Removal of nitrate and pesticides from groundwater by nano zero-valent iron injection pulses under biostimulation and bioaugmentation scenarios in continuous-flow packed soil columns.

This study evaluates the NO3- removal from groundwater through Heterotrophic Denitrification (HDN) (promoted by the addition of acetate and/or an inoculum rich in denitrifiers) and Abiotic Chemical Nitrate Reduction (ACNR) (promoted by pulse injection of zerovalent iron nanoparticles (nZVI)). HDN and ACNR were applied, separately or combined, in packed soil column experiments to complement the scarce research on pulse-injected nZVI in continuous-flow systems mimicking a Well-based Denitrification Barrier. Together with NO3-, the removal of two common pesticides (dieldrin and lindane) was evaluated. Results showed that total NO3- removal (>97%) could be achieved by either bioestimulation with acetate (converting NO3- to N2(g) via HDN) or by injecting nZVI (removing NO3- via ACNR). In the presence of nZVI, NO3- was partially converted to N2(g) and to a lower extent NO2-, with unreacted NO3- being likely adsorbed onto Fe-(oxy)hydroxides. Combination of both HDN and ACNR resulted in even a higher NO3- removal (>99%). Interestingly, nZVI did not seem to pose any toxic effect on denitrifiers. These results showed that both processes can be alterned or combined to take advantage of the benefits of each individual process while overcoming their disadvantages if applied alone. With regard to the target pesticides, the removal was high for dieldrin (>93%) and moderate for lindane (38%), and it was not due to biodegradation but to adsorption onto soil. When nZVI was applied, the removal increased (generally >91%) due to chemical degradation by nZVI and/or adsorption onto formed Fe-(oxy)hydroxides.

Boron recovery from desalination seawater brines by selective ion exchange resins.

The European Union (EU) depends on third markets to supply many important raw materials. Increasing the circularity of critical raw materials within the EU is important not only from an environmental perspective, but also as a competitive advantage for the EU economy. In the case of boron, the EU's import dependency is about 100%. This work aims to evaluate the boron recovery from seawater desalination plants (SWDP) brines using ion-exchange resins in a circular economy approach. Commercial boron selective resins Purolite S108, DIAION CRB03 and CRB05 were tested and compared on batch and dynamic experiments. Thermodynamic and kinetic experiments were performed, and results were fitted by linear and non-linear models. After a comparison, results showed a good fit to the Langmuir isotherm and the pseudo-second order model, respectively, for all the commercial resins tested. The DIAION CRB03 resin presented higher sorption capacity and percentage of boron sorbed than the other resins and was selected as the best option for boron recovery from SWDP brine. Dynamic experiments in fixed bed column using DIAION CRB03 resulted in a sorption capacity of 13 mg/g of resin, a boron recovery of 98% and a concentration factor of 30, for an initial boron concentration of 50 mg/L. In addition, an economic analysis was carried out as a preliminary estimate of the revenues obtained from the production of boric acid from the brine produced by El Prat desalination plant.

Environmental and economic evaluation of implementing membrane technologies and struvite crystallisation to recover nutrients from anaerobic digestion supernatant.

The present study investigates the environmental and economic feasibility of implementing membrane technologies and struvite crystallisation (SC) for nutrient recovery from the anaerobic digestion supernatant. To this end, one scenario combining partial-nitritation/Anammox and SC was compared with three scenarios combining membrane technologies and SC. The combination of ultrafiltration, SC and liquid-liquid membrane contactor (LLMC) was the less environmentally impactful scenario. SC and LLMC were the most important environmental and economic contributors in those scenarios using membrane technologies. The economic evaluation illustrated that combining ultrafiltration, SC and LLMC (with or without reverse osmosis pre-concentration) featured the lowest net cost. The sensitivity analysis highlighted that the consumption of chemicals for nutrient recovery and the ammonium sulphate recovered had a large impact on environmental and economic balances. Overall, these results demonstrate that implementing membrane technologies and SC for nutrient recovery can improve the economic and environmental implications of future municipal wastewater treatment plants.

Advanced Hybrid System for Ammonium Valorization as Liquid Fertilizer from Treated Urban Wastewaters: Validation of Natural Zeolites Pretreatment and Liquid-Liquid Membrane Contactors at Pilot Plant Scale.

This study evaluates a hybrid system combining zeolites as a sorption stage and a hollow fiber membrane contactor (HFMC) for ammonia (NH3) recovery from treated urban wastewater. Ion exchange with zeolites was selected as an advanced pretreatment and concentration step before the HFMC. The system was tested with wastewater treatment plant (WWTP) effluent (mainstream, 50 mg N-NH4/L) and anaerobic digestion centrates (sidestream, 600-800 mg N-NH4/L) from another WWTP. Natural zeolite, primarily clinoptilolite, demonstrated effective desorption of retained ammonium using a 2% NaOH solution in a closed-loop configuration, resulting in an ammonia-rich brine that enabled over 95% NH3 recovery using polypropylene HFMCs. A 1 m3/h demonstration plant processed both urban wastewaters, which were pretreated by ultrafiltration, removing over 90% of suspended solids and 60-65% of COD. The 2% NaOH regeneration brines (2.4-5.6 g N-NH4/L) were treated in a closed-loop HFMC pilot system, producing 10-15% N streams with potential use as liquid fertilizers. The resulting ammonium nitrate was free of heavy metals and organic micropollutants, making it suitable for use as liquid fertilizer. This comprehensive N management solution for urban wastewater applications can contribute to local economies while achieving reduced N discharge and circularity goals.

Sustainability Assessment of Green Ammonia Production To Promote Industrial Decarbonization in Spain.

This article investigates the economic and environmental implications of implementing green ammonia production plants in Spain. To this end, one business-as-usual scenario for gray ammonia production was compared with three green ammonia scenarios powered with different renewable energy sources (i.e., solar photovoltaic (PV), wind, and a combination of solar PV and wind). The results illustrated that green ammonia scenarios reduced the environmental impacts in global warming, stratospheric ozone depletion, and fossil resource scarcity when compared with conventional gray ammonia scenario. Conversely, green ammonia implementation increased the environmental impacts in the categories of land use, mineral resource scarcity, freshwater eutrophication, and terrestrial acidification. The techno-economic analysis revealed that the conventional gray ammonia scenario featured lower costs than green ammonia scenarios when considering a moderate natural gas cost. However, green ammonia implementation became the most economically favorable option when the natural gas cost and carbon prices increased. Finally, the results showed that developing efficient ammonia-fueled systems is important to make green ammonia a relevant energy vector when considering the entire supply chain (production/transportation). Overall, the results of this research demonstrate that green ammonia could play an important role in future decarbonization scenarios.

Towards a sustainable transformation of municipal wastewater treatment plants into biofactories using advanced NH3-N recovery technologies: A review.

Ammonia (NH3), as a prevalent pollutant in municipal wastewater discharges, can impair aquatic life and have a negatively impact on the environment. Proper wastewater treatment and management practices are essential to protect ecosystems and keep human populations healthy. Therefore, using highly effective NH3-N recovery technologies at wastewater treatment plants (WWTPs) is widely acknowledged as a necessity. In order to improve the overall efficiency of NH3 removal/recovery processes, innovative technologies have been generally applied to reduce its concentration when discharged into natural water bodies. This study reviews the current status of the main issues affecting NH3 recovery from municipal/domestic wastewater discharges. The current study investigated the ability to recover valuable resources, e.g., nutrients, regenerated water, and energy in the form of biogas through advanced and innovative methods in tertiary treatment to achieve higher efficiency towards sustainable wastewater and resource recovery facilities (W&RRFs). In addition, the concept of paradigm shifts from WWTP to a large/full scale W&RRF has been studied with several examples of conversion to innovative bio-factories producing materials. On the other hand, the carbon footprint and the high-energy consumption of the WWTPs were also considered to assess the sustainability of these facilities.

Life-cycle assessment and techno-economic evaluation of the value chain in nutrient recovery from wastewater treatment plants for agricultural application.

The recovery of nitrogen and phosphorus is important to promote circular economy in wastewater treatment plants (WWTPs). In this study, the life cycle assessment (LCA) and techno-economic assessment (TEA) of a novel pilot-scale plant aimed at recovering ammonium nitrate and struvite for subsequent application in agriculture was conducted. The nutrient recovery scheme was implemented in the sludge line of the WWTP and included (i) struvite crystallisation and (ii) ion-exchange process combined with gas permeable membrane contactor. The LCA showed that using a fertilizer solution containing the recovered nutrients was environmentally better in most of the impact categories evaluated. Ammonium nitrate was the most important environmental contributor when using the recovered fertilizer solution as a result of the high consumption of chemicals needed for its production. The TEA illustrated that the implementation of the nutrient recovery scheme in the WWTP featured a negative net present value (NPV), primarily attributed to the high consumption of chemicals (representing 30 % of the gross cost). However, the implementation of the nutrient recovery scheme in the WWTP could be economically favourable if the cost of ammonium nitrate and struvite increased to 0.68 and 0.58 €/kg, respectively. The results of this pilot-scale study highlight that nutrient recovery considering the whole value chain for fertilizer application can be an attractive full-scale alternative from a sustainability point of view.

Analysis of Operational Parameters in Acid and Base Production Using an Electrodialysis with Bipolar Membranes Pilot Plant.

In agreement with the Water Framework Directive, Circular Economy and European Union (EU) Green Deal packages, the EU-funded WATER-MINING project aims to validate next-generation water resource solutions at the pre-commercial demonstration scale in order to provide water management and recovery of valuable materials from alternative sources. In the framework of the WATER-MINING project, desalination brines from the Lampedusa (Italy) seawater reverse osmosis (SWRO) plant will be used to produce freshwater and recover valuable salts by integrating different technologies. In particular, electrodialysis with bipolar membranes (EDBM) will be used to produce chemicals (NaOH and HCl). A novel EDBM pilot plant (6.4 m2, FuMa-Tech) has been installed and operated. The performance of EDBM for single pass under different flowrates (2-8 L·min-1) for acid, base and saline channels, and two current densities (200 and 400 A·m-2), has been analyzed in terms of specific energy consumption (SEC) and current efficiency (CE). Results showed that by increasing the flowrates, generation of HCl and NaOH slightly increased. For example, ΔOH- shifted from 0.76 to 0.79 mol·min-1 when the flowrate increased from 2 to 7.5 L·min-1 at 200 A·m-2. Moreover, SEC decreased (1.18-1.05 kWh·kg-1) while CE increased (87.0-93.4%), achieving minimum (1.02 kWh·kg-1) and maximum (99.4%) values, respectively, at 6 L·min-1.

Chlorine resistance property improvement of polyamide reverse osmosis membranes through cross-linking degree increment.

Highly permeable polyamide reverse osmosis (RO) membranes are desirable for reducing the energy burden and ensuring future water resources in arid and semiarid regions. One notable drawback of thin film composite (TFC) polyamide RO/NF membranes is the polyamide's sensitivity to degradation by free chlorine, the most used biocide in water purification trains. This investigation demonstrated a significant increase in the crosslinking-degree parameter by the m-phenylenediamine (MPD) chemical structure extending in the thin film nanocomposite (TFN) membrane without adding extra MPD monomers to enhance the chlorine resistance and performance. Membrane modification was carried out according to monomer ratio changes and Nanoparticle embedding into the PA layer approaches. A new class of TFN-RO membranes incorporating novel aromatic amine functionalized (AAF)-MWCNTs embedded into the polyamide (PA) layer was introduced. A purposeful strategy was carried out to use cyanuric chloride (2,4,6-trichloro-1,3,5-triazine) as an intermediate functional group in the AAF-MWCNTs. Thus, amidic nitrogen, connected to benzene rings and carbonyl groups, assembles a structure similar to the standard PA, consisting of MPD and trimesoyl chloride. The resulting AAF-MWCNTs were mixed in the aqueous phase during the interfacial polymerization to increase the susceptible positions to chlorine attack and improve the crosslinking degree in the PA network. The characterization and performance results of the membrane demonstrated an increase in ion selectivity and water flux, impressive stability of salt rejection after chlorine exposure, and improved antifouling performance. This purposeful modification resulted in overthrowing two tradeoffs; i) high crosslink density-water flux and ii) salt rejection-permeability. The modified membrane demonstrated ameliorative chlorine resistance relative to the pristine one, with twice the increase in crosslinking degree, more than four times the enhancement of the oxidation resistance, negligible reduction in the salt rejection (0.83 %), and only 5 L/m2.h flux loss following a rigorous static chlorine exposure of 500 ppm.h under acidic conditions. The excellent performance of new chlorine resistant TNF RO membranes fabricated via AAF-MWCNTs together with the facile membrane manufacturing process offered the possibility of postulating them in the desalination field, which could eventually help the current freshwater supply challenge.

Recovery of phenolic compounds from wine lees using green processing: Identifying target molecules and assessing membrane ultrafiltration performance.

Winery wastes are rich in polyphenols with high added value to be used in cosmetics, pharmaceuticals, and food products. This work aims at recovering and purifying the polyphenolic fraction occurring in the malolactic fermentation lees generated during the production of Albariño wines. Phenolic acids, flavonoids, and related compounds were recovered from this oenological waste by green liquid extraction using water as the solvent. The resulting extract solution was microfiltered to remove microparticles and further treated by ultrafiltration (UF) using membranes of 30 kDa and 5 kDa molecular weight cut-offs (MWCOs). The feed sample and the filtrate and retentate solutions from each membrane system were analyzed by reversed-phase liquid chromatography (HPLC) with UV and mass spectrometric (MS) detection. The most abundant polyphenols in the extracts were identified and quantified, namely: caftaric acid with a concentration of 200 µg g-1 and trans-coutaric acid, cis-coutaric acid, gallic acid, and astilbin with concentrations between 15 and 40 µg g-1. Other minor phenolic acids and flavanols were also found. The UF process using the 30 kDa membrane did not modify the extract composition, but filtration through the 5 kDa poly-acrylonitrile membrane elicited a decrease in polyphenolic content. Hence, the 30 kDa membrane was recommended to further pre-process the extracts. The combined extraction and purification process presented here is environmentally friendly and demonstrates that malolactic fermentation lees of Albariño wines are a valuable source of phenolic compounds, especially phenolic acids.

Effect of Mn2+/Zn2+/Fe3+ Oxy(Hydroxide) Nanoparticles Doping onto Mg-Al-LDH on the Phosphate Removal Capacity from Simulated Wastewater.

A parent Mg-Al-LDH was upgraded in its adsorption properties due to the incorporation of tri-metal species oxy(hydroxide) nanoparticles obtaining Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite for the phosphate recovery from simulated urban treated wastewater. The physicochemical properties of the synthesized Mn2+/Zn2+/Fe3+/Mg-Al-LDH make promising for real application without being environmentally harmful. The performance of Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite was evaluated through batch adsorption assays. The support of iron, manganese, and zinc (oxy)hydroxide nanoparticles onto the parent Mg-Al-LDH structure was performed by precipitation, isomorphic substitution, and complexation reactions. The main improvement of the Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite was the highest phosphate adsorption capacity (82.3 mg∙g-1) in comparison to the parent Mg-Al-LDH (65.3 mg∙g-1), in a broad range of concentrations and the effective phosphate adsorption at neutral pH (7.5) near to the real wastewater effluents conditions in comparison to the conventional limitations of other adsorbents. The effectiveness of Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite was higher than the conventional metal LDHs materials synthesized in a single co-precipitation step. The phosphate adsorption onto Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite was described to be governed by both physical and chemical interactions. The support of Mn2+/Zn2+/Fe3+ oxy(hydroxide) nanoparticles over the parent Mg-Al-LDH was a determinant for the improvement of the phosphate adsorption that was governed by complexation, hydrogen bonding, precipitation, and anion exchange. The intra-particular diffusion also described well the phosphate adsorption onto the Mn2+/Zn2+/Fe3+/Mg-Al-LDH composite. Three specific stages of adsorption were determined during the phosphate immobilization with an initial fast rate, followed by the diffusion through the internal pores and the final equilibrium stage, reaching 80% of removal and the equilibrium within 1 h. The Mn2+/Zn2+/Fe3+/Mg-Al-LDH was strongly selective towards phosphate adsorption in presence of competing ions reducing the adsorption capacity at 20%. The Mn2+/Zn2+/Fe3+/Mg-Al-LDH has limited reusability, only 51% of the adsorbed phosphate could be recovered in the second cycle of the adsorption-desorption process. Around 14% of phosphate was loosely-bond to Mn2+/Zn2+/Fe3+/Mg-Al-LDH which brings the opportunity to be a new source of phosphorus. The use of eluted concentrates and the final disposal of the exhausted adsorbent for soil amendment applications can be an integral nutrient system (P, Mn, Zn, Fe) for agriculture purposes.

Ammonia Valorization by Liquid-Liquid Membrane Contactors for Liquid Fertilizers Production: Experimental Conditions Evaluation.

Liquid-liquid membrane contactors (LLMCs) were studied as a sustainable technology for ammonia recovery from wastewater. Ammonia can be valorized by LLMCs as a potential nutrient and produce liquid fertilizers. Thus, this work aims for the study of different experimental LLMC conditions to produce ammonium salts by an acid stripping stream. The experiments were conducted using two 3MTMLiqui-CellTM LLMC in a series, located in the vertical position and using HNO3 as the acid stripping solution. The flow rates for the feed and stripping sides were fixed during the tests, and two steps were conducted based on previous works. However, different experimental conditions were evaluated to determine its effect on the overall performance: (i) replacing the feed or stripping solution between the steps, (ii) the initial ammonia concentration of the feed solution, (iii) feed volume and (iv) feed temperature. The results demonstrated that better achievements were obtained replacing the acid stripping solution between steps, whereas the feed temperature did not substantially affect the overall performance. Additionally, a high initial ammonia concentration provided more ammonia recovery, although the concentration factor achieved was higher for the low initial ammonia concentration. Finally, a high feed volume afforded better results for the fertilizer side, whereas more NH3 recovery was achieved using less feed volume.

Removal of nitrate from groundwater by nano-scale zero-valent iron injection pulses in continuous-flow packed soil columns.

Injection of zero-valent iron nanoparticles (nZVI) into aquifers has gained increasing attention of researchers for in-situ treatment of NO3--contaminated groundwater. nZVI has proved efficient in chemically reducing NO3- and, according to recent research efforts, in supporting biological denitrification under favoured conditions. Given the scarce research on nZVI pulsed injection in continuous-flow systems, the objective of this study was to evaluate the effect of nZVI pulses on the removal of NO3- from groundwater in packed soil columns and, more particularly, to elucidate whether or not biotic NO3- removal processes were promoted by nZVI. Three identical columns were filled with aquifer soil samples and fed with the same nitrate polluted groundwater but operated under different conditions: (A) with application of nZVI pulses and biocide spiked in groundwater, (B) without application of nZVI pulses and (C) with application of nZVI pulses. Results showed that the application of nZVI (at 30 mg/L and 78 mg/L doses) resulted in an immediate and sharp removal of NO3- (88-94%), accompanied by an increase in pH (from 7.0 to 9.0-10.0), a drop in redox potential (Eh) (from +420 mV to <100 mV) and a release of Fe(II) and Total Organic Carbon (TOC) in the effluent (to 200 mg/L and 150-200 mg/L, respectively). The released TOC came from the organic polymer used as stabilizer of the nZVI particles. Comparison against the sterilized control column revealed that, under the experimental conditions, no biological denitrification developed and that the removal of NO3- was due to chemical reduction by nZVI. The main by-product of the NO3- removal was NH4+, which at the prevailing pH was partially converted to NH3, which dissipated from the aqueous solution resulting in a net removal of total dissolved N. A mass balance of Fe permitted to quantify the percentage of injected nZVI trapped in the column (>98%) and the NO3- retention capacity of the nZVI particles (13.2-85.5 mg NO3-/g nZVI).

Impact of a new functionalization of multiwalled carbon nanotubes on antifouling and permeability of PVDF nanocomposite membranes for dye wastewater treatment.

Here, novel hydroxyl and carboxyl functionalized multiwalled carbon nanotubes (AHF-MWCNT and ACF-MWCNT) were successfully synthesized and introduced for modification and antifouling improvement of the PVDF membrane. The blending effect of AHF-MWCNT and ACF-MWCNT on the morphology and surface properties of the PVDF membrane was explored by SEM, AFM, water contact angle, and zeta potential analysis. The results indicated that the membrane surface has become more hydrophilic, smoother as well more negative. In addition, the overall porosity and mean pore radius are increased by MWCNTs embedding. The filtration performance, antifouling and dye separation of the nanocomposite membranes were improved by adding any amounts of AHF-MWCNT and ACF-MWCNT in the PVDF membrane matrix. The carboxylic modification presented better performance than the hydroxyl functionalization. The 0.1 wt% ACF-MWCNT blended membrane presented an optimum performance with 46 L m-2 h-1 bar-1 permeability, 93% FRR, and 97.3% dye rejection. Consequently, embedding functionalized MWCNT in the PVDF membrane matrix was led to improvement of membrane characteristics and enhancement of pure water flux, antifouling feature, and dye separation. So, the functionalized MWCNT could be a promising additive for the PVDF membrane modification.

LTA and FAU-X Iron-Enriched Zeolites: Use for Phosphate Removal from Aqueous Medium.

Hydrothermally synthesized Linde type A (LTA) and faujasite X (FAU-X) zeolites are low-cost and environmentally benign inorganic carriers for environmental applications. In this study, (oxy)hydroxides were incorporated onto LTA and FAU-X zeolites to promote the phosphate adsorption. The performance of LTA-Fe and FAU-X-Fe was evaluated through batch adsorption assays. A complete evaluation was performed to recover phosphate from synthetic wastewater. The effect of pH, concentration, equilibrium, and kinetic parameters on phosphate adsorption and its further reuse in sorption-desorption cycles were evaluated. LTA-Fe and FAU-X-Fe are effective for adsorption of phosphate at neutral (e.g., pH 7.0 ± 0.2) and in a broad range of phosphate concentrations. Higher ratios of adsorption capacities were obtained by synthetic zeolites enriched with iron in comparison to their parent forms. The phosphate adsorption occurred through hydrogen bonding and complexation reactions between protonated iron hydroxyl groups and phosphate anions. The phosphate monolayer adsorption was followed by diffusion through the internal pores and 80% of the equilibrium adsorption was reached within 50 min. The LTA-Fe and FAU-X-Fe can be used for phosphate recovery from wastewater treatment plants. The use of LTA-Fe and FAU-X-Fe in a tertiary wastewater treatment stage could allow to reduce the phosphate-phosphorous content, reaching the regulatory levels (equal 1 mg L-1 total phosphorous). The phosphate adsorption using LTA-Fe and FAU-X-Fe does not require pH adjustment, and it is endothermic. The reusability of both iron zeolites is limited, and they can be finally disposed for soil amendment applications.

Fe3+/Mn2+ (Oxy)Hydroxide Nanoparticles Loaded onto Muscovite/Zeolite Composites (Powder, Pellets and Monoliths): Phosphate Carriers from Urban Wastewater to Soil.

The development of an efficient adsorbent is required in tertiary wastewater treatment stages to reduce the phosphate-phosphorous content within regulatory levels (1 mg L-1 total phosphorous). In this study, a natural muscovite was used for the preparation of muscovite/zeolite composites and the incorporation of Fe3+/Mn2+ (oxy)hydroxide nanoparticles for the recovery of phosphate from synthetic wastewater. The raw muscovite MC and the obtained muscovite/sodalite composite LMC were used in the powder form for the phosphate adsorption in batch mode. A muscovite/analcime composite was obtained in the pellets PLMCT3 and monolith SLMCT2 forms for the evaluation in fixed-bed mode for continuous operation. The effect of pH, equilibrium and kinetic parameters on phosphate adsorption and its further reuse in sorption-desorption cycles were determined. The characterization of the adsorbents determined the Fe3+ and Mn2+ incorporation into the muscovite/zeolite composite's structure followed the occupancy of the extra-framework octahedral and in the framework tetrahedral sites, precipitation and inner sphere complexation. The adsorbents used in this study (MC, LMC, PLMCT3 and SLMCT2) were effective for the phosphate recovery without pH adjustment requirements for real treated wastewater. Physical (e.g., electrostatic attraction) and chemical (complexation reactions) adsorption occurred between the protonated Fe3+/Mn2+ (oxy)hydroxy groups and phosphate anions. Higher ratios of adsorption capacities were obtained by powder materials (MC and LMC) than the pellets and monoliths forms (PLMCT3 and SLMCT2). The equilibrium adsorption of phosphate was reached within 30 min for powder forms (MC and LMC) and 150 min for pellets and monoliths forms (PLMCT3 and SLMCT2); because the phosphate adsorption was governed by the diffusion through the internal pores. The adsorbents used in this study can be applied for phosphate recovery from wastewater treatment plants in batch or fixed-bed mode with limited reusability. However, they have the edge of environmentally friendly final disposal being promissory materials for soil amendment applications.

Impact of Sidestream Pre-Treatment on Ammonia Recovery by Membrane Contactors: Experimental and Economic Evaluation.

Membrane contactor is a promising technology for ammonia recovery from the anaerobic digestion centrate. However, high suspended solids and dissolved organic matter concentrations can reduce the effectiveness of the technology. In this study, coagulation-flocculation (C/F) and aeration pre-treatments were evaluated to reduce chemical oxygen demand (COD), turbidity, suspended solids and alkalinity before the ammonia recovery stage using a membrane contactor. The mass transfer coefficient (Km) and total ammonia (TAN) recovery efficiency of the membrane contactor increased from 7.80 × 10-7 to 1.04 × 10-5 m/s and from 8 to 67%, respectively, after pre-treating the real sidestream centrate. The pre-treatment results showed that dosing aluminium sulphate (Al2(SO4)3) at 30 mg Al/L was the best strategy for the C/F process, providing COD, turbidity and TSS removal efficiencies of 50 ± 5, 95 ± 3 and 90 ± 4%, respectively. The aeration step reduced 51 ± 6% the HCO3- content and allowed reducing alkaline consumption by increasing the pH before the membrane contactor. The techno-economic evaluation showed that the combination of C/F, aeration and membrane contactor can be economically feasible for ammonia recovery. Overall, the results of this study demonstrate that C/F and aeration are simple and effective techniques to improve membrane contactor performance for nitrogen recovery from the anaerobic digestion centrate.

A green approach to phenolic compounds recovery from olive mill and winery wastes.

The aim of this study was to evaluate the recovery of phenolic compounds from olive mill and winery wastes by conventional solid-liquid extraction (SLE) using water as the extraction solvent. The studied variables were extraction time (5-15 min), temperature (25-90 °C), solid-to-liquid ratio (1:10-1:100 (kg/L)), pH (3-10) and application of multiple extractions (1-3). The extraction efficiency was evaluated in terms of total phenolic content (TPC), determined by high performance liquid chromatography (HPLC-UV), but also from the recovery of some representative phenolic compounds. The optimized conditions were one extraction step, 10 min, 25 °C, 1:30 (kg/L), pH 5 for olive pomace, and one extraction step, 10 min, 70 °C, 1:100 (kg/L), pH 5 for winery residues. The extraction method is simple and suitable for scaling-up in industry, and the aqueous extracts are fully compatible with further purification schemes based on the use of membranes or resins. The optimized technique was applied to a set of different representative residues from olive mill and winery industries, to assess their suitability as sources for phenolic compounds recovery. The phenolic content in the extracts was evaluated by chromatographic analysis and by the Folin-Ciocalteu assay (FC). Furthermore, the antioxidant capacity was determined by 2,2-azinobis-3-etilbenzotiazolina-6-sulfonat (ABTS), 2,-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. Because of their high contents in phenolic compounds and great antioxidant capacity, olive pomace and lees filters were identified as especially suited sources for phenolic compounds recovery.

Recovery of Natural Polyphenols from Spinach and Orange By-Products by Pressure-Driven Membrane Processes.

Spinach and orange by-products are well recognized for their health benefits due to the presence of natural polyphenols with antioxidant activity. Therefore, the demand to produce functional products containing polyphenols recovered from vegetables and fruits has increased in the last decade. This work aims to use the integrated membrane process for the recovery of polyphenols from spinach and orange wastes, implemented on a laboratory scale. The clarification (microfiltration and ultrafiltration, i.e., MF and UF), pre-concentration (nanofiltration, NF), and concentration (reverse osmosis, RO) of the spinach and orange extracts were performed using membrane technology. Membrane experiments were carried out by collecting 1 mL of the permeate stream after increasing the flow rate in 1 mL/min steps. The separation and concentration factors were determined by HPLC-DAD in terms of total polyphenol content and by polyphenol families: hydroxybenzoic acids, hydroxycinnamic acids, and flavonoids. The results show that the transmembrane flux depended on the feed flow rate for MF, UF, NF, and RO techniques. For the spinach and orange matrices, MF (0.22 µm) could be used to remove suspended solids; UF membranes (30 kDa) for clarification; NF membranes (TFCS) to pre-concentrate; and RO membranes (XLE for spinach and BW30 for orange) to concentrate. A treatment sequence is proposed for the two extracts using a selective membrane train (UF, NF, and RO) to obtain polyphenol-rich streams for food, pharmaceutical, and cosmetic applications, and also to recover clean water streams.

Recovery of Polyphenols from Agri-Food By-Products: The Olive Oil and Winery Industries Cases.

The production of olive oil and wine are two of the main agri-food economic activities in Southern Europe. They generate large amounts of solid and liquid wastes (e.g., olive pomace, olive mill wastewater, grape pomace, grape stems, wine lees, and wine processing wastewater) that represent a major environmental problem. Consequently, the management of these residues has become a big challenge for these industries, since they are harmful to the environment but rich in bioactive compounds, such as polyphenols. In recent years, the recovery of phenolic compounds has been proposed as a smart strategy for the valorization of these by-products, from a circular economy perspective. This review aims to provide a comprehensive description of the state of the art of techniques available for the analysis, extraction, and purification of polyphenols from the olive mill and winery residues. Thus, the integration and implementation of these techniques could provide a sustainable solution to the olive oil and winery sectors.