The Value of UV for Legionella Control

Transcription

1 + Effective Safe Reliable UV disinfection has been proven as an effective treatment for controlling Legionella. UV disinfection is a nonchemical treatment approach that eliminates the handling, storage and use of chemicals. UV disinfection is a costeffective treatment approach that provides continuous protection against the spread of Legionella. The Value of UV for Legionella Control Due to the potential for negative health effects from excessive growth of Legionella in cooling towers and water systems, operators are advised to develop and implement a biofilm prevention and Legionella control program. Goals of the program should include minimizing biofilm growth, biofouling and Legionella. Effective water treatment programs must control growth of other bacteria, algae, and protozoa that may contribute to the nutritional needs of Legionella. Biocides have traditionally been used to combat Legionella. However, studies have shown that amoebae may adapt to biocides and that L. pneumophila within protozoa may not be killed by the biocides. Moreover, chemical treatment requires the handling, safety, risk mitigation, storage and use of chemicals that also fall under strict environmental discharge limits. UV disinfection is a cost-effective and efficient method of reducing biofilm in cooling tower water and providing reliable protection against the spread of Legionella. UV disinfection is effective against all water-borne microorganisms, including those resistant to chlorine. However, all UV technologies are not created equal. UV systems using low pressure lamp technology can not achieve the same mortality rates as the Hydro- Optic UV system from Atlantium that uses a proprietary medium pressure lamp. Studies have shown the Hydro- Optic UV system to achieve 100% mortality of Entamoeba Histolytica at a dose of 8.8 mj/cm 2 while low pressure systems, even at a dose of 90 mj/cm 2, did not achieve 100% mortality. Entamoeba Histolytica was chosen as a model Legionella host organism, due to UV resistivity similarity to other amoebae.

2 Legionella in Cooling Towers Background Various studies have shown that 40-60% of all cooling towers harbor Legionella bacteria. Cooling towers are the largest and most common source of Legionnaire s disease outbreaks because of their risk for widespread circulation. Although 90% of Legionella infections in humans are caused by Legionella pneumophila, there are 45 named species of Legionella of which 19 species have been documented as human pathogens. A multinational study of community-acquired legionnaires disease identified 508 cultureconfirmed cases [Yu VL, Plouffe JF, Pastoris MC, et al., 2002]. L. pneumophila was responsible for the greatest percentage of cases (91.5%), followed by Legionella longbeachae (3.9%) and L. bozemanii (2.4%). The remainder of cases were due to L. micdadei, L. feeleii, L. dumoffii, Legionella wadsworthii, and L. anisa. Legionella in Cooling Towers Cooling towers, because of their mode of operation, can create ideal conditions for microbial growth and they also deliberately require the creation of sprays and aerosols, which can be dispersed over a wide area if not controlled properly. Cooling towers operate at temperatures that can provide an environment for the growth of microorganisms in water (20-45 C), including Legionella. Other operating conditions contributing to the growth of Legionella in cooling towers include: High microbial concentration, including algae, amoebae, slime and other bacteria. Presence of biofilm, scale, sediment, sludge, rust and other organic matter. Presence of degraded plumbing materials that may provide nutrients to enhance bacterial growth. Cooling towers must be properly disinfected and maintained to reduce the risk of Legionella. Controlling Legionella Historically biocides such as chlorine, chlorine dioxide, hypobromite, and ozone have been used for Legionella control in cooling towers. In the natural environment, Legionella lives in three forms: as a free swimming form, in a biofouling and as an amoebic parasite (lives within amoebae). Studies demonstrated that L. pneumophila can use free-living amoebae as host cells for intracellular replication [Skinner et. al., 1983; Newsome et. al., 1985; Fields, 1993]. Legionella and free-living amoebae may be present simultaneously in aquatic environments, hot systems and cooling towers, thus, freeliving amoebae may play a role in the amplification and protection of Legionella and could act as a vector in the transmission of Legionnaires disease [Declerck et. al., 2007]). Amoebae can represent a shield for Legionella against disinfection treatment (e. g. chemicals biocides). Previous data shows that amoebae have resistance to a variety of biocides (additional information in page 9) and therefore protect the Legionella. 2

3 Legionella in Cooling Towers Continued When disinfection by biocides is insufficiently applied, the survival of Legionella and amoebae can promote a rapid growth and therefore can be a source of Legionnaires' disease outbreak [Bargellini et. al., 2011; Thomas et. al., 2004]. The most common source of Legionnaires' disease outbreaks are cooling towers, primarily because of the risk for widespread circulation [Garcia-Fulgueiras et. al., 2003]. UV disinfection offers a nonchemical treatment approach that is effective at Legionella control. UV light has a strong germicidal effect that kills microorganisms by penetrating their cell membranes and damaging their DNA so they are unable to reproduce and die out. Compared with other Gramnegative bacteria, the legionellae are highly susceptible to UV irradiation [Antopol & Ellner, 1979]. Numerous other studies have been undertaken to showcase the efficacy of UV treatment for Legionella control- see the Literature Review section of this document for additional detail. Unlike traditional UV systems, the Hydro-Optic UV technology can track changes in water quality variance and effectively dose pace the UV per application specific conditions. Additionally since the Hydro-Optic UV technology works on the principals of fiber optics and hydraulics, the system has the unique ability to recycle UV throughout the chamber to provide complete germicidal control. UV Dose for Legionella Control There is a large body of published data related to the UV doseresponse of various organisms [Wilson et al., 1992,Gregory B Knudson 1985, Antopol et al 1979, Cervero- Arago S. et al 2014] including Legionella pneumophila for 1-, 2-, 3-, and 4-, log reduction at 9.4 mj/cm 2. In addition, a dose of 30 mj/cm 2 achieved percent (5- log) reduction in 20 minutes [Muraca et al., 1987]. See Table 1 for UV dose (mj/cm 2 ) to inactivate Legionella. Previous literature data shows that the required UV doses produced by LP for inactivation of amoebae are significantly higher than Legionella inactivation doses [Maya et. al., 2003; Cervero-Arago et. al., 2014; Chang et. al., 1985]. The following study was conducted to determine whether the required UV dose for inactivation of amoebae may be lower using the proprietary Atlantium MP (ATL-MP) lamp. Table 1: UV Dose (mj/cm 2 ) to Inactivate Legionella Species 1-log 2-log 3-log 4-log Reference Legionella bozemani Gregory B Knudson, 1985 Legionella dumoffii Gregory B Knudson, 1985 Legionella jordanis Gregory B Knudson, 1985 Legionella longbeachae Cervero- Arago S. et al 2014 Legionella micdadei Gregory B Knudson, 1985 Legionella oakridgensis Gregory B Knudson 1985 Legionella pneumophila Gregory B Knudson, 1985 Legionella pneumophila Antopol et at., 1979 Legionella pneumophila Wilson et al., 1992 Legionella pneumophila Cervero- Arago S. et al 2014 Legionella wadsworthii Gregory B Knudson

4 Determining UV Dose to Inactivate Amoebae Entamoeba histolytica Background Entamoeba histolytica is a protozoan parasite responsible for a disease called amoebiasis. 50 million people are infected worldwide, mostly in tropical countries in areas of poor sanitation. The highest prevalence of amebiasis is in developing countries where barriers between human feces and food and water supplies are inadequate. E. histolytica is transmitted via ingestion of the cystic form of the protozoa. Inside humans E. histolytica lives and multiplies as a trophozoite. In the current study E. histolytica was served as a Legionella host model. Atlantium Technologies studied the effects of UV light produced by Low-Pressure (LP) lamps and the proprietary Atlantium Medium-Pressure (ATL- MP) lamps on the viability of E. histolytica. Thesis There are several studies demonstrating that certain microorganisms such as Adeno virus, are more susceptible to broad spectrum UV light produced by MP lamps, compared to monochromatic UV light produced by LP lamps. The thesis behind this proposal is to evaluate whether E. histolytica may need a lower UV dose using the proprietary ATL-MP lamp. Figure 1: Cultured E. histolytica trophozoite*. *( oeba%20histolytica) Objective Evaluate the reduction equivalent UV doses (RED) required for inactivation of E. histolytica by using a standard bio-dosimetry procedure in a static monochromatic and polychromatic UV set up. Experimental Design The E. histolytica UV dose-response was measured using a standard LP and the ATL-MP collimated beam apparatus devices. UV dose calculation for LP CBA was performed according to the USEPA recommendations [USEPA, 2006]. While the UV dose delivered (UV fluence) by the MP CBA was calculated according to A. Lakretz et al 2010 [Lakretz et.al., 2010] with slight modifications. Exponentially grown trophozoites (7x10 5 ) were washed two times with PBS. One-half of the population was kept in PBS without being exposed to UV and the second half was exposed to UV at various intensities and time settings. The viability of the trophozoites exposed or not to UV was first determined by exclusion of the vital stain Eosin (0.2%). The exposed and non-exposed trophozoites were then transferred to TYI-S-33 medium and they were cultivated for 24 h at 37 o C. After this period of culture, the cells were counted and the number of trophozoites in the non-uvexposed inoculum was used as 100%. 4

5 Results and Conclusions The experimental results were graphically processed as UV doses vs. Vitality percentage (Table 2; Figures 2-3). Immediate counting: only 22% viability was observed after illumination with LP lamp at UV dose of 90 mj/cm 2, while 100% mortality was observed after illumination with ATL-MP lamp at 26.3 mj/cm 2. After 24 h of culture: no total kill (2% viability) was observed after illumination with LP lamp at UV dose of 90 mj/cm 2, while 100% mortality was observed after illumination with ATL-MP lamp at 8.8 mj/cm 2. The ATL-MP lamp is more effective in inactivation of E. histolytica compared to the LP lamp. The enclosed LP results are in agreement with previous results of resistivity of amoebae to LP lamp [Maya et. al., 2003; Cervero-Arago et. al., 2014]. *Acknowledgment: this study was conducted in collaboration with Prof. Ankri Serge; Technion Israel institute of technology; Faculty of Medicine. Hydro-Optic UV 1. Lamps: proprietary MP high intensity lamp that provides 2X more UV energy than other MP lamps and 16X more than LP lamps. 2. Internal Reflection: patented internal reflection technology that has the ability to effectively recycle any required UV dose through the system. 3. Dose Pace: proprietary software logic, sensors and controls to enable automatic dose adjustment that enables lower energy consumption and costs. Table 2: % Vitality as Function of UV Dose UV dose (mj/cm 2 ) % Viability Immediately After Illumination - Control LP Lamp ATL-MP Lamp % Viability After 24 Hours of Culture Following Initial Illumination Note- results are only relevant to the proprietary Atlantium MP lamp; performance for other MP based solutions cannot be assumed. 5

6 Figure 2: Immediate Counting % Vitality as a Function of UV Dose (Purple- LP Lamp; Blue- ATL-MP Lamp) Effect of UV Exposure on Entamoeba Histolytica Viability (immediate counting - eosin staining) % Viability LP MP UV dose (mj/cm 2 ) 100% mortality (0% viability) achieved with the ATL-MP lamp at UV dose of 26.3 mj/cm 2. Maximum of 22% viability achieved with the LP lamp at UV dose of 90 mj/cm 2 Figure 3: After 24-hour Culture % Vitality as a Function of UV Dose (Red- control; Purple- LP Lamp; Blue- ATL-MP Lamp) Effect of UV Exposure on Entamoeba histolytica's Viability (After 24 Hour Culture in TYI) % Viability control UV Dose (mj/cm 2 ) Even a dose of 90 mj/cm 2 the LP Lamp did not achieve 100% mortality while the ATL-MP Lamp achieved it at 8.8 mj/cm 2. 6

7 1 2 UV Treatment for Effective Legionella Control September 2016 Hydro-Optic UV Treatment Solution Quartz Chamber Medium Pressure Lamp Real-time Monitoring Patented Technology based on Fiber Optics and Hydraulics. Air Block The Hydro-Optic UV system automatically adjusts UV dose to meet real-time water quality conditions. Real-time data status, including the actual UV dose being delivered, are displayed on the control screen. UV dose and validation parameters are consistently tracked. Hydro-Optic UV A Proven Track Record Drinking water utilities and industrial facilities across the aquaculture, bio-pharma, food and beverage, and power markets have benefited by using the HydroOptic UV treatment system to meet disinfection requirements. The Hydro-Optic UV system has undergone full-scale third-party validation and is the only commercially available system to achieve a 4-log virus credit using a live adenovirus challenge. The Hydro-Optic UV treatment systems are designed to minimize biofilm growth, biofouling and Legionella. + Real-time Monitoring Real-time Control Validated System Proven Effective 7

8 Literature Review A number of studies have been undertaken to showcase the efficacy of UV disinfection for Legionella control. While the below studies are not specific to the power industry, they are representative of published work confirming the viable role of UV disinfection to control and treat for Legionella. Legionella can be an issue with amoebae that also have resistance to biocides (chemicals). There is a role for UV disinfection to control and treat for Legionella; however, all UV treat systems are not equal. Amoebae can be resistive to UV doses produced from LP lamp system. The Atlantium Hydro-Optic UV system, using a proprietary MP lamp, can treat amoebae and Legionella with a low energy. COMPARATIVE ASSESSMENT OF CHLORINE, HEAT, OZONE, AND UV LIGHT FOR KILLING LEGIONELLA PNEUMOPHILA WITHIN A MODEL PLUMBING SYSTEM PAUL MURACA, JANET E. STOUT, & VICTOR L. YU, APPLIED AND ENVIRONMENTAL MICROBIOLOGY, (1987) - Study showed UV light to inactivate L. pneumophila rapidly and with minimal required maintenance. - Study showed UV light produced a 5-log inactivation of L. pneumophila in less than 1 hour. EFFICACY OF ULTRAVIOLET LIGHT IN PREVENTING LEGIONELLA COLONIZATION OF A HOSPITAL WATER DISTRIBUTION SYSTEM ZEMING LIU, JANET E. STOUT, LAWRENCE TEDESCO, MARCIE BOLDIN, CHARLES HWANG & VICTOR L. YU, Wat. Res (1995) - Study showed UV treatment installed near point-of-use can prevent Legionella recolonization for at least 4 months. PHOTOREACTIVATION OF UV-IRRADIATED LEGIONELLA PNEUMOPHILA AND OTHER LEGIONELLA SPECIES GREGORY B. KNUDSON, APPLIED AND ENVIRONMENTAL MICROBIOLOGY (1985) - Study showed seven Legionella species are very sensitive to low doses of UV. SUSCEPTIBILITY OF LEGIONELLA PNEUMOPHILA TO ULTRAVIOLET RADIATION STEPHEN C. ANTOPOL & PAUL D. ELLNER (1979) - Study showed Legionella pneumophila were found to be sensitive to low doses of UV. STIMULATORY EFFECT OF COOLING TOWER BIOCIDES ON AMOEBAE SUJATA SRIKANTH & SHARON G. BERK, APPLIED AND ENVIRONMENTAL MICROBIOLOGY (1993) - Results from this study suggest cooling tower amoebae may adapt to biocides. - Biocides used to control microbial growth may actually enhance populations of host organisms for pathogenic bacteria. - The cooling towers amoebae not only were not affected by concentrations of biocides that inhibited non cooling towers amoebae but also reproduced faster in the presence of low concentrations of biocides - Cooling tower amoebae survived the manufacturer's recommended doses of the biocides. ADAPTION OF AMOEBA TO COOLING TOWER BIOCIDES SUJATA SRIKANTH & GREENWOOD GENETIC, MICROB ECOL (1994) Results from this study show amoebae can adapt to biocides in a short time. Cross-resistance was also observed; exposure to one biocide caused resistance to other biocides. SURVIVAL OF PROTOZOA IN COOLING TOWER BIOCIDES EE SUTHERLAND & SG BERK, JOURNAL OF INDUSTRIAL MICROBIOLOGY (1996) - Results from this study show that cooling towers amoebae may survive the recommended concentration of certain biocides, and this information may be important in devising procedures for eradicating hosts for legionellae. - It appears that L. pneumophila within protozoa may not be killed by the biocides. Atlantium Technologies, Ltd. 11 HaMelacha Street l Har Tuv Industrial Park l Israel T: l E: info@atlantium.com l