MS2 bacteriophage reduction and microbial communities in biosand filters

Area of Science:

• Environmental microbiology
• Water treatment technologies
• Filtration systems

Background:

• Biosand filters (BSFs) are crucial for safe drinking water, but their virus removal mechanisms require further elucidation.
• Understanding the interplay between physical and biological factors in BSFs is key to optimizing pathogen reduction.

Purpose of the Study:

• To evaluate the role of physical and biological filter characteristics in MS2 bacteriophage reduction within biosand filters.
• To investigate the microbial community structure and its correlation with virus removal efficiency.

Main Methods:

• Utilized three full-scale concrete Version 10 BSFs with defined sand media depth and charge volume.
• Analyzed MS2 bacteriophage reduction over time and assessed microbial communities via genomic, protein, and carbohydrate extraction from sand cores.
• Quantified virus reduction in the top 5 cm versus deeper layers of the filter media.

Main Results:

• BSFs achieved a 4 log10 reduction of MS2 within 43 days, maintaining 4-7 log10 reduction for up to 294 days.
• The top 5 cm of sand media showed significantly higher MS2 reduction (0.56 log10/cm) compared to deeper layers (0.06 log10/cm).
• Higher MS2 reduction correlated with increased microbial diversity, carbohydrate concentrations, and the presence of chemolithotrophs (e.g., Candidatus Nitrosopumilus maritimus) and proteolytic bacteria.

Conclusions:

• Physical factors like filter depth and residence time contribute to MS2 reduction in BSFs.
• The establishment of specific microbial communities, including chemolithotrophs and proteolytic bacteria, significantly enhances virus removal efficiency.
• This study offers novel insights into the microbial ecology of BSFs and their role in pathogen inactivation.