Domestic graywater reuse offers a sustainable approach to mitigate water scarcity. This study explores the potential of bacteriophages as a biocontrol agent for reducing the enteric bacteria in graywater. Graywater was initially quantified and characterised, followed by bacterial isolation and identified by API index via the Vitek system, revealing Escherichia coli (08) and Enterococcus faecalis (03). A total of 15 phages were successfully isolated and purified; among these, five—B28K7b, B28B27b, B28K1a, B28B1a, and B28K32c—were selected for further studies. Phages B28K7b and B28B27b exhibited the broadest host ranges and highest lytic activity compared to other phages, prompting their selection for the reduction study during the treatment process. Transmission Electron Microscopy (TEM) classified B28K7b as Myoviridae and B28B27b as Siphoviridae (order Caudovirales). In a 3000mL system of untreated graywater, phages applied at a multiplicity of infection (MOI) of 2 achieved 1.65 ± 0.05 log₁₀ reductions in total heterotrophic counts and 2.01 ± 0.03 log₁₀ reductions in E. coli (mean ± SD; p < 0.05) after 6 hrs. These results highlight bacteriophages as an effective, eco-friendly alternative for bacterial reduction in graywater, enabling safe non-potable reuse.
Dasgupta et al. (Thu,) studied this question.