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Article

High Schmidt number “Washout” of a soluble contaminant downstream of a backward-facing step

Min, D., Fischer, P.F., Pearlstein, A.J.

2020Intl. J. Heat Mass Transfer159119740

Keywordscavity flow, cleaning, mass transfer

DisciplinesChemical Engineering, Fluid Mechanics, Mechanical Engineering

CategoryNumerical simulations

Non-expert summaryThis is a dynamic simulation of removal of a soluble component by diffusive mass transfer from the shadow region of a 2-D backward facing step. The scenario is this: a fully developed laminar flow (Reynolds number of 10 and 100) between two parallel plates encounters a shallow 90 degree step in the lower plate (the step height is 0.02 x the initial duct height). A nonreactive soluble component is present in the region next to the step, essentially a square of contaminated fluid. The washout of this packet of fluid, by flow over the step and diffusion, is modelled for Schmidt numbers between 7 and 2650. Streamlines and contentration contours over time are mapped and characteristic timescales are computed. The results will be of interest to those interested in the washout of contaminated liquids in shallow recesses.

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Article

Visual inspection of surface sanitation: defining the conditions that enhance the human threshold for detection of food residues

Daeschel, D., Singh Rana, Y., Chen, L., Cai, S., Dando, R. and Snyder, A.B.

2023Food Control149109691

Keywordscleaning, decontamination

DisciplinesSocial sciences

CategoriesField work, Statistical analysis

Scale1e-6 m, 1e-6 to 1e-3 m / 1 to 60 s

Non-expert summaryVisual inspection is widely used in assessing and monitoring cleaning, sanitation and decontamination. This experimental study explored the degree of residual soiling on equipment surfaces that lies below the limit of visual detection. The goal of this study was to evaluate the limit of detection of visual inspections and establish evidence-based strategies to improve the implementation of this activity. 101 respondents completed a visual sensory test where each one looked at viewed 15 stainless steel and 15 white high density polyethylene sheets, clean or soiled with dry wheat flour, in a randomly generated order. They were asked if they could visually detect food residue on each surface and, if so, if the surface should be re-cleaned. They were also asked to answer this when they could touch the surfaces with a gloved hand. The impact of training, use of illumination, viewing angle and colour-contrast are quantified. The results provide a quantitative measure of the effectiveness of visual inspection, and factors than can influence this.

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Article

Experimental investigation of laminar and turbulent displacement of residual oil film

Zhang, Y., Barrouillet, B. and Skadsem, H.J.

2023Scientific Reports1321120

Keywordscleaning, flow displacement, shear flow, thin film

DisciplinesChemical Engineering, Fluid Mechanics, Mechanical Engineering

CategoryLaboratory experiments

Scale1e-6 to 1e-3 m / 1 to 60 s

Non-expert summaryThis paper reports an experimental study of the removal of thin oil films from the wall of a cylindrical tube by a flow of water. The removal of the oil film is measured by monitoring dye concentration in the flushing liquid leaving the system: local extents of removal were not measured. The authors investigated the effect of the flow regime of the displacing fluid (water Reynolds numbers ranged from 1480 to 12690), the duration of the displacing fluid flow, and the estimated wall shear stress imposed on the film. When the volume of fluid is limited, the largest displacement efficiency was observed at Re = 7000-8000 (named the intermediate turbulent regime). The largest Reynolds number flows were most effective for achieving complete cleaning over a long time period.

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Article

Numerical investigation of ice pigging isothermal flow in water-supply pipelines cleaning

Hu, J. and Tao, T.

2022Chemical Engineering Research & Design182428-437

Keywordscleaning, detachment, flow displacement, heat transfer, hydrodynamics, multiphase flow

DisciplinesChemical Engineering, Fluid Mechanics

CategoryNumerical simulations

Scale1e-3 to 1 m / 1e-3 to 1 s, 1 to 60 s

Non-expert summaryIce-pigging is a cleaning method in which a dense slurry (to be removed) is pushed along a channel (often a pipe, but more complex geometries can also be cleaned by this method) by an upstream solid-liquid thick ice slurry. The authors use the commercial CFD code FLUENT to evaluate a numerical model of this multiphase (solid-liquid) material undergoing pipe flow. In this coupled Eulerian-Eulerian description the two phases are treated separately as continuous phases coupled by pressure and interphase forces. They validate their model against experimental data from literature and report the predicted ice volume fraction, wall shear stress and melting rate. The results show strong inhomogeneity in the solid content (ice volume fraction).

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Article

Lessons to learn from roadmapping in cleaning and decontamination

Wilson D. I., Christie G., Fryer P. J., Hall I. M., Landel J. R., Whitehead K. A.

2022Food and Bioproducts Processing135156-164

Keywordscleaning, decontamination

CategoryReview

Scaleless than 1e-9 m, 1e-9 to 1e-6 m, 1e-6 m, 1e-6 to 1e-3 m, 1e-3 m, 1e-3 to 1 m, 1 to 10 m, 10 to 1000 m, greater than 1 km / less than 1e-3 s, 1e-3 to 1 s, 1 to 60 s, 1 to 60 min, 1 to 24 hours, 1 to 30 days, 1 to 12 months, greater than 1 year

Non-expert summaryThis article presents an interdisciplinary roadmap showing the importance of cleaning and decontamination activities across a range of socio-economic sectors and in daily life. It captures the expertise and state-of-the art in terms of the fundamental understanding of the underpinning science behind cleaning and decontamination activities, as well as its practical implementation. The roadmap also highlights shortcomings and critical needs in the field at the scientific and practical levels, with some strategies to address them.

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Article

Aging is important: Closing the fouling–cleaning loop

Ishiyama, E.M., Paterson, W.R., Wilson, D.I.

2014Heat Transfer Engineering35(3)311-326

Keywordscleaning, heat transfer

DisciplinesChemical Engineering

CategoryTheoretical modelling

Scale1e-3 m, 1e-3 to 1 m / 1 to 24 hours, 1 to 30 days, 1 to 12 months, greater than 1 year

Non-expert summaryThis paper considers the management of heat exchanger units subject to regular cleaning and thus regular cleaning. A quantitative model is needed to support the decision of when to clean an exchanger, giving rise to repeated cycles of fouling and cleaning. The initial stages of fouling are strongly influenced by the effectiveness of the most recent cleaning step and, similarly, the effectiveness and rate of cleaning are determined by the extent and nature of the deposit layer present on the surface. Deposit aging is an important factor in this, as an aged deposit is usually more difficult to clean. Ageing therefore introduces an element of choice into fouling–cleaning operating cycles, between in situ “chemical” methods and ex situ “mechanical” methods, with associated differences in effectiveness, time, and cost. The cleaning scheduling problem is presented in terms of the choice of cleaning method, as well as the timing of cleaning. A process scale model is used, with the performance of units described by lumped parameter (i.e. not detailed) models. Dimensionless groups are obtained which capture the scaling involved. Case studies are used to illustrate the concepts.

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Article

Mechanisms of photoresist dissolution

Hunek, B., Cussler, E.L.

2002AIChEJ48(4)661-672

Keywordscleaning, decontamination, mass transfer

DisciplinesChemical Engineering, Chemistry

CategoryLaboratory experiments

Scale1e-6 to 1e-3 m / 1e-3 to 1 s, 1 to 60 s, 1 to 60 min

Non-expert summaryPhotoresists are an example of long chain molecules which dissolve in the presence of alkali. Dissolution involves the transport of hydoxyl ions (OH-) into the layer: they react with the photoresist and, depending on the temperature (above or below the upper critical solution temperature, UCST), it will either be transported by diffusion through the fluid boundary layer (above UCST) or form a gel phase (below the UCST), introducing an additional diffusion step in the reaction and mass transfer processes. A physico-chemical model of the process is presented here, applied to novolak resins, which can be applied to other polymeric systems including printing inks and dairy protein foulants. Experiments are performed with a spinning disk apparatus, which gives well defined mass transfer conditions.

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Miscellaneous

Waste Estimation Support Tool (WEST)

US Environment Protection Agency

2021

Keywordscleaning, decontamination

DisciplinesMicrobiology, Statistics & Probabilities

Scale1 to 10 m, 10 to 1000 m, greater than 1 km / 1 to 60 min, 1 to 24 hours, 1 to 30 days, 1 to 12 months, greater than 1 year

Non-expert summaryThe US Environment Protection Agency (EPA) has generated a number of management tools related to cleaning and decontamination. The EPA website states that "Management of waste from a radiological dispersal device (RDD) incident would likely constitute a large part of the remediation cost and effort. The U.S. EPA’s RDD Waste Estimation Support Tool (WEST) is a planning tool for estimating the potential volume and radioactivity levels of waste generated by a radiological incident and subsequent decontamination efforts. WEST supports decision makers by generating a first-order estimate of the quantity and characteristics of waste resulting from a radiological incident, and allows the user to evaluate various decontamination/demolition strategies to examine the impact of those strategies on waste generation. "

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Technical report

Bio-Response Operational Testing and Evaluation (BOTE) Project – Phase 1: Decontamination Assessment

US Environment Protection Agency

2013

Institution / OrganisationUS Environment Protection Agency

Keywordsbacteria, cleaning, decontamination

DisciplinesMicrobiology

CategoryField work

Scale1 to 10 m, 10 to 1000 m, greater than 1 km / 1 to 60 min, 1 to 24 hours, 1 to 30 days, 1 to 12 months, greater than 1 year

Non-expert summaryThe US Environment Protection Agency led a multi-agency investigation into the response to a release of a biological agent. The report summary states "The Bio-response Operational Testing and Evaluation (BOTE) Project was a multi-agency effort designed to operationally test and evaluate a response to a biological incident (release of Bacillus anthracis spores, the causative agent for anthrax) from initial public health and law enforcement response through environmental remediation. The BOTE Project consisted of two distinct phases, both using the same non-pathogenic simulant (or surrogate) for these spores. Phase 1 was a field-level decontamination assessment, and Phase 2 was an operational exercise involving key federal agencies responsible for the forensic investigation, public health assessment, and remediation following a biological incident. Phase 1 was designed to address site remediation after the release of a simulant within a facility in an operational setting, drawing upon the recent advances in both biological sampling and decontamination. "

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Technical report

Tabletop exercise report – Sample plan development for biological incidents, large and small – Trade-Off Tool for Sampling (TOTS)

Calfee, W., Boe, T., Mickelsen, L., Johnson, C., James, R.

2020

Institution / OrganisationUS Environment Protection Agency

Keywordsbacteria, cleaning, decontamination

DisciplinesMicrobiology

CategoryReview

Scale1e-3 to 1 m, 1 to 10 m, 10 to 1000 m, greater than 1 km / 1 to 60 min, 1 to 24 hours, 1 to 30 days, 1 to 12 months, greater than 1 year

Non-expert summaryThe Report Executive Summary states: "The Trade-off Tool for Sampling (TOTS) is a tool under development that aids planners, responders, and subject matter experts in developing defensible yet practicable sample collection plans following a biological contamination incident. The U.S. Environmental Protection Agency (EPA) held a table-top exercise (TTX) with two separate groups of people. The purpose of the TTX was to gather critical end-user feedback on the utility of the tool for future revisions of TOTS and to increase collective (responders, planners, and researchers) understanding of challenges during the sampling and analysis plan (SAP) development for biological incidents, all for the goal of strengthening EPA’s capabilities in this area. The first TTX session was held at the 2019 EPA International Decontamination Conference in Norfolk, Virginia (November 18, 2019), and the second TTX session was held at the EPA On-scene Coordinator (OSC) Academy in Chicago, Illinois (February 26, 2020). The ultimate goal is to provide EPA planners and operational personnel (e.g., on-scene coordinators) the tools and resources necessary to effectively and efficiently plan and execute EPA’s response obligations."

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Technical report

A Review of biological agent sampling methods and application to a wide-area incident scenario to characterize time and resource demands

Calfee, W., Lee, S., Boe, T.

2017

Institution / OrganisationUS Environment Protection Agency

Keywordsbacteria, cleaning, decontamination, risk

DisciplinesMicrobiology

CategoriesField work, Review

Scale1e-3 to 1 m, 1 to 10 m, 10 to 1000 m, greater than 1 km / 1 to 60 s, 1 to 60 min, 1 to 24 hours, 1 to 30 days, 1 to 12 months, greater than 1 year

Non-expert summaryThe executive summary of this US EPA report states: "A large-scale aerosol release of a persistent, disease-causing biological agent can result in contamination of a wide area, and may require significant time and resources for recovery depending on the severity of adverse health effects on the exposed population(s). Many unknowns are associated with characterization and clearance sampling during response to a wide-area (including indoor, outdoor, and underground area) biological incident. The biological agent and its characteristics, the release mechanism, amount of contaminant released, and a plethora of environmental and meteorological factors are completely separate, yet interconnected processes that greatly influence the extent and level of contamination. Similarly, decisions related to the sampling strategy (i.e., sample medium, sampling area, spacing, etc.) will affect the cost, time, amount of waste generated, and personnel (i.e., resource demand) required to characterize and clear the contaminated area. The process of understanding how these elements influence one another and contribute to the overall problem is referred to as a systems approach. To what degree sampling and, more specifically, variations in the sampling strategy interact and contribute to overall resource demand, following a wide area biological incident, is still largely unknown. To date, there have been no attempts to model characterization sampling following a wide-area biological incident."

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Article

A three-dimensional computer model analysis of three hypothetical biofilm detachment mechanisms

Chambless, J.D., Stewart, P.S.

2007Biotechnology and Bioengineering97(6)1573-1584

Keywordsbacteria, biofilm, cleaning, detachment, flow displacement, shear flow

DisciplinesChemical Engineering, Microbiology

CategoryNumerical simulations

Scale1e-6 m, 1e-6 to 1e-3 m, 1e-3 m / 1e-3 to 1 s, 1 to 60 s, 1 to 60 min

Non-expert summaryThe removal of biofilms by sloughing is a natural phenomenon in biofilm dynamics. Three hypothetical mechanisms of detachment were incorporated into a 3D model of biofilm development. The model integrated processes of substrate utilization, substrate diffusion, growth, cell advection, and detachment in a cellular automata framework. The three detachment mechanisms analyzed represented various physical and biological influences hypothesized to affect biofilm detachment; fluid shear removing protruding material; removal linked to local nutrient availability; and erosion. The detachment mechanisms demonstrated diverse behaviors with respect to the four analysis criteria. The results show that detachment is a critical determinant of biofilm structure and of the dynamics of biofilm accumulation and loss.

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