The Silver Lining
The application of silver zeolites with carbon to achieve bacteriostatic effects in filtration products continues. Here Jeff Trigolo, chief technology officer with Sciessent, discusses with WQP Associate Editor Elizabeth Lisican their effectiveness, as well as the significance of certification for bacteriostatic claims.
Elizabeth Lisican: What are some of the latest trends you have been seeing in antimicrobial treatment technology?
Jeff Trigolo: [I] continue to see growth in the application of silver zeolites with carbon, both block- and granular-activated carbon, to achieve bacteriostatic effects in filtration products. NSF bacteriostatic claims appear to be in demand outside of the food and beverage segment. Globally, there are jurisdictions seeking to achieve a higher standard of 100 CFU HPC/mL, which cannot be achieved with the silver nitrate-treated granular-activated carbon. Microbial growth in carbon-only filtration systems is a recognized problem. Coupling silver zeolites with carbon (actually bonding the two together) has achieved the longevity and efficacy that has not been achieved by simple impregnation and allows the NSF bacteriostatic claim.
There is increased application and interest in treatment of a wide variety of materials that come into contact with water, are havens for bacterial growth and cannot be cleaned by traditional means—the materials are inaccessible. Ahlstrom, for example, has integrated silver zeolites into nonwoven media and Colorite has integrated it into the inner lining of its line of drinking water hoses.
Lisican: Explain what makes an antimicrobial technology effective; what factors are at work?
Trigolo: To achieve the high performance demanded by end-users, antimicrobial technologies must be proven for efficacy and longevity. Environments that come into contact with water are typically considered harsh environments for materials. Silver continues to be the antimicrobial of choice, for reasons that include the following:
- Naturally occurring. This is important because silver is used for chemically sensitive applications;
- Broad spectrum. Silver is proven effective against the widest range of microbes. It is important forcustomers to consider that many of the traditional approaches do not fight some of the microbes most often associated with waterborne bacteria;
- Powerful. Silver is the most effective at the lowest loading levels;
- Tri-modal. Silver controls microbes in three ways: starve, sterilize and suffocate. The result is no shown resistance developed over thethousands of years silver has been used; and
- Long-lasting. The silver ions are encased in a structure that releases in a slow, controlled process, allowing achievement of the longevity required in water-related applications.
Lisican: How important is certification for bacteriostatic claims?
Trigolo: Bacteriostatic claims are critical for the food and beverage industry and are becoming increasingly important for household applications. NSF’s process is relatively straightforward, as the Agion antimicrobial has broad EPA [U.S. Environmental Protection Agency] and FDA [Food and Drug Administration] clearances. The robust data and extensive testing required for EPA and FDA approvals can directly support some of the requirements for NSF approvals. An interesting facet is that a number of technologies make bacteriostatic claims but are not able to achieve the NSF certification because the performance is not consistent throughout the filter life.
Omnipure has recently achieved registration from the California Department of Pesticide Registration for its Aquabond filtration line featuring Agion branded antimicrobial technology; such registration demonstrates the strength of the underlying data.
Lisican: What future trends do you see developing in antimicrobial treatment, and how will they impact the industry from a business, regulatory and water quality perspective?
Trigolo: Industry demand for innovation will continue to drive companies to apply technologies that have proven functional benefits, overcome the limitations of existing solutions, and allow competitive differentiation in a crowded, mature market. For example, in the traditional activated carbon filtration market, new technologies like silver zeolites are delivering increased performance and higher quality for end customers regarding key filter performance criteria, such as ensuring that the level of silver in the drinking water is well within regulatory limits. On the regulatory front, customers continue to demand global registrations, including clearance by the European Food Safety Authority and under the EU Biocidal Products Directive.
Finally, global clean drinking water initiatives are driving companies to seek out new technologies that are easily integrated and solve real world problems. For example, India has embraced silver as a method of controlling bacterial growth.