Keywords
residual chlorine decay
corrosion
hydraulic intrusion
How to Cite
Abstract
Introduction
In many sub-Saharan African cities, aging and intermittently pressurized drinking water distribution networks can compromise water quality beyond the treatment plant. In Kinshasa (Democratic Republic of the Congo [DRC]), hydraulic instability, pipe corrosion, and potential external contamination may alter the physicochemical quality of drinking water during distribution.
Purpose
This study investigated physicochemical degradation processes occurring within the drinking water distribution networks of the communes of Lemba and Kalamu, with emphasis on free residual chlorine stability, corrosion processes, and potential external contamination.
Methods
The distribution network was monitored through three grab-sampling campaigns conducted at selected households in the communes of Lemba and Kalamu. A total of 20 water samples were collected from 20 sampling points, including 10 in Lemba (L1–L10) and 10 in Kalamu (K1–K10), distributed along the network. Physicochemical parameters were analyzed using standard methods. Spearman correlation analysis was applied to identify relationships among variables and to infer dominant degradation mechanisms.
Results
Free residual chlorine (FRC) decreased to 0.10 mg/L at distal points, falling below the World Health Organization’s recommended range (0.2–0.5 mg/L), indicating insufficient disinfectant persistence. Two degradation patterns were identified. In Lemba, an endogenous process was observed, characterized by acidic pH (5.86), iron release (up to 0.15 mg/L) suggesting pipe corrosion, and possible localized nitrification (NO₂⁻ up to 0.028 mg/L). In Kalamu, degradation appeared to be driven primarily by exogenous factors, including high turbidity (7.37 NTU), elevated phosphate concentrations (1.47 mg/L), and a strong correlation with organic matter (r = 0.91), suggesting potential intrusion of urban effluents.
Conclusion
The drinking water distribution network functions as a reactive biogeochemical system rather than a passive conduit, with corrosion, organic loading, and hydraulic instability contributing to water quality degradation. These findings highlight the need for targeted infrastructure rehabilitation and adaptive chlorination strategies to ensure safe drinking water delivery.
References
Abokifa, A. A., Yang, Y. J., Lo, C. S., & Biswas, P. (2016). Water quality modeling in the dead-end sections of drinking water distribution networks. Water Research, 89, 107–117. https://doi.org/10.1016/j.watres.2015.11.025
American Public Health Association. (2022). Standard methods for the examination of water and wastewater (24th ed.). American Water Works Association & Water Environment Federation. https://www.standardmethods.org
ASTM International. (2018). Standard practice for sampling water from closed conduits (ASTM D3370-18). https://doi.org/10.1520/D3370-18
Angassa, K., Mulatu, F., Tessema, I., & Abewaa, M. (2025). Residual chlorine modelling in drinking water distribution system of Bishoftu Town, Ethiopia. Results in Engineering, 25, 104075. https://doi.org/10.1016/j.rineng.2025.104075
Bompangue, D., Giraudoux, P., Handschumacher, P., Piarroux, M., Sudre, B., Ekwanzala, M., Kebela, I., & Piarroux, R. (2008). Lakes as sources of cholera outbreaks, Democratic Republic of Congo. Emerging Infectious Diseases, 14(5), 798–800. https://doi.org/10.3201/eid1405.071260
Calero, C. P., Husband, S., Boxall, J., Del Olmo, G., Soria-Carrasco, V., Maeng, S. K., & Douterelo, I. (2021). Intermittent water supply impacts on distribution system biofilms and water quality. Water Research, 201, 117372. https://doi.org/10.1016/j.watres.2021.117372
Cao, Y., Zhang, Y., Zhao, W., Niu, Y., & Wang, C. (2025). Interactions and integrated optimization between secondary water supply devices and drinking water distribution systems: A review. Water Resources Management, 39, 3625–3639. https://doi.org/10.1007/s11269-025-04185-8
Donghan, L., Zhuang, Y., Hua, Y., & Shi, B. (2022). Impact of initial chlorine concentration on water quality change in old unlined iron pipes. Water Research, 225, 119146. https://doi.org/10.1016/j.watres.2022.119146
Douterelo, I., Husband, S., Loza, V., & Boxall, J. (2016). Dynamics of biofilm regrowth in drinking water distribution systems. Applied and Environmental Microbiology, 82(14), 4155–4168. https://doi.org/10.1128/AEM.00109-16
Douterelo, I., Sharpe, R., & Boxall, J. (2014). Bacterial community dynamics during early biofilm formation in a chlorinated drinking water distribution system. Journal of Applied Microbiology, 117(1), 286–301. https://doi.org/10.1111/jam.12516
Fish, K. E., Osborn, A. M., & Boxall, J. B. (2017). Biofilm structures in drinking water distribution systems are conditioned by hydraulics and influence discolouration. Science of the Total Environment, 593–594, 571–580. https://doi.org/10.1016/j.scitotenv.2017.03.176
ISO. (2008). ISO 10523: Water quality — Determination of pH. International Organization for Standardization.
ISO. (2016). ISO 7027-1: Water quality — Determination of turbidity — Part 1: Quantitative methods. International Organization for Standardization.
ISO. (2017). ISO 7393-2: Water quality — Determination of free chlorine and total chlorine — Part 2: Colorimetric method using N,N-diethyl-p-phenylenediamine (DPD). International Organization for Standardization.
ISO. (1993). ISO 8467: Water quality — Determination of permanganate index. International Organization for Standardization.
Kanakoudis, V., & Tsitsifli, S. (2017). Potable water security assessment: A review on monitoring, modelling and optimization techniques. Desalination and Water Treatment, 99, 18–26. https://doi.org/10.5004/dwt.2017.21784
Kapembo, M. L., Mukeba, F. B., Sivalingam, P., Mukoko, J. B., Bokolo, M. K., Mulaji, C. K., Mpiana, P. T., & Poté, J. (2021). Survey of water supply and groundwater quality in Kinshasa suburbs. Sustainable Water Resources Management, 8(1), 1. https://doi.org/10.1007/s40899-021-00592-y
Kumpel, E., & Nelson, K. (2016). Intermittent water supply: Prevalence, practice, and microbial water quality. Environmental Science & Technology, 50(2), 542–553. https://doi.org/10.1021/acs.est.5b03973
Kwio-Tamale, J. C., & Onyutha, C. (2024). Influence of physical and water quality parameters on residual chlorine decay in water distribution networks. Heliyon, 10(10), e30892. https://doi.org/10.1016/j.heliyon.2024.e30892
Mavakala, B. K., Le Faucheur, S., Mulaji, C. K., Laffite, A., Devarajan, N., Biey, E. M., Giuliani, G., Otamonga, J.-P., Kabatusuila, P., Mpiana, P. T., & Poté, J. (2016). Leachates draining from municipal solid waste landfill: Geochemical characterization and toxicity. Waste Management, 55, 238–248. https://doi.org/10.1016/j.wasman.2016.04.028
Mesalie, R. A., Aklog, D., & Kifelew, M. S. (2021). Failure assessment for drinking water distribution systems. Applied Water Science, 11, 138. https://doi.org/10.1007/s13201-021-01465-7
Mukeba, F., Kapembo, M., Mpiana, P., Mulaji, C., & Poté, J. (2022). Groundwater quality assessment in Kinshasa suburbs. Revue Congolaise des Sciences Humaines et Sociales, 1(2), 1–18. https://doi.org/10.59189/crsh102240
Nsiala, O. G., Mukeba, B. F., Seke, V. M., Bamvingana, K. C., Kacha, M. M., Matumona, K. D., & Biey, M. E. (2025). Waterborne diseases linked to groundwater quality in Kinshasa. Orapuh Journal, 6(12), e1318. https://doi.org/10.4314/orapj.v6i12.118
Oluwaseye, S. D., Yskandar, H., Khalaf, B., & Sadiku, R. (2018). Optimization model for contamination source identification in water distribution networks. Water, 10(5), 579. https://doi.org/10.3390/w10050579
Price, E., Abhijith, G. R., & Ostfeld, A. (2022). Pressure management in water distribution systems. Water Research, 226, 119236. https://doi.org/10.1016/j.watres.2022.119236
Shapiro, S. S., & Wilk, M. B. (1965). An analysis of variance test for normality. Biometrika, 52(3–4), 591–611. https://doi.org/10.1093/biomet/52.3-4.591
Smith, K., & Liu, S. M. (2021). Energy footprint evaluation for water distribution systems. Journal of Cleaner Production, 288, 125463. https://doi.org/10.1016/j.jclepro.2020.125463
Souza, D. E. S., Mesquita, A. L. A., & Blanco, C. J. C. (2023). Pressure regulation in water networks using pumps as turbines. Water Resources Management, 37, 1183–1206. https://doi.org/10.1007/s11269-022-03421-9
Trębicka, A. (2023). Modeling of water age changes in distribution systems. Economics and Environment, 83(4), 91–102. https://doi.org/10.34659/eis.2022.83.4.498
Villanueva, C. M., Cantor, K. P., Grimalt, J. O., Malats, N., Silverman, D. T., Tardón, A., García-Closas, R., et al. (2007). Bladder cancer and exposure to disinfection by-products. American Journal of Epidemiology, 165(2), 148–156. https://doi.org/10.1093/aje/kwj364
Wang, Q., Jiang, G. Z., Sun, Z. Y., Liang, Y., Liu, F., & Shi, J. (2024). Water quality and microecosystem in water tanks. Environmental Science and Pollution Research, 31, 12948–12965. https://doi.org/10.1007/s11356-024-31959-1
Weronika, G., Pytlak, A., Kowalska, B., Kowalski, D., Grządziel, J., Szafranek-Nakonieczna, A., Gałązka, A., Stępniewska, Z., & Stępniewski, W. (2021). Pipe material influence on biofilm microbial communities. Environmental Research, 196, 110433. https://doi.org/10.1016/j.envres.2020.110433
World Health Organization. (2017). Guidelines for drinking-water quality (4th ed., incorporating the first addendum). WHO Press. https://www.who.int/publications/i/item/9789241549950
Zhang, X., Lin, T., Jiang, F., Zhang, S., Wang, S., & Zhang, S. (2021). Impact of pipe material and chlorination on biofilm structure. Chemosphere, 289, 133218. https://doi.org/10.1016/j.chemosphere.2021.133218
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.