Automation with renewable energy to optimize the exploitation of water supply networks in Ninh Thuan province

The research that was conducted on the water supply network of Phan Rang city, Ninh Thuan province, is aimed at using renewable energy to optimize the management and reduce the water loss. The research has conducted DMA (District Metering Area) setup, construction and installation of flow meter and pressure reducing valve chamber for flow and pressure control with active pressure regulation, and the use of hydraulic power generator to generate power at the site. Research results provide management agencies, in particular, water supply companies, with optimal solutions in network management and energy saving, reducing the amount of water loss effectively, thereby increasing revenue and saving clean water precious resources are gradually depleted.


Introduction
Ninh Thuan Water Supply Joint Stock Company manages the water supply network of Phan Rang -Thap Cham city, Ninh Thuan province, with a population of 160,000. The water resource used is the river water and the well water with 3 water treatment plants (WTPs) withtotal capacity of 61,300m3/day, total length of distribution network is 21,700km and serves for 75,689 people.
The current water supply network in Thap Cham is a round network with total flow managed through the WTPs, with a current water loss ratio of 20%, including invisible loss and visible loss [16]. This reserach proposes solutions that help Ninh Thuan Water Supply Company manage its water supply network efficiently, save energy and reduce water loss.
The author proposes to divide the water supply network into 15 DMAs, which is a modern management solution [20]. Each district can be independently analyzed using flow meters and pressure transducers to improve system knowledge, to realize the water balance of the area, and to locate water losses. A DMA is a set of nodes enclosed in specified and permanent boundaries defined in order to install the smallest number of metering devices. DMAs identification is commonly realized using an empirical approach based on technical experience [20]  periodically [21] orgraph theoretic and graph partitioning principles used in distributed computing have recently been proposed.
The equipment installed in the DMA for continuous monitoring of flow and pressure makes the water supply company easy to manage. Water supply network management is becoming more and more of a concern in Viet Nam, in the context of clean water resources is increasingly exhausted threatening national clean water security. But mainly on network research, water quality, hydraulic problems and water loss prevention, the equipment management of the water supply network has not been paid much attentionwhile the water equipment is often of high value. In practice, meter, data transmitters (water meters, pressure sensors and dataloggers) installed on the water supply network are mainly installed in underground sites, sometimes flooded difficult to get the power from the electricity where the main power source is the battery installed in the device. Batteries will be depleted after several years of use and must be replaced to ensure stable operation, the cost of replacement batteries often high due to imports from abroad. In this research, the author also recommends the use of hydraulic power generators to generate electricity for on-site consumption, prolong battery life, and save operating and maintenance costs.
The research also proposed a water loss solution for DMA Ngo Quyen, one of the 15 DMAs in Phan Rang -Thap Cham city. In previous researches, the author found that the majority of water losses occurred as mechanical water losses but mainly at the clamp saddle position, service connections [10,11]. Therefore, to reduce water loss, the study focused on reducing mechanical water losses, regulating the pressure in the DMA based on the partitioning management of the pipe network, such as the PMA (pressure management area) and DMA. PRVs (pressure reducing valves) are installed at the inlet of the PMAs or DMAs and the water pressure inside the zonal network can be regulated by operating the PRVs. To maximize the benefits of pressure management, the installation and operation strategies of PRVs, i.e. quantity, locations and opening adjustment, are optimized [12], when the pressure in the pipeline drops, the water leakage through the hole in the pipeline will decrease [19].

DMA setup and equipment installation
DMA Ngo Quyen was selected with a pilot scale of 500 connections and did not specify the consumption as well as the leakage rate. DMA is set up by closing the boundary valves and installing the bulk flow meter chamber at the DMA input. This bulk flow meter has a pressure probe and a pressure reducing valve installed at downstream of meter to actively regulate the pressure in the DMA.
Equipment installed in DMA including: 1. Electromagnetic flow meter DN150 2. Hydroturbine to generate power 3. Pressure Reducing Valve(PRV) dualsetpoint 4. LS-V Datalogger to archive data (Flow, up-and downstream pressure) and control the PRV P1 is upstream pressure, P2 is downstream pressure, P3 is critical point pressure (The critical point is the place in the zone in question (DMA or PMA) at which the lowest supply pressure occurs during the course of the day) 5. LS42 Datalogger to archive pressure at critical point 6. PCWIN2 SCADA software to store, view and analyze data    Preliminary estimates of energy generated from hydroturbine, with a water flow of 580.86 m3/day (about 24 m3/h). With this flow rate, based on the table, the power generated is about 5W. ISOMAG electromagnetic flowmeter have a power consumption of about 4W, to ensure a stable and reliable metering, the author suggests that the meter be powered directly from the battery and that only the power from the Hydroturbine should be used for LS-V Datalogger.

Adjusting pressure reducing valve to reduce water losses
Pressure-flow results are recorded and displayed as curve plotting using the PCWIN2 SCADA software as follows: The results of input pressure monitoring and pressure points P1, P2, P3 showed that at low demand hours, pressure P3 was up to 2.79 bar, 1.94 bar higher than the minimum pressure, this was Excessive unnecessary pressure can be cut to reduce the rate of mechanical water loss during night time due to leakage. According to Vietnam standards, pressure requirements at each point of the water supply network must be at least 0.1 bar. The research conducted pilot setting pressure reducing valve in two stages. Pressure control schedule.
Stage 01: (21-06 to 30-06-2017): Maintain downstream pressure at setpoint, Pressure P2 = 1.7 bar. The LS-V Datalogger controls the 3-way solenoid valve on the pressure reducing valve to switch between high pressure and low pressure mode. The chart below shows the pressure correlation before and after two modes of pressure regulation.

Pressure P1
Pressure P3 Pressure P2 Flow Fig. 7. Curve of pressure before and after pressure regulating.

Results
Hydraulic generator renewable energy. Based on the average daily flow, monitoring Hydroturbine parameters from 29/05/2017 to 06/06/2017, the electricity generated by the flow as follows:  The curve above shows that the minimum night flow has decreased after pressure regulation Comparing the minimum flow during off-peak periods before and during the pressure regulating, it was found that reducing the off-peak pressure from 2.11 bar (before pressure control) to 1.7 bar and 0.9 bar (during automatic pressure regulating) would reduce flow through bulk meter 8.2% and 14.1% of DMA total flow. This reduced flow is the loss of water that is reduced by regulating the pressure in the DMA.

Conclusions
Hydraulic generator renewable energy.
The Ngo Quyen DMA has a small scale, with a small supply of water so that the generated electricity is just enough to operate the LS-V datalogger. But when installed in the pipe with enough flowrate or large pipelines, installed on by-pass to limit the pressure loss on the main tube, at 6 "diameter, the generated power can be up to 20W for the flow rate of 150m3/h. Electricity can be used for serveral devices at the same time with fully calculated power. In above picture, the unit was installed using a 4" bypass and the partial closing of a valve so that a minimum of 20-30 m3per hour flow through the bypass and spin the turbine. The power is produced to operate a MOSCAD® controller.
Therefore, the hydraulic power generation is renewable energy solutions that can be applied on wide variety of water supply network, in many installation conditions and different size pipe.When installing it should be noted that the pressure loss when passing through the mini generator, this pressure loss can be very high with low pressure places, affecting the pressure of water users.
Regulate pressure in DMA Active pressure regulation at input according tocritical points needs to be rapidly deployed on a large scale. However, when implementing pressure regulation to critical point, it is necessary to consider the most appropriate thresholds for each District Metering Area (DMA), based on the characteristics of consumption and timepattern of main water user in water supply area. Qualitative and quantitative determination of losses in each water supply area should be carried out before implementation the solutions to reduce water loss [28,29]. This is necessary, because in a situation where the water supply network is severely degraded, leakage prevention by leak detection does not solve the problem of new leakage points after repairing. When regulating low pressure, the flow through the customer meter is also reduced. Therefore, it is necessary to study the correlation between water pressure and demand of customers when implementing regulation. If calculated, maintaining a sufficient pressure for living needs will help to save the water used in the tap. This will reduce the burden of water supply to water treatment plants.
The Ninh Thuan Water Supply Company also noted previously in the DMAs behind DMA Ngo Quyen (after crossing the Thong Nhat Bridge) the pressure was usually very low, but after the installation of the pressure regulator, pressure increased. This shows that pressure regulation not only reduces water loss, but also transfers excess pressure at DMA Ngo Quyen to lower pressure areas, which increases the quality of water supply services. Next research direction In the next research, the author will study the correlation in terms of pressure between DMAs in a water supply area after pressure reducing valve installation.