Dataset Information

Sludge disinfection using electrical thermal treatment: The role of ohmic heating.

ABSTRACT: Electrical heating has been proposed as a potential method for pathogen inactivation in human waste sludge, especially in decentralized wastewater treatment systems. In this study, we investigated the heat production and E. coli inactivation in wastewater sludge using electrical thermal treatment. Various concentrations of NaCl and NH4Cl were tested as electrolyte to enhance conductivity in sludge mixtures. At same voltage input (18V), sludge treated with direct current (DC) exhibited slower ascent of temperature and lower energy efficiencies for heat production comparing to that using alternate current (AC). However, DC power showed better performance in E. coli inactivation due to electrochemical inactivation in addition to thermal inactivation. Greater than 6log10 removal of E. coli was demonstrated within 2h using 0.15M of NaCl as electrolyte by AC or DC power. The heat production in sludge was modeled using Maxwell-Eucken and effective medium theory based on the effective electrical conductivity in the two-phase (liquid and solid) sludge mixtures. The results showed that the water and heat loss is a critical consideration in modeling of sludge temperature using ohmic heating. The experimental data also suggested that the models are less applicable to DC power because the electrochemical reactions triggered by DC reduce the concentration of NH4+ and other ions that serve as electrolyte. The results of this study contribute to the development of engineering strategies for human waste sludge management.

SUBMITTER: Yin Z

PROVIDER: S-EPMC5711000 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Sludge disinfection using electrical thermal treatment: The role of ohmic heating.

Yin Ziqiang Z Hoffmann Michael M Jiang Sunny S

The Science of the total environment 20170930

Electrical heating has been proposed as a potential method for pathogen inactivation in human waste sludge, especially in decentralized wastewater treatment systems. In this study, we investigated the heat production and E. coli inactivation in wastewater sludge using electrical thermal treatment. Various concentrations of NaCl and NH<sub>4</sub>Cl were tested as electrolyte to enhance conductivity in sludge mixtures. At same voltage input (18V), sludge treated with direct current (DC) exhibited ...[more]

PMID: 28972902

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Project description:IntroductionImpact of processing on product characteristics, sustainability, traceability, authenticity, and public health along the food chain becomes more and more important not only to the producer but also to the customer and the trust of a consumer toward a brand. In recent years, the number of juices and smoothies containing so called super foods or fruits, which have been "gently pasteurized," has increased significantly. However, the term "gentle pasteurization" related to the application of emerging preservation technologies such as pulsed electric fields (PEF), high pressure processing (HPP) or ohmic heating (OH) is not clearly defined.MethodsTherefore, the presented study investigated the influence of PEF, HPP, OH, and thermal treatment on quality characteristics and microbial safety of sea buckthorn syrup. Syrups from two different varieties were investigated under the following conditions HPP (600 MPa 4-8 min), OH (83°C and 90°C), PEF (29.5 kV/cm, 6 μs, 100 Hz), and thermal (88°C, hot filling). Analyses to test the influence on quality parameters like ascorbic acid (AA), flavonoids, carotenoids, tocopherols, antioxidant activity; metabolomical/chemical profiling (fingerprinting) via U-HPLC-HRMS/MS (here especially flavonoids and fatty acids); sensory evaluation, as well as microbial stability including storage, were conducted.Results and discussionIndependent from the treatment, the samples were stable over 8 weeks of storage at 4°C. The influence on the nutrient content [Ascorbic acid (AA), total antioxidant activity (TAA), total phenolic compounds (TPC), tocopherols (Vit E)] was similar for all tested technologies. Employing statistical evaluation Principal Component Analysis (PCA) a clear clustering based on the processing technologies was observed. Flavonoids as well as fatty acids were significantly impacted by the type of used preservation technology. This was obvious during the storage time of PEF and HPP syrups, where enzyme activity was still active. The color as well as taste of the syrups were found to be more fresh-like for the HPP treated samples.

Project description:IntroductionCarbonyls, a class of compounds strongly linked to pulmonary disease in smokers, are probably the most reported non-nicotine toxicants found aerosols. Reported emissions vary from negligible quantities to those far exceeding combustible cigarettes. Observations of high emissions are commonly attributed to "dry puffing", whereby the ECIG heating filament runs dry of liquid and reaches temperatures that induce thermal degradation of the ECIG vapor components at the filament's metal surface. Using a pyrolysis flow reactor, in this study we examined the potential role of surface chemistry in the formation of carbonyl compounds in ECIGs, and whether the different commercially available filament materials could potentially impact their toxicant emissions through catalysis. This information could inform nascent efforts to regulate the design of ECIGs for public health ends.MethodsNitrogen or air saturated with propylene glycol vapor was drawn through a temperature and residence time controlled tubular quartz pyrolysis flow reactor in which nichrome, Kanthal, or stainless steel ECIG heating filament wires were inserted. A control condition with no inserted wire was also included. Concentrations of carbonyl products at the reactor outlet were measured as a function of temperature, heating filament wire material, and carrier gas composition (N2 vs air). Carbonyls were sampled using DNPH cartridges and analyzed by HPLC.ResultsECIG heating filament wires were found to have a strong catalytic effect. Carbonyl formation initiated at temperatures lower than 250°C in the presence of the metallic wires, compared to 460°C without them. Carbonyl formation was found to be a function of the material of construction, and whether the wire was new or aged. New nichrome wires were the least reactive, but when aged they exhibited the highest reactivity. Carbonyls were formed via dehydration or oxidation reactions of PG.ConclusionsCarbonyl formation chemistry is catalyzed by commonly used ECIG heating filament materials, at temperatures that are well below those expected during "dry puffing". The variability in the distribution and yield of carbonyl compounds across ECIG filament materials suggests that this heretofore unaccounted variable may partially explain the wide ranges reported in the literature to date. More importantly, it suggests that ECIG construction materials may be an important variable for regulations designed to protect public health.

Dataset Information

Sludge disinfection using electrical thermal treatment: The role of ohmic heating.

Publications

Sludge disinfection using electrical thermal treatment: The role of ohmic heating.

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