Please cite this article in press as: Al-Bedyry, N.K., et al., Ranking pipes in water supply systems based on potential to cause discolored water complaints. Process Safety and Environmental Protection (2016), http://dx.doi.org/10.1016/j.psep.2016.08.002 ARTICLE IN PRESS PSEP-843; No. of Pages 6 Process Safety and Environmental Protection x x x ( 2 0 1 6 ) xxx–xxx Contents lists available at ScienceDirect Process Safety and Environmental Protection journal homepage: www.elsevier.com/locate/psep Ranking pipes in water supply systems based on potential to cause discolored water complaints Najah Kadhim Al-Bedyry a , Arumugam Sathasivan b,∗ , Afrah Jaber Al-Ithari c a Department of Civil Engineering, College of Engineering, Babylon University, Babylon, Iraq b School of Computing, Engineering and Mathematics, Western Sydney University, Locked Bag 1797, Penrith, NSW 2751, Australia c Caledonian College of Engineering, Al Hail South, Oman a r t i c l e i n f o Article history: Received 7 December 2015 Received in revised form 1 August 2016 Accepted 2 August 2016 Available online xxx Keywords: Discoloration Hydraulic model Burst pipe Velocity Sediment transport Re-suspension Potential Method (RPM) a b s t r a c t A novel concept to rank pipes based on the potential (risk) to cause discolored water com- plaints when broken is presented. A fixed re-suspension velocity for all sediments was used previously to model sediment transport. However, there is always a risk of sediment re- suspension and discoloration, if the velocity caused by hydraulic disturbance is greater than the conditioning velocity-the maximum daily velocity historically experienced in a pipe before the disturbance. In a full scale system, five pipes of different diameters (99–222 mm) and locations (loop or open) were simulated to break (break main flow at 10 L/s) and the hydraulic response was analyzed using hydraulic software. The total affected length of the pipes where velocity was more than the conditioning velocity was used for ranking. In general, breakage of a smaller diameter pipe (100 mm diameter) caused more widespread disturbance. If proven in the field, the hydraulic software could be modified to rank pipes, making it easy for utilities to prioritise the pipe to replace or pay more attention. © 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved. 1. Introduction Discoloration at the customer tap is one of the most common causes of customer complaints in a drinking water supply system (DWSS). In Australia, it stands at 60–80% (Al-Ithari, 2013). Within Australia there is a large variation in customer complaints between the different utilities, ranging from 1.1 to 17.9 complaints per 1000 customers with an average of 6 per 1000 customers (Polychronopolous et al., 2003). Discolored water may contain potentially harmful pathogens and heavy metals (Gauthier et al., 1999; Kris and Hadi, 2008; Tong et al., 2015). During the discoloration events turbidity increases and is one way of assessing the event. Australian Drinking Water Quality Guidelines (ADWG, 2004), therefore, recommends an ∗ Corresponding author. Fax: +61 02 47360833. E-mail addresses: eng.najah.kadhim@uobabylon.edu.iq (N.K. Al-Bedyry), s.sathasivan@westernsydney.edu.au (A. Sathasivan), Afrah.alithari@caledonian.edu.om (A.J. Al-Ithari). acceptable turbidity at customer tap as below 1 NTU at times of disinfection, but the maximum can reach up to 5 NTU for aesthetic considerations. It is well accepted that the sediments or suspended solids must be present before hydraulic events carry them to the customer to cause discoloration events. Suspended solids can come with the treated water or may form due to physical, chemical and microbiological processes within the pipe. For a discoloration event to occur sediments or particles should be present and it should be disturbed and carried away by moving water. The sediments in the system can originate from a number of different sources. It can come directly from the treatment plant, especially treatment with sand filtration where sediment can be introduced in the network (Vreeburg http://dx.doi.org/10.1016/j.psep.2016.08.002 0957-5820/© 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.