Detail Abstract

Advanced microbiological water monitoring with Flow-Cytometry (FCM)

Abstract

Microbiological water monitoring is essential for risk assessment and protection of raw water used for drinking water production. The currently used cultivation methods for water quality control are useful to show fecal contaminations, but are not suited for a rapid or automatic monitoring of water sources.<br> Flow cytometry is a laser-based technology to quantify bacteria within minutes. In a flow cytometer, bacteria and other particles in a water sample are separated and detected in a laminar flow. Bacterial nucleic acids (DNA and RNA) can be stained with fluorescent dyes and allow a differentiation of bacteria and sample background. In addition to the total bacterial count, flow cytometry allows a separation of bacteria into cells with low and high nucleic acid content (LNA/HNA). Changes of HNA content of water samples can indicate contaminations, regrowth or stagnation effects. Additionally, a live/dead differentiation is possible by addition of the fluorescent dye propidium monoazide which can only enter bacterial cells with a damaged membrane. Thus this new approach has also the potential to monitor water disinfection, e.g. by ozonation. Based on the rapid microfluidic and laser technique, flow cytometry has a high potential for quasi-continuous microbial monitoring. Commercial systems for automated sampling, staining and result calculation are already available.<br> Our studies show that results of flow cytometric counts are comparable to culture based methods and microscopic cell counts. Round robin tests performed in Germany showed good reproducibility and reliability of results with standard deviations of 3 to 5 % for groundwater and drinking water using well-defined protocols. Flow Cytometry represents a promising method also for drinking water analysis and monitoring of complex environmental matrices such as surface water in the Mekong Delta. However, protocols have to be adapted to the site specific conditions.<br> Financial support by the German Technical and Scientific Association for Gas and Water (DVGW, Project FlowDetect, W 201703) and by the German Ministry of Education and Research (BMBF, ViWat: Engineering, 02WCL1474G) is gratefully acknowledged.