Characterisation and optimisation of an automated ultrafiltration system used for the concentration of waterborne viruses, bacteria and protozoa

Waterborne pathogen detection is challenging, requiring effective target organisms enrichment to enable reliable and accurate monitoring of pathogens which could be present at low numbers. However, existing processes are manual, require operator expertise and are optimised for particular applications, e.g. a certain approach for viruses and another for bacteria etc. This study presents the design, development, and optimisation of an easy-to-use automated Rexeed™ dead-end filtration system tailored for concentrating multiple waterborne pathogens including viruses, bacteria and protozoa within a single unit. Knowing the variability in recovery rates across filtration technologies due to factors such as filter type, pre-treatment chemicals, backflush volumes, and flow rates, this system was engineered to optimise pathogen recovery and improve consistency in sample processing, generating a system that reduces manpower requirements and worked well across viruses, bacteria and protozoa.
System parameters were investigated, including flow rates of filtration from 0 to 1200 mL/min, backflush volumes ranging from 0 to 500 mL, chemicals used for backflush water enhanced with surfactants and chemical dispersants. Additionally, pre-treatments with sodium polyphosphate (NaPP) and bovine serum albumin (BSA) were investigated using fluorescent beads as proxies for pathogens.
Key results indicate that high flow rates (≥ 900 mL/min), backflush volume of 250 mL containing NaPP, Tween and antifoam achieved significantly higher recovery rates. Validation using fluorescent particle counting and turbidity measurements confirmed that this automated setup yields recovery rates in line with existing filtration methods. By enabling simultaneous concentration of diverse pathogens, this automated system offers a practical solution for comprehensive waterborne pathogen monitoring, demonstrating that one automated filtration unit can effectively concentrate multiple pathogens.