Impact of pipe material on the wall reaction coefficients and its application in the rehabilitation of water supply system of San Pedro Nexapa, State of Mexico

Abstract

One of the major challenges faced by water companies around the world is the high level of chlorine losses in distribution networks. This paper presents an experimental study to examine chlorine loss in different types of pipe materials and select the ones with low chlorine demand for the rehabilitation of the water distribution network of San Pedro Nexapa, State of Mexico. The materials investigated include: polyvinyl chloride (PVC), galvanized steel (GS), polypropylene (PP) and highdensity polyethylene (HDPE). A 24-h chlorine consumption study was performed in a simulated water distribution network to assess the impact of wall reaction coefficient on chlorine decay. Four sets of independent pipe loops of 50 mm in diameter and 12 m in length were used. Two different scenarios were considered based on different initial chlorine concentration (1.21 mg/L and 1.60 mg/L). Samples were collected at each loop in two hour intervals and physicochemical analyses were conducted. Results from the experimental distribution network showed that the wall coefficient values for GS, HDPE, PP and PVC were 0.165 h−1, 0.059 h−1, 0.043 h−1 and 0.026 h−1, respectively. Experimental results showed that wall reaction coefficient values depend on initial chlorine concentration and the characteristics of pipe material. The rate of free chlorine decay was found to be faster in Steel pipe and slower in the plastic pipes. Based on its lowest chlorine demand compared to the other pipes, PVC pipe would be selected to rehabilitate Nexapa water distribution network, State of Mexico. The wall coefficients from the experimental study were incorporated into EPANET through four simulation runs to predict chorine decay of San Pedro Nexapa water distribution network, State of Mexico. In the PVC and PP pipes higher residual chlorine concentrations were observed that ranged from 0.30 to 0.90 mg/L and 0.50 to 0.95 mg/L, respectively. This study is important for utilities to operate their system effectively and protect public health.

Residential Water Softeners Release Carbon, Consume Chlorine, and Require Remediation after Hydrocarbon Contamination

“…Free chlorine disinfectant concentrations were best fit using a first order rate constant: 0.06 h –1 for FL7 (r 2 = 0.98), 0.023 h –1 for FL8 (r 2 = 0.99), and 0.057 h –1 for PUR (r 2 = 0.99), and decay constants were similar to those of polyvinyl chloride pipes [0.0133 to 0.177 h –1 ] and polyethylene pipes [0.05 h –1 ]. 58 − 60 Chlorine decay for the aged resin did not follow a first order reaction ( Figure 3 ) likely due to the heterogeneity of the reactants: resin scale, biofilm, microorganisms, and synthetic organic matter present in the bulk water and on the resin surface. Little chlorine decay was observed for the control water (no resin).…”

Using Symbolic Machine Learning to Assess and Model Substance Transport and Decay in Water Distribution Networks

“…The chlorine reactions have been classically modelled using first order kinetics [5], but several second order models have also been proposed [6], [7]. The second order model with a single reactant species has been applied by authors such as [8]- [10]. Other second order models with multiple competing species have also been introduced [7], [11].…”

Using symbolic machine learning to assess and model substance transport and decay in water distribution networks

“…The chlorine reactions have been classically modelled using first order kinetics 10 , but several second order models have also been proposed 11,12 . The second order model with a single reactant species has been applied by authors such as [13][14][15] . Other second order models with multiple competing species have also been introduced 12,16 .…”