing PEM membranes with membrane properties in the loose nanofiltration range.

In recent years, accumulation of pharmaceutical compounds in the environment has been an issue of growing concern. Conventional wastewater treatment has limited effectiveness with many pharmaceuticals at concentrations of ppb or ppt scale. An intuitive solution would be to treat the pharmaceuticals-contaminated wastewaters at the source sites before dilution in sewer networks. Health institutions with concentrated drug consumption provide logical point sources for pharmaceuticals entering the sewage. This paper describes the pilot-scale removal of a wide range of pharmaceuticals from real wastewaters via gas-phase pulsed corona discharge oxidation. The process was studied for raw sewage from a public hospital and for biologically treated wastewater of a health-care institute. The non-selective oxidation of the observed pharmaceuticals (32 compounds) was effective at reasonable energy cost: 87-% reduction in residual pharmaceuticals (excluding biodegradable caffeine) from raw sewage was attained with 1 kWh m−3from the raw sewage and 100% removal was achieved for biologically treated wastewater at only 0.5 kWh m−3. The impact for affected aquatic environments upon the present solution would be a dramatically reduced load of pharmaceutical accumulation.

Conventional activated sludge treatment plants have limited capability to remove micropollutants from municipal wastewater, and as a consequence, concentrations of micropollutants in water bodies are increasing. This creates concerns due to their potentially harmful effects on the aquatic environment, as well as needs to improve or replace the traditional wastewater treatment processes with novel process concepts. In this study, two novel process concept alternatives for enhanced removal of micropollutants are examined. The experiments were done in pilot scale with real wastewater of a small municipality. In the first concept, a membrane bioreactor process (MBR) without phosphorus precipitation was combined with high permeability nanofiltration (NF), and in the other, the MBR with the precipitation of phosphorus was combined with advanced oxidation implemented by pulsed corona discharge (PCD). The results showed that the MBR processes were insufficient for removing unreadily biodegradable micropollutants, such as carbamazepine and diclofenac. However, combining the nanofiltration or PCD oxidation step with the MBR enabled significant enhancement in the removal of micropollutants. Over 84% removal was reached with nanofiltration (NF270) for most of the studied micropollutants, except caffeine and hydrochlorothiazide. The performance of PCD oxidation (oxidation energy 0.2 kWh/m 3 ) in the removal of micropollutants exceeded the one of nanofiltration; over 90% removal of most of the studied micropollutants was reached, and the pollutants were degraded below 0.1 µg/L concentration. Thus, the total removal of micropollutants was better in the concept combining MBR and oxidation treatment. However, the concept combining MBR and nanofiltration provided better overall removal of organic compounds (removal of COD and DOC > 99%), and it also enabled the recovery of phosphorus as a concentrated solution.

A new application for used reverse osmosis (RO) membranes as gas separation membranes was studied. In this regard, firstly, three pretreatment procedures were used to remove the foulants from the surface of used membrane and then they were coated with polydimethylsiloxane (PDMS). The results indicated that PDMS-coated used RO membranes were capable of separating O 2 /N 2 and CO 2 /N 2 . The maximum O 2 /N 2 and CO 2 /N 2 selectivities of coated membranes were 5.9 and 32.5, respectively. The O 2 /N 2 and CO 2 /N 2 selectivities of PDMS membrane were reported in the range of 2.1–2.2 and 11–12, respectively. Finally, an economic assessment was carried out to compare prepared PDMS coated RO membranes with commercial PPO membrane. This showed that coated membranes are less expensive than PPO membrane for CO 2 /N 2 gas separation. The outcome of the research was a simple method for converting used RO membranes to cost effective gas separation membranes.

The possibility to detect and identify early stage membrane fouling in real-time is a key to understand fouling phenomena. In this study normal Raman spectrocopy was explored as a novel online tool for monitoring membrane fouling. Raman spectra were measured during cross-flow experiments in which vanillin was used with different concentrations as a model compound for organic foulants. The measured Raman spectra were analyzed and interpreted by using principal component analysis and external calibration in order to determine the adsorbed amount of vanillin during the fouling process. Fouling induced changes in pure water permeabilities and off-line measured FTIR spectra were also analyzed in order to confirm the results of the real-time monitoring system. It was found that an increase in the solution concentration increased the degree of vanillin adsorption and led to better water permeabilities. The procedure used is able to provide results that describe well the accumulation of foulants in a straightforward and semi-quantitative way. The results demonstrate that the introduced monitoring tool has potential for gaining new knowledge about fouling layer formation.

Pharmaceutical blister packages usually comprise of aluminium and plastic layers. Due to their multi-material structure, the discarded packages are typically landfilled, although when separated, both metallic and polymeric fractions would be recyclable. In the present study, separation of aluminium and polymeric layers of waste pharmaceutical blisters was conducted by exploitation of deep eutectic solvent (DES, lactic acid – choline chloride) and pure lactic acid, both of which are considered green solvents. The separation of aluminium and plastic was investigated at different temperatures, solvent concentrations, solid-liquid ratios and agitation speeds. The complete separation was achieved with both studied solvents. The fastest separation was obtained when temperature was increased, more solvent with respect to solid was used and when agitation was introduced to the system. The effect of solvent concentration varied depending on the used solvent. Separation by lactic acid was the fastest with pure solvent (90 wt%), and separation by DES was the fastest with diluted solvent (50 wt%) due to strong dissolution of aluminium and formation of aluminium lactate precipitate. Polyvinyl chloride (PVC) and acrylic based adhesive were detected in all the investigated samples. After the separation by pure DES, the recovered aluminium fraction was corroded, containing 65 wt% of aluminium and 23 wt% of oxygen whereas after lactic acid treatment, aluminium surfaces contained at its best about 95% of aluminium (aluminium foil contains 96% of Al). The results showed that the DES used and lactic acid can offer viable green separation methodology for aluminium and plastic from blister packages.

New directions in wastewater treatment consider not only the adequate purification efficiencies but also water and material recovery for recycling and reuse. Freeze crystallization offers the potential for the simultaneous separation of water (ice) and material (i.e., salts and nutrients) from wastewater using a single wastewater purification process. However, the impurity-separation performance of freeze crystallization applied to multi-component wastewaters is still unclear, particularly for industrial or municipal scales. In this study, a prototype was developed to demonstrate the application of freeze crystallization to wastewater purification on the industrial scale. This freeze crystallizer, a 120 L jacketed vessel equipped with stirring and ice scraping mechanisms, produced relatively large (500 µm) ice crystals, primarily in water suspension. To evaluate the purification efficiencies of the prototype system, a comprehensive number of water-quality indicators were measured following the purification of highly concentrated landfill leachates. The prototype system achieved a >95% average impurity removal efficiency for both organic and inorganic matter, including heavy metals. This excellent separation ability, given the variety of impurities present in the leachates, shows the non-selective nature of freeze separation for wastewater treatment. These outcomes represent an important step forward in scaling up and developing the full scale freeze purification process for wastewaters. Post-print / Final draft

This study evaluates the usability of a novel two-stage tertiary nanofiltration process concept for further purification of membrane bioreactor (MBR) permeate from municipal wastewater treatment and minimization of nanofiltration concentrate volume. In addition to water purification, the studied process aims to recover phosphorus from the second stage. The process concept for tertiary wastewater treatment includes two nanofiltration modules in series, where first stage is a nanofiltration of MBR permeate with a spiral-wound element and in the second stage a minimization of the NF concentrate is done by shear-enhanced nanofiltration combined with spontaneous precipitation and removal of precipitates from the concentration process. A volume reduction factor (VRF) of 300 was achieved with the studied process concept. The average permeabilities of the NF270 membranes used in both stages were 4.3 L/(m2 hbar) (first stage, spiral wound module) and 8.9 L/(m2 hbar) (second stage, high shear rate module). The two-stage NF process efficiently decreased the chemical oxygen demand (COD) and total organic carbon (TOC) content of the treated water, giving retentions higher than 99% for COD and 97% for TOC. About 52% of phosphorus was spontaneously precipitated as calcium phosphate (presumably as hydroxyapatite, purity 80%) at the second stage of the process. High turbulence (rotor tip speed 13.7 m/s) at the membrane surface during the second stage tertiary filtration prevented the formation of inorganic scale and membrane fouling. Precipitation occurred in the settling tank after the filtration when the turbulent flow conditions subsided. This enabled the continuation of the filtration to a high VRF value of 300 despite the significant calcium and phosphorus concentrations. The results presented here confirm that shear-enhanced nanofiltration is a promising approach for efficient minimization of the NF concentrate volume, as well as for simultaneous phosphorus recovery without the need for precipitation chemicals.

Nanofiltration is studied to separate glucose from dilute ionic liquid [emim][OAc]–water solutions. The aim of the research is to evaluate the effect of filtration pressure, temperature and ionic liquid (IL) concentration on the separation of ionic liquid and glucose. This kind of separation challenge can be formed in the regeneration of cellulose fibres in a wet spinning bath. The separation tests are done with an NF270 nanofiltration membrane. The tolerance of the NF membrane in ionic liquid is also estimated. Effective osmotic pressures and viscosity were found to have a major role in the permeability of the membrane when filtration was done at dilute IL solutions. Temperature was found to have a significant effect on the flux due to reduced viscosity at higher temperatures. The flux was increased by about 50% when the temperature increased from 20 °C to 40 °C. The best possible separation factor values were achieved when the feed solution contained 1 wt% [emim][OAc] at 20 °C temperature and the filtration pressure was 6 bars. On the basis of the IL concentration and temperature test series, a good separation window for this kind of solution would be at permeate flux values from 50 L m−2 h−1 to 100 L m−2 h−1. After a test series in concentrations of IL from 0.5 wt% to 10 wt%, the pure water permeability (PWP) was reduced by 23% from the original. The decline of PWP during the temperature tests series was 33%.

This study aimed to increase the knowledge on the influence of alkaline cleaning on performance of polyamide based nanofiltration membranes. In the experiments the Desal-5 DL, XN45 and NF270 membranes were exposed to alkaline conditions at temperatures of 40, 50, 60 and 70 °C and the influence of the extended alkaline exposure to the membrane permeability, glucose and MgSO 4 retention was measured. The characteristic features of the experimental kinetic data for permeability were a rapid increase in permeability after a short time exposure and a subsequent steady increase when the exposing time was continued while the characteristic features for the retention data were a rapid decrease in retentions of glucose and MgSO 4 after a short time exposure and a subsequent steady decrease when the exposing time was continued. The model developed in this study described well the both rapid and slow changes and it can be used to predict the performance of the tested membranes at the temperature range between 40 and 60 °C. The increase in exposure temperature accelerated the changes in membrane performance. The alkali induced changes caused at the 70 °C exposure could not be described with the simple rate law. However, only minor changes in chemical structure of the membranes were noticed in IR spectra after the exposure to alkaline conditions at 70 °C. This indicates that changes observed in permeability and retention could mainly be linked to conformational changes occurring in the polymeric matrix of the membrane skin layers. It was also shown that after a relatively long recovery time (144.5 h) the alkali induced changes in membrane performances were at least partly recovered.

Recovery of hemicelluloses from wood extracts often requires membranes with molecular weight cutoffs (MWCO) below 5 kDa, but higher than 2 kDa. Both the availability of commercial membranes within that MWCO range and their performance in wood extract filtrations is limited. In this study polyelectrolyte multilayers (PEM) were deposited on a polyethersulfone (PES) membrane substrate to obtain ultrafiltration membranes within the desired MWCO range. PEM coated ultrafiltration membranes were prepared by depositing poly(diallyldimethylammonium chloride)/poly(sodium 4-styrenesulfonate) (PDADMAC/PSS) or poly(diallyldimethylammonium chloride)/poly(acrylic acid) (PDADMAC/PAA) multilayers on the PES membrane via dip-coating. The PEM coated membranes were compared to two commercial ultrafiltration membranes. The membranes were characterized via pure water permeability (PWP) measurements, polyethylene glycol (PEG) model compound rejections to obtain a molecular weight cutoff (MWCO), Fourier transform infrared spectroscopy and electrokinetic surface potential measurements. The membranes were also characterized via the filtration of a birch wood extract. The PEM coated ultrafiltration membranes had significantly higher PWPs than a commercial membrane with a similar MWCO. The MWCO of the PEM coated membranes was successfully tuned to obtain advantageous ultrafiltration properties correlating to a narrower pore size distribution. The PEM coated membranes also exhibited improved performance during the wood extract filtration, but had comparably higher PWP reductions after the filtration experiment than the commercial ultrafiltration membranes due to increased electrostatic interaction between foulants and the membrane surface.

In this study vanillin was tested as the hydrophilicity promoter in a PES membranes to improve the feasibility of the membranes in the treatment of a biorefinery stream, namely a pressurized hot water extract (PHWE). The commercial PES membranes are typically prepared by phase inversion technique and thus, phase inversion is also used in this study. The ultimate structure of the phase inversion prepared membranes is asymmetric and it can be affected by various key parameters such as the temperature and the concentration of the PES solution, the solvent and additives which are used in PES solution, the coagulation bath temperature as well as the thickness of the cast PES film. In the present study, the effect of vanillin (0–6 wt.%) as a hydrophilic promoter agent, water as strong non-solvent additive in dope solution (0–2 wt.%) and coagulation bath temperature (CBT) on the formation of PES membranes was investigated in order to improve the understanding on the manufacturing of PES/vanillin membranes. The mentioned fabrication parameters were optimized and their effects on the membrane morphology, hydrophilicity, thickness, PHWE permeability, fouling and rejection properties were sequentially analyzed. It can be concluded that a small quantity of vanillin and water together in dope solution can preferably change the membrane morphology and increase the surface hydrophilicity and thus lead to formation of membrane with better wood extract permeability and antifouling characteristics. Post-print / Final draft

Membrane fouling, i.e. accumulation of unwanted material on the surface of the membrane is a significant problem in filtration processes since it commonly degrades membrane performance and increases operating costs. Therefore, the advantages of early stage monitoring and control of fouling are widely recognized. In this work, the potential of using Raman spectroscopy coupled to chemometrics in order to quantify degree of membrane fouling in real-time was investigated. The Raman data set collected from adsorption experiments with varying pHs and concentrations of model compound vanillin was used to develop a predictive model based on principal component analysis (PCA) for the quantification of the vanillin adsorbed on the membrane. The correspondence between the predicted concentrations based on the PCA model and actual measured concentrations of adsorbed vanillin was moderately good. The model developed was successful in monitoring both adsorption and desorption processes. Furthermore, the model was able to detect abnormally proceeding experiment based on differentiating PCA score and loading values. The results indicated that the presented approach of using Raman spectroscopy combined with a PCA model has potential for use in monitoring and control of fouling and cleaning in membrane processes.

Supported cellulose ultrafiltration membranes are cast from a cellulose-ionic liquid solution by the immersion precipitation technique. The effects of coagulation bath temperature and polymer concentration in the casting solution on the membrane morphology, wettability, pure water flux, molecular weight cut-off, and fouling resistance are studied. Scanning electron microscopy, contact angle measurements, atomic force microscopy, and filtration experiments are carried out in order to characterise the obtained ultrafiltration cellulose membranes. The results show the effect of coagulation bath temperature and polymer concentration on the surface morphology and properties of cellulose ultrafiltration membranes. Optimisation of the two parameters leads to the creation of dense membranes with good pure water fluxes and proven fouling resistance towards humic acid water solutions. Publishers version