stabilisation of water supply and reduction of non …
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STABILISATION OF WATER SUPPLY AND REDUCTION OF NON-REVENUE WATER IN THE KWANYUSWA SUPPLY ZONE
Author: I.M. Peña*; Co-Authors**: M.A. Shepherd PrEng and V.A. Poona * JOAT Group, Postnet Suite 23, Private Bag X4, KLOOF, 3640; Tel: 031 700 1177; Fax: 031 700 9853: email: [email protected] ** JOAT Group, Postnet Suite 23, Private Bag X4, KLOOF, 3640; Tel: 031 700 1177; Fax: 031 700 9853: email: [email protected] ** JOAT Group, Postnet Suite 23, Private Bag X4, KLOOF, 3640; Tel: 031 700 1177; Fax: 031 700 9853: email: [email protected] ABSTRACT The KwaNyuswa area of supply was selected as one of the priority zones to reduce water losses in the Western Operational Area of eThekwini Municipality. The water supply in the area had been deteriorating drastically over the years, due to service connection growth and influx of population from rural areas which was not accompanied by planned capital investment or infrastructure maintenance. While some parts of the supply system received intermittent supply, other areas which had a permanent water supply experienced significantly high pressures and as a consequence high water losses. After a year of carrying out various interventions, real losses declined by 46%, system input volume reduced by 23%. Furthermore, prior to the start of the project only 65% of the consumers received a permanent water supply which has improved to 85% receiving the same service levels. This paper demonstrates that using a non-revenue water reduction approach to the situation, losses were reduced, the system operates more efficiently and ultimately the interventions completed will help extend the service life and quality of the network system. 1 INTRODUCTION A joint venture of companies was appointed as the Non-Revenue Water (NRW) Reduction Consultant for the Western Operational Area of eThekwini Municipality (EWS) in March 2009. The KwaNyuswa supply area was selected as one of the priority zones to reduce water losses. Before the NRW project started, KwaNyuswa water supply system was characterised by intermittent supply and high levels water loss. In the years preceding the appointment, the water supply service in the area had been deteriorating drastically. This was due to service growth which was not accompanied by planned capital investment, operations skills or infrastructure maintenance. Factors that contributed to the process of deteriorating infrastructure and service delivery included: remote supply areas, high water pressure in certain areas, no community awareness regarding responsible water usage or reporting water losses, illegal tampering with the distribution network and service connections, extremely low confidence in system characteristics and infrastructure information, no coordination between different departments of the service provider, reduced budgets and limited operational staff skills. Further problems developed when a large-scale water mains replacement program started in January 2008. Insufficient technical skills, management and coordination by the Municipality for overseeing the re-laying of the pipelines was an additional challenge.
As a consequence of these factors two major problems developed. Some parts of the supply system received intermittent supply whilst other areas that had a fully charged system, 24 hours a day, received high pressures hence water losses in those systems were high as well. In February 2010 the NRW by Volume was 71% and real losses were 504 litres/conn/day. An estimated 65% of the consumers had constant water supply. The Operations Department of the Municipality were manually operating valves in the system on a daily basis in order to shut down water to certain areas and in this way provide water to other areas. Step testing in the supply area was carried out to help identify consumptions for each District Metered Area (DMA) and ranked these DMA’s to prioritise interventions. Real loss reduction was addressed using pressure reduction interventions, advanced pressure management and leak detection surveys. 2 OBJECTIVE According to Charalambous, “Intermittent water supply is enforced not only in cases where there is water shortages, but also where the hydraulic capacity of a network is such that it is not possible to satisfy demand and where the networks are severely deteriorating (…) However, in most cases water authorities seem to overlook the obvious, which is to manage the water networks in the most efficient and effective way in order to minimise losses “(1). The main objectives of the project was to increase the number of households that received water on full-time basis and simultaneously reduce levels of leakage in the supply area of KwaNyuswa by undertaking several interventions. Real losses were addressed using various methods such as pressure reduction, advanced pressure management and leak detection surveys, and the resultant “saved water” was to be used to further the extent of water supply in the area. 3 BASELINE SITUATION 3.1. System Characteristics KwaNyuswa is a rural area, with 6,500 scattered properties and approximately 45,000 inhabitants. The supply area consists of one inlet that supplies a trunk pipeline. From this trunk pipeline a number of branches provide water to different districts or zones, including small reservoirs and Break Pressure Tanks (BPT) like Thanduhule Reservoir, Mnamatha Res and Ngolosi BPT. Intermittent supply to the area was affecting water quality and water distribution. The resultant ingress of sediments caused blockages in several components of the system which included water mains, service connections, meters, strainers, pressure reducing valves, pilots and needle valves. The billing aspect was consequently affected due to high levels of theft, low confidence in domestic metering and meter blockages. Additionally, water pressure surges caused leaks and bursts which reduce water pipelines life expectancy. The system characteristics for the KwaNyuswa Supply Zone are as follows:
Average Operating Pressure: 700 kPa (7.0 bar) Number of registered connections: 3743
Number of formal properties: 700 Number of informal properties: 50 Number of rural properties: 6,500 Number of existing PRV’s: 64 Length of water mains: 180 km Estimated population: 45,000 Percentage of system 100% pressurized 24hours/day: 65% (estimated).
KwaNyuswa was divided into 11 District Metered Areas (DMA’s) namely DMA A to K. These 11 DMAs were individually identified and prioritised based on water losses or potential water savings. A complete shut-down of the area was done in April 2010. The shut-down was done in different steps in order to identify consumptions for each DMA. In the higher part of KwaNyuswa, three DMA’s with significantly high Minimum Night Flows (MNF) and low billed consumption were identified. The discreteness of these three areas were investigated and confirmed. Table 1 shows detailed supply characteristics and selected Key Performance Indicators (KPI’s) of the three DMA’s.
Table 1: District Metered Areas selected for NRW interventions in the KwaNyuswa Supply Zone. District Zone
Ave Flow
[kl/day]
No of Conn.
Billed Consump.
[kl/conn/day]
Length of
Pipes [km]
Ave Flow [kl/conn/day]
Ave Flow [kl/km/day]
Billed Consump.
[kl/day]
Total Water Losses
[l/conn/day]
NRW by
Vol.
C 270 530 0.16 19.1 0.51 14.2 88 305 67% H 245 197 0.38 7.5 1.2 32.6 76 771 69% J 250 495* 0.17 9.8 0.5 25.5 84 298 66%
* 495 formal properties fed by 38 EBUs1.
3.2. Supply Flow Baseline The discreteness of the DMAs was difficult to confirm due to the following challenges:
1. Intermittent water supply in certain areas of the supply zone; 2. Extremely low confidence with respect to the infrastructure in the ground versus the
GIS information from the Client; and 3. Operations staff only had partial knowledge about the system in the ground.
Prior to any work being carried out the baseline flow profile was logged as indicated in Figure 1 and a standard water balance built using this information.
1 EBU (Electronic Bailiff Units) consist of an electronic device that limits water supply to a number of connections on a time or flow basis
Figure 1: Baseline flow profile for KwaNyuswa area of supply before interventions
4 Programme The Project started in March 2010 and all real loss reduction activities and apparent loss reduction/billing improvement activities were targeted to be completed before the end of November 2010. Due to increased scope of work due to the results achieved the project is still on-going. 5 Activities 5.1. Supply Areas Discreteness KwaNyuswa supply system was originally operated by another service provider and was transferred to EWS two years before the commencement of this project. Most of the system and infrastructure information was lost during the transfer and as such reservoir and DMA boundary confirmation were a major challenge for the project at the outset. This important activity, or at least the definition of the supply area had to take place before the commencement of system stablising measures. 5.2. Pressure Reduction and Advanced Pressure Management DMA C: At the start of the project, there were three existing direct-acting PRV’s (DV1526, DV1527 and DV0716). None of them were working so maintenance was carried out on these valves. This was followed by pressure optimisation which took several months to complete. Eventually they were all replaced with piloted PRVs and advanced controllers were installed to reduce the excess pressure during the night. The DV1526 PRV zone was found to be breached. Field work and shut downs were needed in order to find the breach, confirm the extent of the supply area and re-commission the PRV. The DV1527 and DV0716 PRV zones had different problems and site visits and a series of shutdowns were needed to make the time-modulated controllers function properly. An unusually large variation in pressure was detected between night and day and after some analysis and site investigations it was concluded that the pipelines
were undersized for the present supply and that water mains needed to be replaced and upsized to resolve this problem.
During the program, new water pipelines were laid by the Client’s Construction Department but were not commissioned due to potential damages that an intermittent water supply would cause to the new infrastructure. Under the monitoring and coordination of the Professional team, the water utility commissioned all the pipelines. The DMA bulk meters and average zone pressures were monitored during the commissioning process in order to guarantee supply to customers and as a precautionary measure, determine if any extreme minimum or maximum flowrates or pressures occurred. Additionally, the area was rezoned to the new pressure regime standard (from 30m – 90m to 25m – 60m as the minimums and maximums respectively) which was followed by the installation of eight new PRV’s in the zone. The commissioning of the new pipelines and PRV’s took longer than originally estimated and was completed in June 2011. Table 2 and Figure 2 show a comparison of the baseline flow and pressure profiles and for flow at the end of June 2011 and for pressure till the end of September 2011. Water losses in the area were still high and water conservation measures were continued. As can be noted from the graphs, the pressure range experienced significantly improved having a more stabilized value, while the flow profile shows a permanent water supply but still high minimum night values.
Table 2: DMA C - Main Characteristics and Indicators District Zone
Ave Flow
[kl/day]
No of Conn.
Billed Consump.
[kl/conn/day]
Length of
Pipes [km]
Ave Flow [kl/conn/day]
Ave Flow [kl/km/day]
Billed Consump.
[kl/day]
Total Water Losses
[l/conn/day]
NRW by
Vol.
January 2010
270 530 0.16 19.1 0.51 14.2 88 305 67%
June 2011
331 650 0.25 22 0.51 15.0 130 247 60%
Figure 2: DMA Zone C - Flow and Pressure profiles before and after WC/WDM interventions As previously mentioned the programme is still underway and DMA C is one of the areas that is still quite unstable and will need further interventions and monitoring. DMA H: According to GIS information, there were eight PRV’s (one piloted and seven direct-acting) before the commencement of the project. All direct-acting PRV’s were either not found (DV0845 or DV0848), not working properly (DV0620, DV0844 and DV0847), missing i.e. chamber was found with no PRV (DV0846) or incorrectly installed on the wrong pipeline (DV0843). All located PRV’s were inspected, maintained, parts installed if necessary and were then optimised in terms of downstream pressure settings.
One piloted PRV (DV1509) fed the entire DMA H and all the direct-acting PRV’s were located downstream of it. A time-modulated PRV controller was installed to regulate flow until water losses in the area were reduced. The primary objective was to control inlet flow to the area, reduce losses and build up pressure in areas with low pressure or no supply at all. The controller and PRV downstream settings are summarised in Table 3.
Table 3: Pressure control settings for PRV DV1509
Time controller period PRV Downstream Setting
Comments
Peak consumption period
04h00 to 07h00 15h00 to 18h00
1.5 bar CP at PRV
Off Peak consumption period
00h00 to 04h00 07h00 to 15h00 18h00 to 24h00
0.5 bar Downstream set to keep the line pressurized during off peak periods.
Once leak detection surveys were completed the MNF reduced drastically. A reduced port PRV was then proposed and installed to replace the existing piloted PRV in order to cope with the low flows that were now being experienced. Similarly to DMA C, new pipelines were installed but not commissioned occurred. The same protocol was observed as before and flows and pressures were monitored and the entire DMA rezoned with a new design approved for six new PRVs as per the new pressure regime stipulated earlier. Table 4 displays the comparison of selected KPI’s for DMA H before and after pressure management and leak detection interventions.
Table 4: DMA H - Main Characteristics and Indicators
District Zone
Ave Flow
[kl/day]
No of Conn.
Billed Consump.
[kl/conn/day]
Length of
Pipes [km]
Ave Flow [kl/conn/day]
Ave Flow [kl/km/day]
Billed Consump.
[kl/day]
Total Water Losses
[l/conn/day]
NRW
January 2010
245 197 0.38 7.5 1.2 32.6 76 771 69%
Dec 2010
144 212 0.37 8.1 0.67 17.7 82 193 42%
Figure 3 graphically represents the System Input Volume (SIV) for DMA H before and after all interventions and Figure 4 shows the pressure profile at the Critical Point using a time-modulated PRV controller.
Figure 3: DMA H - Flow before and after pressure management and leak detection
Figure 4: DMA H – Pressure profile at the Critical Point with Advance Pressure Management.
DMA J: There were two existing PRV’s at the start of the project; a piloted PRV (DV1131) and a direct acting PRV (DV1130). Each PRV fed an area inside the DMA. DV1131 fed the majority of consumers in DMA J (which included a housing project). A time-modulated controller was installed to regulate flow until water losses in the area were reduced by leak detection surveys. The primary objective was to control inlet flow to the area, reduce losses and build up pressure in areas with low pressure or no supply at all. The consumers in the housing project were fed by 38 Electronic Bailiff Units (EBU’s). The EBUs were programmed to supply at time intervals during a 24 hour cycle (04h00 to 05h00 and 14h00 to 16h00). Field survey and research indicated that these EBU’s were tampered with and by-passed in order to get a 24 hour supply. Taking this into account, the time-modulated controller and PRV were set up as detailed in Table 5. Figure 5 presents the pressure profile at the PRV with controller setup.
Table 5: Pressure control settings for PRV DV1131 Time controller
period PRV Downstream Setting
Comments
Peak consumption period
03hs00 to 06hs00 13hs00 to 16hs00
1.5 bar CP at PRV. First consumer 10m meters below CP.
Off Peak consumption period
00hs00 to 03hs00 06hs00 to 13hs00 16hs00 to 24hs00
0.5 bar Downstream set to keep the line pressurized during off peak periods.
Figure 5: DMA J – Pressure profile at the PRV with Advance Pressure Management.
Table 6 displays the comparison of selected KPI’s for DMA J before and after pressure management and leak detection interventions.
Table 6: District Subzone J - Main Characteristics and Indicators District Zone
Ave Flow
[kl/day]
No of Conn.
Billed Consump.
[kl/conn/day]
Length of
Pipes [km]
Ave Flow [kl/conn/day]
Ave Flow [kl/km/day]
Billed Consump.
[kl/day]
Total Water Losses
[l/conn/day]
NRW
January 2010
250 495* 0.17 9.8 0.5 25.5 84 298 66%
January 2011
126 495* 0.2 9.8 0.25 12.8 96 60 30%
* 495 formal properties fed by 38 EBUs.
5.3. Leak Detection and Repair Leak detection in these DMA’s only commenced in June 2010 due to the intermittent supply. The first approach was to get plumbers to survey and repair all visible leaks in the DMA H and use a qualified leak detection Contractor to carry out surveys in DMA C and J. The number of leaks found and repaired in DMA H was significantly high and the total estimated water recovered once repaired was 45 m3/hr. The estimated recovered volume has not yet completely reflected in the SIV profiles due to the dynamic nature of a network system and more importantly that the volumes “recovered” are now being used to feed other parts of the DMA that had no supply previously.
Table 7: Leak Detection results for DMA H (24 May 2010 to 4 October 2010)2
Because KwaNyuswa is a rural area, leaks are extremely hard to locate due to the terrain and over-grown vegetation. Another aggravating factor is the lack of commitment to water conservation by local consumers. Leaks are rarely reported by consumers and water conservation, awareness and educational campaigns are urgently needed in the area. During the length of the project, the Professional team erected advertisement boards urging the community to be pro-active and assist the Municipality as depicted in Figure 6. Additional challenges were certain pipelines being laid on the surface and when grass fires occurred pipelines were damaged.
Figure 6: Water Conservation awareness boards deployed in the area 6 Results 6.1. Water losses reduction The inlet bulk meter for the area is constantly monitored. Figure 8 represents the flow profile before and after the interventions took place. Table 8 gives a summary and comparison of Water Balance components and Water Loss and Water Service indicators previous and after interventions.
2 note that “Average flow recovered” is the theoretical recoverable volume when all leaks were fixed.
Ave spilling Leaks Ave flow
Leaks Min Rate Max Rate Ave Rate flow repaired recovered
# litres/hr litres/hr litres/hr litres/hr # litres/hr
Trickle (T) 191 1 10 5.5 1050.5 191 1050.5
Spray (S) 91 10 20 15 1365 91 1365
Light Flow (LF) 147 20 50 35 5145 147 5145
Medium Flow (MF) 124 50 200 125 15500 124 15500
Heavy Flow (HF) 27 200 500 350 9450 27 9450
Burst (BR) 10 500 2000 1250 12500 10 12500
Total 590 45010.5 45010.5
Figure 7: Flow profile before and after pressure management and leak detection in KwaNyuswa
Table 8: Water Balance for KwaNyuswa Valley – Before and after interventions
Units Previous NRW interventions March 2010
After NRW interventions March 2011
Difference
Water Supply Service
length of mains km 180 180 0%
AZP m 70 65 ‐7%
Number of connections No. 3743 3900 4%
density of connections conn/km 20.8 21.7 4%
Permanent water supply % of the area 65% 85% 31%
Water Balance components
System Input Volume (SIV) kl/day 3 720 (*) 2 880 ‐23%
Billed Authorised Consumption (BAC) kl/day 1 043 1 237 19%
Unbilled Authorised Consumption (UAC) kl/day 320 320 0%
Apparent Losses (AL) kl/day 471 300 ‐36%
Real Losses (RL) kl/day 1 886 1 023 ‐46%
Water losses Indicators
Unavoidable Annual Real Losses (UARL) l/service conn/day 117 106 ‐9%
Current Annual volume of Real Losses (CARL) l/service conn/day 504 262 ‐48%
Infrestructure Leakage Indicator (ILI) 4.3 2.5 ‐43%
Non‐Revenue Water (NRW) kl/day 2 677 1 643 ‐39%
Non‐Revenue Water (NRW) % SIV 72% 57% ‐21%
(*): when the system is pressurized
6.2. Water supply increase Pressure loggers were installed in areas where previously the water supply was not constant. These areas are mainly located in the Thandukhule Reservoir and Ngolosi BPT. All pressure logging files are reflecting continuous water service for the last month, but with pressures very erratic. In the baseline section and estimated 65% of system is 100% of the time pressurized when the project started. Estimation for the present situation is that 85% of the supply system is getting continuous water service. 7 Conclusions The following conclusions could be drawn from the stabilisinf interventions carried out in KwaNyuswa:
1. Using a NRW reduction approach to the area not only helped to reduce water losses and optimise a network system but more importantly to extended the quality and service of a water supply system.
2. Subjecting the system to intermittent supply has significantly deteriorated the water supply infrastructure.
3. PRV maintenance was proved to be very poor causing many sectors to suffer from high water pressure, requiring pressure rezoning and new pressure control devices.
4. All these factors contribute to a high number of leaks. 5. Advanced pressure management can be used to control demand profiles and
spread available water into areas where intermittent supply is experienced. 6. A combination of leakage reduction interventions in KwaNyuswa extended the
continuously served area of supply from 65% to 85%. 8 References 1. Charalambous B, The high costs of resorting the intermittent supplies, IWA
publication Water 21 Magazine, p. 29 December 2011.