A thesis submitted in partial fulfillment of the requirements for the Master of Science Degree in Integrated Water Resources Management. Additional information for the entire water supply area, such as population, length of pipelines and water costs, was collected from documentation reviews for the purpose of exploring an appropriate decision tool for pipeline replacement.
INTRODUCTION
Background
However, it should be emphasized that despite some encouraging research success stories, most water systems around the world still face high water loss rates, most of which are almost certainly above economic levels (Lambert, 1997). In this regard, reducing leakage, which is an integral part of NRW, is the most obvious and immediate area of water demand management (WDM) in the BWB catchment area to achieve water consumption levels consistent with equitable, efficient and sustainable use. of limited water resources, as stated by Robinson, showed that in Malawi as a whole, a large part of the population still does not have access to portable water.
Problem statement and justification of the study
Problem statement
Justification of the study
Objectives of the study
Main objective
Specific objectives
LITERATURE REVIEW
Introduction
Water demand management (WDM)
Non revenue water
Definition of water loss and leakage
Real and apparent losses
Liemberger (2005) explained that real losses can be assessed by one of the following three different methods: McKenzie (1999) explained that real losses are those where the water has left the system and has not been utilized in any way.
The water balance
However, Liemberger and McKenzie (2005) noted that all water balance calculations are somewhat approximate due to the difficulty of assessing all the components with complete accuracy. Several software packages have been designed for water balance preparation, such as the aqualibre™ water balance package according to Liemberger and McKenzie (2003).
Minimum night flows (MNF)
The preparation of a standard water balance will make it possible to produce a catalog of actions needed to improve efficiency. Studies undertaken by Liemberger as reported by GoM (2007) showed that the water balance for the Blantyre water supply area is as predicted in Table 2.2. the first few hours is a matter of judgment, not fact.
Pipe failure modes
Causes of failure
Where ESPB is the mean service pipe burst flow rate at the operating pressure for the DMA or zone, AZOP is the mean operating pressure of the zone, and N1 is the leakage exponent (a coefficient relating pressure to leakage). The excess night flow for each DMA can be expressed as the number of ESPBs by dividing the excess night flow by the mean post-burst flow rate in the service pipe (McKenzie, 1999).
Failure mechanisms
Theory of leakage
- Burst and background leakage
- Reported and unreported bursts
- Natural rate of rise of leakage
- Unavoidable annual real losses (UARL) and current annual real losses (CARL)
This phenomenon is known as the natural rate of rise in leakage (NRR) according to Mathis et al. The lowest technically feasible annual volume of real losses for well-maintained and well-managed systems is known as unavoidable annual real losses (UARL) according to Radivojević et al.
Leakage control
General
Where UARLr is the revised UARL, UARL50 is the UARL at 50 m standard pressure, P is the working pressure, and N1 is the leakage exponent (a coefficient relating pressure to leakage).
Passive leakage control
Active leakage control (ALC)
In other words, it is the annual amount lost due to all types of leaks, bursts and overflows and depends on the frequencies, flows and average duration of individual leaks. The main factor of choice is the value of water, which determines whether a particular methodology is economical for the savings achieved (Sturm and Thornton, 2007).
Leakage management components/management tools for real loss reduction
- Speed & quality of repair
- Pressure management
- Asset/pipeline management (replacement)
- Component based leakage management or BABE concept
- District metered area (DMA) theory
- Economic level of leakage (ELL)
- Performance indicators
The economic level of leakage (ELL) is the level of leakage at which the additional cost of reducing leakage is equal to the additional benefit obtained from further leakage reductions, in other words it refers to that level of leakage at which it would cost more to makes a further reduction in leakage than producing the water from another source (Balkaran and Wyke, 2003). This method uses economic intervention principles and defines it as 'the frequency of intervention at which the marginal cost of ALC is on average equal to the variable cost of the leaking water'.
Relationships of pressure with leakage, MNF and burst frequency
- Calculation of average pressure in water distribution systems
- Relationship of pressure and minimum night flow
- Relationship of pressure and leakage
- Relationship of pressure and burst frequency
Additionally, data on changes in fracture frequency following pressure management for a low-pressure, high-fracture-frequency pumped system in the Bahamas indicated that there is a relationship between pressure and burst frequency at low pressures ( Fanner and Thornton, 2005). Conversely, UKWIR (2005) indicated that there is no evidence of a relationship between pressure and burst frequency. From the discussion, it shows that there is a relationship between pressure and burst frequency, but it can be a complicated relationship.
STUDY AREA
Geographical location, catchment morphology and climate issues
Blantyre in regional and national context
The 1987 National Spatial Development Plan states that the southern region has historically been the most attractive region of Malawi, both for foreign and internal migrants, because it was the most developed part of Malawi with the best opportunities for paid employment (GoM, 1987). Its importance as the commercial center of Malawi and the southern region was clear and further enhanced the strategic importance of this city. According to the National Spatial Development Plan (GoM, 1987), Blantyre is classified as a national hub, defined as a settlement with a high level of service/capacity that has a country-wide sphere of influence.
Socio-economic issues
Service infrastructure
Most residents living in THA and squatter areas do not have access to this system. The provision of sanitation services is generally inadequate and threatens the health of the population residing in these areas (BCA, 1999).
History of bulk water supply network
Water resources and demand
Raw Water Intake Raw Water Pumps Main Raw Water Treatment Plant Main Clean Water Pumps in Chileka Main Pump Capacity Chileka Chileka. While it is recognized that wet season demand is being met, there is believed to be significant pent-up demand in the dry season (BCA, 1999). BWB (2006b) further states that water demand will increase by an additional 40,000 m3/day in the next 20 years, but it is possible to reduce this figure by improving network management, improving demand management and reducing of losses.
Water supply
Mudi Dam supplements Walker's Ferry production because the current pumping and distribution system cannot keep up with the water demand. However, initiatives were being taken by the service provider to plant tree saplings and also construct contours to protect the Mud basin (BWB, 2006a). Within the distribution system, there are two levels of water supply service available to consumers that prevail.
Current initiatives by Blantyre Water Board to reduce and control non revenue water
These are described by quantitative standards and are: service connections to individual plots and collective water supply points (kiosks) according to GoM (2002). According to BWB (2006a), the service provider struggled to provide continuous water services due to operational inefficiencies, so rationing measures were put in place to ensure that most areas could be served at most times.
Specific study areas
BCA district metered area (BCA DMA)
Chinyonga DMA
MATERIALS AND METHODS
Study design
The study chose two specific study areas due to their different residential patterns to obtain data from different cases to be able to match the results with other areas with similar characteristics for rapid leakage management decisions throughout the water supply area. The decision was also made as a check on whether the relationships achieved in one area would also be found in the other area.
Data collected and tools
- Non revenue water trend
- Minimum night flow (MNF) analysis
- Investigation of pressure relationships with leakage, minimum night flow, and
- Pipe failure modes examination
- Pipeline replacement prediction tools
The pressure and flow measurements as explained earlier were also used for establishing relationships with leakage (calculation of N1 leakage exponent, which is a coefficient relating leakage and pressure). The pressure and flow measurements were also used to confirm a relationship between pressure and minimum night flow. The purpose of collecting this data was for the establishment of pressure and burst frequency relationship (calculation of N2 burst frequency exponents, coefficient relating pressure and burst frequency).
Analytical techniques
- Non revenue water (NRW) trend determination
- Analysis of minimum night flows
- Investigation of pressure relationships with leakage, minimum night flow, and
- Examination of pipe failure modes
- Investigation of prediction tools for pipeline replacement
The analysis to confirm the relationship between pressure and MNF was performed following a statement by McKenzie et al. An equation was developed to confirm a relationship between pressure and MNF, based on the theoretical relationship between pressure and leakage as indicated by Lambert (2001a). The calculated MNF values were compared to the values of measured MNF at the same AZNP by calculating deviations to confirm the relationship between pressure and MNF.
RESULTS AND DISCUSSION
Determination of non revenue water (NRW) trend
The increase in the levels of NRW can be due to factors such as: age of the supply infrastructure, increased number of illegal connections (Annex B9), inaccurate billing, reservoir overflow and vandalism of pipelines. Also note that the value of NRW in the last columns has been converted to per year. The increase in the level of NRW may be due to factors such as: age of the supply infrastructure, increased number of illegal connections, inaccurate billing, reservoir overflow, and vandalism of pipelines as suggested by Balkaran and Wyke (2003).
Analysis of minimum night flows
Excess night flows
The difference in NRW levels for the two areas may be due to the fact that the BCA DMA is unplanned and the data shows that there are more illegal connections in the area (Appendix B9) compared to the Chinyonga DMA. Excessive night flows are the result of unexplained leaks in the systems as suggested by McKenzie (1999). Therefore, the results of this study show that there are high levels of leakage in DMA which are not known to the service provider.
Estimation of service pipe bursts
Pressure relationships with leakage, minimum night flow, and burst frequency
Pressure – leakage relationship
The relationship was investigated by performing calculations using Equation 4.3 as well as the principles of the Hour-Day Factor (HDF) model, where all possible combinations of pressure and flow data as given in Table 5.6 were used. Warren (2005) indicated that in most cases, service connections are the main source of water leaks. As a result, from Warren's argument and the age factor, it is justified that Chinyonga DMA has high N1 values compared to BCA DMA.
Pressure – minimum night flow relationship
Results of the calculated MNF compared to the measured MNF values are shown in Table 5.9. From the results of the Chinyonga DMA data, it can be concluded that there is a relationship between pressure and minimum night flow. The results of the comparison of the measured MNF and calculated MNF values are shown in Table 5.10.
Pressure – burst frequency relationship
The analysis using both approaches confirms that there is a relationship between pressure and minimum night flow (MNF). The results show that there is a relationship between pressure and burst frequency, but not unique with the provisional equation used given the standard deviations of 1.6 and 2.0 for Chinyonga and BCA that were found. It can therefore be concluded that the average pressure burst frequency exponent, N2 for Chinyonga and BCA DMAs is 1.9 and the results have confirmed that there is a relationship between pressure and burst frequency but not unique based on the applied provisional equation and other operational problems.
Examination of pipe failure modes
Observations showed that most of the pipes that were broken during the study period were service connection pipes. The results of the failure modes could also be compared with the N1 values calculated in this study. The composition of the pipe materials in the specific study areas confirms that the leakage exponents (N1) found are related to pipe materials.
Prediction tools for pipeline replacement
Further observations of the lost water curve show that it runs almost parallel to the total cost curve and appears to form a large part of the total cost curve. The findings are in line with those of Government M (2007) who conducted an infrastructure assessment study in the Blantyre water supply area and found that at least 46 km of the entire pipeline needed to be replaced based on the frequency of bursting. This technique could be used in all developing countries, as according to WHO (2001) and Farley and Trow (2003), the cost of lost water is mostly higher than the cost of ALC intervention in contrast to developed countries, indicating that the economics of pipeline replacement would be entitled.
CONCLUSION AND RECOMMENDATION
Conclusion
Recommendations
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Paper presented at the IWA and AWWA Conference on Efficient Mgt of Urban Water Supply, April, Tenerife, available at: http://www.liemberger.cc, accessed December 2007. Paper presented at the 4th World Water Congress of the IWA, Marrakesh, September 2004, (in review for Wat. Technol: Water Supply Journal), available at: http://www.iwahq.org/uploads, accessed January 2008.
