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.

Removal of natural organic matter though membrane filtration and subsequent effect on disinfectant decay

This study aims to evaluate the effectiveness of membrane filtration in removing natural organic matters (NOMs) from four different source waters and the subsequent effect that it has on total chlorine (TC) demand of these waters. Source water samples were filtered sequentially through membranes with molecular weight cut-off of 3,500, 1,000 and 200 Da as well as RO membrane. The source waters and sequentially filtered samples were dosed with chlorine and the residual chlorine data were used to estimate the TC demand of these waters. A robust chlorine decay model constructed in AQUASIM software was used to do so. More than 80% of the chlorine demand in untreated surface water sources was found to be contributed mainly by NOMs that were larger than 3,500 Da. However, for water treated by granular filtration, the chlorine demand was found to be contributed by NOMs which were down to 200 Da. Sequential filtration through all four membranes reduced chlorine demand by more than 94% in surface waters and 84% in waters treated by granular filtration. Significant reduction in the formation of trihalomethane can be achieved if water is treated by appropriate membranes after granular media filtration. © 2014 © 2014 Balaban Desalination Publications. All rights reserved.

Aspectos Microbiológicos e Demanda de Cloro de Amostras de Água de Dessedentação de Frangos de Corte Coletadas em Bebedouros Pendulares

Foram analisadas 72 amostras da água de dessedentação de frangos de corte, 18 da entrada e 54 dos bebedouros pendulares. As amostras foram submetidas às mensurações de coliformes totais, coliformes fecais, estreptococos fecais, Escherichia coli e organismos mesófilos, além da detecção da presença de Salmonella sp e da taxa de demanda de cloro. Os resultados evidenciaram uma elevada contaminação bacteriológica, já na primeira semana, com os indicadores na ordem de 10³ a 10(5). Não houve isolamento de nenhuma cepa de Salmonella sp, provavelmente por não haver ave infectada no plantel. A taxa de demanda de cloro mostrou-se elevada, devido ao maior acúmulo de matéria orgânica nos bebedouros, com o ápice na quinta semana (98,7%), seguida de uma leve diminuição na sexta semana (98,5%). As análises dos resultados evidenciam o bebedouro pendular como um instrumento depreciativo e ineficiente em relação às qualidades higiênico-sanitárias das águas fornecidas aos frangos de corte, contribuindo para um alto risco de contaminação por patógenos de veiculação hídrica. Preconizam-se a utilização de modelos de bebedouros menos deletérios e o monitoramento semanal de cloro residual nos bebedouros pendulares, a fim de se obter uma desinfecção satisfatória da água.

Qualidade Higiênico-Sanitária e Demanda de Cloro da Água de Dessedentação de Galinhas de Postura Coletadas em Bebedouros Tipo Nipple e Taça

O objetivo deste estudo foi avaliar a influência de dois tipos de bebedouros nipple e taça, utilizados na dessedentação de aves de postura e o incremento da demanda de cloro na água oferecida pelos dois tipos de bebedouros estudados. Foram realizadas as contagens de coliformes totais, coliformes fecais, Escherichia coli, estreptococos fecais e microrganismos mesófilos. Os resultados obtidos figuraram que as amostras de água dos reservatórios, de ambos os bebedouros, apresentaram-se contaminadas microbiologicamente antes de passarem pelos bebedouros. A contaminação por bactérias de poluição fecal foi maior nas amostras colhidas nos bebedouros tipo taça, assim como eles foram responsáveis por um maior acúmulo de matéria orgânica, tendo então uma elevada demanda de cloro e uma maior influência na depreciação da qualidade da água fornecida às aves. Dos dois tipos de bebedouros estudados, o tipo nipple mostrou ser o menos deletério no que concerne à qualidade da água entretanto, independente do tipo de bebedouro utilizado na dessedentação das aves, a desinfecção da água é um ato imprescindível à manutenção de sua qualidade e à eliminação de futuros patógenos.

Comportamento cinético do cloro livre em meio aquoso e formação de subprodutos da desinfecção

One indirect approach to predict the disinfection by-product (DBP) formation potential for a given water source is by evaluation of the kinetic behavior of free chlorine in the liquid phase and chlorine demand determination for different operation conditions of the chlorination process. The objective of this work was to evaluate the kinetic behavior of free chlorine in water or a number of different raw water sources, as well as to investigate the impact of the coagulation process on chlorine demand reduction and DBP formation. It was observed that the higher the total organic carbon (TOC) removal efficiency through coagulation, the lower the liquid phase chlorine demand. Regarding trihalomethane (THM) formation, a ratio of 28 ug/L formed per mg/L of applied chlorine was observed for the waters employed in the experimental investigation.

Dinâmica da contaminação fecal e uso do cloro na desinfecção da água oferecida a bezerras em propriedade leiteira

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

UASB reactor effluent disinfection by ozone and chlorine

This research studied the sequential ozone and chlorine process with respect to, the inactivation of indicator bacteria and the formation of ozone disinfection byproducts in sanitary wastewater effluent. The applied ozone doses were 5, 8 and 10 mg.O3.L(-1), followed by chlorine doses of 10, 20 and 30 mg.L(-1), respectively. After the sequential ozone/chlorine process, the mean reduction in chemical oxygen demand ranged from 9 to 37%. Total coliform inactivation ranged from 1.59 to 3.73 log10, and E. coli was always <1 CFU 100 mL(-1). Ozonation resulted in the formation of aldehydes, which were not significantly impacted by the subsequent chlorine dose (P ≤ 0.05).

Growing demand for emergency health services in Queensland, Australia

Introduction: The demand for emergency health services (EHS), both in the prehospital (ambulance) and hospital (emergency departments) settings, is growing rapidly in Australia. Broader health system changes have reduced available health infrastructure, particularly hospital beds, resulting in reduced access to and congestion of the EHS as demonstrated by longer waiting times and ambulance “ramping”. Ambulance ramping occurring when patients have a prolonged wait on the emergency vehicle due to the unavailability of hospital beds. This presentation will outline the trends in EHS demand in Queensland compared with the rest of Australia and factors that appear to be contributing to the growth in demand. Methods: Secondary analysis was conducted using data from publicly available sources. Data from the Queensland Ambulance Service and Queensland Health Emergency Department Information System (EDIS) also were analyzed. Results: The demand for ambulance services and emergency departments has been increasing at 8% and 4% per year over the last decade, respectively; while accessible hospital beds have reduced by almost 10% contributing to the emergency department congestion and possibly contributing to the prehospital demand. While the increase in the proportion of the elderly population seems to explain a great deal of the demand for EHS, other factors also influence this growth including patient characteristics, institutional and societal factors, economic, EHS arrangements, and clinical factors. Conclusions: Overcrowding of facilities that provide EHS are causing considerable community concern. This overcrowding is caused by the growing demand and reduced access. The causes of this growing demand are complex, and require further detailed analysis in order to quantify and qualify these causes in order to provide a resilient foundation of evidence for future policy direction.

How does ambulance service utilisation impact demand for Emergency Departments in Queensland, Australia?

Background: There are indications that pre-hospital emergency care and management of patients can help reduce the demand for hospital emergency departments (EDs). Ambulance services play a significant role at this stage of care. In 2003, the Queensland Government introduced a Community Ambulance Cover (CAC) levy in return for a free ambulance service at the point of access to all Queenslanders. This may have led to the impression in consumers of an entitlement to free ambulance services under any circumstances regardless of the urgency of the matter which may have in turn contributed to the crowding of EDs in Queensland. Objectives: This paper aims to answer the following questions: - How many patients arrive at hospital EDs by ambulance in Queensland, compared to other modes of arrival? - How has this changed over time, particularly after the CAC introduction in 2003? What percentage of ambulance arrivals are urgent ED patients? - Has the perceived free ambulance services created extra demand for EDs in Queensland, compared with other Australian jurisdictions that charge patients for ambulance services? Methods: We will secondary analyse the data from sources such as Queensland Ambulance Services, Department of Health and Australian Bureau of Statistics to answer the research questions. Findings and Conclusions Queensland has the highest utilization rate of ambulance services (about 18% in 2007-08) and the highest annual growth rate in demand for these services (7.7% on average since 2000-01), well above the population growth. On the other hand, the proportion of ED patients arriving by ambulance in Queensland has increased by about 4% annually. However, when compared with other states and territories with charge at the point of access, it seems that the growth in demand for EDs cannot be explained solely or mainly by CAC or ambulance utilisation in Queensland.