u& £j)o k)[o* |nn V (Jt, \h(oL\0 STUDY OF TRANSPORT OF CONTAMINANTS IN A PIPE NETWORK USING MODEL EPANET f.LU-' by I.N. Jayatilake (Nee Hewa) ©0oc5gO 3g$0 § e*2»3© ®0odg0. DEPARTMENT OF CIVIL ENGINEERING UNIVERSITY OF MORATUWA SRI LANKA bbo£8 ^ M T^estf Co!!.1996 696 96 626 .B23.'r ■&7r ■ •\Cs ",o C £ 66058 STUDY OF TRANSPORT OF CONTAMINANTS IN A PIPE NETWORK USING MODEL EPANETi by I.N. Jayatilake (Nee Hewa) j This thesis was submitted to the Department of Civil Engineering of the University of Moratuwa, Sri Lanka, as a partial fulfillment of the requirements of the degree of Master of Engineering in Hydraulic Engineering. ; ; ; ! l l ;: i ! } !, I | I * ;This thesis has not been previously presented in whole or part to any University or Institute for a higher degree. : :' '. ! : : .* ! | | 1 ; i ! I.N. Jayatilake (08-11-1996) i; ! I ; ; : T■ j I ACKNOWLEDGEMENT I ! I am greatly in debted and thankful to my Project Supervisor Prof. Mrs. N. Ratnayake for her valuable instructions, corrective advice and guidance which she readily and ungrudgingly gave me right throughout my research work. I would not have been able to complete this study without her help. i i ) j ! I sincerely thank the Dean of the Faculty of Engineering, Prof. L.L. Ratnayake who awarded me a grant to carry out my research. , i ! i I also thank Mr. J.P. padmasiri of National Water Supply & Drainage Board, Peradeniya, & Mrs. Malani Jayawardana of National Water Supply & Drainage Board, Ratmalana for giving me valuable information and data with reference to my study. ! i : I should also thank the Head of the Department of Civil Engineering and Members of the academic staff for advising and guiding me. ! ! : j ABSTRACT i The aim of this study was to get an understanding of the transport of contaminants in a water distribution system, using the Model EPANET, in order to meet water quality regulations and customer expectations. : ! i For the application of the model a rural water supply system , having two probable water sources, an elevated tank, three schools and a hospital was selected. The transport of a conservative substance introduced at source, within the system was analysed by varying the hydraulic and water quality parameters for a predetermined demand pattern. The model was also used to design an effective operating program in a two-source distribution system in which pumping schedules were changed to get the contaminant levels below the maximum permissible values. Another application that was studied was the travel of a contaminant introduced at a point in the distribution system other than the source. Here, the study was confined to the behaviour of a conservative tracer introduced at the hospital node. Finally, the behaviour of a non conservative substance entering the system at source was studied. Here the substance considered was residual chlorine, and the decay of the residual chlorine introduced at the source with time and distance was studied. This is helpful in determining the lowest residual chlorine levels in the system, which is a useful parameter in maintaining a safe water supply. i i: 1 ! ■ ; 1 ! It was revealed that, under average demand conditions, time of travel of a contaminant to any point within the distribution system is the same irrespective of the contaminant concentration, and also it was observed that, if the contaminant is removed promptly the maximum concentration appearing at the nodes in the distribution system can be reduced to a great extent. Thus it was concluded that close monitoring of the source is extremely important in protecting the water supply from contamination. 5-7 ; : In the application of the model to the pollution tracing situation, the observation was that, under average flow conditions, the maximum concentration reached at all nodes located downstream of the node at which the contaminant entered within about 3hrs, irrespective of the concentration of contaminant. wasi In the two source supply situation, it was observed that the water quality at the critical points in the system could be maintained below the permissible fluoride levels when the pump drawing water from the high fluoride content source was operated during the reak demand period of 13 to 24 hrs only, (with the assumed pump characteristics). ! i ; ; When the behaviour of residual chlorine in the system was studied, it was observed that the model can be used to find out the chlorine booster points to maintain the required minimum residual chlorine content at the distribution ends. ! 1 : 1 Thus it was concluded that the Model EPANET can satisfactorily be used to study the behaviour of contaminants in a water distribution system, and also we use this to get an effective operating program in a multy-source system which satisfy the water quality requirements. can ! j iii ! TABLE OF CONTENTS ACKNOWLEDGEMENT ABSTRACT .................. LIST OF FIGURES___ LIST OF TABLES......... i ii vi IX Chapter 1: INTRODUCTION...................... 1.1 Water distribution Systems • • 1.2 Objective and scope of Project 1.3ModeI EPANET.................... 1 1 1 2 Chapter 2: LITERATURE REVIEW...................................................... 2.1 Impurities in water.......................................................... (a) Fluoride removal and Fluoridation of water.................... (b) Presence of coiiform bacteria and residual chlorine content 2.2 Water Borne Diseases.................................................... 2.3 Objective Water quality & Water Quality Standards......... 2.4 Water Quality Monitoring in water distribution systems- • 2.5 Tracing Pollution............................................................. 3 3 5 11 12 12 13 14 Chapter 3: METHODOLOGY................................................................... 3.1 Description of the distribution system.................................. 3.2 Description of the Model.................................................... 3.3 Data collected...................................................................... 3.4 Application of the Model.................................................... (1) Transport of a Conservative Contaminant in the distribution system introduced at the source node.................................. (2) Tracing Pollution by a Conservative Contaminant................ (3) Mixing of water from two sources, of which one has a high concentration of fluoride...................................................... (4) Transport of a non-conservative substance in the distribution system................................................................................ 16 16 17 24 24 i 25 25 26 26 Chapter 4: RESULTS 27 4.1 Transport of a Conservative Contaminant in the distribution system introduced at the source node................................ 4.2 Tracing Pollution by a Conservative Contaminant.............. 4.3 Mixing of water from two sources, of which one has a high concentration of fluoride.................................................... 27 1 27 31 4.4Transport of a non-conservative substance in the distribution system...............................................................................: 32 iv 33Chapter 5: DISCUSSION OF RESULTS........................................................ 5.1 Transport of a Conservative Contaminant in the distribution system introduced at the source node.................................. 5.2 Tracing Pollution by a Conservative Contaminant............... 5.3 Mixing of water from two sources, of which one has a high concentration of fluoride........................................................ 5.4Transport of a non-conservative substance in the distribution system...................................................................................... 33 33 34 34 36Chapter 6: CONCLUSIONS AND RECOMMENDATIONS 6.1 Condjwri&ns................................................... 6.2 Recommendations for further study............ 36 37 .38REFERENCES 39 APPENDIX A:FIGURES 75APPENDIX B: TABLES ! . V LIST OF FIGURES Figure 2.1 Common impurities of water and their effects. Figure 2.2 Distribution of fluoride in the deep wells of Sri Lanka. Histograms showing fluoride concentration of ground water of sri lanka.Figure 2.3 Figure 2.4 Low cost defluoridator Figure 4.1a Map of the network Figure 4.1b Map with node ID numbers. Figure 4.1c Map with link ID numbers Figure 4. Id Penetration of contaminant after 6hrs for case (1) Figure 4.1e Graphs of contaminant concentration vs time for case (1)- node 191 & node 14 Figure 4. If Graphs of contaminant concentration vs time for case (1)- node 1& node 84 Contaminant concentration vs time for node 1 when the simulation period is 72 hrs Figure 4.1g Blending of dye after 3 hrs for case (2)Figure 4.2a Concentration of dye vs time for pipe 59 when node 84 concentration = lmg/1 Figure 4.2b Concentration of dye vs time for pipe 59 when node 84 concentration = lmg/1 Figure 4.2c Concentration of dye vs time for pipe 47 when node 84 concentration = lmg/1 Figure 4.2d Concentration of dye vs time for pipe 47 when node 84 concentration =500mg/l Figure 4.2e Concentration of dye vs time for node 175 when node 84 concentration = lmg/1 Figure 4.2f vi Figure 4.2g Concentration of dye vs time for node 175 when node 84 concentration =500 mg/1 Figure 4.3a Demand pattern for node 84 for case (3) Figure 4.3b Pump curve for pump 200 for case (3) Figure 4.3c Pump curve for pump 250 for case (3) Figure 4.3d Penetration of low quality water after 20 hours for case (3) Figure 4.3e Percentage of low quality water penetration with time for node 191 Figure 4.3f Percentage of low quality water penetration with time for node 1 Figure 4.3g Percentage of low quality water penetration with time for node 84 Figure 4.3h Percentage of low quality water penetration with time for node 66 Figure 4.3i Percentage of low quality water penetration with time for node 17 Figure 4.3j Percentage of low quality water penetration with time for pipe 76 Figure 4.3k Percentage of low quality water penetration with time for pipe 74 Figure 4.31 Variation of fluoride concentration for node 1 Figure 4.3m Variation of fluoride concentration for node 17 Figure 4.3n Variation of fluoride concentration for node 84 Figure 4.4a Variation of residual chlorine content with time for 24 hr simulation period for pipe 77 Figure 4.4b Variation of residual chlorine content with time for 24 hr simulation period for tank 20 Variation of residual chlorine content with time for 24 hr simulation period for node 84 Figure 4.4d Variation of residual chlorine content with time for 24 hr simulation period for node 141 Variation of residual chlorine content with time for 72 hr simulation period for node 141 Figure 4.4c Figure 4.4e vii Figure 4.4f Variation of residual chlorine content with time for 72 hr simulation period for node 84 Figure 4.4g Variation of residual chlorine content with time for 72 hr simulation period for tank 20 Figure 4.4h Variation of residual chlorine content with time for 72 hr simulation period for pipe 77 Figure 4.4i Output summary for residual chlorine analysis Figure 4.4j Distribution of residual chlorine within the system after 24 hrs of simulation LIST OF TABLES Table 1 WHO guidelines Table 2 SLS standards Table 3 Input file for case (1) Table 4.1b Tabular results for node 1, for case (1) when the simulation period is 72 hrs Table 4.3a Input file for case (3) Table 4.3b Output results for case (3) at 20 hrs Table 4.4 Output results for node 84 when the simulation period is 72 hrs ix i