Authors : Nwogbu Peter; Dr. Yassin Osman; Dr. Stephen Ikporo; Mkpumah Emmanuel

Volume/Issue : Volume 11 - 2026, Issue 3 - March

Google Scholar : https://tinyurl.com/5fj4rwjp

Scribd : https://tinyurl.com/2mn2fty5

DOI : https://doi.org/10.38124/ijisrt/26mar1692

Note : A published paper may take 4-5 working days from the publication date to appear in PlumX Metrics, Semantic Scholar, and ResearchGate.

Abstract : This paper evaluates how Bolton Wastewater Treatment Works (WWTW) influences the physicochemical water quality of the River Irwell using an integrated multivariate statistical approach. Weekly grab samples were collected for four weeks at three sites: upstream control, effluent discharge, and downstream recovery. Parameters measured includes BOD5, dissolved oxygen, electrical conductivity, turbidity, pH, temperature, and flow conditions following APHA standard methods with strict QA/QC procedures. Primary data were complemented by Environment Agency records, operator discharge data, and CSO events. Data were standardized and analysed using descriptive statistics and multivariate methods including. The multivariate analysis showed distinct and statistically significant division of the upstream, effluent, and downstream areas of sampling (PERMANOVA pseudo-F = 4.19, p = 0.005). Factor Analysis revealed two latent factors of the most prominent result that explained 59.28 percent of the overall variance. Factor 1 was a great chemical gradient with high positive loadings of EC (+0.82) and negative loadings of DO ( -0.96) and pH ( -0.81), which is in line with the effects of treated wastewater effluent. A rather low loading of BOD5 (−0.26) demonstrated positive removal of biodegradable organic matter during the treatment process and a minor contribution of turbidity to this main gradient. Factor 2 was an independent process related to sediments and turbidity expressed the greatest positive loading to oxygen and organic pollution dynamics (+0.55). Biplot analysis showed clear zonal clustering: upstream samples were linked to oxygen-rich, low-conductivity conditions; and effluent samples to oxygen-depleted, high-conductivity conditions; and downstream samples occupied an intermediate position, indicating partial chemical recovery and sediment influence. Dissolved oxygen was the most sensitive indicator of effluent impact, with mean depletion at the effluent site exceeding 55%, while electrical conductivity showed a consistent downstream gradient. A weighted effluent impact index (EII) classified baseline, impacted, and recovering zones without upstream false positives or effluent false negatives. Comparison of primary and secondary data showed differences in BOD5 and pH but strong agreement in temperature, highlighting the need for harmonized monitoring standards.

Keywords : River Irwell; Bolton Wastewater Treatment Works; Urban River Pollution; Wastewater Effluent Impacts; Multivariate Statistical Analysis; Dissolved Oxygen; Electrical Conductivity.

References :

1. Anderson, M.J. (2001) A new method for non-parametric multivariate analysis of variance. Austral Ecology, 26(1), pp. 32–46. https://doi.org/10.1111/j.14429993.2001.01070.pp.x (Accessed: 12 December 2025).
2. Begum, S., Firdous, S., Naeem, Z., Chaudhry, G.S., Arshad, S., Abid, F., Zahra, S., Khan, S., Adnan, M., Sung, Y.Y. and Tengku Muhammad, T.S. (2023) ‘Combined multivariate statistical techniques and Water Quality Index (WQI) to evaluate spatial variation in water quality’, Tropical Life Sciences Research, 34(3), pp. 129–149. https://doi.org/10.21315/tlsr2023.34.3.7 (Accessed: 13 November 2025).
3. de la Torre, M.L., Barata, A. and Pico, Y. (2020) Multivariate statistical analyses for water and sediment quality index development: a study of susceptibility in an urban river’, Ecotoxicology and Environmental Safety, 200, 110742. https://doi.org/10.1016/j.ecoenv.2020.110742 (Accessed: 27 October 2025).
4. Ecosystems Knowledge Network (2025) Irwell catchment water quality issues. Available at: https://ecosystemsknowledge.net/ (Accessed: 20 December 2025).
5. Environment Act 2021 (UK). Available at: https://www.legislation.gov.uk/ukpga/2021/30/contents (Accessed: 1 January 2026).
6. Environment Agency (2023) Water quality monitoring methods and tools. Environment Agency, Government of the UK. Available at: https://assets.publishing.service.gov.uk/media/5be99782e5274a084382c559/Book_204.pdf (Accessed: 30 December 2025).
7. FloodMapper (2024) Bolton Wastewater Treatment Works spill record. Available at: https://www.floodmapper.co.uk (Accessed: 15 December 2025).
8. Iloms, E., Ololade, O.O., Ogola, H.J.O. and Selvarajan, R. (2020) ‘Investigating industrial effluent impact on municipal wastewater treatment plant in Vaal, South Africa’, International Journal of Environmental Research and Public Health, 17(3), p. 1096. https://doi.org/10.3390/ijerph17031096 (Accessed: 2 January 2026).
9. Ioele, G., De Luca, M., Grande, F., Durante, G., Trozzo, R., Crupi, C. and Ragno, G. (2020) ‘Assessment of surface water quality using multivariate analysis: Case study of the Cratis River, Italy’, Water, 12(8), p. 2214. https://link.springer.com/article/10.1007/s11356-020-10219-y (Accessed: 22 December 2025).
10. Ma, X., Wang, L., Yang, H., Li, N. and Gong, C. (2020) ‘Spatiotemporal analysis of water quality using multivariate statistical techniques and the Water Quality Identification Index in the Qinhuai River Basin’, Water, 12(10), p. 2764. https://doi.org/10.3390/w12102764 (Accessed: 3 January 2026).
11. Phungela, T.T. (2020) Impact of wastewater treatment effluent on the water quality of the Crocodile River, Ehlanzeni District, Mpumalanga. MTech Dissertation, Cape Peninsula University of Technology. Available at: https://etd.cput.ac.za/handle/20.500.11838/3458 (Accessed: 3 January 2026).
12. Rodríguez, R. and Pérez, J. (2021) ‘Assessment of physicochemical water quality in urban river systems’, Journal of Environmental Management, 280, 111783 (Accessed: 23 December 2025).
13. Rosenqvist, J., Nilsson, C., Hering, D. et al. (2021) Storm overflow impacts on riverine ecosystems’, Science of the Total Environment, 778, 146173. https://doi.org/10.1016/j.scitotenv.2021.146173 (Accessed: 3 January 2026).
14. Rufino, M., Gallego-Schmid, A., Stamford, L., & Azapagic, A. (2022). Environmental sustainability assessment of wastewater treatment technologies: A life cycle perspective. Journal of Environmental Management, 303, 114162. https://doi.org/10.1016/j.jenvman.2021.114162 (Accessed: 23 December 2025).
15. United Utilities (2022) Storms Overflow Report 2022. United Utilities. Available at: https://www.unitedutilities.com/globalassets/documents/pdf/united-utilities-storm-overflow.pdf (Accessed: 22 December 2025).
16. United Utilities (2024a) United Utilities to upgrade Bolton wastewater treatment works. United Utilities Newsroom, 8 February. Available at: https://www.unitedutilities.com/corporate/newsroom/latest-news/united-utilities-to-upgrade-bolton-wastewater-treatment-works/ (Accessed: 22 December 2025).
17. United Utilities (2024b) Major milestone reached as part of improvements to Bolton wastewater treatment works. United Utilities Newsroom, 30 September. Available at: https://www.unitedutilities.com/corporate/newsroom/latest-news/major-milestone-reached-as-part-of-improvements-to-bolton-wastewater-treatment-works/ (Accessed: 22 December 2025).
18. Zhang, Y., Yu, H., Liu, M. et al. (2023) ‘Analysis of water quality and habitat suitability for benthic macro-invertebrates in the Majiagou urban river, China’, Water, 15(12), 2269. https://doi.org/10.3390/w15122269 (Accessed: 4 January 2026).
19. Zhao, L., Wang, S. and He, Q. (2022) ‘Rainfall-driven variability in urban river water quality’, Water Research. https://doi.org/10.1016/j.watres.2022.118961 (Accessed: 5 September 2025).
20. Datasets: https://drive.google.com/drive/folders/10F9PVaxYBg2PyFcQ5oN85do5yq7Zwgm8?usp=sharing