Tastes and odours in potable water:perception versus reality

Tastes and odours are amongst the few water quality standards immediately apparent to a consumer and, as a result, account for most consumer complaints about water quality. Although taste and odour problems can arise from a great many sources, from an operational point of view they are either ”predictable” or ”unpredictable”. The former - which include problems related to actinomycete and algal growth - have a tendency to occur in certain types of water under certain combinations of conditions, whereas the latter - typically chemical spills - can occur anywhere. Long-term control is one option for predictable problems, although biomanipulation on a large scale has had utile success. Detection and avoidance is a more practicable option for both predictable and unpredictable problems, particularly if the distribution network can be serviced from other sources. Where these are not feasible, then water treatment, typically using activated carbon, is possible. In general there is a reasonable understanding of what compounds cause taste and odour problems, and how to treat these. An efficient taste and odour control programme therefore relies ultimately on good management of existing resources. However, a number of problems lie outside the remit of water supply companies and will require more fundamental regulation of activities in the catchment

Report of the 1988 2-D Intercomparison Workshop, chapter 3

Several factors contribute to the errors encountered. With the exception of the line-by-line model, all of the models employ simplifying assumptions that place fundamental limits on their accuracy and range of validity. For example, all 2-D modeling groups use the diffusivity factor approximation. This approximation produces little error in tropospheric H2O and CO2 cooling rates, but can produce significant errors in CO2 and O3 cooling rates at the stratopause. All models suffer from fundamental uncertainties in shapes and strengths of spectral lines. Thermal flux algorithms being used in 2-D tracer tranport models produce cooling rates that differ by as much as 40 percent for the same input model atmosphere. Disagreements of this magnitude are important since the thermal cooling rates must be subtracted from the almost-equal solar heating rates to derive the net radiative heating rates and the 2-D model diabatic circulation. For much of the annual cycle, the net radiative heating rates are comparable in magnitude to the cooling rate differences described. Many of the models underestimate the cooling rates in the middle and lower stratosphere. The consequences of these errors for the net heating rates and the diabatic circulation will depend on their meridional structure, which was not tested here. Other models underestimate the cooling near 1 mbar. Suchs errors pose potential problems for future interactive ozone assessment studies, since they could produce artificially-high temperatures and increased O3 destruction at these levels. These concerns suggest that a great deal of work is needed to improve the performance of thermal cooling rate algorithms used in the 2-D tracer transport models

Developing Multi-Scale Models for Water Quality Management in Drinking Water Distribution Systems

Drinking water supply systems belong to the group of critical infrastructure systems that support the socioeconomic development of our modern societies. In addition, drinking water infrastructure plays a key role in the protection of public health by providing a common access to clean and safe water for all our municipal, industrial, and firefighting purposes. Yet, in the United States, much of our national water infrastructure is now approaching the end of its useful life while investments in its replacement and rehabilitation have been consistently inadequate. Furthermore, the aging water infrastructure has often been operated empirically, and the embracement of modern technologies in infrastructure monitoring and management has been limited. Deterioration of the water infrastructure and poor water quality management practices both have serious impacts on public health due to the increased likelihood of contamination events and waterborne disease outbreaks. Water quality reaching the consumers’ taps is largely dependent on a group of physical, chemical, and biological interactions that take place as the water transports through the pipes of the distribution system and inside premise plumbing. These interactions include the decay of disinfectant residuals, the formation of disinfection by-products (DBPs), the corrosion of pipe materials, and the growth and accumulation of microbial species. In addition, the highly dynamic nature of the system’s hydraulics adds another layer of complexity as they control the fate and transport of the various constituents. On the other hand, the huge scale of water distribution systems contributes dramatically to this deterioration mainly due to the long transport times between treatment and consumption points. Hence, utilities face a considerable challenge to efficiently manage the water quality in their aging distribution systems, and to stay in compliance with all regulatory standards. By integrating on-line monitoring with real-time simulation and control, smart water networks offer a promising paradigm shift to the way utilities manage water quality in their systems. Yet, multiple scientific gaps and engineering challenges still stand in the way towards the successful implementation of such advanced systems. In general, a fundamental understanding of the different physical, chemical, and biological processes that control the water quality is a crucial first step towards developing useful modeling tools. Furthermore, water quality models need to be accurate; to properly simulate the concentrations of the different constituents at the points of consumption, and fast; to allow their implementation in real-time optimization algorithms that sample different operational scenarios in real-time. On-line water quality monitoring tools need be both reliable and inexpensive to enable the ubiquitous surveillance of the system at all times. The main objective of this dissertation is to create advanced computational tools for water quality management in water distribution systems through the development and application of a multi-scale modeling framework. Since the above-mentioned interactions take place at different length and time scales, this work aims at developing computational models that are capable of providing the best description of each of the processes of interest by properly simulating each of its underlying phenomena at its appropriate scale of resolution. Molecular scale modeling using tools of ab-initio quantum chemical calculations and molecular dynamics simulations is employed to provide detailed descriptions of the chemical reactions happening at the atomistic level with the aim of investigating reaction mechanisms and developing novel materials for environmental sensing. Continuum scale reactive-transport models are developed for simulating the spatial and temporal distributions of the different compounds at the pipe level considering the effects of the dynamic hydraulics in the system driven by the spatiotemporal variability in water demands. System scale models are designed to optimize the operation of the different elements of the system by performing large-scale simulations coupled with optimization algorithms to identify the optimal operational strategies as a basis for accurate decision-making and superior water quality management. In conclusion, the computational models developed in this study can either be implemented as stand-alone tools for simulating the fundamental processes dictating the water quality at different scales of resolution, or be integrated into a unified framework in which information from the small scale models are propagated into the larger scale models to render a high fidelity representation of these processes

A Preliminary Study Exploring Racial Differences in Triage, Hospitalization Status, And Discharge Medication in an Emergency Department in Graniteville, SC

Purpose This study seeks to identify any racial differences present in assigned triage scores, hospitalization status and discharge medications in a rural hospital likely experiencing a surge after a mass casualty incident involving chlorine gas as a result of a train derailment. Differences were examined between Non-Hispanic White and African American adults who were moderately ill and who presented to the emergency department of the closest hospital to the accident site within 24 hours of the incident. Methods Non-Hispanic White and African American adults who presented to the emergency department of the closest hospital to the accident site and who complained of chlorine exposure symptoms were included in this descriptive epidemiological study (n=25). Data used was obtained from medical records, utilizing a standardized medical abstraction form. Toxidrome, a compilation of five symptoms specific to chlorine exposure: eye irritation or pain, ear, nose, and throat irritation or pain, cough/wheezing and/or nausea/vomiting documented in the emergency room, was used as a proxy variable for exposure to chlorine gas. Triage score is defined by classifying patients as urgent or non-urgent based on the Simple Triage Rapid Treatment (START) algorithm. Hospitalization status is defined by a coding system created by the Center for Disease Control (CDC) and South Carolina Department of Health and Environmental Control (SC DHEC) to evaluate the severity of patients\u27 symptoms. Patients were assigned to a hospitalization status group based on this coding system; hospitalized or not hospitalized. Both groups consisted of patients with similar severity symptoms. Discharge medications are defined by the prescribed biologic agents given to each patient upon discharge. Patients were grouped in oral medication or non-oral medication categories. Frequency distributions were calculated for all categorical variables and mean age was calculated for the only continuous variable. All categorical variables were assessed with Chi square or Fishers exact test to determine if racial differences were present in assigned triage scores, hospitalization status, and discharge medications received. Age, the only continuous variable, was assessed with a t-test. Results The data suggests that all victims sustained equal effects caused by exposure to chlorine gas (p= 0.283) and that there was no significant difference between demographic characteristics: age, sex, smoking status, and pre-existing pulmonary disease. There was no statistically significant difference between Non-Hispanic Whites and African Americans in discharge medications (p=0.131). The data suggests a significant difference in hospitalization status (p=0.024) by race, where 100% of Non-Hispanic Whites and 62.5% of African Americans were hospitalized. For patients presenting with similar injury severity, a statistically significant difference was observed between Non-Hispanic Whites and African Americans (p=0.027). The percentage of Non-Hispanic Whites (82.4%) was higher than that of African Americans (50.0%) who were given an urgent triage classification. Conclusion The present work suggests a difference in triage scores assigned and hospitalization status between Non-Hispanic White and African American adults, who sought treatment at the closest hospital to the accident site during a mass casualty incident. The differences observed may be attributed to non-clinical factors influencing triage decisions and care provided. The implications of differential care based on race are a critically important public health concern. Further research should is needed to investigate why there are racial differences in hospitalization status and triage score assignment for equally exposed patients with similar severity of injuries

Lost in optimisation of water distribution systems? A literature review of system operation

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Optimisation of the operation of water distribution systems has been an active research field for almost half a century. It has focused mainly on optimal pump operation to minimise pumping costs and optimal water quality management to ensure that standards at customer nodes are met. This paper provides a systematic review by bringing together over two hundred publications from the past three decades, which are relevant to operational optimisation of water distribution systems, particularly optimal pump operation, valve control and system operation for water quality purposes of both urban drinking and regional multiquality water distribution systems. Uniquely, it also contains substantial and thorough information for over one hundred publications in a tabular form, which lists optimisation models inclusive of objectives, constraints, decision variables, solution methodologies used and other details. Research challenges in terms of simulation models, optimisation model formulation, selection of optimisation method and postprocessing needs have also been identified