The Issue for the Drinking Water Industry
One of the most important issues for drinking water is ensuring public health protection against bacteria, viruses, and protozoan parasites. Particularly in finished drinking water, it is difficult to ensure the absence of these pathogens because of limitations with standard methods, particularly high detection limits and/or reliance on infrequent grab samples. Therefore, the existing regulatory framework allows drinking water utilities to focus on treatment process performance and monitor for indicator microorganisms, such as E. coli. Although E. coli are not necessarily pathogenic, their presence indicates that other pathogens might be present in the water, thereby representing a potentially higher risk to public health.
Drinking water utilities like SNWA routinely monitor for total coliform bacteria and E. coli to verify treatment process efficacy and ensure there are no spikes in bacteria that might indicate some other type of pathogen contamination. With standard methods, the time from sample collection to result ranges from 18 to 24 hours, which means that water might be delivered to consumers before a potential problem is detected. In the drinking water industry, the ability to speed up this process can help utilities identify and respond to potential contamination events more rapidly, thereby improving public health protection.
SNWA looked to microLAN, an on-line sensor technology company from the Netherlands, to address this need. The company’s BACTcontrol technology has the potential to detect total coliform bacteria, E. coli, or total bacterial activity within hours, instead of the 18+ hours required for standard methods.
One of the most promising aspects of the BACTcontrol technology is that it relies on proven methods for bacterial detection that have been automated and equipped with sensitive detection capabilities to shorten analysis time. Traditional methods involve a similar approach but rely on the naked eye to detect changes, while the BACTcontrol employs a sensitive fluorescence detector. Because of this, small changes in color or fluorescence caused by bacterial activity can be detected with minutes to hours instead of nearly 24 hours.
microLAN currently has installations in Europe monitoring source water quality and treated drinking water. Although the existing applications are limited to Europe, similar drivers for the technology exist in the US, thereby indicating potential for broader deployment in the future.
Results of the Pilot
As part of the WaterStart funding, microLAN and SNWA collaborated with UNLV to conduct side-by-side bench-scale experiments with an independent spectrofluorometer, a BACTcontrol sensor, and the standard Colilert assay from IDEXX Laboratories, Inc. The team succeeded in developing a comprehensive understanding of the underlying detection mechanisms and in identifying several concerns related to the existing sensor technology. Most importantly, the sensor was unable to reliably detect total coliform bacteria and E. coli at low concentrations (i.e., excessive false negatives) and sometimes indicated ?hits? in the absence of the target bacteria (i.e., excessive false positives).
In drinking water applications, utilities are often dealing with “non-detect” situations so false positives are highly problematic from a compliance and operational perspective. Similarly, false negatives can have significant implications for public health. According to Daniel Gerrity, Associate Professor at UNLV and now Principal Laboratory Research Scientist at SNWA, “It was primarily a detection limit issue. The BACTcontrol sensor shows promise at higher concentrations, but the current technology is unable to provide reliable results at the levels typically observed in finished drinking water applications.”
Dr. Gerrity indicated that the BACTcontrol is currently a better fit for applications with higher levels of contamination. This might include monitoring recreational water quality, identifying bacterial spikes in agricultural irrigation applications, or possibly monitoring bacteriological water quality in impaired drinking water sources. The technology could be useful for establishing baseline bacteriological water quality and then identifying major spikes, although there would still be potential for false positive results.
“In principle, the microLAN technology has considerable promise because its underlying mechanisms are based off of traditional methods that are currently used to monitor for E. coli,” said Gerrity. “However, the technology still requires further refinement before it is ready for full-scale implementation in a finished drinking water setting.”
Further Development and Potential
Although the existing configuration of the BACTcontrol sensor may not be suitable for finished drinking water, recent events in other industries might justify adoption and/or testing in other applications. For example, there have been a number of recent disease outbreaks related to romaine lettuce and spinach. Although the exact source of those outbreaks has not been confirmed, expanded monitoring of bacteriological water quality might be warranted to increase public health protection and reduce risks associated with agricultural irrigation waters. Considering that irrigation waters are not always treated, the BACTcontrol technology might offer an alternative, early warning system for farmers.
microLAN, based in Waalwijk, the Netherlands, is a company specialized in early warning systems for water quality monitoring. microLAN has developed a range of fully automated online monitoring technologies for drinking, surface, and process water. The company’s existing products include the ALGcontrol, BACTcontrol, and TOXcontrol for monitoring algae, bacteria, and chemical toxicity, respectively.
microLAN’s online technologies rely on proven absorbance, fluorescence, and luminescence-based methods for detecting algae, bacteria, and toxicity. For bacteriological testing, the BACTcontrol relies on enzymatic activity that triggers a fluorescence response. The sensor’s reagents are target-specific so that changes in fluorescence are indicative of the presence of total coliform or E. coli, for example.