1
CONTROL OF
LEGIONELLA GROWTH IN DISTRIBUTION SYSTEMS.
E. Dahlen, Chem Risk, Inc., San Francisco, CA; M. Shum, Exponent Failure Analysis Associates, Menlo Park, CA.
Legionnaires’ disease is possibly the most common airborne bacterial infection associated with contamination in building systems. Generally, Legionella bacteria are associated with larger multicellular organisms (i.e., amoeba) and biofilm, which are better protected from harmful effects of disinfectants as compared to planktonic bacteria. Once Legionella becomes established in a building plumbing system, there are a variety of methods that have been used to disinfect the distribution system. We have conducted a comparison of the efficacy of different disinfection methods. Some of the most common methods of disinfection such as thermal flushing and superchlorination are effective at treating planktonic and sessile bacteria and the surfaces of biofilm, but are usually not very effective in removing biofilm. Both UV irradiation and ozonation do not penetrate biofilm or exhibit a residual effect. Copper-silver ionization is effective and has a long-term residual effect, but is not used to treat the cold water supply, which may need treatment. Chlorine dioxide has several advantages in that it is effective against bacterial cells and spores and in attacking biofilms of Legionella. One disadvantage of using chlorine dioxide is the production of disinfection by-products, such as chlorite and chlorate, but an advantage is it does not react with naturally-occurring organic matter or with ammonia and most nitrogen-containing compounds to produce trihalomethanes. This paper also addresses the use of chloramination of drinking water and its impact on the control and mitigation of biofilm growth; the organic structure that sustains Legionella in plumbing systems. Distribution systems have been implicated as a source of Legionella organisms that have caused legionellosis in several instances. This paper addresses the mechanism of contamination and treatment alternatives.
2
DISCOVERY OF
LEGIONELLA IN POTABLE WATER DISTRIBUTION SYSTEM:
FOLLOW-UP INVESTIGATION AND REMEDIATION.
M. Gillie, GeoTrans Inc., King of Prussia, PA.
The potable water distribution system of an 18-story commercial building was investigated to identify the extent of Legionella bacterial contamination following the initial discovery of Legionella in a drinking water fountain. Several emergency measures were implemented to prevent inadvertent employee contact with the potentially widespread microbial contamination in the potable water system, including draining and shutting down of the drinking water fountain supply, prohibiting access to restrooms, employee notification of preliminary findings, protective measures, and planned response actions. The building owner’s environmental consultant conducted an initial reconnaissance of the potable water distribution system, reviewed available building plans and preliminary water sampling data, and interviewed facility maintenance staff. Potential sources of Legionella bacteria included an unused emergency water tank, emergency water main, hot water tank, chilled water system, and unused water piping on unoccupied floors. On-site analysis for free and total chlorine was conducted to identify where the free chlorine disinfectant was present in the potable water system. Bulk water sampling and swab samples from fittings were collected for Legionella culture analysis. Duplicate samples from select floors were submitted for analysis by Polymerase Chain Reaction. Laboratory findings showed that Legionella was present in the water system at alarming concentrations and no free chlorine disinfectant was identified in the system above the ground floor. Subsequent free chlorine and chlorine demand analyses were conducted to identify the source and cause of the Legionella contamination and identify parameters for remediation. Water usage patterns and building occupancy were also evaluated. Investigation findings showed that low building occupancy, unused plumbing, low water usage, and insufficient free chlorine for potable water disinfection at user locations were contributing factors for Legionella growth in the potable water distribution system. Remedial actions included installation of computer-controlled flush valves, removal/disconnection of unused piping, and disinfection with chlorine dioxide.
3
MANAGING RISK
OF WATERBORNE PATHOGENS IN BUILDING WATER SYSTEMS.
M. Freije, HC Information Resources Inc., Fallbrook, CA.
Recently published papers have outlined evidence that the source of contamination responsible for outbreaks of disease is often pathogens proliferating water systems. For example, mycobacteria can persist in domestic water systems for several years, and have been implicated in serious outbreaks among hospital patients. Hospital-acquired pneumonias caused by waterborne Pseudomonas aeruginosa result in an estimated 1400 deaths each year in the United States. Waterborne fungi, including Aspergillus which had previously been considered only an airborne threat, have also caused infections. And Legionella bacteria continue to cause thousands of Legionnaires’ disease cases each year, resulting not only in illness and death, but also in expensive lawsuits, emotional stress, wasted time, and damaging press. In this session the speaker will outline facts that need to be considered in developing a risk reduction strategy for waterborne pathogens that is responsible and reasonable. Researchers have identified numerous waterborne pathogens, and more are being identified each year. The speaker will discuss potential sources of contamination, suggest the pathogens that should be addressed in various types of buildings based on published research to date, and outline key strategies for reducing health and legal risks.
4
CONTROL OF
EMISSIONS FROM A SEWAGE SLUDGE PELLETIZING FACILITY LOCATED IN AN URBAN
ENVIRONMENT.
P. Morey, Air Quality Sciences Inc., Atlanta, GA.
A study was carried out on potential emissions of bioaerosols and volatile organic compounds (VOCs) into ambient (outdoor) air around a facility where sewage sludge is dried and converted into fertilizer pellets. Volatile emissions from the tipping through the pelletizing work areas are removed from workplace air by collection and transport to a regenerative thermal oxidizer (incinerator) and discharge through an exhaust stack. Air scrubbers are used to remove particulate contaminants generated during pelletizing operations. Total VOC levels varied from about 0.5 to 3.5 mg/m3 with cyclohexane and aliphatic hydrocarbon derivatives being predominant individual VOCs. Low concentrations (less than 10 µg/m3) of sulfhydro compounds were present in various workplace areas. Outdoor VOC levels were approximately two orders of magnitude less then indoor levels (sulfhydro compounds not detected). Concentrations of fungi and bacteria both upwind and downwind of the facility were similar and low. The types (genus, species) of microorganisms found in upwind and downwind locations were typical of those normally found in outdoor air. Airborne endotoxin levels were about 1.0 endotoxin units/m3 or less in locations both upwind and downwind from the palletizing facility. Ergosterol was not detected in stack emissions from the incinerator. This study showed that the sewage processing (pelletizing) facility did not contribute to the bioaerosol and VOC burden in outdoor air in nearby neighborhoods.
5
THE USE OF UV
IN LIEU OF CHEMICAL FUMIGANTS FOR DISINFECTING HEPA FILTERS.
J. Kwan, S. Yu, P. Yue, Hong Kong University of Science and Technology, Kowloon, Hong Kong Special Administrative Region of China.
For decades, HEPA filters have been used for removal of biohazardous agents in various clinical, industrial, and laboratory settings. Its effectiveness in trapping submicron size particles and microorganisms are well proven. However, before maintenance or replacement of these filters can be performed, disinfection is a standard requirement. Currently, accepted procedures involve fumigation with formaldehyde. Since formaldehyde has recently been classified as a human carcinogen, fumigation with such toxic material generates concerns.
Various alternative disinfection procedures have been studied in recent years. These include using alternative fumigants of lower toxicity, such as vaporized hydrogen peroxide, and the employment of ultraviolet radiation for disinfection.
This paper reports an effort to couple ultraviolet disinfection with HEPA filters. This combination offers the potential advantages of continuous disinfection of microorganisms trapped on the HEPA filter surface, and reduction or elimination of the need for chemical fumigation. The study covered critical issues such as physical coupling of the filter and irradiating source, penetration of UV light, design parameters, effectiveness of disinfection, and material compatibility. Findings of this study reveal the potentials, as well as challenges, of UV coupled with HEPA filtration as an alternative to the traditional biohazard control practice.
6
RAPID ON-SITE
DETECTION OF ASPERGILLUS USING AN ELECTROCHEMICAL-BASED MICROARRAY
DETECTOR.
M. Mathews, L. Williams, M. Frasier, P. Williams, AnzenBio, Salt Lake City, UT.
In the United States, the Centers for Disease Control estimate that tens of thousands of individuals suffer from asthma induced by exposure to indoor bioaerosols. The industrial hygiene community has an existing requirement for the ability to rapidly and accurately assess schools, office complexes, hospitals, and homes for the presence of clinically relevant mold antigens.
Current testing for Aspergillus from industrial hygiene samples typically involves culturing of the samples followed by microscopic identification. We have developed a modified electrochemical ELISA assay which uses antibodies raised against the exoantigens that are produced by the Aspergillus. The testing protocol involves binding the sample to a prepared electrode surface, washing, adding a secondary antibody, again washing away unbound material, and adding substrate immediately followed by detection using an electrochemical detector. This assay has several advantages over growth and identification: (1) it is much faster, giving a readout within two hours rather than the days required to grow the organism; (2) it is more specific, by using antibodies misidentification errors are eliminated; (3) the reagents and detector are small and portable allowing on-site testing rather than sending samples to off-site laboratories; and (4) we are detecting for the exoantigens produced by the organism rather than the organism itself, which is the actual agent in bioaerosols.
We have developed a field deployable, rapid, and easy to use platform for the detection of Aspergillus exoantigen from air and dust samples. This platform is based on the use of an ELISA assay coupled to an electrochemical microarray. The technologies of microfabrication, bionanotechnology, and antigen-antibody interactions all contribute to the design of a miniaturized, specific, and sensitive detection system. This new capability allows for accurate and immediate answers during an Aspergillus inspection.
Posted May 30, 2005