Sub Zoning as a Measure for Water Supply Optimization—Case Study of the City of Nikšić †
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- Collecting all relevant data about the WSS (physical part, consumption, and management),
- Construction of the existing hydraulic net WSS model, with all appropriate links and conditions,
- Model calibration of the existing state of the system, based on measurements of pressures and flows, which are performed at numerous measuring points in the system.
- Proposal for improvement of the system performance, defined on the appropriate (adapted calibrated) model, with results, which clearly indicate improvements of system work.
- Division of the system into consumption zones, each characterized by a unique feeding pipeline, with the absence of transverse connections with adjacent zones,
- Flow and pressure measurement activities, followed by simultaneous readings on water meters and model testing, formed in several standard methods (balance and night flow methods),
- System analysis on a calibrated net model, aimed to identify the parts where significant loss occurrence is expected and defining a priority plan for further detailed field research.
2. Water Supply System of Nikšić
- Vidrovan—capped springs, located 15 km north of the city, with used capacity of 250–450 L/s,
- Poklonci—well spring, located 5 km east of the city, with capacity of 200 L/s.
- QPmaxmonth—the average monthly production in the month of maximum production,
- QPmaxday—the average daily production in the day of year of maximum production,
- Kmaxmonth (Kmaxday)—quotients between QPmaxmonth and QPavyear (i.e., QPmaxday and QPavyear).
- Specific QPOPavyear = 100 L/s × 86,400/65,000 = 133 L/con/day; (in the summer up to 160 L/con/day),
- Specific QPavyear = 400 L/s × 86,400/65,000 = 532 L/con/day; (in the summer up to 640 L/con/day).
3. Calibration of Nikšić Water Distribution Model
- System database creation, by usage of the Mapinfo software,
- Definition of consumption zones in WSS and selection of the measurement’s points (Figure 3),
- Acquisition of measuring equipment—fixed flow meters and pressure meters and their installation in selected points of the distribution system (fixed measuring points). Procurement of mobile flow/pressure meters and leak detection equipment (aqua phones and correlators),
- Linkage of the fixed measuring points into a unique system for remote data transfer and installation of appropriate software (SCADA system).
4. Analysis of the Nikšić WSS Existing State
- The transport of almost the entire sum of consumption in WSS through the BPS Duklo (small amounts spent in the area between Vidrovan and BPS Duklo), which inevitably leads to an ever-changing pressure regime. That causes rapid fatigue and represents a source of defects, even at a greater extent, in comparison with the work in a constant high pressure mode. This conceptual problem is absurd, given the existence of the source Vidrovan on a hill (664 m a.s.l.), which enables the comfortable gravity placement into the system (the largest part is between 610 and 630 m a.s.l.).
- A lack of tank space in the system of 65,000 consumers (R Trebjesa is out of order) for equalizing daily unevenness leads to the use of pumping with all the above-mentioned adverse effects.
- The mutual damping of flows from two sources (Vidrovan and Poklonci), which occurs due to the pipelines (φ1000 and φ500) that transport water from these two sources to the BPS Duklo, is directly connected to each other, immediately upstream of the BPS Duklo.
- The appearance of flow with an incomplete profile in the main pipeline Vidrovan—BPS Duklo (φ1000, L = 15 km), which happens due to the source capacity decrease in the summer months. In that period, the piezometric level is much lower than the Vidrovan elevation (664 m. a.s.l.) and causes the work of BPS Duklo to be in a higher pressure and lower flow regime.
5. Proposed System Concept Alteration and Conclusions
- Construction of the Vidrovan tank (R Vidrovan, BA/OA = 659/664 m a.s.l., V = 1800 m3), on the source location, aimed to establish the flow with a full profile on the whole length of the appropriate inlet pipeline φ1000. This will also provide needed space for leveling the unevenness of consumption (net demand 15 L/s) of those consumers between the Vidrovan source and BPS Duklo;
- Construction of the Uzdomir tank (R Uzdomir, BA/OA = 650/654, V = 5500 m3) on the slopes of the Uzdomir hill, near the downstream parts of supplying pipelines φ1000 and φ500, from two system sources. This conceptual measure also includes the construction of the connecting pipelines φ1000 and φ500 from R Uzdomir to the downstream parts of the existing inlets φ1000 and φ500. These measures will enable the full use of existing sources and eliminate damping. Moreover, R Uzdomir will be located at the elevation that is appropriate for the supply of a part of the lower altitude zone at the central city area (to which belongs half the city’s consumption), located below 630 m a.s.l.
- Separation of the lower central subzone, which will be under R Uzdomir influence, from the rest of the network. This measure should be easily carried out and conducted by the use of on/off valves in the system (majority of them already exist). This measure, contained in subzoning, will enable the production of regular, but significantly lower, pressure (2–4 bars) in the central city area (Figure 5).
- Realization of booster pump station BPS Centre: (Q = (3 + 1) × 80 L/s, H = 65 m), below the Trebjesa hill, which will allow transport of excess water during the night from the central area to R Trebjesa. Water, accumulated in the R Uzdomir (400 L/s at the level of today’s average production), will be placed gravitationally into the central subzone. After satisfying consumption in the central area (about half of the production), the remaining part will be transported to R Trebjesa, through the BS Center (also about 200 L/s).
- With installation of a pressure reducing valve at the entrance to each of the peripheral zones of consumption—R Trebjesa will be activated as a distribution tank for the peripheral part of the system, which will be separated from the central subzone (high people density area with R Uzdomir as a vital facility) by the closing on/off valves in the network (Figure 6). The future area, where R Trebjesa will be activated as a vital structure, will cover a much greater surface, but the water amount of consumption is similar—about 200 L/s in each. In that way the central area will be out of the R Trebjesa impact where such an approach is quite difficult due to the presence of a multi-ring network and basically a two-way flow of water. Some areas under the future R Trebjesa covering are already zoned with a single entrance and, generally, a one-way flow of water.
- Proposed measures will allow both lower pressures in all parts of the system and good subzoning of the whole network. That will further allow more successful leakage detection in the subzones, and generally better loss control in the WSS.
- Exclusion of BPS Duklo from the operating mode—realization of the described measures will eliminate the need for its regular work. Duklo BPS will stay only in terms of securing the hot reserve in WSS.
- Gravitation as a dominant mode of flow in the distribution system will be established, which will be followed by a stable pressure regime and, in total, a significantly higher level of service,
- Significant pressure reduction in the network (a lower operating level—produced by the presence of R Uzdomir in the central subzone). The reduction of pressure, produced by an inlet from R Trebjesa, will be realized at the entrance to each of the peripheral zones (Figure 5),
- The only reservoir capacity in the existing system will be activated, and WSS will be operating with enough capacity for equalization of consumption unevenness,
- The available source capacity will be used to its full extent and according to the actual needs,
- The reasons that produce systemic failure will be eliminated—the implementation of the proposed measures represents a showdown with the causes of defects and they are not designed as a simple recovery of consequences.
Conflicts of Interest
- Pilot Areas and Papers for DRINKADRIA EU Project 2013–2016. 2016. Available online: https://www.researchgate.net/project/DRINKADRIA-http-wwwdrinkadriaeu-project (accessed on 30 August 2020).
- DRINKADRIA Shared Platform. Available online: http://drinkadria.fgg.uni-lj.si/ (accessed on 30 August 2020).
- Kanakoudis, V.; Tsitsifli, S.; Papadopoulou, A.; Curk, B.C.; Karleusa, B. Estimating the Water Resources Vulnerability Index in the Adriatic Sea Region. Procedia Eng. 2016, 62, 476–485. Available online: http://www.sciencedirect.com/science/article/pii/S1877705816334002 (accessed on 30 August 2020). [CrossRef]
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Daničić, A.; Dimkić, D.; Papović, M.; Kovač, D. Sub Zoning as a Measure for Water Supply Optimization—Case Study of the City of Nikšić. Environ. Sci. Proc. 2020, 2, 37. https://doi.org/10.3390/environsciproc2020002037
Daničić A, Dimkić D, Papović M, Kovač D. Sub Zoning as a Measure for Water Supply Optimization—Case Study of the City of Nikšić. Environmental Sciences Proceedings. 2020; 2(1):37. https://doi.org/10.3390/environsciproc2020002037
Daničić, Aleksandar, Dejan Dimkić, Mira Papović, and Darko Kovač. 2020. “Sub Zoning as a Measure for Water Supply Optimization—Case Study of the City of Nikšić” Environmental Sciences Proceedings 2, no. 1: 37. https://doi.org/10.3390/environsciproc2020002037