Search Results (23)

Wood plastic composites (WPCs) have recently gained attention as alternatives to traditional wood materials for outdoor use, thanks to their enhanced moisture resistance and durability, which extends their service life. Discolouration as well as surface erosion has been observed during weathering for both WPCs with untreated and heat-treated wood. However, aspects such as changes in surface hydrophobicity, chemistry, and erosion in terms of microplastic formation have received less attention; this research aimed to evaluate these factors during natural weathering. Four types of WPC samples, consisting of 50% wood particles (untreated and heat-treated) and 50% polypropylene, were naturally weathered in Latvia for two years. The samples measured 240 mm × 240 mm × 5 mm. Results showed rapid colour changes, microcracks, and exposed wood particles, suggesting microplastic formation. ATR-FTIR analysis showed increased absorption at 1715 cm⁻¹ (carbonyl groups) and at 3410 cm⁻¹ and 3460 cm⁻¹, typical of wood, indicating chemical changes on the surface. These changes influenced surface hydrophobicity, roughness, and water penetration. In a relatively short exposure time, WPCs without proper additives undergo significant changes in their aesthetic and physical properties, leading to surface erosion and potential microplastic formation. This could challenge the perception of WPCs as environmentally friendly materials. Full article

This paper presents machine learning analysis to understand the factors impacting iron concentrations and discolouration customer contacts in drinking water distribution systems. Fourteen years of network sampling and additional data from a large UK utility were collated, analysed, and interpreted using self-organising maps (SOMs), which include complex network theory (CNT) centrality metrics for the first time, investigating how possible explanatory variables interact. The outputs are used to inform ensemble decision trees for risk estimation of iron exceedance and customer contacts for each of the utility’s DMAs, helping inform proactive maintenance. Full article

The dynamics of biofilm detachment from the pipe walls of drinking water distribution systems was investigated through experiments in a full-scale pipe loop laboratory system. Biofilms grown under steady-state and transitory flow rates were compared. Flow cytometry was used to quantify the microbial cells of the biofilms, and biofilm shear strength was evaluated based on their capacity to resist mobilization when subjected to elevated flushing flow rates. The results suggest that biofilms grown under transitory flow regimes may develop stronger adhesion strength to the pipe wall. This paper contributes to the enhanced understanding of biofilm behaviour in drinking water systems and its potential impacts on water quality. Full article

This research explores the influence of chronic, small-amplitude hydraulic transients on biofilm development within water distribution systems (WDSs). Utilizing a unique experimental setup, it contrasts the biofilm dynamics under steady and transient hydraulic conditions. Findings reveal biofilms developed by transient conditions notably enhance adhesion and resistance to flushing, challenging the conventional focus on steady-state hydraulic scenarios. The research underscores the importance of integrating transient hydraulic effects into water distribution system management and design, to improve water quality and system integrity. Full article

A water treatment works in the UK endured elevated inlet turbidity and iron concentrations following increased demands in the raw water supply main, reducing its capacity by blocking filters that required costly extra cleaning. Adding flow and turbidity monitoring allowed novel raw water main variable condition discolouration model (VCDM) simulations to track the accumulation and mobilisation behaviour, showing the full 18.7 km contributing material and risk returning in only 2 months, helping explain the multiple annual events. The utility is now applying operational efficient flow conditioning, developed here using the VCDM, to manage risks and capacity. Full article

Understanding the interactions between hydraulic conditions and the accumulation of discolouration material in drinking water distribution systems is crucial to help identify risk locations and inform effective maintenance. With two accumulation processes now acknowledged and the known range in size and characteristics of discolouration material, this is not a trivial challenge. A full-scale pipe loop system, adapted for precise flow control and with multiple turbidity monitors, was dosed with discolouration material collected from operational networks. By tracking changes in bulk water material loading, this study indicates that at above 1.25 L/s (0.25 m/s, Re 15,000, 0.213 N/m²), a change in accumulation behaviour occurs. Full article

While disinfection residuals in drinking water limit planktonic microorganism regrowth during distribution, their impact on biofilms remains uncertain. This study examined how different water qualities, specifically chlorine versus chloramine disinfection residuals, affect drinking water biofilm growth in controlled, fully representative, pipe loop experimental facilities. For the first time, pipe loops were deployed at distribution system extremities, enabling the assessment of biofilms grown in bulk waters with higher water ages than previously studied. Biofilms were grown for three months under comparable hydraulic conditions and temperatures in two operational DWDS (chlorine and chloramine). After three months, experiments regarding hydraulic changes (flushing) were performed to mobilise the biofilm and assess the water quality response. Analysis revealed elevated levels of iron and turbidity, exceeding UK regulatory limits, especially in the chloramine system. Cell count data showed a complex response, with differences likely associated with the residual type. The data provide evidence that chloramine does not restrict biofilm growth and that biofilms grown within chloramine DWDS can present an equal, if not greater, risk to water quality than chlorine counterparts. Full article

Facial prostheses are created from special elastomers modified for their specific physical and mechanical properties; however, they also show two common major clinical problems: gradual discolouration of the prosthesis over time in service environment and deterioration of static, dynamic, and physical properties. As a result of external environmental factors, facial prostheses may become discoloured and discolour by changing colour from intrinsic and extrinsic colouring, and this is associated with the intrinsic colour stability of elastomers and colourants. Thus, in this in vitro study, a comparative evaluation of the effect of outdoor weathering on the colour stability of A-103 and A-2000 room-temperature vulcanised silicones used for maxillofacial prosthesis was conducted. To accomplish this study, a total of 80 samples were fabricated, 40 samples of each material were grouped as clear (20) and pigmented (20). These samples were mounted on wooden board and the assembly was placed on the roof of the dental school from October 2021 to March 2022. To maximise the amount of sunlight on the specimens, the exposure rack was set on five 68° angles from horizontal and also to prevent standing water. The specimens were left uncovered during exposure. The testing of samples was conducted with the help of a spectrophotometer. The colour values were recorded in the CIELAB colour system. It describes the three colour coordinates (colour values) x, y, and z in three new reference values of L, a, and b, aiding in numerically classifying colour differences. After 2, 4, and 6 months of weathering, testing was conducted using a spectrophotometer and the colour change (ΔE) was calculated. The A-103 RTV silicone group with pigmentation showed the maximum change in colour after six months of environmental conditioning. The data for colour difference within groups were analysed using a one-way ANOVA test. Tukey’s post hoc test assessed the pairwise mean comparison’s contribution to the overall significant difference. The nonpigmented A-2000 RTV silicone group showed the maximum change in colour after six months of environmental conditioning. After 2, 4, and 6 months of environmental conditioning, pigmented A-2000 RTV silicone showed better colour stability than A-103 RTV silicone. The patients requiring facial prosthesis do need to work on outdoor fields, and thus weathering will have deleterious effects on such prosthesis. Hence, the selection of appropriate silicone material with respect to the Al Jouf province region is crucial, which includes economic, durable, and colour stability. Full article

Background and Objectives: Resin composites represent a class of materials widely used in restorative dentistry due to patient demands for better aesthetics. Colour changes in composite resins can occur due to intrinsic and extrinsic factors. Beverages, such as vegetable juices, can be some of these extrinsic factors. The purpose of this study was to investigate the colour stability and modification of microhardness of two resin composites before and after immersion in different vegetable juices. Materials and Methods: The colour of two resin composite materials (Gradia Direct Anterior-shade A2 and Valux Plus—shade A2) was measured before and after immersion in four different solutions: distilled water (as control), beetroot, carrot, and tomato juice. Colour values (L *, a *, b *) were measured over a white background with a colorimeter, using the CIE L *a *b * system. Colour change values were calculated after 1, 3, 5, and 7 days of immersion. Microhardness measurements were taken before and after seven days immersion in test media. Repeated measures analysis of variance (ANOVA) and independent t-tests were applied for statistical analysis. Results: All vegetable juices produced statistically different discolouration after immersion for 7 days (p < 0.05). Tomato juice produced the most discolouration for the Gradia Direct specimens, whereas beetroot juice and carrot juice produced the most discolouration for the Valux Plus specimens. Microhardness of the materials immersed for 7 days in vegetable juices was reduced compared to the ones immersed in distilled water. Conclusions: Vegetable juices, immersion time, and dental resin composites are significant factors that may affect colour stability and microhardness of composite resins. Full article

This work evaluates the effects of accelerated aging on the discolouration of surface-treated spruce wood and oak wood coated with solvent-based polyurethane lacquers, and surface-treated spruce wood coated with water-based transparent coating systems. All concerned coating materials were intended for indoor use. It was also explored how the colour stability of spruce wood and oak wood surfaces treated with solvent-based polyurethane lacquers was affected by wood surface layer modifications with pigment or stain mordants applied before these lacquers. Another issue studied was how the lignin stabilizer admixed into the primer and pigments admixed into the top coating layers affected the stability of water-based coating systems on spruce. The experimental results showed that the accelerated aging process with a simulation of indoor conditions induced significant discolouration of wood surfaces coated with solvent-based polyurethane lacquers and water-based coating systems. There were also confirmed significant impacts of all the studied factors (wood species, lacquer/coating system type, lacquer modification, wood pre-treatment with pigment and stain mordants). The spruce wood surfaces coated with solvent-based polyurethane lacquers were less stable (ΔE = 10–19, dependent on the lacquer type) than the oak surfaces treated in the same ways (ΔE = 4–11). There were also confirmed significant impacts of the particular surface treatment on the colour stability as well as significant impacts of wood surface pre-treatment with pigment and stain mordants (ΔE = 4–17—for spruce wood, and ΔE = 5.5–13—for oak wood). In the case of water-based lacquers, the ΔE values ranged between 3 and 11 (according to the coating system type). The results show that an appropriate UV absorbent combined with an appropriate lignin stabilizer and pigment mordant may enable attaining the required colour stability for a given surface treatment applied on a given wood species. Full article

Wood in outdoor applications is exposed to various environmental factors that cause weathering. Weathering is important, primarily from an aesthetic standpoint and predominantly in wooden claddings. However, not all parts of claddings are equally exposed to weathering. Sections exposed to UV radiation and moisture discolour faster than less exposed sections, such as wood under roof overhangs. Architects and owners seek a uniform appearance in buildings. To achieve fast and uniform greying, a surface treatment with iron(II) sulphate can be used. Such a treatment results in an appearance that is similar to that resulting from natural greying. However, iron compounds do not exert a biocidal effect; therefore, it is desirable to upgrade iron(II) sulphate aqueous solution with boric acid and quarterly ammonium compounds. To this end, spruce and larch samples were treated with varying concentrations of iron(II) sulphate and biocides. After treatment, the inherent durability, water performance and resistance dose (D_Rd) were determined according to the Meyer-Veltrup model. The samples were also exposed outdoor conditions. During exposure, colour changes and iron leaching were monitored. The results show that the addition of biocides does not affect the rate of colour change and the final colour, which is similar to natural greying after 36 weeks of outdoor exposure. The addition of biocides exerted a positive effect on the durability of treated wood, despite the low retention of preservative solutions. The water behaviour of the treated wood had little effect on the resistance dose, with a more considerable influence on inherent durability. The addition of biocides can increase the resistance dose up to 2.4 (Fe5B0.2Q0.2). On all spruce and larch samples treated with iron(II) sulphate and exposed to outdoor conditions, the colour change in the first week was roughly comparable to the final state. However, 40% of the iron had leached from the surface after only one week of exposure. Full article

The processing of faba beans generates great quantities of hulls, which are high in bioactive compounds with demonstrated radical-inhibiting properties. There is no research on the impact of using faba bean hull nanoparticles (FBH-NPs) to improve the quality and extend the shelf-life of beef products. Hence, the target of this investigation was to assess the inhibiting influence of adding FBH-NPs at two different concentrations (1 and 1.5%) on the physical attributes, lipid and protein oxidation, colour degradation, and microbiological safety of burgers during refrigerated storage (4 ± 1 °C/12 days). The FBH-NPs presented great phenolic content (103.14 ± 0.98 mg GAE/g dw) and antioxidant potential. The water holding capacity and cooking properties in burgers including FBH-NPs were improved during storage. The FBH-NPs significantly (p < 0.05) decreased the reduction rate of redness and lightness during the burger refrigerated storage and the FBH-NPs were more beneficial in preventing cold burger discolouration. In the FBH-NPs-treated burgers, peroxide values, TBARS, and protein carbonyl content were lower than in the control (up to 12 days). The microbiological load of burgers including FBH-NPs was lower than the load of the control during refrigerated storage. The findings revealed that FBH-NPs were more efficient in enhancing the cooking characteristics, retarding lipid or protein oxidation, preventing colour detrition and improving the microbial safety of burgers. Full article

This study aimed to find alternatives to sulphite as a preservative for dried fruits. Granny Smith apples were sanitised in a 200 ppm sodium chlorite solution, de-cored, peeled, and cut into slices. The sliced apples were pre-treated/dipped in a water solution containing the three weak acids, namely, ascorbic acid (AA), citric acid (CA), and potassium sorbate (PS) as well as Moringa oleifera leaf extract powder (MOLEP). A screening fractional factorial experiment consisting of five independent variables (AA, CA and PS, time and temperature and MOLEP) constrained at their upper and lower levels (AA: 0.5 to 2.0%, CA: 0.3 to 2.0%, MOLEP: 0.1 to 0.2%, time: 7 to 15 h and temperature: 57 to 70 °C) were evaluated for their effect on the colour of the dried sliced apples. An increase in the concentration of the CA significantly increased the lightness (p = 0.05) and decreased the redness (p = 0.0022) of the dried apple slices. AA and PS did not impact the lightness of the dried sliced apples. A dipping solution of citric acid at 2.0%, Moringa oleifera leaf extract powder at 0.1%, and drying time of 7 h at 70 °C effectively minimized the discolouration of the dried sliced apples. Full article

In the Water, Energy and Waste Directive, the European Commission provides for the use of household washing programmes with lower temperatures (30–40 °C) and lower water consumption. However, low washing temperatures and the absence of oxidising agents in the liquid detergents, and their reduced content in powder detergents, allow biofilm formation in washing machines and the development of an unpleasant odour, while the washed laundry can become a carrier of pathogenic bacteria, posing a risk to human health. The aim of the study was to determine whether the addition of hydrogen peroxide (HP) to liquid detergents in low-temperature household washing allows disinfection of the laundry without affecting the properties of the washed textiles even after several consecutive washes. Fabrics of different colours and of different raw material compositions were repeatedly washed in a household washing machine using a liquid detergent with the addition of 3% stabilised HP solution in the main wash, prewash or rinse. The results of the antimicrobial activity, soil removal activity, colour change and tensile strength confirmed the excellent disinfection activity of the 3% HP, but only if added in the main wash. Its presence did not discolour nor affect the tensile strength of the laundry, thus maintaining its overall appearance. Full article

TiO₂-containing photocatalysts, which combine TiO₂ with carbon-based materials, are promising materials for wastewater treatment due to synergistic photodegradation and adsorption phenomena. In this work, TiO₂/AC composites were produced by the in situ immobilization of TiO₂ nanoparticles over activated carbon (AC) derived from spent coffee grains, using different TiO₂/AC proportions. The TiO₂/AC composites were tested as adsorbents (dark) and as photocatalysts in a combined adsorption+photocatalytic process (solar irradiation) for methylene blue (MB) removal from ultrapure water, and from a secondary effluent (SecEf) of an urban wastewater treatment plant. All the materials were characterized by XRD (X-ray powder diffraction), N₂ adsorption–desorption isotherms at −196 °C, SEM (scanning electron microscopy), UV-Vis diffuse reflectance, FTIR (Fourier-transform infrared spectroscopy), TPD (temperature programmed desorption), XPS (X-ray photoelectron spectroscopy) and TGA (thermogravimetric analysis). The TiAC60 (60% C) composite presented the lowest band gap (1.84 eV), while, for TiAC29 (29% C), the value was close to that of bare TiO₂ (3.18 vs. 3.17 eV). Regardless of the material, the solar irradiation improved the percentage of MB discolouration when compared to adsorption in dark conditions. In the case of simultaneous adsorption+photocatalytic assays performed in ultrapure water, TiAC29 presented the fastest MB removal. Nevertheless, both TiAC29 and TiAC60 led to excellent MB removal percentages (96.1–98.1%). UV-induced photoregeneration was a promising strategy to recover the adsorption capacity of the materials, especially for TiAC60 and AC (>95%). When the assays were performed in SecEf, all the materials promoted discolouration percentages close to those obtained in ultrapure water. The bulk water parameters revealed that TiAC60 allowed the removal of a higher amount of MB, associated with the overall improvement of the SecEf quality. Full article