Isolation and characterisation of bacteria and fungi from biofilm build up in pipes in a water treatment plant in Harare · Electronic Theses and Dissertations

Author

Dandajena, Fortunate I.

Title

Isolation and characterisation of bacteria and fungi from biofilm build up in pipes in a water treatment plant in Harare

Abstract

Biofilms are complex microbial communities that adhere to surfaces and are embedded in a protective extracellular matrix. In water treatment plants (WTPs), biofilms form on the internal surfaces of pipelines and contribute to reduced water quality, resistance to disinfection, and infrastructure damage. This study aimed to isolate and characterize bacteria and fungi from biofilm buildup in WTP pipelines and to evaluate potential chemical treatment methods for biofilm removal. Samples were cultured on Nutrient Agar, MacConkey agar, and Potato Dextrose Agar. Sugar fermentation and biochemical tests, including catalase, oxidase, and urease were used for presumptive identification at genus level.While these methods offer useful metabolic and physiological insights, they do not provide definitive species-level identification without molecular confirmation. The bacterial isolates included Escherichia coli and Klebsiella spp., while fungal isolates inclulded Candida albicans, Cryptococcus spp., and moulds likely to be Fusarium and Trichoderma spp. Crystal violet (CV) assay was used to investigate the efficacy of four treatments, Sodium Dodecyl Sulphate (SDS), Benzalkonium Chloride (BAC), Tween 80, and Sodium Hypochlorite (NaOCl), each applied at 5% concentration for 5, 10, and 15 minutes. OD595 values showed that NaOCl and BAC achieved the greatest biofilm reduction, while Tween 80 was least effective. A two-way ANOVA confirmed statistically significant effects of both treatment type and exposure time on biofilm reduction (p < 0.001), including a significant interaction between the two variables. These results suggest that time and chemical agent both contribute significantly to biofilm disruption and that certain detergents may serve as viable alternatives to conventional chlorination. The study concludes that integrating effective chemical treatments and microbial profiling can enhance biofilm control strategies in water treatment infrastructure.

Date

June 2025

Publisher

BUSE

Keywords

Biofilms

microbial communities

water quality

Supervisor

Mr. C Siamayuwa