Continuous Microbial Monitoring: on site, real time & fully automated In Part One of this two-part series, we see how onCyt ensures high water quality by tackling rising challenges through modern engineering.
INSIGHT | 23 P roviding safe drinking water with consistently high quality is one of the top challenges today – worldwide and especially in emerging regions. <strong>Water</strong> utilities face rapidly rising water demands, increasing environmental pollution, and more and more extreme climatic conditions affecting water resources. In order to overcome these challenges, suitable infrastructure for water treatment, storage, and distribution needs to be engineered. Modern engineering covering the whole infrastructure lifecycle – design, construction, operation, and maintenance – requires adequate information to ensure desired performance. This is why sensors for online measurements of chemical and physical water quality parameters in real time have become an absolute standard throughout the water industry. MICROBIAL WATER QUALITY: INADEQUATE MONITORING APPROACHES In sharp contrast, microbial water quality is still tested very infrequently with manual grab samples and laborious, inaccurate, and extremely slow detection methods such as heterotrophic plate counts. These traditional methods have served the water industry for over a hundred years and greatly contributed to solving major hygienic issues. However, they are completely useless for modern approaches of ensuring water quality through risk management based on process monitoring and control (WHO, 2003a; WHO, 2003b; van Nevel et al. 2017). While indicator organism testing (e.g., E. coli, Enterococcus) remains an official requirement, risk-based concepts such as “Hazard Analysis and Critical Control Points” or “No Abnormal Change” are rapidly being implemented and also required in regulatory frameworks such as WHO <strong>Water</strong> Safety Plans and European <strong>Water</strong> Directives. These approaches follow established product quality standards and management strategies used across various industries and documented in norms such as ISO-9001. This strongly reflects the above-mentioned paradigm shift that high water quality – hygienically but also in terms of taste, smell, discolouration, etc. – can only result from well-managed resources and infrastructure. However, these requirements are impossible to fulfil with current standard methods for microbial monitoring. FLOW CYTOMETRY: A MODERN STANDARD FOR MICROBIAL WATER QUALITY TESTING An important answer to this problem is the new, standardised microbial detection method of flow cytometry. This is a rapid, laser-based, direct detection method for single cells originally only used in medicine since the 1970s. Thanks to optimisation and standardisation work by the Swiss Federal Institute of Aquatic Science and Technology (Eawag), the technology became applicable for bacteria in water (Hammes and Egli 2005; Berney et al. 2008; Hammes et al. 2008). The major advantages of flow cytometric detection of cells include: (1) rapidness (< 15 min time-to -result), (2) reproducibility (< 10 standard deviations), (3) reliability and relevance (all cells detected), (4) robustness (linear range from clean groundwater to treated wastewater), (5) versatility (total and viable cells differentiated), (6) cost-effectiveness (break even with HPC samples for more than 15 samples per day), and (7) ease of use (bench-top instruments and standardised protocols for sample preparation, instrument settings, and data analysis/interpretation). This has also been recognised in the water industry and flow cytometry is applied routinely by many major water utilities in Europe (e.g., Switzerland, UK, Netherlands, Germany, Austria, Sweden) and spreading to <strong>Asia</strong> and North America. This also leads to an increasing industry push to finally replace expensive and outdated methods such as HPC in regulations. ONLINE FLOW CYTOMETRY: FROM MANUAL WORK TO A SENSOR APPROACH With a rapid and meaningful detection method available, the remaining bottleneck became sampling at high frequency. Hence, the same Eawag research group developed an automation device, which carries out all manual steps on site but in accordance to the standardised laboratory method: in situ sample acquisition, sample preparation (i.e., staining, dilution, pH adjustment, temperature-controlled incubation), transfer to flow cytometer, triggering of measurement, cleaning (to avoid cross contamination and biofilm formation), and data analysis (Hammes et al. 2012; Besmer et al. 2014). This whole cycle is carried out 24/7 every 15 minutes and results in highly resolved time series of concentrations for both total and viable bacteria in real time. Samples can be drawn from multiple parallel water streams (e.g., before and after a treatment, parallel treatment trains). onCyt Microbiology is the official Eawag spin-off company founded in 2017 by former group members to make this invention and the industry-leading know-how commercially available to users worldwide. The goals are to leave out manual sampling, minimise timeto-result, reduce costs and uncertainty, and produce highly resolved and truly meaningful microbial monitoring data for effective and efficient process control. In short, moving from infrequent, labour-intensive snapshots to an integrated, state-of-the-art sensor approach. Three application examples from source to tap will be presented in Part Two of “Continuous Microbial Monitoring: on site, real time & fully automated”, which will be published in the November/December issue of <strong>Water</strong> & <strong>Wastewater</strong> <strong>Asia</strong>. WWA <strong>Water</strong> & <strong>Wastewater</strong> <strong>Asia</strong> • <strong>September</strong> / <strong>October</strong> <strong>2019</strong>