Browsing by Author "Figoli, Alberto"

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Development of membrane bioreactor (MBR) process applying novel low fouling membranes
(2013-11-12) Deowan, Shamim Ahmed; Drioli, Enrico; Molinari, Raffaele; Figoli, Alberto; Hoinkis, Jan
Water is a part and parcel of human life. Water contaminated from industry and agriculture with heavy metal ions, pesticides, organic compounds, endocrine disruptive compounds, nutrients (phosphates, nitrates, nitrites) has to be effi-ciently treated to protect humans from being intoxicated with these compounds or with bacteria. Clean water as basis for health and good living conditions is too far out of reach for the majority of the population in the world (Bionexgen, 2013). Water recycling is now widely accepted as a sustainable option to re-spond to the general increase of the fresh water demand, water shortages and for environmental protection. Water recycling is commonly seen as one of the main options to provide remedy for water shortage caused by the increase of the water demand and draughts as well as a response to some economical and environmental drivers. The main options for wastewater recycling are industri-al, irrigation, aquifer recharge and urban reuse (Pidou, M., 2006). Among the industrial wastewaters, the textile industry is long regarded as a water intensive sector, due to its high demand of water for all parts of its pro-cedures. Accordingly, textile wastewater includes quite a large variety of con-tents, chemicals, additives and different kinds of dyestuffs. The main environ-mental concern with this waste water is about the quantity and quality of the water discharged and the chemical load it carries. To illustrate, for each ton of fabric products, 20 – 350 m3 of water are consumed, which differs from the color and procedure used. The quality of the textile wastewater depends much on the employed coloring matters, dyestuffs, accompanying chemicals, as well as the process itself (Brik et al., 2006). MBR technology is recognised as a promising technology to provide water with reliable quality for reuse. It provides safely reuse water for non-potable use. But the treated textile wastewater by MBR technology alone can’t comply with the reuse or discharge standard in many countries due to its colouring matters and dyestuffs remained in the effluent, if otherwise, MBR is associated with other technology like NF, RO, other processes or the applied membrane is modified or a novel MBR is applied. Fouling is another limiting factor for worldwide application of MBR technology especially in high-strength industri-al wastewater like textile wastewater. Moreover, membrane fouling is regarded as the most important bottleneck for further development of MBR technology. It is the main limitation for faster development of this process, particularly when it leads to flux losses that cleaning cannot restore (Howell et al. 2004). In this thesis work, a novel membrane bioreactor (MBR) process was devel-oped by modifying a applied commercial PES UF membrane in MBR module by nano-structured novel coating through polymerisable bicontinuous micro-emulsion (PBM) process with the purpose of having higher hydrophilicity and low fouling propensity. Before starting the MBR experiments, some characteri-sation tests such as SEM, AFM images analysis, roughness measurements, pore geometry, contact angel, standard salt rejections, model textile dye rejec-tions were performed. In addition, fouling tests using two laboratory cross flow testing units were conducted as well. To reach the ultimate goal of research, 6 sheets of novel coated membranes with size of 30 cm × 30 cm were prepared and these were used to prepare a three-envelope MBR module of 25 cm × 25 cm in size (total membrane area 0.33 m2) similar to that of a commercially available three-envelope PES UF MBR module. This novel MBR module was tested in a submerged lab-scale MBR pilot plant (tank volume ca. 60 L) for about 6 months using model textile dye wastewater (MTDW) as test media for all experiments with the aim of having uniform compositions with respect to time. The tests were done based on carefully selected operation conditions. Prior to testing of the novel membrane module MBR, experiments were carried out with a commercial PES UF MBR module using the same pilot plant set up and the same selected operating conditions for about 10 months. After comple-tion of trials with the novel coated MBR module, similar experiments were carried out again with a commercial PES UF MBR module to check the simi-larity of the biological sludge conditions and other operation conditions as well. In short, the sequences of the experiments were as follows: Commercial PES UF MBR (10 months) →novel membrane coated MBR (6 months)→PES UF MBR (1.5 months) The ultimate goal of the experiments was to compare the results between the commercial MBR and novel coated MBR module in order to demonstrate im-provement regarding fouling propensity and permeate water quality. The performance analysis shows that the novel coated MBR module compared to the commercial MBR module has 7% points higher COD removal efficien-cy, 20% points higher blue dye removal efficiency, high antifoul-ing/antimicrobial properties, resulting in a very low-fluctuating and highly ro-bust MBR process which looks promising with regard to economic viability. Since the newly developed MBR module worked excellent on laboratory scale it consequently should be deployed at an industrial site to be tested with real ii wastewater. Therefore, this novel three-envelope MBR module is on the way to be tested with real wastewater in a textile factory in Tunisia. The findings of these on-site pilot trials will serve as a basis for further improvement and even-tually pilot trails with larger membrane area will be addressed
Experimental investigation of system performance for combined desalination processes with membrane capacitive deionisation (MCDI)
(Università della Calabria, 2021-10-31) Cañas Kurz, Edgardo E.; Critelli, Salvatore; Gabriele, Bartolo; Figoli, Alberto; Hoinkis, Jan
The water supply in many coastal regions worldwide is affected by progressive salinization. Here, the use of desalination technologies is a viable solution for obtaining freshwater. In this thesis, two modular concepts for brackish water (BW) desalination by the use of membrane capacitive deionization (MCDI) and low-pressure reverse osmosis (LPRO) were developed and tested at laboratory and pilot-scales with two pilot plants installed in Vietnam. The two concepts were developed by using computer-based calculations (software: WAVE) and evaluated in a socioeconomic and environmental multi-criteria analysis. The first plant consisting of subsurface arsenic removal (SAR) as pre-treatment and MCDI for desalination was installed in Tra Vinh, in the Mekong Delta for the treatment of arseniccontaminated groundwater with a concentration of total dissolved solids (TDS) of 1.65 g/L. Results showed the feasibility of the modular concept for producing drinking water (TDS<0.45 g/L) with a specific energy consumption (SEC) of <3 kWh/m³. The relationship between feed salinity and specific ion removal of the MCDI was evaluated in real environment and compared with laboratory experiments. The use of renewable energies such as solar and wind for autonomous supply was proven feasible for these technologies. The second pilot plant was installed in a riverine estuary in the region of Cần Giờ, where no access to freshwater is available due to the progressive salinization of river water and groundwater. Here, river water showed TDS concentrations of up to 25 g/L. The combined system consisted of UF pre-treatment, LPRO and MCDI to produce drinking water and product water with TDS of <0.45 g/L and <1.5 g/L, respectively with a total SEC of 5.8 kWh/m³. Additionally, the performance of the LPRO was compared to seawater-RO (SWRO) in pilot trials, which showed a SEC of 5.5 kWh/m³. Although the SEC of single-stage SWRO was lower, the separate production of drinking and product water by LPRO+MCDI showed different advantages including a reduced SEC of 5.2 kWh/m³ for product water and additional 0.6 kWh/m³ for drinking water. Finally, an optimization of the LPRO+MCDI can be possible by increasing the desalination efficiency of the MCDI, increasing the efficiency of LPRO-pump and the MCDI power supply, and by aiming at feed water qualities with lower salinity.
Geochemical modelling of natural contaminants in groundwaters and their removal by membrane processes
(Università della Calabria, 2021-10-25) Fuoco, Ilaria; Critelli, Salvatore; Apollaro, Carmine; Marini, Luigi; Bartolo, Gabriele; Figoli, Alberto; De Rosa, Rosanna
The presence of harmful elements dissolved in groundwaters represents one of the main environmental issues of present times. The aim of my PhD Thesis was to study the rock-to-water release and the fate of some inorganic pollutants dissolved in the groundwaters of the Calabria Region, and sometimes in other Italian areas, as well as to select suitable membrane technologies for their removal based on the acquired geochemical knowledge. Taking into account the peculiar characteristics of the groundwaters of the Calabria Region, three elements were considered: arsenic (As), fluorine (F) and chromium (Cr). The salient results of my PhD studies are presented in this Thesis, which is organized in four self-consistent Chapters structured as follows. Chapter 1. Geochemical modelling of As and F release into the crystalline aquifers of the Calabria Region. This section has been devoted to understanding the water-rock interaction processes occurring in the crystalline aquifers of the Calabria Region. Three different reaction path modeling exercises of granite dissolution were performed, reconstructing the water-rock interaction processes which occur: (i) in shallow and relatively shallow crystalline aquifers in which no As and F anomalies were observed; (ii) in As-rich areas, coupling the reaction path modeling of granite dissolution with the simulation of the adsorption of dissolved As onto precipitating crystalline and amorphous hydrous ferric oxide (HFO); (iii) in deep crystalline aquifers where high F concentrations were detected. A total of 160 water samples discharging from the crystalline aquifers of the Calabria region were used to fix the boundary conditions as well as to validate the outcomes of geochemical modeling. The results of the three geochemical modeling exercises of granite dissolution are in agreement with the analytical data and, therefore, it is reasonable to assume that they reproduce satisfactorily the water-rock interaction processes occurring during the travel of meteoric waters from shallow to deep crystalline aquifers, hosted both in granite rocks without mineralizations and in mineralized granites. Moreover, based on the results of the geochemical survey, some As- and F- rich groundwaters were selected and used as feeds for the treatment tests. Some relevant results have been already published by Fuoco et al. (2021a). Chapter 2. Geochemical modelling of Cr(VI) release into the ophiolite aquifers of Italy. This section has been focused on the water-rock interaction processes occurring in the main ophiolite aquifers of Italy. The obtained results were already published by Apollaro et al. (2019a). Reaction path modelling of serpentinite dissolution was performed varying the Fe2O3/(FeO +Fe2O3) weight ratio of serpentine and reproducing the analytical concentrations of relevant solutes, including Cr(VI), in the Mg-HCO3 groundwaters hosted in the ophiolite aquifers of Italy. The occurrence of geogenic Cr(VI) in these groundwaters appears to be potentially controlled by the oxidation of trivalent Cr to the hexavalent redox state, driven by the reduction of trivalent Fe to the divalent redox state. In fact, trivalent Fe is the only oxidant present in suitable amounts in serpentinite rocks, and even serpentine contains high contents of trivalent Fe as proven by recent studies. In contrast, the generally accepted hypothesis that geogenic Cr(VI) in waters interacting with serpentinites is driven by the 2 reduction of trivalent and tetravalent Mn is questionable. To validate the outcomes of the geochemical modeling of serpentinite dissolution and rock-to-water release of Cr(VI), the redox state of Fe in serpentine minerals of different Italian areas was measured (see next section). Moreover, the water sample characterized by the highest concentration of Cr(VI) was selected for the treatment tests. Chapter 3. Determination of the iron redox state in serpentine minerals by using TEMEELS analysis and its environmental implications. This section has been addressed to determine the Fe3+/FeT ratio of the serpentine minerals hosted in five serpentinite samples coming from the main ophiolite areas of Italy, in order to validate the results of the geochemical modeling of serpentinite dissolution and rock-to-water release of hexavalent chromium (see previous section). The electron energy-loss spectroscopy (EELS) combined with transmission electron microscopy (TEM) was selected as most suitable analytical technique because it provides the highest spatial and energy resolution allowing to obtain a good qualitative and quantitative information on iron redox speciation compared to other analytical techniques. Ten site-specific TEM foils were prepared and analyzed in the laboratories of the GFZ German Research Centre for Geosciences, in Potsdam. It has not been the simple application of a well-established analytical technique, but rather a challenging study, because it has been necessary to develop a new spectra processing method and prove its validity. The performed analyses provided in-depth knowledge on nanoscale structures of the studied samples and showed that Fe3+ represents from 75 to 85 % (median values) of total iron. The obtained results provide further support to the hypothesis concerning the oxidation Cr(III) to Cr(VI) driven by the concurrent reduction of Fe(III) to Fe(II), as suggested by geochemical modeling (see previous section). Chapter 4. Application of membrane processes to remove As, F and Cr(VI) from contaminated groundwaters. This section has been devoted to the removal of As, F and Cr from polluted groundwaters by means of membrane processes. Relevant results have been already published by Figoli et al. (2020), Fuoco et al. (2020) and Fuoco et al. (2021b). The geochemical approach was used as strong-scientific tool for pre-selection of suitable remediation systems and the contaminated groundwaters were chosen from the previous data collections. Several type of commercial nanofiltration/reverse osmosis membranes, not already tested in the pertinent literature, were selected depending on the type of application. Their efficiency was evaluated in terms of arsenic, fluoride and chromium rejection, water production and feed composition. The other main ions that contribute to water chemistry were also taken into account to evaluate the possible intended use of the considered waters after the treatments. Satisfactory results were obtained for each specific case of contamination. Moreover, an innovative membrane with absorbent capacities against As(III) and As (V) species was developed and the preliminary results are quite promising. Summing up, the findings obtained in this work are useful for the understanding of the rock-to-water release of the chemical elements of interest and their fate in natural waters. Moreover, the treatment of natural As, F, and Cr-contaminated groundwaters improved the knowledge and the data availability for future scientific and application developments in similar geological settings worldwide.
Innovative fluorinated membranes for water and organic solvent treatment application
(2017-09-19) Ursino, Claudia; Carbone, Vincenzo; Gabriele, Bartolo; Figoli, Alberto
The aim of this thesis was to study the use of different types of fluoropolymer in order to prepare membranes for chemical and pharmaceutical applications. In fact, the potential use of fluoropolymeric membranes respect to other materials, at industrial levels, has several advantages such as high mechanical strength, high efficiency and stability. However, the unique properties of these materials such as excellent chemical and thermal strength make them extremely versatile but at the same time very difficult to process. As example, Ethylene-Chlorotrifluoroethylene (ECTFE) is insoluble in common organic solvents, and it can only be processed at high temperature, depending on the solvent used. In this work, three types of fluoropolymers have been studied, such as low-melting ECTFE (Halar®LMP-ECTFE), poly(vinylidene fluoride) (PVDF grade 1015) and perfluoropolyether (PFPEs) (Fluorolink®AD1700 and Fluorolink®MD700). Moreover, low-toxic solvents for humans and the environment have been appropriately selected and used for first time for solubilising the fluoropolymers of interest. -The Halar®LMP-ECTFE polymer was studied and characterized in terms of solubility parameters, compared with the standard Halar® ECTFE 901 polymer. In fact, this new grade of Halar® shows comparable properties with standard Halar® (hydrophobicity and mechanical properties), but lower crystallinity and lower melting point. Porous membranes and dense film were produced by thermally induced phase separation (TIPs). Two solvents, Diethyl Adipate (DEA) and Dibutyl Itaconate (DBI), never tested before, were selected. The chemical stability of the dense film was evaluated over time (192h) by swelling tests with aggressive organic solvents. Porous Halar®LMP-ECTFE membranes have been tested for organic solvents ultra- (UF) and nano-filtration (NF), such as methanol, ethanol and dimethylformamide. The results show that Halar®LMP ECTFE membranes are promising candidates to be used in separation processes under harsh conditions, such as chemicals production, purification and processing of food, nutraceuticals products and solvents recycling. - The influence of three different solvents in the membrane formation, using PVDF 1015 as polymer, was studied. Plasticizers from to Citroflex family, such as acetyl tributylcitrate (ATBC), acetyl triethylcitrate (ATEC) and triethylcitrate (TEC) have been selected and used. In particular ATEC and TEC as solvents, were used for the first time. Membranes were produced by thermally induced phase separation (TIPs) technique. The flat sheet membranes produced have been tested in microfiltration process (MF). These membranes can be used in several industrial applications such as sterilisation and clarification of pharmaceuticals or applied to separate contaminants from the water. - Perfluoropolyethers (PFPE) (Fluorolink®AD100 and Fluorolink®MD700) studied are new types of PFPE, UV cross-linkable. These PFPE photo-reticulated, have been used for coating commercial hydrophilic membrane, such as polyamide (PA) and polyethersulfone (PES) membranes. The aim of this work was to produce hydrophilic/hydrophobic coated membranes, keeping the morphology of the started membrane, unchanged. The study focused on morphological analysis, and on the influence of coating on the support membrane. The membranes produced, hydrophilic/hydrophobic, were characterized and the coating resistance was evaluated over time by direct contact with several chemical agents. The membranes were then tested, in membrane distillation process for direct contact (DCMD), using both deionized water and 0.6M saline. The results show that these coated membranes can be applied to desalination of seawater and wastewater treatment.
Innovative UV-LED polymerised bicontinuous microemulsion coating for membranes with special emphasis on MBRs
(2017-07-11) Schmidt, Slefan-André; Pantano, Pietro; Curcio, Efrem; Gabriele, Bartolo; Figoli, Alberto
The main objective of this work is the preparation of polymerisable bicontinuous microemulsion (PBM) coatings applied onto commercial membranes for improving the anti-fouling properties and performance, in terms of water flux and foulants rejection. Microstructured and nanostructured materials obtained by PBM have been widely investigated in the course of the last 30 years. The interest in microemulsion lies mainly in the possibility of dissolving larger amounts of oil and water by using polymerisable and non-polymerisable surfactants. By polymerising the bicontinuous microemulsion it is possible to produce transparent porous polymeric solids [Gan et al. (1995), Gan and Chew (1997)]. This thesis represents the follow-up of the work done by Galiano et al. (2015) and Deowan et al. (2016). Galiano et al. (2015) developed the PBM composition that based on a non-polymerisable surfactant (DTAB) and another polymerisable surfactant (AUTEAB). In their work the PBM was polymerised by redox initiators leading to a process that is very difficult to up-scale for a commercial application. Critical issues were, the polymerisation time (at least 20 minutes), and the reproducibility of the coating. Therefore, it is the aim of this work to develop another polymerisation technique that increases the polymerisation speed and allows the easy reproduction of membranes with defined properties. The polymerisation by photoinitiators excited by UV-light represents a promising possibility for this requirement as it has the potential of decreasing the polymerisation time down to a few seconds. Several photoinitiators were selected for their compatibility with the PBM, and studied for their conversion rate efficiency (section 5.1.5). As there is a wide range of potential UV-light sources available, several technologies are studied for their coating performance (section 5.1.3). Subsequent to that, experiments were done in order to define the ideal photoinitiator type and concentration while polymerising onto glass plates. The coating onto commercial membranes is studied deeply for e.g. different casting knife thickness or ambient temperature (section 5.2.2 As the polymerisation under inert conditions is expected to increase the polymerisation speed, experiments are done, both under inert and non-inert conditions. The final membrane, coated under the optimum conditions, is further characterised for their permeability under different conditions like transmembrane pressure (TMP), model foulant experiments and a fixed volume flow (section 5.2.3). Further characterisation is done by contact angle, SEM, AFM (section 5.2.5 to 5.2.7). The prepared PBM membranes are foreseen to be finally applied for model textile dye wastewater treatment by Membrane BioReactor (MBR) technology. According to the previous results of Deowan et al. (2016) higher permeate quality through increased COD, TOC, dyestuffs removal efficiency and stronger anti-fouling properties are expected. Consequently, lower operation/maintenance costs due to reduced necessary aeration for scouring purposes and reduced membrane cleaning cycles as well as less membrane replacement are of special interest for commercial applications. In the previous work of Deowan et al. (2016) a lab scaled MBR with a single membrane housing was used. As of the biocenosis of the bacteria inside the reactor tank, a comparison of the membrane performance of the PBM and commercial membrane is difficult to achieve. Therefore an existing MBR system was redesigned to allow the simultaneous run of a commercial and a PBM coated membrane (section 4.1). As the revamp requires also additional sensors, the data acquisition needs to be adapted as well. To assure the proper function of the MBR the system was running for long term with two commercial membranes using a model textile wastewater (see 5.3.2). Finally the PBM coated membrane was compared with a commercial one for their performance in the MBR. Initial experiments for the water permeability are done as preparation for future work (see 5.3.3).
Preparation and characterisation of polymerisable bicontinuous microemulsion membranes for water treatment application
(2013-12-02) Galliano, Francesco; Bartolino, Roberto; Gabriele, Bartalo; Figoli, Alberto; Veltri, Lucia
Climate changes, population growth and urbanization are some of the causes of water shortage in many countries of the world. Water is essential to the life of all living organisms and its preservation and responsible use are some of the challenges that humanity will face in the near future. In particular, the possibility of treating and re-using municipal and industrial wastewaters can represent an important solution to water scarcity. Technological breakthroughs have led to the development of a number of technologies that can be efficiently applied in wastewater treatment. Among them, membrane applications are receiving an increasing attention thanks to their versatility, low environmental impact, easy scale-up and high product quality. Aim of this thesis was to produce polymeric membranes obtained through the polymerisation of a polymerisable bicontinuous microemulsion (PBM). Bicontinuous microemulsions consist of an interconnected network of oil and water channels stabilised by a surfactant. Oil channels can be polymerised, forming the membrane matrix, while water channels remain unaffected, forming the pores. In the present work, for the first time PBM membranes were applied, by polymerisation, as coating material for commercial polyether sulfone (PES) membranes. In the first part of the work, the polymerisable surfactant acryloyloxy undecyltriethylammonium bromide (AUTEAB) was synthesised and used for microemulsion formulation. The possibility of using a non-polymerisable surfactant such as dodecyltrimethylammonium bromide (DTAB) was also evaluated. In the second part of the work, novel membranes prepared by microemulsion polymerisation were characterised in order to select the proper membrane with suitable characteristics and properties. Characterization tests carried out on PBM membranes showed the great potential that these membranes could have on wastewater treatment in membrane bioreactor (MBR) applications. In particular, the very smooth surface, the relatively high hydrophilicity and the channel-like structure (typical of the bicontinuous microemulsion) make PBM membranes less prone and highly resistant to fouling. This aspect is the key point if we consider that fouling is one the major drawbacks affecting almost all membrane processes. Fouling is mainly due to the deposition of organic and/or inorganic matter on the surface of the membrane, causing therefore a decline in membrane performance, an increase in energy consumption and (in severe cases) damage of the membrane structure. Furthermore, PBM membranes, due to the presence of a cationic surfactant, present an interesting antimicrobial activity. The possibility of having membranes with antimicrobial properties prevents the phenomenon of biofouling caused by the adhesion and the accumulation of microorganisms at membrane surface. PBM coated membranes were, then, successfully applied to the MBR process for the treatment of wastewater from textile dying. PBM coated membranes, when compared with commercial PES membranes, showed superior results for a long time (6 months) in terms of permeability and dye rejection. Moreover, less cleaning efforts were required leading to lower costs. Novel PBM coated membranes developed can be, thus, also applied to other membrane processes for wastewater treatment.
Theoretical Models for Membrane Capacitive Deionization for the design of Modular Desalination Processes
(Università della Calabria, 2021-12-08) Hellriegel, Ulrich; Critelli, Salvatore; Gabriele, Bartolo; Figoli, Alberto; Hoinkis, Jan
Due to climate change, water scarcity will be exacerbated around the globe. To increase the water availability in regions at risk, water desalination plants can be a solution. Especially in rural areas, energy e cient technologies are needed so that an operation with renewable energy as photovoltaic modules can be feasible. Recent publications showed that the novel technology membrane capacitive deionization (MCDI) can achieve a lower speci c energy consumption (SEC) than reverse osmosis (RO), for brackish water desalination with salt concentrations below 2.5 g L-1. There is still a gap in research between laboratory operation and applied commercial scaled desalination, regarding experimental but also theoretical model studies. Therefore the latter is elaborated in the present PhD thesis. Hereby, existing models are reviewed, adapted and further developed to t to applied MCDI operation for drinking water production. Two dimensional nite element methods (FEM) modelling of ion transport, according to the Gouy-Chapman-Stern theory for electrical double layers (EDL) as well as computational uid dynamics (CFD) is combined with an adjusted semi-analytical modi ed Donnan (mD) model, with a constant excess chemical potential att = 2:33 kT, for the electrosorption of ions into porous active carbon electrodes. It predicts the e uent salt concentration time-dependently for di erent inputs of applied electrical currents Icell and voltages as well as inlet concentrations and volume ows. Applied MCDI operation was optimized for drinking water production with practical experiments, which support the evaluation of the theoretical ndings. The model ts to experimental data for Icell = 20 A, however the equations for the voltage over the electrodes need to be re-assessed so that the model ts for further input parameters. A CFD model of the water ow through large scaled MCDI modules (> 50 pairs of electodes) shows the need of constructing spacer thicknesses Sp small enough, to ensure equal retention times of the water between the electrodes in the module, which is important for stable diluate concentrations. Furthermore, an analytical calculation tool is developed, by adjusting the mD model and introducing an e ective salt adsorption capacity 􀀀salt; , to predict the maximum e cient charging time tmax,ch, removal- and recovery rate as well as SEC values for optimized operation of applied MCDI processes. The model reaches an accuracy of 87% for the prediction of salt removal, 86% for tmax,ch and 75% for SEC values, compared with an experimental study and thus can be used to optimize the process design of applied MCDI desalination plants.