Numerical simulation of quantitative and qualitative parameters in water supply networks by WaterGEMS

WaterGEMS software provides a numerical model which simulates different parameters in water supply systems based on the principles of hydraulics. The most remarkable chemical substance used in water refinement procedure is the chlorine. Hence, WaterGEMS software models the chlorine to detect its concentration in each pipes of the water supply system. If the chlorine concentration exceeds 3mg/lit, it would be dangerous for the Man health. In addition, the model may calculate water age in water supply networks. And more, the WaterGEMS can trace the chlorine substance as well. In this research, the chlorine concentration, water age and chlorine trace parameters have been simulated by WaterGEMS for a case study: Vahidieh district (located on the west part of Tehran province). Meanwhile, other quantitative items have also been calculated in Vahidieh water supply network system. For example, flow discharge, flow velocity, water head loss in pipe networks. This is because, there are important relationships between qualitative and quantitative parameters for the optimization design of water supply networks. For more comfortable comparison and interpretation of the above concept, three pipes in different places of Vahidieh water supply network have been chosen (i.e. 18th,168th and 293th pipes put in the left, middle and right side of water supply network, respectively). The innovation of present research work is to provide quantitative and qualitative items for the simulation of Vahidieh region where it has not yet been found out up to now. In addition, modeling of all mentioned items will result in a comprehensive view to the design of water supply networks. A miniature previous research work on the subject is mentioned. Aghasi (2018) who has presented a model by WaterGEMS to determine appropriate points for injecting of chlorine in a part of Mashhad water supply network. He concluded that the appropriate points for chlorine injection dependent upon the network geometry, pipes diameter and the pattern of consumption. Javadinejad et al. (2019) utilized a pump and gravitational statuses in Semirom water supply by using WaterGEMS. They stated that in pumping method, water qualitative management may guarantee a better system. Vidhi and Geeta (2019) simulated a rural region in India by WaterGEMS. They resolved that the remained chlorine concentration in the pipes are in standard status (i.e. less than 3mg/lit).

The WaterGEMS numerical model has been designed by Haestad Methods company. Meanwhile, it is dependent upon the American hydraulics council. In the software, the analysis of water distribution networks is given step by step as: firstly, network drawing based on the nodes coordinates, pipes situation, reservoirs, tanks and other elements. Secondly, defining the network hydraulic traits. Thirdly, defining the distribution network for a hydraulic performance. Fourthly, defining the network analysis method. After that by running the software, the network parameters are obtained. Finally, the network quantitative and qualitative results may be achieved. The Vahidieh town water supply network where used as a case study; its population will be 78600 person at the end of 30 years design period. In so, for the total consumption of water will be 215lit/day per capita. The amount of water consumption in the region has been estimated 195lit/s. There are 2 reservoirs and 2 tanks in the new water supply network system. Volume of each reservoir is 5000m^3 and the volume of each tank is 500m^3. Meanwhile, a chlorination house has been designed to disinfect the region water that the maximum chlorine injection will be 3mg/lit. The pipes material was polyethylene. For modeling Vahidieh town water distribution network by WaterGEMS software, first of all, the nodes and pipes are drawn by AutoCAD software. Secondly, the reformed information imports to the WaterGEMS software. In this step, it is necessary to extract nodes altitude codes from ArcView software. Thirdly, other elements of network, consumption pattern and different scenarios are defined. Finally, the software reports will be analyzed and the results are obtained.

In this paper, a successful simulation has been carried out of a water supply network using WaterGEMS software. The numerical simulation reproduced the complex flow patterns in the pipes network associated with a particular water consumption in the Vahidieh water supply network are presented as a case study. On the basis of the analysis made by applying WaterGEMS, the following results are obtained: The chlorine concentration in 18th, 168th and 293th pipes were selected and have been studied, in more detail. Meanwhile, three defined scenarios are used: (1). Primary concentration in reservoirs, tanks, pumps, valves and nodes are 2, 0.5, 1, 1, 0.1 mg/lit. (2). The chlorine concentration reaches to 10 mg/lit in reservoirs, while its concentration is the 1st scenario in other ingredients. (3). The chlorine concentration reaches to 5 mg/lit in tanks, while its concentration is the 2nd scenario in other ingredients. Based upon the numerical model reports in 18th pipe, water age is higher than that of 168th and 293th pipes. According to the Vahidieh town population distribution, less population surrounded by 18th pipe in comparison to the other two pipes. Plus, in 18th pipe, the maximum water age is 3 times of maximum water age in 168th pipe. According to the WaterGEMS reports, under the different scenarios, chlorine concentration in 168th pipe is equal to injected chlorine concentration to reservoirs (the pipe which is closer to reservoirs). In addition, 168th pipe chlorine concentration is 10% higher than the other two pipes under three scenarios. The chlorine concentration computation in the selected pipes indicates much higher influence on the reservoirs chlorine concentration on chlorine concentration in water supply network pipes. Furthermore, based on the third scenario, when the chlorine concentration increases in the tanks, there is not tangible variation in pipes chlorine concentration. The reason is that much higher volume of reservoirs in comparison with the tanks volume occurs. Based upon the obtained results from WaterGEMS reveals that in 18th pipe the maximum water provision probability from the 1st tank is about 45%. Additionally, 168th pipe water provision probability from two reservoirs is the same. Also, 293th pipe water has surely been supplied from 2nd tank. As well, flow velocity, water head loss and water discharge can be studied in each 24hour period based on hourly consumption pattern. Based on the WaterGEMS outputs, the maximum water flow velocity in 18th pipe is 0.3 m/s. This result is reasonable, because of water age item in the pipe which is higher than that of the other two pipes. As a consequent, it seems that sedimentation probably occurs along pipe 18th. Moreover, 168th pipe reaches a maximum head loss of 0.4 meter, and 293th pipe receives a maximum water discharge of 8lit/s.