Reliability Modelling For Asset Management in South East Water

Over the years, the reliability modelling of water assets has generated increasing interest among both researchers and practitioners. Statistical methods and software packages for assessing asset reliability have been developed in order to improve asset availability, indirectly reduce water losses, and hence improve the efficiency of water assets. OFWAT, which is the economic regulator of the water sector in England and Wales, aims to ensure that water companies operate under their statutory functions and have sufficient financial means to perform these functions adequately. Water companies need to prepare a five-year business plan for OFWAT, in order to certify they have enough capital and are transparent when carrying out their statutory functions. Hence, this thesis aims to analyse the reliability of two selected types of assets at South East Water to help plan their future investments on vehicles and future maintenance costs on borehole assets. This thesis will provide an extensive literature review on reliability modelling in water distribution networks. An MS Excel-based decision support system will be developed for both vehicles and borehole assets, using data collected from South East Water. For the transport model, a block replacement policy will be developed by using Visual Basic, to obtain the optimum time of replacing a vehicle. Performance analysis will be conducted on the borehole data to pinpoint the worst performers among the 16 boreholes under analysis

Wastewater irrigation: the state of play

As demand for fresh water intensifies, wastewater is frequently being seen as a valuable resource. Furthermore, wise reuse of wastewater alleviates concerns attendant with its discharge to the environment. Globally, around 20 million ha of land are irrigated with wastewater, and this is likely to increase markedly during the next few decades as water stress intensifies. In 1995, around 2.3 billion people lived in water-stressed river basins and this could increase to 3.5 billion by 2025. We review the current status of wastewater irrigation by providing an overview of the extent of the practice throughout the world and through synthesizing the current understanding of factors influencing sustainable wastewater irrigation. A theme that emerges is that wastewater irrigation is not only more common in water-stressed regions such as the Near East, but the rationale for the practice also tends to differ between the developing and developed worlds. In developing nations, the prime drivers are livelihood dependence and food security, whereas environmental agendas appear to hold greater sway in the developed world. The following were identified as areas requiring greater understanding for the long-term sustainability of wastewater irrigation: (i) accumulation of bioavailable forms of heavy metals in soils, (ii) environmental fate of organics in wastewater-irrigated soils, (iii) influence of reuse schemes on catchment hydrology, including transport of salt loads, (iv) risk models for helminth infections (pertinent to developing nations), (v) microbiological contamination risks for aquifers and surface waters, (vi) transfer efficiencies of chemical contaminants from soil to plants, (vii) health effects of chronic exposure to chemical contaminants, and (viii) strategies for engaging the public.<br /

Hydrogeology of the Split Rock Creek aquifer with emphasis on calibration of a numerical flow model, southeast Minnehaha County, South Dakota /

Shipping list no.: 98-0197-P.Includes bibliographical references (p. 38-39).Mode of access: Internet

Water resources of Minnehaha County, South Dakota /

Shipping list no.: 92-265-P.Includes bibliographical references (p. 78-80).Mode of access: Internet

Assessing rural small community water supply in Limpopo, South Africa: Water service benchmarks and reliability

Although a number of studies have reported on water supply improvements, few have simultaneously taken into account the reliability of the water services. The study aimed to assess whether upgrading water supply systems in small rural communities improved access, availability and potability of water by assessing the water services against selected benchmarks from the World Health Organisation and South African Department of Water Affairs, and to determine the impact of unreliability on the services. These benchmarks were applied in three rural communities in Limpopo, South Africa where rudimentary water supply services were being upgraded to basic services. Data were collected through structured interviews, observations and measurement, and multi-level linear regression models were used to assess the impact of water service upgrades on key outcome measures of distance to source, daily per capita water quantity and Escherichia coli count. When the basic system was operational, 72% of households met the minimum benchmarks for distance and water quantity, but only 8% met both enhanced benchmarks. During non-operational periods of the basic service, daily per capita water consumption decreased by 5.19 l (p < 0.001, 95% CI 4.06–6.31) and distances to water sources were 639 m further (p = 0.001, 95% CI 560–718). Although both rudimentary and basic systems delivered water that met potability criteria at the sources, the quality of stored water sampled in the home was still unacceptable throughout the various service levels. These results show that basic water services can make substantial improvements to water access, availability, potability, but only if such services are reliable