The Effect of Pipe Age and Piping Materials on Chlorine Decay in a Pilot Loop Water Distribution Network

Chlorination is one of the most widely used methods of disinfectant in many developing countries water distribution network due to its inexpensive, highly effective, and stable nature. In the transmission and distribution network, the water quality can deteriorate with age due to various factors like pipe wall materials, biomass growth, and reaction with ammonia, iron, and organic compounds. In the present study, the impact of service age of the pipe and the pipe materials on the chlorine decay in a pilot loop water distribution network was performed. The two distinct zones in South India with a partial water distribution network with dissimilar water source and piping material were selected for the study. The network 1 has 35 piping with 24 junction was constructed with galvanized steel material with a Hazen Williams roughness coefficient as 120. In network 2, there were 60 piping system with 33 junctions and were constructed with cast iron material having Hazen Williams roughness coefficient as 100. The results show that the chlorine first order wall decay is highly governed by the pipe service age and the piping material. The results indicate that quality of the residual chlorine above the standard value of 0.2 mg/L was maintained at a constant rate immediately after the flow in the galvanized steel pipe. However, in the cast iron piping due to the roughness and aging factor, it takes more time to achieve the desired concentration of above 0.2 mg/L. Additionally, in the cast iron pipe, the quality is changing periodically. Therefore, the study concludes that chlorine decay is not affected in the galvanized steel pipe and recommended for the pipe networks in South India.