Guaya, D.; Valderrama, C.; Farran, A.; Sauras, T.; Cortina, J. Science of the total environment Vol. 612, p. 728-738 DOI: 10.1016/j.scitotenv.2017.08.248 Data de publicació: 2018-01-15 Article en revista
The removal of nutrients (nitrogen (N), phosphorous (P)) from waste water has become a resource recovery option in recent regulations worldwide, as observed in the European Union. Although both of these nutrients could be recovered from the sludge line, > 70–75% of the N and P is discharged into the water line. Efforts to improve the nutrient recovery ratios have focused on developing low-cost technologies that use sorption processes. In this study, a natural zeolite (clinoptilolite type) in its potassium (K) form was impregnated with hydrated metal oxides and used to prepare natural hybrid reactive sorbents (HRS) for the simultaneous recovery of ammonium (NH4 +) and phosphate (PO4 3 -) from treated urban waste water. Three unfertile soils (e.g., one acidic and two basic) amended with N-P-K charged HRS were leached with deionized water (e.g. to simulate infiltration in the field) at two- and three-day time intervals over 15 different leaching cycles (equivalent to 15 bed volumes). The N-P-K leaching profiles for the three charged hybrid sorbents exhibited continuous nutrient release, with their values dependent on the composition of minerals in the soils. In the basic soil that is rich in illite and calcite, the release of potassium (K+) and ammonium (NH4 +) is favoured by-ion exchange with calcium (Ca2 +) and accordingly diminishes the release of phosphate (PO4 3 -) due to its limited solubility in saturated calcite solutions (pH 8 to 9). The opposite is true for sandy soils that are rich in albite (both acidic and basic), whereas the release of NH4 + and K+ was limited and the values of both ions measured in the leaching solutions were below 1 mg/L. Their leaching solutions were poor in Ca2 +, and the release of PO4 3 - was higher (up to 12 mg P-PO4 3 -/L). The nutrient releases necessary for plant growth were provided continuously and were controlled primarily by the soil mineral dissolution rates fixing the soil aqueous solution composition (e.g. pH and ionic composition; in particular, the presence of calcite is a determinant for nutrient release, especially in alkaline soils). The N-P-K charged HRS sorbents that were used for soil amendment may be an alternative for avoiding nutrient leaching and reaching the goals of soil sustainability in agriculture and reducing the nutrient overloading of surface waters.
Phosphorus (P) is a vital macronutrient required to improve the agricultural yields but its excessive use as a fertilizer has resulted in pollution of water bodies leading to eutrophication. With no reserves of phosphorus source in Spain, increased dependence on phosphorus in agriculture have not only increased dependence on imports but also has raised concerns on its future availability as a resource. A Phosphorous Flow Analysis (PFA) was conducted for Spain for the year 2012 focusing on the food production and consumption systems. The results obtained were finally compared with PFA at both country level and continent level (EU-27). To quantify food and non-food flows systems, country specific data were considered. The sectors covered were crop production (CP), animal production (AP), food processing (FP), non-food production (NF) and consumption (HC). The findings reveal that a total of 325 kt P was imported by Spain in 2012; 66% of which was accumulated in markets stock of food and feed, fertilizers and non-food (91 kt P) while 33% was lost to the environment through land-fill, losses to water bodies, land accumulation and incineration. The largest proportion of losses is associated with water bodies (44.7 kt P) followed by agriculture and land accumulation (42.1 kt P). Wastewater treatment plants (WWTPs) received around 79.5 kt P within wastewater, with 60% being removed in sewage sludge. The 31.7 kt P discharged within final effluent represented the 71% of the total losses to water bodies. Around 69% of the sewage sludge was recycled to agriculture and 27% was sent directly to landfill including the ashes from incineration. Net accumulation was 1.84 kg P/cap which was similar to values reported for the EU-27 average (2.5 kg P/cap).
Reig, M.; Vecino, X.; Valderrama, C.; Gibert, O.; Cortina, J. Separation and purification technology Vol. 195, p. 404-412 DOI: 10.1016/j.seppur.2017.12.040 Data de publicació: 2017-12-19 Article en revista
In this work, selectrodialysis (SED) was used to separate arsenic (As(V)) from copper (Cu(II)) and (Zn(II)) of acidic metallurgical process streams by integrating non-selective and selective membranes. The separation process is determined by the chemical speciation of the involved elements. In this case, As(V) is mainly present as anionic species (H2AsO4-), while Cu(II) and Zn(II) are mainly present as cationic species although partially complexed as neutral complexes (CuSO4 and ZnSO4). A lab set-up was used to conduct the experimental tests with different type of standard and mono-selective ion-exchange membranes. The results obtained showed that by SED configuration it was possible to recover around 80±0.2 % of Cu(II), 87±0.2 % of Zn(II) and 95±0.3 % of As(V) from the feed solution to the rich-product streams with an energy consumption of 2.6±0.2 kWh/kg CuSO4+ZnSO4. Furthermore, a Cu/Zn-rich stream with a purity of both divalent cations of 99.8 % (0.02 % of As(V)) was achieved by means of SED. Overall, the results herein gathered suggest that SED is an efficient separation technology for Cu(II) and Zn(II) recovery from mining and metallurgical acidic streams.
Nitrogen recovery and valorization is gaining interest due to the current need for nitrogen removal, so it is of great interest that ammonium-selective sorbents be evaluated. In this study, a zeolitic material synthesized from coal fly ash (Ze–Na) in sodium form as well as its modification to potassium form (Ze–K) were evaluated as sorbent materials for the recovery of ammonium from wastewater effluents. The sorption performance was assessed through three consecutive sorption-desorption cycles reporting opposite behavior in terms of ammonium sorption capacity. Decreasing in the case of Ze–Na and to slightly increase for Ze–K due to alkaline activation of zeolite surface. The maximum sorption capacities obtained were 109 ± 4 mg NH4/g and 33 ± 1 mg NH4/g for Ze–Na and Ze–K, respectively. It is important to point out that in the case of Ze–Na, the maximum sorbent capacity was obtained during the first sorption cycle whereas in the case of Ze–K, it was obtained during the last working cycle due to the alkaline regeneration. Kinetic studies showed that after every regeneration step, the sorption kinetics turn faster as alkaline desorption increased the zeolite-specific surface, thus increasing the size of porous and enhancing the diffusion through the particle. Results obtained indicate that sorption capacity decreased significantly after every working cycle using Ze–Na whereas Ze–K followed the opposite behavior despite its initial lower sorption capacity.
Nowadays, chemical industries produce high amounts of concentrated effluents and/or aqueous solutions rich in heavy metals or rare-earth elements. Then, industries wanted to reduce the concentration of these streams or valorize these elements. For this reason, in this work we propose the use of a new electrodialysis-based technology, named selectrodialysis (SED), in order to reduce the effluent concentration, separate monovalent from divalent ions, and at the same time concentrate them in order to be reused in the same industry. By means of SED it could be possible to valorize heavy metals, such as zinc or arsenic, from an industrial acid effluent. The main objective of this work is to separate zinc and arsenic in two different streams and also obtain an almost desalinated feed stream. Several experiments were carried out in a lab-scale set-up (ED 64-4 from PCCell, Germany) by means of monovalent selective cationic (MCV) and standard ion-exchange membrane (IXM) from two different companies: PCCell and Fujifilm, which they have different synthesis processes and physical-chemical properties. Two membrane configurations were used: one using MVC and standards Fujifilm membrane, and the second one mixing MCV membrane from Fujifilm with standards IXM from PCCell. Experiments were conducted using synthetic acid sulfuric solution containing ZnSO 4 and HNa 2 AsO 4 salts. Four main streams were differentiated in the SED experiments: electrode rinse, feed solution (which will be desalinated), Zn-rich stream (the Zn concentration would increase over time) and As-rich stream (the As concentration would increase over time). For all the experiments, a total desalination of the acid feed stream, containing ZnSO 4 and HNa 2 AsO 4, was achieved; while As and Zn were separated and concentrated in the corresponding streams. Best concentration factors (> 500) for Zn were obtained with the first membrane configuration (Fujifilm membranes) in comparison with the values reached (< 400) through the combination of MVC Fujifilm membranes and standard PCCell ones. Additionally, almost the same energy consumption values were obtained for each membrane combination, although lower values were achieves for the Fujifilm combination around 6.4 kWh/kg ZnSO 4, whereas 8.2 kWh/kg ZnSO 4 was calculated for the PCCell-Fujifilm combination. Besides, the Fujifilm membranes configuration obtained a higher faradic yield, so it could be concluded that this is the more appropriate membrane combination for the Zn/As separation
Viader, G.; Casal, O.; Licon, E.; Lefevre, B.; de Arespacochaga, N.; Echevarria, C.; Valderrama, C.; Cortina, J. International Congress on Membranes and Membrane Processes p. 1 Data de presentació: 2017-07-29 Presentació treball a congrés
Lopez, J.; Reig, M.; Vecino, X.; Valderrama, C.; Gibert, O.; Yaroshchuk, A.; Cortina, J. International Congress on Membranes and Membrane Processes Data de presentació: 2017-07-29 Presentació treball a congrés
Hermassi, M.; Valderrama, C.; Gibert, O.; Moreno Palmerola, Natàlia; Querol , X.; Harrouch, N.; Cortina, J. Science of the total environment Vol. 599-600, p. 422-430 DOI: 10.1016/j.scitotenv.2017.04.140 Data de publicació: 2017-05-05 Article en revista
Here, an alternative nutrient (N-P-K) recovery route from potassium-rich sludge anaerobic digestion side-streams using powder reactive sorbents (PRSs) is presented. In the first step, the optimum PRS system was determined in batch experiments with mixtures of: a) a sodium zeolite (NaP1) to facilitate the NH4+ and K+ sorption; b) a Ca-zeolite (CaP1) to facilitate the removal of P by formation of Ca-phosphates (e.g., CaHPO4(s)), and c) caustic magnesia containing mixtures of MgO to facilitate the formation of Mg/NH4/PO4 minerals (e.g., struvite and magnesium phosphates). Evaluation of the continuous and simultaneous N-P-K removal with mixtures of PRSs was carried out using a hybrid sorption/filtration system with ultrafiltration (UF) hollow-fibre membranes. The dosing ratios of the PRS mixtures were optimised on the basis of the equilibrium and kinetic sorption data, and a PRS dose (< 2–5 g PRS/L) was selected to ensure the hydraulic performance of the system. Under such conditions, and with synthetic anaerobic side-stream removal capacities (qt) of 220 ± 10 mg N-NH4/g, 35 ± 5 mg P-PO4/g, and 8 ± 2 mg K/g, removal efficiencies of 32 ± 3, 78 ± 5, and 26 ± 3% for ammonium, phosphate, and potassium, respectively, were obtained for the binary mixtures of NaP1/CaP1 zeolites. Contrary to the batch results, the use of tertiary mixtures of NaP1/CaP1/MgO only improved the K removal capacity and efficiency to 18 ± 2 mg K/g and 55 ± 4%, respectively, while the phosphate removal capacity and efficiency remained unchanged (ca. 35 ± 3 mg P-PO4/g; 80 ± 5%) and the ammonium capacity and efficiency were reduced to 185 ± 12 mg N-NH4/g and 20 ± 2%, respectively, due to the competing Mg2 + ion effect. Nutrient removal trials with real anaerobic side-streams using binary mixtures of Na/Ca zeolites showed a reduction of both the hydraulic performance and the nutrient removal ratios due to the presence of dissolved organic matter. However, constant removal ratios of N, P, and K were recorded throughout the filtration experiments. The loaded PRSs exhibited suitable nutrient release rates and bioavailability as co-substrates for soil quality improvement. Chemical analyses detected the formation of Ca/P/O and Mg/N/P/O neo-minerals; however, the mineralogical data revealed only the formation of struvite, even when no magnesium oxide was used.
Sancho, I.; Licon , E.; Valderrama, C.; de Arespacochaga, N.; Lopez-Palau, S.; Cortina, J. Science of the total environment Vol. 584-585, p. 244-251 DOI: 10.1016/j.scitotenv.2017.01.123 Data de publicació: 2017-04-15 Article en revista
The integration of up-concentration processes to increase the efficiency of primary sedimentation, as a solution to achieve energy neutral wastewater treatment plants, requires further post-treatment due to the missing ammonium removal stage. This study evaluated the use of zeolites as a post-treatment step, an alternative to the biological removal process. A natural granular clinoptilolite zeolite was evaluated as a sorbent media to remove low levels (up to 100 mg-N/L) of ammonium from treated wastewater using batch and fixed bed columns. After being activated to the Na-form (Z-Na), the granular zeolite shown an ammonium exchange capacity of 29 ± 0.8 mg N-NH4+/g in single ammonium solutions and 23 ± 0.8 mg N-NH4+/g in treated wastewater simulating up-concentration effluent at pH = 8. The equilibrium removal data were well described by the Langmuir isotherm. The ammonium adsorption into zeolites is a very fast process when compared with polymeric materials (zeolite particle diffusion coefficient around 3 × 10- 12 m2/s). Column experiments with solutions containing 100 mg N-NH4+/L provide effective sorption and elution rates with concentration factors between 20 and 30 in consecutive operation cycles. The loaded zeolite was regenerated using 2 g NaOH/L solution and the rich ammonium/ammonia concentrates 2–3 g/L in NaOH were used in a liquid-liquid membrane contactor system in a closed-loop configuration with nitric and phosphoric acid as stripping solutions. The ammonia recovery ratio exceeded 98%. Ammonia nitrate and di-ammonium phosphate concentrated solutions reached up to 2–5% wt. of N.
A natural clinoptilolite zeolite (Z-N) and its hybrid form (Z-Mn) prepared by impregnation with hydrated manganese oxide have been evaluated for the simultaneous removal of ammonium and phosphate. The ammonium sorption capacity reported by Z-Mn was 23 ± 2 mg N-NH4+/g; while the phosphate uptake reached 5.6 ± 0.2 mg P-PO43-/g at pH 7.5. Both ammonium and phosphate uptake were slightly influenced coexisting ions commonly found in treated wastewater effluents. The Mn(II) activated zeolite (Z-Mn) improved the phosphate uptake capacity, in the pH range 7 to 9, by formation of surface complexes of P(V) anions with the precipitated Mn(II) hydrated oxide or by formation of mineral phases as Mn(II)--NH4-PO4 (e.g., (NH4MnPO4·H2O)) which was detected by XRD analysis. The soil bio-availability test of loaded impregnated zeolites reported higher ammonium than phosphate bio-availability. The desorption of ammonium and phosphate from the loaded manganese impregnated zeolites using 40 gL-1 NaOH solution in dynamic experiments reported higher recoveries and concentration factors of ammonium than phosphate.
Hermassi, M.; Valderrama, C.; Moreno Palmerola, Natàlia; Font, O.; Querol , X.; Batis, N.; Cortina, J. Journal of Environmental Chemical Engineering Vol. 5, num. 1, p. 160-169 DOI: 10.1016/j.jece.2016.11.027 Data de publicació: 2017-02-01 Article en revista
There is interest in recovering phosphate (P(V)) from secondary sources, such as waste water streams for potential use as fertilizers reducing the environmental impacts of P(V) discharges and providing alternative phosphorus sources. The goal of this work was to provide an understanding of P(V) removal by fly ash (FA) from coal power plants. Phosphate removal using Ca(II) rich FA was evaluated in terms of i) sorption equilibrium, ii) sorption kinetics under the expected pH values and P(V) concentrations in wastewaters effluents, and iii) P(V) availability of the FAs in agricultural applications. At the pH values (6–9) expected for wastewater effluents, P(V) removal proceeds as a combination of CaO(s) dissolution and brushite (CaHPO4(s)) formation on the FA particles. This process avoids the formation of relatively insoluble Ca–phosphates, such as, hydroxyapatite (Hap) with limited fertilizing properties. High P-loadings were achieved (up to 50 mgP-PO4/g FA (5% P(V) by weight)) at a pH of 8. The removal kinetics data were well described as a diffusion-based process of phosphate ions (H2PO4- and HPO42-) on FA particles, and the CaO(s) dissolution process was discarded as the rate controlling step. The P(V) availability from loaded samples was determined via an agronomical assay with NaHCO3 solutions with P(V) release ratios of 10–30 mgP-PO4/g in FA, confirming the appropriateness of this material as a potential fertilizer, even in calcareous soils.
Generally, in the tertiary process of industrial wastewater treatment plants, the content of ammonia from industrial effluents decreases from 0.5-2 g/L to 0.05-0.1 g/L. Nevertheless, in order to accomplish the EU legislation, the amount of ammonia in the wastewater streams should be lower than 1 mg/L . Ammonia presents serious environmental problems cause by its excess in the ecosystem generates the eutrophication phenomenon . Therefore, the quantity of ammonia in wastewater effluents can be reduced by the use of novel, low-cost and eco-friendly membrane technology such as liquid-liquid membrane contactors (LLMCs). The current work has a double objective: the use of hollow fiber LLMCs as ammonia separation and concentration step as well as the valorization and production of ammonium nitrate as liquid fertilizer solution. Several closed-loop experiments were carried out using the hollow fiber LLMCs lab mode (2.5x8 Liqui-Cel Membrane Contactor X-50 PP fiber, supplied by 3M Company) during 4 h at room temperature (25 ºC). Following the methodology described in previous works , the ammonia feed solution (1800 mg/L, pH=12), was pumped through the lumen side of the LLMC contactor at 7.5 cm 3 /s, whereas the stripping nitric acid solution (0.5 mol/L) was circulated into the shell side in a counter current mode. The volumes of the feed and stripping solutions were 30 L and 0.5 L, respectively. Samples were taken from the feed solution tank for the determination of the total ammonium concentration. The results showed that the recovery of ammonia was about 80-90% after the LLMC treatment. Additionally, the concentration of ammonia as ammonium nitrate was around 6% (w/w). Overall, these results highlight the possibility to separate and valorize ammonia from industrial streams for producing liquid fertilizers.
There is an environmental challenge for the metallurgical and mining industries, especially for smelting, mining and processing of copper, due to the numerous environmental regulations imposed as well as the human health impact of heavy metal pollution. Copper metallurgical
processes is generating complex residuals streams with high copper contents where it is
accompanied by other base metals as zinc, nickel and cadmium and toxic non-metals as arsenic and bismuth, among others. Due to the economic value of such copper streams several techniques such as chemical precipitation, adsorption and ion exchange, among others, are being proposed for its selective separation and concentration. In this study the use of ion selective membrane electrodialysis (IX-ED) has been evaluated to achieve a double objective: the separation and concentration of Cu(II) from streams containing mixtures of H2SO4/H3AsO4 by using an ion exchange membrane process with cation monovalent selective membranes, named ‘‘selectrodialysis (SED)”.
The SED configuration is based on conventional ED (PCCell ED 64–004 with a cell of 11×11cm) by adding one monovalent selective cation exchange (MVC) membrane between the standard anion (AEM) and cation exchange (CEM) membranes. In addition, the SED system
was composed by four streams: electrode rinse (0.1 M Na2SO4), feed solution (10 g/L CuSO4 and 8.5 g/L Na2HAsO4, pH=2.3), Cu-rich product (0.1 M H2SO4) and As-rich product (0.1 M H2SO4). The initial volume introduced in each tank was 1L, the flow rates were set at 90–100 L/h in the electrode rinse stream and 15–20 L/h in the others, and the voltage was constant at 7V.
The preliminary results show that the feed stream was deconcentrated from approximately 7.5 to 0.4 g/L of CuSO4 reaching arsenic free pure copper concentrates of 5 g Cu/L after 100 min.
Water scarcity in the Mediterranean basin has been solved by using seawater desalination reverse osmosis technology (SWD-RO). This technology produces brine which is discharged back into the sea resulting in an environmental impact on marine ecosystems. Under the circular economy approach, the aim of this work is to recover resources from NaCl-rich brine (~60-70 g/L), e.g. in the form of NaOH and HCl, by integration of two ion exchange-based membrane technologies and quantify the electrical energy consumption. Electrodialysis (ED) incorporating monovalent selective cation exchange membranes as divalent ions purification and concentration of the NaCl present in the SWD-RO brine, was integrated with bipolar membrane ED (EDBM) to produce NaOH and HCl. Current densities of 0.30–0.40 kA/m2 at two temperature ranges simulating different seawater temperature regimes (15-18 ºC and 22-28ºC) were tested and a pure NaCl solution was used as starting concentrate stream. NaCl-rich brines with 100 or 200 gNaCl/L were obtained by ED and then introduced in the EDBM stack producing HCl and NaOH up to 2 M, depending on the initial concentrations. A minimum energy consumption of 1.7 kWh/kgNaOH was calculated when working by EDBM with initial concentrations of 104 g NaCl/L and 0.24 M HCl and NaOH.
The removal of ammonium from tertiary effluents by zeolites generates basic ammonia concentrates (up to 1–3 gNH3/L in 1–2 g NaOH/L). This study evaluates the use of hollow fibre liquid–liquid membrane contactors (HFMCs) as a concentration and purification step for ammonia effluents to produce NH4NO3 and (NH4)2(HPO4) solutions for potential use as liquid fertilizers. The influence of various operational parameters (i.e., flow rate, initial ammonia concentration and stripping acid concentration) was investigated using a closed-loop setup. Due to the high basicity of the ammonia feed streams (pH > 12), the mass transport process was primarily controlled by the free acid concentration in the stripping phase (e.g., HNO3 and H3PO4). A mass transport algorithm to predict the pH of the stripping stream was developed to describe the contactor performance, predict the requirements of the free acid concentration in the stripping phase and optimize the ammonia recovery. Therefore, the closed-loop configuration allowed for ammonia recovery ratios higher than 98% when the required free acid concentration of the stripping phase was maintained. The exhausted NH3/NaOH streams after NH3 removal can be re-used for regeneration of the ammonium-exhausted zeolite filters.
In this study, heat extraction from both the gradient and heat storage zones of a salinity-gradient solar pond (SGSP) has been evaluated. For this purpose, an experimental solar pond pilot plant was constructed in 2009 in Barcelona (Spain). The structure of the pond is a cylindrical tank of 3-m height and 8 m diameter with a total area of 50 m(2). The main objective was to evaluate a heat-extraction system from the SGSP designed to enhance the system efficiency under different conditions. Thus, an in-pond heat exchanger covering all of the lateral wall area of the pond was installed, and its performance was compared with the traditional in-pond heat exchanger situated on the bottom of the pond. Heat extraction experiments were performed using both heat exchangers individually or both at the same time. The study covers the experiments performed at three different seasonal temperature conditions: winter (December), summer (July) and autumn (October and November). The variations of the temperature inside the pond during the heat extraction were measured and analyzed. The results demonstrated that the efficiency of the pond increases when the heat is removed from the lateral heat exchanger alone compared to either using the bottom heat exchanger or using both heat exchangers simultaneously
Guaya, D.; Hermassi, M.; Valderrama, C.; Farran, A.; Cortina, J. Journal of Environmental Chemical Engineering Vol. 4, num. 3, p. 3519-3526 DOI: 10.1016/j.jece.2016.07.031 Data de publicació: 2016-09-01 Article en revista
A natural clinoptilolite in its potassium form (KNC) was modified by impregnation of hydrated metal oxides (HMO) of aluminium (III) (KAlC), iron (III) (KFeC) and manganese (IV) (KMnC) for the simultaneous ammonium and phosphate recovery from urban wastewaters. The resulting pHpzc of the HMOs on the modified zeolites (7.3 ± 0.3 for KAlC, 6.4 ± 0.4 for KFeC and 6.9 ± 0.3 for KMnC) are suitable for phosphate sorption at pH of treated urban wastewaters (6–8). The sorption capacity for phosphate for KAlC and KFeC zeolites is higher at the lower pH range while for KMnC is higher at the upper pH range. Differences were associated to the intrinsic complexing properties of the MOH groups to form outer and inner sphere MOH-phosphate complexes. The maximum phosphate sorption capacity for the three zeolites were 6.8 mg-P/g for KAlC, 7.2 mg-P/g for KFeC and 8.2 mg-P/g for KMnC. Contrary maximum ammonium sorption capacity is kept constant between pH 4–9 for the tree zeolites as the main sorption mechanism is the ion-exchange reaction with K+ ions of the zeolite. The maximum ammonium sorption capacity for the three zeolites ranged from 29 to 33 mg-N/g. These differences on the nature of the sorption processes are also reflected in a much faster sorption kinetic for ammonium than for phosphate although for both species the rate determining step was ions diffusion on the zeolite particles. Modified zeolites shown high selectivity towards ammonium and phosphate in the presence of the dissolved organic matter as well as other ionic species present in the treated wastewaters. Finally, phosphorous (P) fractionation assays of the loaded zeolites confirmed a high phosphate bioavailability if these are applied as phosphate slow release fertilizers in soil applications
Chemical industries generate large amounts of wastewater rich in different chemical constituents. Amongst these, salts at high concentrations are of major concern, making necessary the treatment of saline effluents before discharge. Because most of these rejected streams comprise a combination of more than one salt at high concentration, it is reasonable to try to separate and revalorize them to promote circular economy at industry site level. For this reason, ion-exchange membranes based technologies were integrated in this study: selectrodialysis (SED) and electrodialysis with bipolar membranes (EDBM). Different process brines composed by Na2SO4 and NaCl at different concentrations were treated first by SED to separate each salt, and then by EDBM to produce base (NaOH) and acids (HCl and H2SO4) from each salt. The optimum of both electrolyte nature and concentration of the SED stack streams was evaluated. Results indicated that it was possible to separate Cl- and SO42- depending on the anionic membrane, initial electrolytes and concentrations of each stream. Pure NaOH and a mixture of HCl and H2SO4 with different purities could be obtained. Energy consumption evolutions were plotted and an optimal zone work was found where the consumption values were acceptable.
BACKGROUND: The incorporation of Fe(III) was performed in a natural clinoptilolite (Z-N) for simultaneous phosphate and ammonium removal. RESULTS: The existence of hydroxyl groups (congruent to Fe-OH) in the iron zeolite (Z-Fe) enhances the phosphate uptake from 0.6 +/- 0.1 mg-P g(-1) in Z-N to 3.4 +/- 0.2 mg-P g(-1) in Z-Fe. However, the ammonium sorption capacity slightly decreases from 33 +/- 2 mg-N g(-1) in Z-N to 27 +/- 2 mg-N g(-1) in Z-Fe. The equilibrium and kinetics sorption were well explained by the Langmuir isotherm and the intraparticle diffusion model, respectively. CONCLUSIONS: Both the phosphate and ammonium uptake were slightly affected by the coexistence of competing ions. The phosphate sorption capacity of iron zeolite was decreased in the regeneration cycles. Desorption using a 1 mol L-1 NaOH solution under dynamic conditions provided higher enrichment factors for ammonium than phosphate
Hermassi, M.; Valderrama, C.; Gibert, O.; Moreno Palmerola, Natàlia; Font, O.; Querol , X.; Batis, N.; Cortina, J. Industrial & engineering chemistry research Vol. 55, num. 21, p. 6204-6212 DOI: 10.1021/acs.iecr.6b00878 Data de publicació: 2016-05-04 Article en revista
The feasibility of continuous phosphate recovery, by adsorption on powdered Ca-activated zeolite (PAZ), was assessed in a hybrid sorption membrane ultrafiltration (UF) system. The objective was to explore the influence of process parameters such as initial P(V) concentration, pH, and PAZ dose on P(V) recovery from a tertiary treatment effluent. The hydrodynamic parameters of the UF operation were also evaluated as a function of the PAZ dose. The P(V) recovery profiles as a function of the initial P(V) concentrations, at pH 8 and 2.5 gpAz/L, indicated that the sorbent was not saturated, and recoveries reported were 1.8 +/- 0.2, 5.7 +/- 0.3, and 47.2 +/- 2 mg P(V)/gpAz for 10 +/- 1, 25 2, and 100 +/- 6 mg P(V)/L, respectively. The increase of the pH of the feed solution from 8 to 9 increased the P(V) recovery up to 70 4%. A P(V) fractionation protocol of the loaded samples confirmed that the phosphate -sorption process involves the formation of calcium phosphate mineral forms
The chapter introduces the fundamentals of solar pond technology as a thermal storage process. It includes a brief description of solar pond technology in the context of energy storage, history, fundamentals; a classification of the different ponds used for capture and storage of solar energy; the fundamentals of the salinity gradient solar pond, describing the research efforts over recent decades; the design, construction, and the establishment of the salinity gradient, operation, and control; and finally the heat extraction systems. A discussion of investment, construction, and operational cost is also presented together with a review of the different applications in which solar ponds have the potential to supply low-grade thermal energy
Nanofiltration (NF), as a selective Mg(II) and Ca(II) separation and concentration treatment, and electrodialysis with bipolar membranes (EDBM) were evaluated for the valorization of seawater desalination reverse osmosis brines (60 NaCl/L) to produce both rich Mg(II) and Ca(II) brines for phosphate recovery and HCl and NaOH as chemicals for desalination treatments. A NF pilot plant, using NF270 membranes at 20 bar, provided a rich Mg(II) (8.3 g Mg(II)/L) and Ca(II) (2.1 g Ca(II)/L) brine on the concentrated stream with enrichment factors of 3.2 for Mg(II) and 2.5 for Ca(II). The NF permeate stream containing 50 ± 2 g NaCl/L was treated to remove residual Mg(II) (760 mg/L) and Ca(II) (415 mg/L) by chemical precipitation with Na2CO3 and NaOH before the EDBM unit. Divalent cations free brine containing NaCl (50 g NaCl/L) were fed into the EDBM stack in order to produce NaOH and HCl under recirculation configuration. Constant voltage and acid and base concentrations at different initial conditions were evaluated to obtain the maximum acid and base concentration (approximately 1 M NaOH/HCl) at 9 V. No substantial effect of initial acid and base concentrations on the overall performance was observed. An energy consumption of 2.6 kWh/kg NaOH and current efficiency of 77 ± 3% were calculated
You, X.; Guaya, D.; Farran, A.; Valderrama, C.; Cortina, J. Journal of chemical technology & biotechnology Vol. 91, num. 3, p. 693-704 DOI: 10.1002/jctb.4629 Data de publicació: 2016-03-01 Article en revista
BACKGROUND: This study evaluated a polymeric ion exchanger impregnated with nanoparticles of hydrated ferric oxide as a selective sorbent for anionic P(V) species. The hybrid impregnated anion exchanger (HAIX) employed as sorbent combines the durability and mechanical strength of a polymeric weak base anion exchange resin with the high sorption affinity of hydrated ferric oxide towards P(V) species.; RESULTS: The P(V) loading capacity of the sorbent at a pH simulating the expected conditions in treated wastewaters was 92+/-3mg P-PO4 g(-1) in single component solutions. The sorption of P(V) is affected slightly by the common ions typically present in these effluents such as Cl-, SO42- and NO3-, and a reduction of only 5% was observed (89+/-2 mg P-PO4 g(-1)) in multicomponent solutions. The sorbent can be regenerated (95+/-3%) using 4% (w/w) sodium hydroxide solution.; CONCLUSIONS: HAIX displays high selectivity for phosphate and small affinity for SO42-, NO3- and Cl- ions, which provides excellent conditions for its application at pH values typical of secondary wastewater effluents. HAIX exhibits higher and competitive phosphate removal capacity compared with data reported in the literature for materials based on HFO and for adsorbents prepared by impregnation of HFO onto polymeric supports. (C) 2015 Society of Chemical Industry
Due to increasing demand for potable and irrigation water, water suppliers have to use alternative resources. They either have to regenerate wastewater or deal with contaminated surface water. This book brings together the experiences of various experts in preparing of innovative materials that are selective for arsenic and chromium removal, and inventing some innovative processes to extract these elements from water. The book should be of high interest to engineers and decision-makers responsible for production and delivery of safe water. The book is divided into three parts. The first one shows the effect of arsenic and chromium ions on living organisms. The second one presents the studies on preparation of innovative materials with improved affinity towards arsenic as well as chromium. The third part shows the innovative methods for removal of these toxic elements, with special attention paid to chromatographic, membrane, and hybrid systems. The book is the first ever scientific work addressed to two most harmful elements appearing in water and provides a comprehensive review of materials and methods useful for making the water safe. The book discusses in detail the various fabrication techniques for sorbents and membranes that are now commercially available or appear in the development stage and will be commercialized in the next decades. Some of the technologies described in the third part will be implemented at the industrial scale in the future as well
La nanofiltració (NF) s’ha utilitzat com a tractament per a concentrar i separar Mg(II) i Ca(II) d’una salmorra (60 gNaCl/L) d’osmosi inversa (OI) provinent de la dessalinització d’aigua de mar. Mitjançant la NF es poden obtenir salmorres riques en Mg(II) i Ca(II) per a la recuperació de fosfats. Per altra banda, l’electrodiàlisi amb membranes bipolars (EDMB) ha estat utilitzada per a la producció d’HCl i NaOH com a reactius per a tractaments de dessalinització. D’aquesta manera, es pot dur a terme un procés basat en l’economia circular per tal d’aprofitar els residus convertint-los en productes químics. A partir de la salmorra d’OI i mitjançant una planta pilot de NF amb diverses membranes Dow Chemical NF270 treballant a 20 bars, es va proporcionar una salmorra rica en Mg(II) (8.3 g/L) i Ca(II) (2.1 g/L) en el corrent de concentrat amb un factor d’enriquiment de 3.2 pel Mg(II) i 2.5 pel Ca(II). El corrent de permeat de la NF, el qual contenia 50±2 g NaCl/L va ser tractat mitjançant precipitació química per tal de remoure el Mg(II) (760mg/L) i Ca(II) (415mg/L) residual amb Na2CO3 i NaOH abans d’utilitzar el corrent com a alimentació per a la EDMB. Finalment, una salmorra de NaCl (~50 gNaCl/L) lliure d’ions divalents es va tractar amb EDMB per tal de produir NaOH i HCl sota condicions de recirculació. Es va avaluar l’efecte del voltatge i de les concentracions inicials d’àcid i base per tal d’obtenir les concentracions màximes d’àcid i base (~1 M NaOH/HCl a 9 V). Pel que fa a les concentracions inicials d’àcid i base, no es van veure canvis importants en els resultats experimentals. Es va calcular un consum energètic de 2.6 kWh/kgNaOH i una eficiència elèctrica del 77±3 %.
Hermassi, M.; Valderrama, C.; Moreno Palmerola, Natàlia; Font, O.; Querol, X.; Batis, N.; Cortina, J. Journal of chemical technology & biotechnology Vol. 91, num. 7, p. 1962-1971 DOI: 10.1002/jctb.4867 Data de publicació: 2016-01-08 Article en revista
Background: A powdered zeolitic material synthesised from ¿y ash (FA) (NaP1-FA) and its calcium modi¿ed form (CaP1-NA) were studied as sorbent materials for the recovery of phosphate from treated waste-water effluents. Phosphate-sorption equilibrium experiments were performed by varying the experimental conditions, including solution pH, phosphate concentration, and the presence of competing ions. Results: The maximum phosphate-sorption capacities were 57 ± 5 and 203 ± 11 mgP–PO4g-1 for NaP1-FA and CaP1-NA, respectively. The sorption capacities of both zeolites in the pH range expected for waste-water effluents (pH 7 to 9) were slightly dependent on pH, exhibiting maxima at pH 8. Phosphate removal proceeds through two main mechanisms: (a) surface complexation with ¿AlOH and ¿FeOH groups of the zeolitic structure or unreacted minerals from the FA; and (b) the formation of Ca–phosphate phases, mainly brushite. Conclusions: The removal mechanisms were con¿rmed by XRD analyses and P speciation. The stabilities of the phosphate-loaded zeolite samples evaluated by the extraction experiments con¿rmed their potential availabilities in soil applications. Finally, the higher solubility of brushite compared with that of Hap makes this zeolitic material promising as a novel inorganic zeolite/CaP1-NA/brushite fertiliser
Background: A powdered zeolitic material synthesised from fly ash (FA) (NaP1-FA) and its calcium modified form (CaP1-NA) were studied as sorbent materials for the recovery of phosphate from treated waste-water effluents. Phosphate-sorption equilibrium experiments were performed by varying the experimental conditions, including solution pH, phosphate concentration, and the presence of competing ions. Results: The maximum phosphate-sorption capacities were 57 ± 5 and 203 ± 11 mgP–PO4g-1 for NaP1-FA and CaP1-NA, respectively. The sorption capacities of both zeolites in the pH range expected for waste-water effluents (pH 7 to 9) were slightly dependent on pH, exhibiting maxima at pH 8. Phosphate removal proceeds through two main mechanisms: (a) surface complexation with ≅AlOH and ≅FeOH groups of the zeolitic structure or unreacted minerals from the FA; and (b) the formation of Ca–phosphate phases, mainly brushite. Conclusions: The removal mechanisms were confirmed by XRD analyses and P speciation. The stabilities of the phosphate-loaded zeolite samples evaluated by the extraction experiments confirmed their potential availabilities in soil applications. Finally, the higher solubility of brushite compared with that of Hap makes this zeolitic material promising as a novel inorganic zeolite/CaP1-NA/brushite fertiliser
High-temperature electrolysis (also called steam electrolysis) is the water electrolysis at temperatures that ranged between 700 and 1,000 °C in which electrical energy is the driving force of water splitting to produce oxygen (O2) and hydrogen (H2). The core of an electrolysis unit is an electrochemical cell, which is filled with pure water and has two electrodes connected with an external power supply. At a certain voltage, which is called critical voltage, between both electrodes, the electrodes start to produce hydrogen gas at the negatively biased electrode (Eq. 1) and oxygen gas at the positively biased electrode (Eq. 2). The amount of gases produced per unit time is directly related to the current that passes through the electrochemical cell (Wendt and Kreysa 1999)
High-pressure electrolysis (also called high-pressure electrolysis HPE) is the water electrolysis performed at pressures higher than ambient in which electrical energy is the driving force of the water decomposition to produce oxygen (O2) and hydrogen (H2). The core of an electrolysis unit is an electrochemical cell, which is filled with pure water and has two electrodes connected with an external power supply. Electric current causes positively charged hydrogen ions to migrate to the negatively charged cathode, where a reduction takes place in order to form hydrogen atoms. The atoms formed then combine to form gaseous hydrogen molecules (Eq. 1). On the other hand, oxygen is formed at the other electrode (the positively charged anode) (Eq. 2). The amount of gases produced per unit time is directly related to the current that passes through the electrochemical cell (Wendt and Kreysa 1999)
The influence of Mg(II) on phosphorous recovery as hydroxyapatite (Hap) from alkaline phosphate concentrates using desalinated industrial brines as the calcium source in a batch reactor was evaluated. Two synthetic brines with Mg/Ca molar ratios of 2.2 and 3.3 were continuously fed to reach a Ca/P molar ratio of ~1.67 to promote Hap formation under different constant pH values (8, 9.5, 10.5, 11.5 and 12). For both brines, inhibition of Hap precipitation and formation of the amorphous mineral phases of Ca-, Mg- and Ca/Mg-phosphates were observed at pH > 9.5. Mg(II) severely inhibited phosphate precipitation, allowing the formation of amorphous calcium phosphate from meta-stable clusters due to Mg(II) incorporation into Ca-phosphate. For the Mg/Ca (3.3) brine, a more soluble Mg-phosphate mineral (cattiite) was formed at pH 11.5. Thermal treatment of the amorphous solids to increase crystallinity confirmed the presence of Hap and chlorapatite as Ca-phosphate, stanfieldite as Ca–Mg-phosphate and farringtonite as Mg-phosphate. In the experiments at pH 8, the formation of stable nanometer-sized pre-nucleation clusters promoted nucleation inhibition, even in supersaturated solutions, and no solids were recovered after filtration. Although sulfate was involved in some of the precipitation reactions, its role in the inhibition of Hap formation is not clearly elucidated
You, X.; Farran, A.; Guaya, D.; Valderrama, C.; Cortina, J.; Soldatov, V. Journal of Environmental Chemical Engineering Vol. 4, num. 1, p. 388-397 DOI: 10.1016/j.jece.2015.11.032 Data de publicació: 2016 Article en revista
This study presents the evaluation of a fibrous ion exchanger impregnated with nanoparticles of hydrated ferric oxide (HFO) as a selective sorbent for phosphate. The hybrid impregnated anion exchanger (FIBAN-As) combines the durability and mechanical strength of a polymeric weak base anion exchange resin with the high sorption affinity of HFO towards phosphate species. The phosphate loading capacity at the common pH of waste waters treatment plant secondary effluents was 162 ± 12 mg PO43-/g sorbent. Dynamic experiments were carried out and data obtained was fitted to fixed-bed sorption models. The theoretical sorption capacities reported by the Thomas model were in good agreement to the breakthrough experimental capacities determined from the sorption data. The sorption capacity decreased in multicomponent system due to the faster ion exchange of competing anions compared to phosphate ions. The loaded FIBAN-As was efficiently regenerated by using a sodium hydroxide solution, reporting up to 90% of recovery. Finally, reuse of FIBAN-As was evaluated in three successively sorption–desorption cycles by using two regeneration solutions. A sorption capacity reduction of 23% and 30% was observed for acid and alkaline solutions, respectively after the third cycle
Licon , E.; Alcaraz, A.; Casas, S.; Valderrama, C.; Cortina, J. Journal of chemical technology & biotechnology Vol. 91, num. 12, p. 2983-2993 DOI: 10.1002/jctb.4923 Data de publicació: 2016-01-01 Article en revista
de Arespacochaga, N.; Valderrama, C.; Peregrina, C.; Mesa, C.; Bouchy, L.; Cortina, J. Journal of power sources Vol. 300, p. 325-335 DOI: 10.1016/j.jpowsour.2015.09.086 Data de publicació: 2015-12-30 Article en revista
Biogas from anaerobic digestion of organic matter is a promising renewable energy source and fuel cells appear as a breakthrough technology to improve the performance of the biogas-to-energy valorisation chain. The vast majority of studies addressing biogas energy recovery through Solid Oxide Fuel Cells published in recent years correspond to simulations and lab-scale performance with synthetic biogas. This paper assesses the pilot performance of a 2.8 kWe SOFC unit powered with cleaned sewage biogas for around 700 h in a Wastewater Treatment Plant. The biogas thorough treatment consisting of a biological desulphurisation with a biotrickling filter followed by a deep cleaning step based on adsorption is successful for removing sulphur compounds, siloxanes and hydrocarbons. The influence of the heat-to-power ratio on fuel cell performance is investigated operating the system at O/C ratio of 2, reforming temperature of 550 °C, stack temperature of 800 °C and at a constant voltage of 43 V. At optimized conditions for electrical production satisfying heat demand in the WWTP, system electrical and thermal efficiencies account for 34% and 28%. Cogeneration efficiency remains constant at around 59–62% for all the heat-to-power ratios tested. Furthermore, the impact of the oxygen content in the biogas is also studied
El subministrament d'energia sostenible i segur és un dels reptes més rellevants per a les properes generacions, on la dependència actual en les fonts d'energia basades en combustibles fòssils haurà de ser substituïda per l'autosuficiència i l'ús dels recursos energètics renovables. El tractament convencional d'aigües residuals urbanes és un procés que consumeix grans quantitats d'energia, o més específicament, grans quantitats d'electricitat. En aquest sentit, l'energia a les Estacions Depuradores d'Aigües Residuals s'ha de tractar no només en termes de reducció del consum, sinó també en termes de producció d'energia renovable a partir del biogàs. Avui en dia, no és possible assolir l'autosuficiència energètica a causa de les baixes eficiències elèctriques dels sistemes de cogeneració convencionals alimentats per biogàs. Tot i això, en els darrers anys, la tecnologia de les piles de combustible està apareixent en escena, oferint una millor eficiència elèctrica i una reducció en l'impacte ambiental. La valorització energètica de biogàs en piles de combustible combina una tecnologia d'elevada eficiència per a la generació d'energia (la pila de combustible), amb l'ús d'un combustible renovable (el biogàs).S'ha de tenir en compte que el biogàs brut conté una àmplia gamma de contaminants, especialment compostos de sofre i de silici orgànic (siloxans), que comporten un risc operatiu per al correcte funcionament de les piles de combustible d'òxid sòlid. Per tant, s'ha d'instal·lar una etapa d'acondicionament i neteja exhaustiu del biogàs abans que es pugui introduïr a la pila de combustible. D'altra banda, la monitorització de les concentracions de siloxans presenta discrepàncies en relació al procediment òptim per al seu mostreig i en la tècnica analítica de quantificació; dificultant d'aquesta manera el disseny i la operació de les tecnologies d'eliminació d'aquests compostos.Aquest treball es centra en l'estudi i validació de tota la línia de valorització energètica, incloent el sistema de tractament de biogàs i la operació de la pila de combustible. S'ha estudiat la integració de tecnologies de dessulfuració biològica de baix cost i de processos d'adsorció fisicoquímica amb una pila de combustible d'òxid sòlid en una planta pilot industrial de 2.8 kWe instal·lada en una Estació Depuradora d'Aigües Residuals a Catalunya (Mataró). Els resultats experimentals han demostrat que les tecnologies de tractament de biogàs són capaces d'assolir els exigents nivells de qualitat de 0.5 ppmv S i 1 mg Si/Nm3 tant en el curt com en el llarg plaç. Per altra part, s'ha realitzat una estudi tècnic-econòmic comparatiu entre les piles de combustible (d'òxid sòlid i de carbonat fos) amb els motors de combustió interna i les microturbines per a diferents tamanys de planta i composicions del biogàs. D'aquesta manera, s'ha confirmat el paper important que poden jugar les piles de combustible en l'assoliment d'un tractament d'aigües residuals autosuficient; particularment en plantes de tamany petit i mitjà.Avui en dia, els projectes de valorització energètica de biogàs a través de piles de combustible encara s'han de justificar per raons ambientals ja que es requereixen millores tant en el rendiment tècnic com en els costos d'inversió. No obstant, aquesta tesi demostra que aquesta tecnologia de pròxima generació serà econòmicament viable en el curt termini i podrà competir amb les tecnologies convencionals. La investigació col·laborativa entre productors de biogàs, proveïdors de tecnologies de tractament i fabricants de piles de combustible serà imprescindible durant els propers anys per tal que la tecnologia pugui convertir-se en una realitat en el sector del tractament d'aigües residuals urbanes.
Tesi per compendi de publicacions. La consulta íntegra de la tesi, inclosos els articles no comunicats públicament per drets d'autor, es pot realitzar prèvia petició a l'Arxiu UPC
A more sustainable and secure energy supply is required for the forthcoming generations; where the actual dependence on the fossil fuel reserves should be replaced by self-sufficiency and use of renewable energy resources. Conventional sewage treatment is an energy consuming process, or more specifically, an electricity consuming process. Notwithstanding, energy on Waste Water Treatment Plants is not only considered in terms of consumption reduction, but also in terms of production of renewable energy in form of biogas. Today, achieving energy self-sufficiency is limited by the low electrical efficiencies of conventional biogas-powered Combined Heat and Power systems; but fuel cell technology is appearing on the scene in the recent years offering both a higher electrical efficiency and a further reduced environmental impact. Biogas energy valorization in fuel cells combines a high-efficient technology for electrical generation, i.e.: fuel cell, with the use of a renewable fuel, i.e.: biogas.
Raw biogas contains a wide range of contaminants, mainly sulfur and organic silicon compounds (siloxanes), which pose a risk to Solid Oxide Fuel Cell operation; hence biogas requires a thorough conditioning and cleaning process upstream the fuel cell unit. Moreover, monitoring of siloxanes levels remained somewhat controversial with discrepancies on optimal sampling procedure as well as quantification technique; hindering the design and operation of siloxanes removal technologies.
This work is devoted to studying and validating the whole biogas energy valorization line, including the biogas treatment system and the fuel cell operation. The integration of low-cost biological desulphurization and deep polishing physico-chemical adsorption processes with a Solid Oxide Fuel Cell has been studied in an industrial 2.8 kWe pilot plant installed in a Waste Water Treatment Plant in Spain, showing that the stringent gas quality requirements of 0.5 ppmv S and 1 mg Si/Nm3 can be satisfied with over the long-term. The technical and economic comparison of Solid Oxide and Molten Carbonate Fuel Cell performance with conventional Internal Combustion Engines and Micro-Turbines has been also conducted for different plant sizes and raw biogas compositions, confirming the relevant role that fuel cells can play on carbon neutral sewage treatment; particularly in small- and medium-size plants.
Today the final justification for biogas valorization in fuel cell systems needs to be found in environmental issues as some improvements both in the performance and costs are still required. Nonetheless, this thesis demonstrates that the economics for this next-generation technology are expected for the short-term. Further collaborative research between biogas producers, suppliers of biogas treatment systems and manufacturers of fuel cells is required in the near future for Solid Oxide Fuel Cell technology deployment in the sewage sector.
El subministrament d'energia sostenible i segur és un dels reptes més rellevants per a les properes generacions, on la dependència actual en les fonts d'energia basades en combustibles fòssils haurà de ser substituïda per l'autosuficiència i l'ús dels recursos energètics renovables. El tractament convencional d'aigües residuals urbanes és un procés que consumeix grans quantitats d'energia, o més específicament, grans quantitats d'electricitat. En aquest sentit, l'energia a les Estacions Depuradores d'Aigües Residuals s'ha de tractar no només en termes de reducció del consum, sinó també en termes de producció d'energia renovable a partir del biogàs. Avui en dia, no és possible assolir l'autosuficiència energètica a causa de les baixes eficiències elèctriques dels sistemes de cogeneració convencionals alimentats per biogàs. Tot i això, en els darrers anys, la tecnologia de les piles de combustible està apareixent en escena, oferint una millor eficiència elèctrica i una reducció en l'impacte ambiental. La valorització energètica de biogàs en piles de combustible combina una tecnologia d'elevada eficiència per a la generació d'energia (la pila de combustible), amb l'ús d'un combustible renovable (el biogàs). S'ha de tenir en compte que el biogàs brut conté una àmplia gamma de contaminants, especialment compostos de sofre i de silici orgànic (siloxans), que comporten un risc operatiu per al correcte funcionament de les piles de combustible d'òxid sòlid. Per tant, s'ha d'instal·lar una etapa d'acondicionament i neteja exhaustiu del biogàs abans que es pugui introduïr a la pila de combustible. D'altra banda, la monitorització de les concentracions de siloxans presenta discrepàncies en relació al procediment òptim per al seu mostreig i en la tècnica analítica de quantificació; dificultant d'aquesta manera el disseny i la operació de les tecnologies d'eliminació d'aquests compostos. Aquest treball es centra en l'estudi i validació de tota la línia de valorització energètica, incloent el sistema de tractament de biogàs i la operació de la pila de combustible. S'ha estudiat la integració de tecnologies de dessulfuració biològica de baix cost i de processos d'adsorció fisicoquímica amb una pila de combustible d'òxid sòlid en una planta pilot industrial de 2.8 kWe instal·lada en una Estació Depuradora d'Aigües Residuals a Catalunya (Mataró). Els resultats experimentals han demostrat que les tecnologies de tractament de biogàs són capaces d'assolir els exigents nivells de qualitat de 0.5 ppmv S i 1 mg Si/Nm3 tant en el curt com en el llarg plaç. Per altra part, s'ha realitzat una estudi tècnic-econòmic comparatiu entre les piles de combustible (d'òxid sòlid i de carbonat fos) amb els motors de combustió interna i les microturbines per a diferents tamanys de planta i composicions del biogàs. D'aquesta manera, s'ha confirmat el paper important que poden jugar les piles de combustible en l'assoliment d'un tractament d'aigües residuals autosuficient; particularment en plantes de tamany petit i mitjà. Avui en dia, els projectes de valorització energètica de biogàs a través de piles de combustible encara s'han de justificar per raons ambientals ja que es requereixen millores tant en el rendiment tècnic com en els costos d'inversió. No obstant, aquesta tesi demostra que aquesta tecnologia de pròxima generació serà econòmicament viable en el curt termini i podrà competir amb les tecnologies convencionals. La investigació col·laborativa entre productors de biogàs, proveïdors de tecnologies de tractament i fabricants de piles de combustible serà imprescindible durant els propers anys per tal que la tecnologia pugui convertir-se en una realitat en el sector del tractament d'aigües residuals urbanes.
Removal of ammonium from tertiary wastewater treatment effluents by zeolites generates rich ammonia concentrates (1-3 g NH3/l) in NaOH brines. This work evaluates Hollow Fiber liquid-liquid Membrane
Contactors (HFMC) as concentration and purification step of ammonia concentrates from urban waste water treatment plants as nitrate and phosphate fertilizers (NH4NO3 and (NH4)2(HPO4)). Influence of
the operational conditions (flow-rate, ammonia and stripping acids concentration) were evaluated under a closed-loop setup in order to achieve concentrated fertilizers streams. Due to the high basicity of the
NH3/NaOH feed streams the mass transport process are mainly controlled by the free acid concentration (HNO3 and H3PO4) in the stripping phase. Accordingly, the closed-loop configuration allowed maintaining the needed reagents in the system without the necessity of any disposal, making this concentration procedure a cleaner waste to resource valorization process. Two types of ammonia concentrate solutions were prepared: On one hand, solutions were prepared simulating the composition of the concentrated streams generated in the regeneration of zeolites used in the recovery of ammonium from concentrates generated in recovery of ammonium in tertiary treatments from domestic and urban waste water treatment plants. Their composition is approaching that one from desorption columns experiments using zeolites. On the other hand, ammonia feed solutions were prepared after loading and elution of zeolites (Natural
Clinoptinolite, Zeocem, Slovaka Republica) and elution with 8 g/l NaOH (pH=12.5). Experiments were carried out by using a HFMC module, two peristaltic pumps and two tanks of polypropylene, one for the
NH3/NaOH solutions and the other for the nitric and phosphoric acid solution. All test components were connected by clear PVC flexible tubes. The propylene HFMC module used was a Liquid-Cel 2.5x8” Extra
Flow X30HF from Membrane–Charlotte (Celgard, USA). An algorithm for the prediction of the pH on the stripping stream provides a good description of the contactor performance with minimal deviations
when compared against experimental results and HFMC technology showed enough removal efficiencies. The quality of the by-products generated in terms of potential minor components (inorganic and organic species incorporated in the adsorption-elution step) is high as the transport of those on the LLHFC is restricted. The exhausted NH3/NaOH streams once NH3 is removed can be re-use for regeneration of the ammonium loaded zeolites filters.
Nowadays, the high quality of drinking and industrial waters and the recovery of valuable compounds from concentrate streams are very important challenges. Integrating ion-exchange and membrane technologies presents alternative processes to improve organic and inorganic contents in process and surface waters. In this study, the efficiency of a hybrid MIEX-UF (magnetic ion-exchange resin coupled with UF) bench-pilot to remove disinfection precursors (dissolved organic carbon (DOC) and Br-) and inorganic anions (SO42- and NO3-) is evaluated
de Arespacochaga, N.; Valderrama, C.; Raich-Montiu, J.; Crest, M.; Mehta, S.; Cortina, J. Renewable and sustainable energy reviews Vol. 52, p. 366-381 DOI: 10.1016/j.rser.2015.07.106 Data de publicació: 2015-08-14 Article en revista
This paper reviews the effects of the origin, occurrence, monitoring, control, fate and removal of siloxanes on the energetic valorization of sewage biogas, which can be severely compromised by its volatile organic silicon compound (VOSiC) content. Almost 25 years after identifying silicon dioxide in the exhaust gases from engines powered using sewage and landfill gas, a wide range of studies have been conducted addressing the different stages of the siloxane life cycle. The cycle starts with the production and use of polydimethylsiloxane polymers in a wide range of industrial and domestic applications and its further dispersal into environmental compartments. Siloxanes are subsequently introduced into wastewater treatment plants, where as a result of their low biodegradability and high affinity to dissolved and particulate matter, they are first transferred from wastewater into sludge and later volatilized in biogas in anaerobic digesters. Biogas treatment technologies can reduce siloxane concentrations to less than 0.1 mg/m3; adsorbent materials with micro- and mesoporous structures appear to be the most relevant technology in technical and economic terms. The state-of-the-art on siloxanes is vast and extensive, but there are still some knowledge gaps to be addressed in the future, such as the standardization of the methodology for off-line analysis, the development of on-line monitoring equipment, better understanding the fates of siloxanes in wastewater treatment processes to operate at specific conditions to avoid siloxanes-related problems, the development of more selective and regenerative removal technologies from biogas to reduce operating costs and even to recover silicon, and better understand the detrimental effects on energy recovery technologies to determine the inlet concentration limits. This work compiles the most relevant results available in the literature for each stage of the siloxane life cycle