Corrosion impact on drinking water distribution systems : a review and future research direction

At present water treatment and distribution is of high priority to ensure that communities have access to safe and affordable drinking water. Current information states that in the United States a total annual cost of $36 billion (US) is spent replacing aging infrastructure, lost water from unaccounted-for leaks, corrosion inhibitors, internal mortar linings, external coatings, and cathodic protection as a result of corrosion. In order to reduce the cost incurred as a result of corrosion in the water distribution industry, it is essential that better corrosion management and preventative strategies are implemented. However through investigation of research previously undertaken by others, it was found that there was a lack of study of corrosion within distribution systems in the tropics taking into account the related seasonal temperature variations. To assist in the development of management strategies to improve the outcomes of drinking water distribution systems, the authors propose to implement a pilot study involving the installation of a corrosion reactor based on standard corrosion assessment technologies in a water distribution system located in the tropics.

Prediction of chlorine and trihalomethanes concentration profile in bulk drinking water distribution systems from laboratory data

Nearly all drinking water distribution systems experience a "natural" reduction of disinfection residuals. The most frequently used disinfectant is chlorine, which can decay due to reactions with organic and inorganic compounds in the water and by liquid/solids reaction with the biofilm, pipe walls and sediments. Usually levels of 0.2-0.5 mg/L of free chlorine are required at the point of consumption to maintain bacteriological safety. Higher concentrations are not desirable as they present the problems of taste and odour and increase formation of disinfection by-products. It is usually a considerable concern for the operators of drinking water distribution systems to manage chlorine residuals at the "optimum level", considering all these issues. This paper describes how the chlorine profile in a drinking water distribution system can be modelled and optimised on the basis of readily and inexpensively available laboratory data. Methods are presented for deriving the laboratory data, fitting a chlorine decay model of bulk water to the data and applying the model, in conjunction with a simplified hydraulic model, to obtain the chlorine profile in a distribution system at steady flow conditions. Two case studies are used to demonstrate the utility of the technique. Melbourne's Greenvale-Sydenham distribution system is unfiltered and uses chlorination as its only treatment. The chlorine model developed from laboratory data was applied to the whole system and the chlorine profile was shown to be accurately simulated. Biofilm was not found to critically affect chlorine decay. In the other case study, Sydney Water's Nepean system was modelled from limited hydraulic data. Chlorine decay and trihalomethane (THM) formation in raw and treated water were measured in a laboratory, and a chlorine decay and THM model was derived on the basis of these data. Simulated chlorine and THM profiles agree well with the measured values available. Various applications of this modelling approach are also briefly discussed.

Evaluation of chlorine decay kinetics expressions for drinking water distribution systems modelling

The decay of chlorine in drinking water involves a complex set of reactions that is usually simplified to first order kinetics in models of water quality in distribution systems. However, to be useful in optimising chlorine dosing regimes, the kinetics expression should accurately describe the shape of the chlorine decay curve for different chlorine doses and be able to simulate re-chlorination. After considering the nature of the reactions involved in chlorine decay, five simplified reaction schemes were evaluated for their suitability to describe chlorine concentration in bulk water. Each scheme was fitted to a sample of experimental data of chlorine decay in raw water obtained from Warragamba Dam (the major source of water supplied to Sydney, Australia). A scheme involving two parallel reactions of organic carbon compounds with chlorine is both necessary and sufficient to satisfy the requirements of modelling chlorine decay accurately.

Rapid water quality characterization for chlorine demand and THM formation in drinking waters

The quality of drinking water generally deteriorates when it is delivered through a distribution system due to the decay of disinfectant, which subsequently allows the re-growth of microorganisms in the distribution system in addition to the formation of trihalomethane (THM). Therefore, a model which describes the changes that occur in the water quality in the distribution system is needed to determine whether to enhance the treatment processes or to improve the distribution system so that microbiological criteria are met. In this paper the chlorine decay kinetics and THM formation in treated water is modeled considering the reaction of chlorine with fast and slow reacting organic and nitrogenous compounds which are present in that water. The treated water was also passed through three types of resins to fractionate very hydrophobic acids (VHA), slightly hydrophobic acids (SHA), hydrophilic charged (CHA) and hydrophilic neutral (NEU) compounds which are present in the water. Chlorine decay tests were conducted on the effluents emerging from the resins to evaluate the chlorine demand and THM formation potential of those organic fractions. The model shows that the CHA presented in the waters has a very high THM formation potential (around 62% of the THM produced). VHA, NEU and CHA contributed to chlorine demand in the water.

Evaluating the drinking water quality through an efficient chlorine decay model

The performance of a treatment plant in reducing chlorine consuming substances as well as total trihalomethane formation (TTHM) could be evaluated rapidly using an accurate chlorine decay model as used in this study. The model could estimate the concentrations of fast and slow reacting agents (FRA and SRA–including organic and inorganic substances) and fast and slow reacting nitrogenous compounds (FRN and SRN) that are present in test waters. By estimating those concentrations in source and treated waters one could evaluate the performance of the treatment plant as well as provide options such as better catchment management for source water protection or treatment upgrades (e.g. enhanced coagulation) to remove chlorine consuming compounds which also have the potential to form THMs.

Modeling bacterial growth in drinking water : effect of nutrients

This article presents a model of growth of naturally occurring heterotrophic bacteria in the bulk water phase in the absence of disinfectant. The model considers growth with carbon, phosphorus, and nitrogen balance, death and lysis of bacteria, and conversion of less biodegradable organic carbon to assimilable organic carbon. Experimental data from two raw and two treated waters were used to test the model. The model describes the increase of live and dead bacterial cells in the water phase, and its output closely matches the experimental data. Such a model has the ability to characterize water nutrient status as well as to predict behavior of indigenous heterotrophic bacteria. The ability to predict bacterial population dynamics with respect to nutrients is beneficial for water treatment optimization. The model, based on microbiological measurements, helps to characterize treated water quality and project performance in terms of water quality into a distribution system.

Modelling biofilm growth and disinfectant decay in drinking water

A simple biofilm model was developed to describe the growth of bacteria in drinking water biofilms and the subsequent interactions with disinfectant residuals incorporating the important processes, such as attachment of free bacteria to the biofilm on a wall surface, detachment of bacteria from the biofilm, growth of biofilm bacteria with chloramine inhibition, chloramine decay in the bulk water phase, and chloramine decay due to biofilm bacteria and wall surfaces. The model is useful in evaluating the biological stability of different waters, as it can predict concentration of organic substances in water. In addition, the model can be used to predict the bacterial growth and biofilm decay in distribution systems. A model of this kind is a useful tool in developing system management strategies to ultimately improve drinking water quality.

Sydney 1998 - lessons from a drinking water crisis

From July to September 1998, high concentrations of Cryptosporidium and Giardia were detected episodically in the water supply and distribution systems of Sydney, Australia. The resulting drinking water crisis triggered three consecutive boil-water advisories and a government inquiry into the management of the water supply. The episodic nature of the detections focused attention on the veracity of the laboratory results and triggered an investigation of the transport of these pathogens in Sydney's water supply system. This article provides information submitted to the Sydney Water Inquiry that explains the episodic occurrence of pathogens in the reticulated water supply, attributing it to rapid fluctuations in the quality of the water reaching the water treatment plant

How easy can the barley brie : drinking culture and accounting failure at the end of the nineteenth century in Britain

Purpose – This paper seeks to extend the development of the historical accounting research agenda further into the area of popular culture. The work examines the discourses that surrounded the drinking of alcohol in nineteenth century Britain and explores how an accounting failure disrupted the tension between the two established competing discourses, leading to a significant impact on UK drinking culture at the end of the nineteenth century.

Design/methodology/approach – The paper employs both primary and secondary sources. Secondary sources are used to develop the main themes of the discourses deployed by the temperance societies and the whisky companies. Primary sources derived from the contemporary press are employed, as necessary, in support.

Findings – The paper demonstrates that accounting, although it may not be central to a discourse or other social structure, can still have a profound impact upon cultural practices. The potential for research into culture and accounting should not therefore be dismissed if no immediate or concrete relationship between culture and accounting can be determined. Further support is provided for studies that seek to expand the accounting research agenda into new territories.

Originality/value – The study of popular culture is relatively novel in accounting research. This paper seeks to add to this research by exploring an area of cultural activity that has hitherto been neglected by researchers, i.e. by exploring how an accounting incident impacted upon the historical consumption of Scotch whisky in the UK.

The influence of families on early adolescent school connectedness : evidence that this association varies with adolescent involvement in peer drinking networks

School connectedness is central to the long term well-being of adolescents, and high quality parent–child relationships facilitate school connectedness. This study examined the extent to which family relationship quality is associated with the school connectedness of pre- and early teenagers, and how this association varies with adolescent involvement in peer drinking networks. The sample consisted of 7,372 10–14 year olds recruited from 231 schools in 30 Australian communities. Participants completed the Communities that Care youth survey. A multi-level model of school connectedness was used, with a random term for school-level variation. Key independent variables included family relationship quality, peer drinking networks, and school grade. Control variables included child gender, sensation seeking, depression, child alcohol use, parent education, and language spoken at home. For grade 6 students, the association of family relationship quality and school connectedness was lower when peer drinking networks were present, and this effect was nonsignificant for older (grade 8) students. Post hoc analyses indicated that the effect for family relationship quality on school connectedness was nonsignificant when adolescents in grade 6 reported that the majority of friends consumed alcohol. The results point to the importance of family-school partnerships in early intervention and prevention.