Coherent terahertz laser feedback interferometry for hydration sensing in leaves.

The response of terahertz to the presence of water content makes it an ideal analytical tool for hydration monitoring in agricultural applications. This study reports on the feasibility of terahertz sensing for monitoring the hydration level of freshly harvested leaves of Celtis sinensis by employing a imaging platform based on quantum cascade lasers and laser feedback interferometry. The imaging platform produces wide angle high resolution terahertz amplitude and phase images of the leaves at high frame rates allowing monitoring of dynamic water transport and other changes across the whole leaf. The complementary information in the resulting images was fed to a machine learning model aiming to predict relative water content from a single frame. The model was used to predict the change in hydration level over time. Results of the study suggest that the technique could have substantial potential in agricultural applications.

Understanding the Effect of Free Nitrous Acid on Biofilms.

Free nitrous acid (FNA, i.e., HNO2) has been recently applied to biofilm control in wastewater management. The mechanism triggering biofilm detachment upon exposure to FNA still remains largely unknown. In this work, we aim to prove that FNA induces biofilm dispersal via extracellular polymeric matrix breakdown and cell lysis. Biofilms formed by a model organism, Pseudomonas aeruginosa PAO1, were treated with FNA at concentrations ranging from 0.2 to 15 mg N/L for 24 h (conditions typically used in applications). The biofilms and suspended biomass were monitored both before and after FNA treatment using a range of methods including optical density measurements, viability assays, confocal laser scanning microscopy, and atomic force microscopy. It was revealed that FNA treatment caused substantial and concentration-dependent biofilm detachment. The addition of a reactive nitrogen species (RNS) scavenger, that is, 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, substantially reduced biofilm dispersal, suggesting that the nitrosative decomposition species of HNO2 (i.e., RNS, e.g., •NO + •NO2) were mainly responsible for the effects. The study provides insight into and support for the use of FNA for biofilm control in wastewater treatment.

Probing peptide nanowire conductivity by THz nanoscopy.

Significant efforts have recently been invested in assessing the physical and chemical properties of microbial nanowires for their promising role in developing alternative renewable sources of electricity, bioelectronic materials and implantable sensors. One of their outstanding properties, the ever-desirable conductivity has been the focus of numerous studies. However, the lack of a straightforward and reliable method for measuring it seems to be responsible for the broad variability of the reported data. Routinely employed methods tend to underestimate or overestimate conductivity by several orders of magnitude. In this work, synthetic peptide nanowires conductivity is interrogated employing a non-destructive measurement technique developed on a terahertz scanning near-field microscope to test if peptide aromaticity leads to higher electrical conductivity. Our novel peptide conductivity measurement technique, based on triple standards calibration method, shows that in the case of two biopolymer mimicking peptides, the sample incorporating aromatic residues (W6) is about six times more conductive than the negative control (L6). To the best of our knowledge, this is the first report of a quantitative nano-scale terahertz s-SNOM investigation of peptides. These results prove the suitability of the terahertz radiation-based non-destructive approach in tandem with the designer peptides choice as model test subjects. This approach requires only simple sample preparation, avoids many of the pitfalls of typical contact-based conductivity measurement techniques and could help understanding fundamental aspects of nature's design of electron transfer in biopolymers.

Electrochemical Production of Magnetite Nanoparticles for Sulfide Control in Sewers.

Recently, naturally occurring magnetite (Fe3O4) has emerged as a new material for sulfide control in sewers. However, unrefined magnetite could have high heavy metal contents (e.g., Cr, Zn, Ni, Sn, etc.) and the capacity to remove dissolved sulfide is reasonably limited due to relatively large particle sizes. To overcome the drawbacks of unrefined magnetite we used an electrochemical system with mild steel as sacrificial electrodes to in-situ generate high strength solutions of plate-like magnetite nanoparticles (MNP). MNP with a size range between 120 and 160 nm were electrochemically generated at 9.35 ± 0.28 g Fe3O4-Fe/L, resulting in a Coulombic efficiency (CE) for iron oxidation of 93.5 ± 2.8%. The produced MNP were found to effectively reduce sulfide levels in sewage from 12.7 ± 0.3 to 0.2 ± 0.0 mg S/L at a sulfide-to-MNP ratio of 0.26 g S/g Fe3O4-Fe. Subsequently, MNP were continuously generated with polarity switching at stable cell voltage for 31 days at 4.53 ± 0.35 g Fe3O4-Fe/L with a CE for iron oxidation of 92.4 ± 7.2%. The continuously produced MNP reduced sulfide at similar levels to around 0.2 mg S/L at a ratio of 0.28 g S/g Fe3O4-Fe.

Modeling cell membrane perturbation by molecules designed for transmembrane electron transfer.

Certain conjugated oligoelectrolytes (COEs) modify biological function by improving charge transfer across biological membranes as demonstrated by their ability to boost performance in bioelectrochemical systems. Molecular level understanding of the nature of the COE/membrane interactions is lacking. Thus, we investigated cell membrane perturbation by three COEs differing in the number of aromatic rings and presence of a fluorine substitution. Molecular dynamic simulations showed that membrane deformation by all COEs resulted from membrane thinning as the lipid phosphate heads were drawn toward the center of the bilayer layer by positively charged COE side chains. The four-ringed COE, which most closely resembled the lipid bilayer in length, deformed the membrane the least and was least disruptive, as supported by toxicity testing (minimum inhibitory concentration (MIC) = 64 µmol L(-1)) and atomic force microscopy (AFM). Extensive membrane thinning was observed from three-ringed COEs, reducing membrane thickness to <3.0 nm in regions where the COEs were located. Severe localized membrane pitting was observed when the central aromatic ring was unfluorinated, as evident from AFM and simulations. Fluorinating the central aromatic ring delocalized thinning but induced greater membrane disorder, indicated by changes in deuterium order parameter of the acyl chains. The fluorinated three-ringed compound was less toxic (MIC 4 µmol L(-1)) than the nonfluorinated three-aromatic-ringed COE (MIC 2 µmol L(-1)); thus, hydrophobic polar interactions resulting from fluorine substitution of OPV COEs dissipate membrane perturbations. Correlating specific structural features with cell membrane perturbation is an important step toward designing non-antimicrobial membrane insertion molecules.

Direct observation of athermal photofluidisation in azo-polymer films.

The surface relief gratings (SRGs) can be generated when azo-polymer films are exposed to laser beam interference as a result of mass migration. Despite considerable research effort over the past two decades this complex phenomenon remains incompletely understood. Here we show, for the first time, the athermal photofluidisation of azo-polysiloxane films exposed to 488 nm light, directly monitored by optical microscopy. A process of surface relief erasure occurring in parallel with its inscription was also observed during laser irradiation. We therefore propose a new mechanism of SRG formation, based on three different processes: (1) the polymer photo-fluidization in illuminated regions, (2) the mass displacement from illuminated to dark regions and (3) the inverse mass displacement, from dark to illuminated regions. The mechanical properties of the films during UV light irradiation were investigated by classical rheology and, for the first time, by using amplitude modulation-frequency modulation atomic force microscopy (AM-FM AFM).

Flame oxidation of stainless steel felt enhances anodic biofilm formation and current output in bioelectrochemical systems.

Stainless steel (SS) can be an attractive material to create large electrodes for microbial bioelectrochemical systems (BESs), due to its low cost and high conductivity. However, poor biocompatibility limits its successful application today. Here we report a simple and effective method to make SS electrodes biocompatible by means of flame oxidation. Physicochemical characterization of electrode surface indicated that iron oxide nanoparticles (IONPs) were generated in situ on an SS felt surface by flame oxidation. IONPs-coating dramatically enhanced the biocompatibility of SS felt and consequently resulted in a robust electroactive biofilm formation at its surface in BESs. The maximum current densities reached at IONPs-coated SS felt electrodes were 16.5 times and 4.8 times higher than the untreated SS felts and carbon felts, respectively. Furthermore, the maximum current density achieved with the IONPs-coated SS felt (1.92 mA/cm(2), 27.42 mA/cm(3)) is one of the highest current densities reported thus far. These results demonstrate for the first time that flame oxidized SS felts could be a good alternative to carbon-based electrodes for achieving high current densities in BESs. Most importantly, high conductivity, excellent mechanical strength, strong chemical stability, large specific surface area, and comparatively low cost of flame oxidized SS felts offer exciting opportunities for scaling-up of the anodes for BESs.

Unravelling the physicochemical and antimicrobial mechanisms of human serum albumin/tannic acid coatings for medical-grade polycaprolactone scaffolds.

Biofilm-related biomaterial infections are notoriously challenging to treat and can lead to chronic infection and persisting inflammation. To date, a large body of research can be reviewed for coatings which potentially prevent bacterial infection while promoting implant integration. Yet only a very small number has been translated from bench to bedside. This study provides an in-depth analysis of the stability, antibacterial mechanism, and biocompatibility of medical grade polycaprolactone (mPCL), coated with human serum albumin (HSA), the most abundant protein in blood plasma, and tannic acid (TA), a natural polyphenol with antibacterial properties. Molecular docking studies demonstrated that HSA and TA interact mainly through hydrogen-bonding, ionic and hydrophobic interactions, leading to smooth and regular assemblies. In vitro bacteria adhesion testing showed that coated scaffolds maintained their antimicrobial properties over 3 days by significantly reducing S. aureus colonization and biofilm formation. Notably, amplitude modulation-frequency modulation (AMFM) based viscoelasticity mapping and transmission electron microscopy (TEM) data suggested that HSA/TA-coatings cause morphological and mechanical changes on the outer cell membrane of S. aureus leading to membrane disruption and cell death while proving non-toxic to human primary cells. These results support this antibiotic-free approach as an effective and biocompatible strategy to prevent biofilm-related biomaterial infections.

Removal of the X-ray contrast media diatrizoate by electrochemical reduction and oxidation.

Due to their resistance to biological wastewater treatment, iodinated X-ray contrast media (ICM) have been detected in municipal wastewater effluents at relatively high concentrations (i.e., up to 100 µg L(-1)), with hospitals serving as their main source. To provide a new approach for reducing the concentrations of ICMs in wastewater, electrochemical reduction at three-dimensional graphite felt and graphite felt doped with palladium nanoparticles was examined as a means for deiodination of the common ICM diatrizoate. The presence of palladium nanoparticles significantly enhanced the removal of diatrizoate and enabled its complete deiodination to 3,5-diacetamidobenzoic acid. When the system was employed in the treatment of hospital wastewater, diatrizoate was reduced, but the extent of electrochemical reduction decreased as a result of competing reactions with solutes in the matrix. Following electrochemical reduction of diatrizoate to 3,5-diacetamidobenzoic acid, electrochemical oxidation with boron-doped diamond (BDD) anodes was employed. 3,5-Diacetamidobenzoic acid disappeared from solution at a rate that was similar to that of diatrizoate, but it was more readily mineralized than the parent compound. When electrochemical reduction and oxidation were coupled in a three-compartment reactor operated in a continuous mode, complete deiodination of diatrizoate was achieved at an applied cathode potential of -1.7 V vs SHE, with the released iodide ions electrodialyzed in a central compartment with 80% efficiency. The resulting BDD anode potential (i.e., +3.4-3.5 V vs SHE) enabled efficient oxidation of the products of the reductive step. The presence of other anions (e.g., chloride) was likely responsible for a decrease in I(-) separation efficiency when hospital wastewater was treated. Reductive deiodination combined with oxidative degradation provides benefits over oxidative treatment methods because it does not produce stable iodinated intermediates. Nevertheless, the process must be further optimized for the conditions encountered in hospital wastewater to improve the separation efficiency of halide ions prior to the electrooxidation step.

Effects of surface charge and hydrophobicity on anodic biofilm formation, community composition, and current generation in bioelectrochemical systems.

The focus of this study was to investigate the effects of surface charge and surface hydrophobicity on anodic biofilm formation, biofilm community composition, and current generation in bioelectrochemical systems (BESs). Glassy carbon surfaces were modified with -OH, -CH3, -SO3(-), or -N(+)(CH3)3 functional groups by electrochemical reduction of aryl diazonium salts and then used as anodes with poised potential of -0.2 V (vs Ag/AgCl). The average startup times and final current densities for the -N(+)(CH3)3, -OH, -SO3(-), and -CH3, electrodes were (23 d, 0.204 mA/cm(2)), (25.4 d, 0.149 mA/cm(2)), (25.9 d, 0.114 mA/cm(2)), and (37.2 d, 0.048 mA/cm(2)), respectively. Biofilms on different surfaces were analyzed by nonturnover cyclic voltammetry (CV), fluorescence in situ hybridization (FISH), and 16S rRNA gene amplicon pyrosequencing. The results demonstrated that 1) differences in the maximum current output between surface modifications was correlated with biomass quantity, and 2) all biofilms were dominated by Geobacter populations, but the composition of -CH3-associated biofilms differed from those formed on surfaces with different chemical modification. This study shows that anode surface charge and hydrophobicity influences biofilm development and can lead to significant differences in BESs performance. Positively charged and hydrophilic surfaces were more selective to electroactive microbes (e.g. Geobacter) and more conducive for electroactive biofilm formation.

Near-Field Localization of the Boson Peak on Tantalum Films for Superconducting Quantum Devices.

Superconducting circuits are among the most advanced quantum computing technologies; however, their performance is limited by losses found in surface oxides and disordered materials. In this work, we demonstrate the identification and spatial localization of a near-field signature of loss centers on tantalum films using terahertz scattering-type scanning near-field optical microscopy. By utilizing terahertz nanospectroscopy, we observe a localized excess vibrational mode around 0.5 THz and identify this resonance as the boson peak, a signature of amorphous materials. Grazing-incidence wide-angle X-ray scattering reveals that oxides on freshly solvent-cleaned samples are amorphous, whereas crystalline phases emerge after aging in air. Through nanoscale localization of defect centers, our findings provide valuable insights for the optimization of fabrication procedures for new low-loss superconducting circuits.

Terahertz imaging of human skin pathologies using laser feedback interferometry with quantum cascade lasers.

Early detection of skin pathologies with current clinical diagnostic tools is challenging, particularly when there are no visible colour changes or morphological cues present on the skin. In this study, we present a terahertz (THz) imaging technology based on a narrow band quantum cascade laser (QCL) at 2.8 THz for human skin pathology detection with diffraction limited spatial resolution. THz imaging was conducted for three different groups of unstained human skin samples (benign naevus, dysplastic naevus, and melanoma) and compared to the corresponding traditional histopathologic stained images. The minimum thickness of dehydrated human skin that can provide THz contrast was determined to be 50 µm, which is approximately one half-wavelength of the THz wave used. The THz images from different types of 50 µm-thick skin samples were well correlated with the histological findings. The per-sample locations of pathology vs healthy skin can be separated from the density distribution of the corresponding pixels in the THz amplitude-phase map. The possible THz contrast mechanisms relating to the origin of image contrast in addition to water content were analyzed from these dehydrated samples. Our findings suggest that THz imaging could provide a feasible imaging modality for skin cancer detection that is beyond the visible.

Reactive nitrogen species from free nitrous acid (FNA) cause cell lysis.

Free nitrous acid (FNA, i.e. HNO2) has been demonstrated to have broad biocidal effects on a range of microorganisms, which has direct implications for wastewater management. However, the biocidal mechanisms still remain largely unknown. This study aims to test the hypothesis that FNA will induce cell lysis via cell membrane perforations, and consequently cause cell death via proteolysis, through the use of two model organisms namely Escherichia coli K12 and Pseudomonas putida KT2440. A combination of analytical techniques that included viability assays, atomic force microscopy (AFM), protein abundance assays and proteomic analysis using Quadruple-Orbitrap™ Mass spectrometry was used to evaluate the extent of cell death and possible cell lysis mechanisms. FNA treatment at 6.09 mg/L for 24 h (conditions typically applied in applications) induced 36 ± 4.2% and 91 ± 3.5% cell death/lysis of E. coli and P. putida, respectively. AFM showed that the lysis of cells was observed via perforations in the cell membrane; cells also appeared to shrink and become flat following FNA treatment. By introducing a reactive nitrogen species (RNS) scavenger to act as a treatment control, we further revealed that it was the nitrosative decomposition species of FNA, such as .NO that caused the cell lysis through the destruction of protein macromolecules found in the cell membrane (proteolysis). Subsequently, the RNS went on to cause the destruction of protein macromolecules within the cells. The death of these model organisms E. coli and P. putida following exposure to FNA treatment provides insights into the use of FNA as an antimicrobial agent in wastewater treatment.

Melimine-Modified 3D-Printed Polycaprolactone Scaffolds for the Prevention of Biofilm-Related Biomaterial Infections.

Biomaterial-associated infections are one of the major causes of implant failure. These infections result from persistent bacteria that have adhered to the biomaterial surface before, during, or after surgery and have formed a biofilm on the implant's surface. It is estimated that 4 to 10% of implant surfaces are contaminated with bacteria; however, the infection rate can be as high as 30% in intensive care units in developed countries and as high as 45% in developing countries. To date, there is no clinical solution to prevent implant infection without relying on the use of high doses of antibiotics supplied systemically and/or removal of the infected device. In this study, melimine, a chimeric cationic peptide that has been tested in Phase I and II human clinical trials, was immobilized onto the surface of 3D-printed medical-grade polycaprolactone (mPCL) scaffolds via covalent binding and adsorption. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of melimine-treated surfaces confirmed immobilization of the peptide, as well as its homogeneous distribution throughout the scaffold surface. Amino acid analysis showed that melimine covalent and noncovalent immobilization resulted in a peptide density of ∼156 and ∼533 ng/cm2, respectively. Furthermore, we demonstrated that the immobilization of melimine on mPCL scaffolds by 1-ethyl-3-[3-(dimethylamino)propyl] carbodiimide hydrochloride (EDC) coupling and noncovalent interactions resulted in a reduction of Staphylococcus aureus colonization by 78.7% and 76.0%, respectively, in comparison with the nonmodified control specimens. Particularly, the modified surfaces maintained their antibacterial properties for 3 days, which resulted in the inhibition of biofilm formation in vitro. This system offers a biomaterial strategy to effectively prevent biofilm-related infections on implant surfaces without relying on the use of prophylactic antibiotic treatment.

Aggregation of fullerol C60(OH)24 nanoparticles as revealed using flow field-flow fractionation and atomic force microscopy.

The effects of solution pH and 1:1 electrolyte concentration on the aggregation behavior of fullerol C(60)(OH)(24) nanoparticles were investigated using flow field-flow fractionation (FlFFF). Particle separations were confirmed by examining FFF fractions using atomic force microscopy (AFM). Results showed that fullerol C(60)(OH)(24) nanoparticles remain stable at low salt concentration (0.001 M NaCl) and basic pH (pH 10). Changing the pH did not affect the size significantly, but increasing the salt concentration promoted some aggregation. Fullerol C(60)(OH)(24) nanoparticles did not form large clusters and reached a maximum size of at most several nanometers. Particle interaction analysis using the colloid interaction theory as described by the energetics of electrostatic repulsion and van der Waals attraction explained the differences in the colloidal stability of the fullerol C(60)(OH)(24) nanoparticles under different solution conditions.

Silica fouling during groundwater RO treatment: The effect of colloids' radius of curvature on dissolution and polymerisation.

Silica fouling during groundwater reverse osmosis (RO) treatment can have a significant impact on filtration performance. To better understand this phenomenon, the equilibrium kinetics of amorphous colloidal silica were studied at conditions relevant to RO of silica-rich alkaline groundwater. The impact of particle size was investigated using synthetic monodisperse silica nanoparticles. Bench scale experiments were conducted by monitoring dissolved silica concentration of aqueous suspensions of colloids of 100 and 300 nm diameter and pH 8.5 to 9.5. The equilibrium data was determined from existing established rate law equations. This study concluded that surface energy has a major impact on silica dissolution rate constant, particularly for colloidal silica. Observations of Ostwald ripening in bidisperse silica dispersions further confirmed these results, which indicate that dissolution and redeposition is responsible for the problematic silica fouling behaviour during RO treatment. 2D modelling based on inferred equilibrium data allows visualization of scale layer growth in agreement with cross-sectional scanning electron micrographs of autopsied membranes.

Selective laser assisted impairment of reverse osmosis membranes.

Monitoring the loss of integrity in reverse osmosis (RO) membranes is crucial for protection of public health as small imperfections can result in catastrophic pathogen outbreaks. However, understanding the phenomena accompanying the loss of integrity in RO membranes relies on properly characterizing and interpreting performance data. Reproducing chemical and mechanical damage in model membranes that mimic the conditions of real-time operation is difficult. Mechanical impairment is particularly challenging, since one needs to damage selectively and in a controlled manner (producing holes of desired size) the barrier (polyamide) and/or the support layer (polyether sulfone and polyester). In this work we develop a straightforward approach to produce arrays of micro-holes in a commercially available RO membrane employing nanosecond pulsed laser ablation. The new approach is used to prepare four samples with different number of holes with constant diameter and increasing hole depth. These samples were further tested to reveal the impairment impact on filtration performance. It was observed that the flux was linked with the laser pulse density/penetration.•Uniform radius defects were created in RO membranes.•Higher pulse density leads to deeper defects.•Ablation of all three layers can be attained.

Combating Antibiotic-Resistant Gram-Negative Bacteria Strains with Tetracycline-Conjugated Carbon Nanoparticles.

Nontoxic carbon nanoparticle samples prepared by both bottom-up and top-down approaches do not inhibit Gram-negative bacterial growth, indicating excellent biocompatibilities. However, cell growth inhibitory efficacies increase considerably when the carbon nanoparticles are conjugated with the antibiotic tetracycline. In tetracycline-resistant bacteria, these efficacies can approach tenfold higher activities when compared to tetracycline alone. No structural abnormality such as membrane disruptions is evident in the tested bacterial strains; this is in contrast with other nanocarbon systems such as graphene oxides, carbon nanotubes, and amine-functionalized carbon nanoparticles which do exhibit membrane disruptions. In comparison, the tetracycline-conjugated carbon nanoparticles induce membrane perturbations (but not membrane disruptions), inhibiting bacterial efflux mechanisms. It is proposed that when tetracycline is conjugated to the surface of carbon nanoparticles, it functions to direct the nanoparticles to membrane-associated tetracycline efflux pumps, thereby blocking and subsequently inhibiting their function. The conjugation between biocompatible carbon nanoparticles and subtherapeutic but well-established antibiotic molecules may provide hybrid antibiotic assembly strategies resulting in effective multidrug efflux inhibition for combating antibiotic resistance.

Recovery of in-sewer dosed iron from digested sludge at downstream treatment plants and its reuse potential.

Iron-based coagulants are dosed in enormous amounts and play an essential role in various segments of our urban water infrastructure. In order for the water industry to become circular, a closed-loop management strategy for iron needs to be developed. In this study, we have demonstrated for the first time that in-sewer dosed iron, either in the form of FeCl3 or ferric-based drinking water sludge (Fe-DWS) as a means to combat sewer corrosion and odour, can be recovered in the form of vivianite in digested sludge in down-stream wastewater treatment plants. Importantly, about 92 ± 2% of the in-sewer dosed Fe was estimated to be bound in vivianite in digested sludge. A simple insertion of Neodymium magnet allowed to recover 11 ± 0.2% and 15.3 ± 0.08% of the vivianite formed in the digested sludge of the in-sewer dosed iron in the form of FeCl3 and Fe-DWS, respectively. The purity of recovered vivianite ranged between 70 ± 5% and 49 ± 3% for in-sewer dosed FeCl3 and Fe-DWS, respectively. Almost complete (i.e. 98 ± 0.3%) separation of Fe in the form of ferrihydrite was achieved from vivianite after alkaline washing. Subsequent batch experiments demonstrated that the recovered ferrihydrite can be directly reused for efficient sulfide control in sewers. At a ferrihydrite-Fe:S molar ratio of 1.2:1, sewage dissolved sulfide concentrations was reduced from 15 mgS/L to below 0.5 mgS/L within 1 h of reaction. Overall, the results obtained in our study flag a first step for utilities towards a closed-loop iron-based coagulant management approach.

Effects of aging of ferric-based drinking water sludge on its reactivity for sulfide and phosphate removal.

Recent studies demonstrated the practical potential of multiple beneficial reuse of ferric-rich drinking water sludge (ferric DWS) for sulfide and phosphate removal in wastewater applications. In practice, ferric DWS is often stored on-site for periods ranging from days to several weeks (or even months), which may affect its reuse potential through changes in iron speciation and morphology. In this study, we investigated for the first time the impact of ferric DWS 'aging' time on the iron speciation and morphology and its subsequent impact on its reactivity and overall sulfide and phosphate removal capacity. A series of coagulation tests were conducted to generate ferric DWS of a practically relevant composition by using raw influent water from a full-scale drinking water treatment plant (DWTP). A comparison with ferric DWS from 8 full-scale DWTPs confirmed the similitude. The presence of akaganeite (ß-FeOOH) was detected in ferric DWS (through XRD analyses), independent of the DWS storage time. However, the morphology of akaganeite changed over time from a predominant poorly-crystalline phase in 'fresh' DWS (8 ± 0.1% of total Fe) to a highly crystalline phase (76 ± 3% of total Fe) at a sludge aging time of 30 days which was confirmed by means of Rietveld refinement in XRD analyses (n = 3). Subsequent batch tests showed that its sulfide removal capacity decreased significantly from 1.30 ± 0.02 mmol S/mmol Fe (day 1) to 0.60 ± 0.01 (day 30), a decrease of 54 % (p < 0.05). The level of crystallinity however had no impact on sulfide removal kinetics, most sulfide being removed within 10 minutes. Upon aeration of sulfide-loaded ferric DWS in activate sludge, amorphous iron oxides species were formed independent of the initial DWS crystallinity which resulted in efficient P removal at capacities similar to that of conventional FeCl3 dosing.