Test of electrodialytic upgrading of MSWI APC residue in pilot scale: focus on reduced metal and salt leaching

In this study a pilot plant for electrodialytic treatment of municipal solid waste incineration (MSWI) air pollution control (APC) residue was tested and proposed as a treatment method which can lead to reuse of this otherwise hazardous waste. The pilot plant was developed based on a design that is adapted from conventional electrodialysis, e.g. used in desalination of solutions. The APC residue was treated in a suspension (8 kg APC residue and 80 L tap water) and circulated through an electrodialytic (ED) stack consisting of 50 cell pairs separated by ion exchange membranes. A direct current was applied to the ED stack for removal of heavy metals (As, Ba, Cd, Cr, Cu, Mn, Ni, Pb, Zn) and salts (Cl, Na, SO₄) from the APC residue suspension. Different tank designs for mixing the APC residue suspension were tested as well as changing experimental conditions. A part of the raw experimental APC residue was carbonated by reaction with CO₂ under moist conditions prior to electrodialytic treatment. The carbonation alone reduced the leaching of some heavy metals. However, it was not sufficient to reduce the heavy metal or salt leaching to meet the Danish Category 3 guideline levels for waste material reuse and could not stand as a treatment method alone. Leaching of both heavy metals and salts were significantly reduced by the electrodialytic treatment for both the raw and carbonated APC residue. In the electrodialytically treated carbonated APC residue only Cr exceeded the Category 3 levels while in the electrodialytically treated raw APC residue both Pb and Zn leaching exceeded the Category 3. Optimization of the electrodialytic upgrading method is necessary to meet the Category 3 levels for all heavy metals. Removal of Na and SO₄ to below the Category 3 leaching levels were obtained in all the experiments. Cl removal was not sufficient in all experiments even if up to 1 kg of Cl was removed, the optimal conditions for Cl removal was a constant current of 5 A over the ED stack. The results of this study suggest that, with some optimization, electrodialytic upgrading, possibly in combination with carbonation, could be used as a treatment method for MSWI APC residue.     

Electrochemical peroxidation as a tool to remove arsenic and copper from smelter wastewater

Electrochemical peroxidation (ECP) is a method that recently has been applied in the treatment of heavy metal polluted wastewater. This method is based on the anodic dissolution of iron to ferrous ions that reacts with H₂O₂ to produce tiny particles of ferric oxides. These oxides adsorb metals efficiently from aqueous solutions. In the present study, the technique was tested experimentally on copper smelter wastewaters with high concentrations of copper and arsenic. A completely mixed airlift batch reactor was used, and the copper and arsenic removal was measured both for synthetic and real wastewater samples. The concentric iron electrodes acted as ferrous ion source when applying a constant direct current with current reversal every minute and the H₂O₂ was added dropwise. Initial pH was fixed at 3.5, 5.0 and 6.5, respectively. The best results with the synthetic wastewater showed >99% removal of copper and 80% removal of arsenic (at pH 6.5). When treating the real wastewater samples, both arsenic and copper could be removed more than 99% for all pH levels studied. It can be concluded that presence of other substances in the real wastewater favours the arsenic adsorption and/or precipitation. The copper and arsenic removal velocity was found to be dependent of pH—with the fastest removal at pH 3.5. The ECP could be regarded as a promising remediation method for treating highly contaminated wastewaters since arsenic (from 1000 mg L⁻¹) and copper (from 300 mg L⁻¹) was removed nearly completely from copper smelter wastewaters.     

Effect of different extracting solutions on the electrodialytic remediation of CCA-treated wood waste Part I. Behaviour of Cu and Cr

Removal of Cu and Cr from chromated copper arsenate (CCA)-treated wood waste under batch electrodialytic conditions was studied. The effect of different types of extracting solutions, such as deionised water or aqueous solutions of NaCl, formic acid, oxalic acid, and EDTA, on the magnitude and direction of the fluxes of Cu- and Cr-containing species in the electrodialytic cell was investigated. Oxalic acid was found to have the best performance if simultaneous removal of the two elements is required (removal efficiencies of 80.5% for Cu and 87.4% for Cr, respectively). A mixture of oxalic acid and formic acid also led to similar removal efficiencies. In these experiments, the target elements were accumulated in both the anode and cathode compartments of the electrodialytic cell due to the formation of negatively charged complexes with the organic acids used besides the free cationic forms. The latter were not present if EDTA was the extracting solution resulting in directing the Cu and Cr fluxes to the anode compartment. Contrary, these fluxes were exclusively to the cathode compartment if deionised water or an aqueous solution of NaCl were used. These extracting solutions proved suitable for solubilising (re-mobilisation) of Cu but were less efficient for Cr removal (less than 20% removal). Overall, the results obtained show the important role of the proper selection of the type and composition of the extracting solution for the success of subsequent electrodialytic removal of Cu and Cr from CCA-treated wood waste.     

EduGene: A UIDP-Based Educational App Generator for Multiple Devices and Platforms

Education is key to a just and progressive society. It is specially provided by schools and reflects on various areas of our lives. The importance of education has led to new schemes in the development of educational applications. The goal of this research is to propose the design of an architecture for educational application development that relies on a set of user interface design patterns (UIDPs) to facilitate the laborious, time-consuming task of application development. To this end, this article presents the EduGene as the proof of concept. Applications generated with EduGene are compatible with four operating systems, Android?, Firefox® OS, macOS®, and Windows Phone®, and with the Web. Furthermore, EduGene is compatible with three types of devices: mobile (smartphones and tablets), desktop, and television. The evaluation results prove that EduGene is a user-friendly educational application generator, since it provides an intuitive interface that facilitates user interaction. The e-learning tools selected to perform EduGene’s comparative evaluation are Moodle, Sakai, and ATutor. It is important to mention that the goal of the evaluation was only to highlight the benefits of EduGene as an educational app development tool.     

Chemical stability of açai fruit (Euterpe oleracea Mart.) anthocyanins as influenced by naturally occurring and externally added polyphenolic cofactors in model systems

The influence of different classes of naturally occurring and externally added polyphenolic cofactors on the phytochemical and colour stability of anthocyanins in açai fruit (Euterpe oleracea) was investigated. Model systems were based on anthocyanin isolates from açai fruit, rich in cyanidin-3-rutinoside (311 ± 27 mg/l) and cyanidin-3-glucoside (208 ± 18 mg/l), and isolated groups of naturally occurring polyphenolic cofactors in açai fruit (phenolic acids, procyanidins, and flavone-C-glycosides, each adjusted to ∼50 mg/l). Anthocyanin degradation kinetics were assessed as a function of pH (3.0, 3.5, and 4.0) and storage temperature (5, 20 and 30 °C). During storage, anthocyanins experienced pH and temperature-dependent losses, and the half life cyanidin-3-rutinoside (t_1/2 = 2.67–210 days) was consistently longer than cyanidin-3-glucoside (t_1/2 = 1.13–144 days). The presence of flavone-C-glycosides induced significant hyperchromic shifts and enhanced anthocyanin stability at all pH and temperature combinations, while no significant effects were attributed to the presence of phenolic acids or procyanidins. Additional models using externally added cofactors from rooibos tea, also rich in flavone-C-glycosides, resulted in up to 45.5% higher anthocyanin colour and up to 40.7% increased anthocyanin stability compared to uncopigmented anthocyanin isolates and had similar copigmentation effects to a commercial rosemary-based colour enhancer. Results suggest flavone-C-glycosides offer potential for their use as colour enhancers and stabilizing agents in products rich in cyanidin glycosides, particularly açai fruit-containing foods, juice blends, and beverages.     

Desiccation of adhering and biofilm Listeria monocytogenes on stainless steel: Survival and transfer to salmon products

The foodborne bacterial pathogen, Listeria monocytogenes, commonly contaminates foods during processing, where the microorganisms are potentially subjected to low relative humidity (RH) conditions for extended periods of time. The objective of this study was to examine survival during desiccation (43% RH and 15 °C) of biofilm L. monocytogenes N53-1 cells on stainless steel coupons and to assess subsequent transfer to salmon products. Formation of static biofilm (2 days at 100% RH and 15 °C) prior to desiccation for 23 days significantly (P < 0.05) improved survival of cells desiccated in initial low salt concentrations (0.5%) compared to the survival for non-biofilm cells also desiccated in low salt, indicating the protective effect of the biofilm matrix. Osmoadaptation of cells in 5% NaCl before formation of the static biofilm significantly (P < 0.05) increased long-term desiccation survival (49 days) irrespectively of the initial salt levels (0.5% and 5% NaCl). The efficiency of transfer (EOT) of desiccated biofilm cells was significantly (P < 0.05) lower than EOTs for desiccated non-biofilm bacteria, however, as biofilm formation enhanced desiccation survival more bacteria were still transferred to smoked and fresh salmon. In conclusion, the current work shows the protective effect of biofilm formation, salt and osmoadaptation on the desiccation survival of L. monocytogenes, which in turn increases the potential for cross-contamination during food processing.     

Effect of leaving milk trucks empty and idle for 6 h between raw milk loads

The US Pasteurized Milk Ordinance (PMO) allows milk tanker trucks to be used repeatedly for 24 h before mandatory clean-in-place cleaning, but no specifications are given for the length of time a tanker can be empty between loads. We defined a worst-case hauling scenario as a hauling vessel left empty and dirty (idle) for extended periods between loads, especially in warm weather. Initial studies were conducted using 5-gallon milk cans (pilot-scale) as a proof-of-concept and to demonstrate that extended idle time intervals could contribute to compromised raw milk quality. Based on pilot-scale results, a commercial hauling study was conducted through partnership with a Pacific Northwest dairy co-op to verify that extended idle times of 6 h between loads have minimal influence on the microbiological populations and enzyme activity in subsequent loads of milk. Milk cans were used to haul raw milk (load 1), emptied, incubated at 30°C for 3, 6, 10, and 20 h, and refilled with commercially pasteurized whole milk (load 2) to measure cross-contamination. For the commercial-scale study, a single tanker was filled with milk from a farm known to have poorer quality milk (farm A, load 1), emptied, and refilled immediately (0 h) or after a delay (6 h) with milk from a farm known to have superior quality milk (farm B, load 2). In both experiments, milk samples were obtained from each farm's bulk tank and from the milk can or tanker before unloading. Each sample was microbiologically assessed for standard plate count (SPC), lactic acid bacteria (LAB), and coliform counts. Selected isolates were assessed for lipolytic and proteolytic activity using spirit blue agar and skim milk agar, respectively. The pilot-scale experiment effectively demonstrated that extended periods of idle (>3 h) of soiled hauling vessels can significantly affect the microbiological quality of raw milk in subsequent loads; however, extended idle times of 6 h or less would not measurably compromise milk quality in subsequent loads in commercial tankers. Current tanker sanitation practices appear to be sufficient for maintaining raw milk SPC, LAB, and coliform levels, which are important measures of milk quality.     

Phytochemical composition and thermal stability of two commercial açai species, Euterpe oleracea and Euterpe precatoria

Açai fruit are native to the Amazon region of South America and two predominant species are commercially exported as fruit pulps for use in food and beverage applications. Detailed characterisation of the polyphenolic compounds present in the de-seeded fruits of Euterpe oleracea and Euterpe precatoria species were conducted by HPLC–ESI–MSⁿ analyses and their thermal stability and overall influence on antioxidant capacity were determined. Anthocyanins were the predominant polyphenolics in both E. oleracea (2247 ± 23 mg/kg) and E. precatoria (3,458 ± 16 mg/kg) species, and accounted for nearly 90% of the trolox equivalent antioxidant capacity in both E. oleracea (87.4 ± 4.4 μmol TE/g) and E. precatoria (114 ± 6.9 μmol TE/g) fruits. Various flavones, including homoorientin, orientin, taxifolin deoxyhexose and isovitexin; various flavanol derivatives, including (+)-catechin, (−)-epicatechin, procyanidin dimers and trimers, and phenolic acids, including protocatechuic, p-hydroxybenzoic, vanillic, syringic and ferulic acids, were also present in both species. Thermal stability of these compounds was evaluated, following a thermal holding cycle (80 °C for up to 60 min) in the presence and absence of oxygen. Both species experienced only minor changes (<5%) in non-anthocyanin polyphenolic contents during all thermal processes whereas 34 ± 2.3% of anthocyanins in E. oleracea and 10.3 ± 1.1% of anthocyanins in E. precatoria were lost under these conditions, regardless of the presence of oxygen. Proportional decreases (10–25%) in antioxidant capacity accompanied the anthocyanin changes. Results suggest that both açai species are characterised by similar polyphenolic profiles, comparable antioxidant capacities, yet only moderate phytochemical stability during heating.