Barbados Water Authority Leak Detection

Transcription

1 Barbados Water Authority Leak Detection By: Gary Fricke- Sales Manager Hetek Solutions Inc. Shelley Chase- Engineer, Waste Control/ Distribution, Barbados Water Authority

2 Abstract Water suppliers are under increasing pressure to reduce leakage rates and provide a consistent, high integrity water supply. Resource development is expensive and reductions in Non Revenue Water (NRW) are an attractive and economically viable means of increasing the headroom between supply and demand. New techniques in leak detection are emerging to help water suppliers achieve their objectives. Based on 1997 estimates, the Barbados Water Authority (BWA) have set a target of reducing the 60% NRW, to a target of 30% by the year This projected reduction can be achieved using.best Practice. principals including district monitoring and leak detection. For leak detection, the BWA has chosen the advanced leak detection methods developed by Palmer Environmental and Hetek Solutions Inc. Initial leak detection utilized step testing and conventional sounding methods. However, these prohibitively high costs associated with overtime and the inconvenience of night work led the BWA to investigate alternate methods. With the introduction of the Palmer Environmental.s Permalog leak localization system, the BWA is achieving and maintaining lower leakage levels at lower cost, as well as improving customer service by maintaining continuity of supply, in addition to reducing the overall water lost through leakage. Initial trials in a major UK water company have shown the potential of Permalog to reduce leakage to record low levels and for water suppliers to maintain these over a 10 year period at low cost and with significantly improved customer service. Permalog units are deployed on a rotation basis throughout the distribution system to provide continuous surveying of leakage. These loggers are used to focus the leakage surveys in specific areas of the network. Easily installed on main lines and hydrant valves, they are retained in place by a strong magnet and are battery-powered for at least 10 years. Loggers are immersion-tested to IP68 and will continue to operate even in flooded chambers with no maintenance required. Each unit adapts itself automatically to its environment. If no leak is present a signal is transmitted to indicate normal background conditions. However, as soon as a possible leak is detected, the Permalog unit enters an alarm state and transmits leak data. This paper describes how the BWA uses an innovative approach to leak detection.using Permalog equipment, and shows that in many cases, the reduction in leakage within the system can lead to a drastic reduction in NRW throughout the island.

3 Introduction Leak Detection in the water supply industry is focused on the location of leaks on distribution network appurtenances and to a lesser extent on leaks directly associated with water production before it is put into the distribution network. In order to determine the appropriate method by which leak detection should be undertaken for the entire utility, it is important that this forms a part of a comprehensive Leakage Management and Assessment Programme. The activities carried out in this programme will output the priority for leak surveys and investigation throughout the distribution network and utility as a whole. In the first section of the paper, the Leakage Management approach recommended by the most recent studies on this aspect of the Water Industry is discussed, as well as where the focus of leak detection will stem based on this approach. In the second section of the paper the discussion focuses on the experience of the Barbados Water Authority with respect to Leakage Management and its decision to use the Permalog Leak Detection system in its current operations. Please note that the Addendum contains more detailed information on an actual leak survey carried out using the Permalog Leak Detection system and the reduction in leakage, which was observed through its use at the time. Leakage Management and Assessment

4 This section of the paper deals with the Leakage Management approach, which should be adopted by a water utility as recommended by the most recent studies on Leakage Management and Assessment. Leakage Management and Assessment in a water utility are primarily focused on the measurement and reduction of leakage in the production and distribution systems of the company. Leakage Assessment Estimates for leakage are obtained by two (2) means. The first is via the use of the Water Balance Calculation. This is the method recommended by the International Water Association Task Force for the review of existing Methodologies for International comparisons of Water Losses from Water supply systems. The use of this calculation brings about the analysis of records of production and consumption, which are analysed, together with assumptions or prediction of those quantities listed in the calculation, which are not measured. Billed metered consumption (including water exported) Billed Authorized Consumption Billed Unmetered consumption Revenue Water Unbilled Metered Consumption Authorized Consumption Unbilled Authorized Consumption Unbilled Unmetered Consumption Unauthorized Consumption Apparent Losses Customer Metering Inaccuracies Leakage on Transmission and/or Distribution Mains Leakage and Overflows at Storage Tanks System Input Volume

5 Water Losses Real Losses Leakage on Service Connections up to point of customer metering Non Revenue- Water I II III IV V Reference: Fig 1-.The IWA Standard Annual Water Balance.. Leakages in Water Distribution Networks within an international context.. Figure 1: An illustration showing a Water Balance used in the calculation of Non-Revenue Water. The Water Balance Calculation is preformed in a top-down approach whereby the estimates for quantities listed in Column IV in Figure 1, are assembled starting from the top of the column- Billed metered consumption (including water exported). The estimate for Water Losses obtained via this method is referred to as a.crude. estimate. Please note however that this estimate is subject to calculation error due to errors inherent in the individual components. The second method by which an estimate for leakage is obtained is the collection of data from District Metering and Nightline flows. The sub-division of the distribution system into districts is important for the estimation of the level of leakage. This leakage level is usually the minimum flow during the off-peak demand period, occurring early in the morning (approximately 2:00 a.m. when usage is approximated to be at a minimum), hence the description Minimum Night Flow (MNF). This MNF is the water loss occurring in a particular district due mostly to Real Losses (Refer to Figure One). A significant part of the Leakage Assessment process is the component analysis of Real Losses. The components into which it may be sub-divided are listed in Column IV of the Figure 1. Concepts that may be used to carry out this component analysis include the Bursts And Background Estimates (BABE) Method and the Fixed and Variable Area Discharges (FAVAD). These however will not be detailed in this paper. Table 3: Parameters used for calculation Components of Annual Real Losses. Component of Infrastructure Background

6 (undetectable) leakage Report Bursts and Overflows Unreported Bursts and Overflows Mains Length Min. Loss/km* Number/year Average flow rate* Average Duration Number/year Average flow rate* Average Duration Service Reservoirs Leakage Throughout structure, % of capacity/day No. of reported overflows/yr Average flow rate Average duration No. of unreported overflows/year Average flow rate Average Duration Service Connections, Main to Property Boundary Number of service connections Min loss rate/conn* Number/ year Average flow rate* Average duration Number/year Average flow rate* Average duration Service Connections after Property Boundary Length Min loss rate/km Number/year Average flow rate* Average duration Number/year Average flow rate* Average duration *At some standard pressure, later corrected for actual pressure using FAVAD

7 Figure 3: Table from Leakage Management The department concerned with Leakage Management is primarily concerned with the comparison of Real Losses from period to period, and the effect of Leak Detection on the Reduction of Real Losses. The comparison of Real Losses from one period to another is an important management tool. The units used for comparison for a given period (usually a year) are referred to as performance indicators. Real Losses are also used as performance indicators for the comparison of one Utility to another and as to the conformity of one utility to International Industry Standards. The quantification of Real Losses as a performance indicator include: A % of Input volume. A figure per length of mains per day or hour. (m3/km/day) A figure per service connection per day or hour. (m3/connection/day) A figure per property per day or hour. A figure per length of system per day or hour. A figure per number of incidents (confirmed service interruptions) per 1000 properties served). an estimation of continuity of service. (Where length of system = length of mains + length of service connections up to the point of customer metering.). Those performance indicators highlighted are the Best Practice Basic Performance Indicators for Operational management of Real Losses as recommended by the International Report on Water Losses Management Techniques (see references). However with each of these quantities there are disadvantages. These are as follows: (i) % Of input volume is too strongly influenced by consumption and changes in consumption, making it unsuitable for this purpose. (ii).per billed account. or.per property. should not be used, as some service connections supply multiple billed properties, yet there is only one service connection with potential to leak. (iii) The choice of.per service connection. or.per km of mains. as a scaling factor

8 depends upon the density of connections for the system under consideration. Recommendations from the International Report on Water Losses Management Techniques suggest the use of the following process (IWA PI Op 24) for the selection of performance indicator types in the determination of Real Losses. Figure 3: Process to determine Level 1 PI For Operational Management of Real Losses Specify: Number of Service Connections (Nc) Length of Mains (Lm km) Calculate: Density of Service Connection/km DC= Nc/Lm DC< 20 Conns/km? Use litres/service Connection/ day as Real Losses Level 1 PI Use m3 /km Mains/day as Real Losses Level 1 PI No Yes Recent Studies also indicate the use of the following techniques in Leakage Management. - Pipeline and assets management - Management (which may either be by the increase or reduction in pressure) - Speed and quality of reports - Active leakage control, to locate unreported leaks The extent to which these four activities are carried out directly determine whether or not the value of annual Real Losses will increase, decrease or remain the same.

9 The use of the methods described in this section of the paper are those recommended for use by the International Water Association in several of their papers which are published online. Some of these are listed in the References section of the paper. It is the international trend, to develop the use of performance indicators for measurement of leakage as well as the other operations within water utilities. This has come about as the result of much research, due to constraints such as reduced rainfall events connected to climate change worldwide. The B.W.A. Experience The Waste Control Department of the B.W.A. established in the late 1970.s, is the department primarily responsible for leakage assessment and management.

10 The Barbados Water Authority has no well-maintained records verifying that any detailed analysis of leakage in the water distribution system was carried out before a study done in This will be discussed further later in this paper. The main practices of the department included the determination of leakage by use of.night-lines., that is the minimum flow at off-peak demand usage- approximately 2:00 a.m. This information was in turn used for step testing (this process involves the sequential shutting down of mains in a district while monitoring flows to determine the location of a leak). Refer to Figure 1. Figure 1 Over time, methods such as listening for leak noise (particular frequency generated by leaks as they escape from the water main) by use of a ground microphone, were incorporated into the process in order to decrease overall time taken. Since the inception of the department several studies have been carried out to improve operations in the department. These include: (i) Notes prepared for Waste Control Unit Training- BINNIE AND PARTNERS London SW1- July (ii) Draft Report on Waste Control, prepared for the Government of Barbados, Ministry of Communication and Works- Water Works Department by BINNIE AND PARTNERS Consulting Engineers, London, February (iii) Water Resources Management and Water Loss Study (WRMWLS), carried out for the B.W.A. by KLOHN. CRIPPEN CONSULTANTS Ltd. In association with Stanley Associates Engineering Ltd.- Draft Reports 5,6,7. The first two studies and reports focused on an initial training of the Waste Control department to use District Metering and Minimum Night Flows as well as the basics of pressure management as it was understood at the time for leak detection and reduction of water wastage. At that time, much of the leakage in the network was attributed to poor mains laying practices, that is compliance with international standards was not adhered to very strictly.

11 A detailed analysis of a water supply system- from water service reservoirs to pumping stations to transmission and distribution mains was carried out during the WRMWLS. Estimates for Leakage were provided for the island in general as well, and an Active Leakage Control Programme carried out for three specific areas within the distribution system. It was during this study that cutting edge techniques and technology were introduced to the department. These included computerised ways of collection data in the field, in the form of logging equipment for flows and pressures. The main innovation introduced at this stage was the use of the computer to perform a hydraulic network model of the distribution system inclusive of inputs from reservoirs etc. This provided a virtual quantum leap and greatly improved the way in which leakage management and assessment could be carried out. The hydraulic network model provided a computer-generated estimate for leakage based on simulations of the network, using the data collected from the logging equipment, as well as computerised data input on the distribution mains. Further advances have been made on the software used for this purpose, as well as the logging equipment and have been recommended for use in current operations in the near future. The department has already installed and made use of telemetric loggers, which collect information from remote location and is downloaded via modem and telephone lines to the office site for analysis. The department is also currently investigating the acquisition of similar loggers making use of GSM technology currently becoming available in the region. In addition to these improvements, for the purpose of leak detection in the field, the department has made use of the Correlator for uses similar to that described for the

12 ground microphone. But finally and most important to our operations at present is the use of the Palmer Permalog Leak Detection system. This system was chosen primarily due to a need to reduce the high expenses of the department incurred during step testing. High costs could be not readily justified economically since in most cases, leakage could not be readily quantified, nor its reduction after step tests were carried out. The elimination of this method of searching for leaks also meant that the following disadvantages of step testing were also eliminated: - Disruption of service to customers to carry out the step test. - Disruption of service for extended periods due to bursts caused by the step tests in high-pressure areas. - Water quality complaints after step-tests had been carried out, due to the shutting down of water supply to mains and accumulation of debris inside mains - Tedious Checking of valves before and during tests to ensure operation during the actual test. Hence, the Permalog Leak detection system proved to be the best solution since the main requirements were installation either directly onto the mains or network appurtenances (valves or hydrants). It also forms a part of active leak detection whereby the time taken entire leak survey process is greatly reduced and can be performed on a more regular basis. Figure 4 The use of the Permalog system has allowed the department to conduct and complete leak surveys in a much more effective manner, making use of a reduced number of persons and leak detection for a much wider area in less time. After the deployment of the Permalogs, a patrol of the network area is conducted the following day. Generally, a

13 patrolled area can be completed in a few hours compared with several weeks using conventional stop tap bashing or sounding. Figure 5 The following is a diagram illustrating the Water Saving which can be realised before during and after the use of the Leak Detections system in the identification of leaks and repairs. Water Savings Industrial Allowance Domestic Allowance Leakage Minimum night flow (m3/h) Weeks Permalog deployed

14 Leaks repaired Benefits of the Permalog System 100% of distribution system monitored More leaks found, more quickly Faster response to mains bursts Automates and de-skills surveying Independent of metering/balancing No opening/closing of valves Improves overall detection efficiency and motivation Operates continuously over a 10 year period Potential to comprehensively cover a network without small flow zones Permanent monitoring of.sensitive. pipelines. The Future of Leak Detection in the BWA Long term plans for the use of this leakage equipment mainly focus on the acquisition of enough equipment that semi-permanent installations can take place for large areas of the network. Due to the extents of this network (that is, a total length of 16km of mains), it is not foreseeable that permanent installation on all mains will happen. However, it is intended that additional acquisitions of the Permalog leak detection system will aid in the Water Supply Improvements Programme under which detailed Water Loss Reduction programmes, which have been planned for the department in the upcoming financial year. The Permalog Leak Detection system is foreseen to play a significant role in the leak detection aspect of departmental activities and the reduction of leakage in the distribution network as a whole.

15 References 1. Notes prepared for Waste Control Unit Training. BINNIE AND PARTNERS, London SW1. July Draft Report on Waste Control, prepared for the Government of Barbados- Ministry of Communication and Works. Water Works Department by BINNIE AND PARTNERS Consulting Engineers, London, February Water Resources Management and Water Loss Study carried out for the Barbados Water Authority- Ministry of Labour, Public Works, Community Development and Sports by KLOHN-CRIPPEDN CONSULTANTS LTD. in association with Stanley Associates Engineering Ltd.- Draft Report on Tasks 5, 6 and International Water Association- The Blue pages- Losses from Water Supply Systems Standard Terminology and Recommended Performance Measures. ( f/bp0001.pdf) 5. Leakages in Water Distribution Networks within an International Context, Allan Lambert- International Water data Comparison Ltd, LL30 1SL, UK