Control Of Pseudomonas Aeruginosa And Bromate Through Medium-Pressure Ultraviolet Systems
Friday, November 23rd, 2018 | 501 Views
Manufacturers are turning to environment-friendly and physical water treatment methods to answer the call for less chemical addition in the final packaged water products through improved control of manufacturing process, says George Wang, AP director, Hanovia.
At present, the water packaging industry is facing a series of challenges, including health consciousness, a preference for natural grade products from consumers, and a tightening of standards and stricter enforcement by various agencies. With the exposé of bromate and other disinfection by-products by ozone disinfection in recent years, identifying ‘what’s next’ has become an important element in most water packaging manufacturers’ risk management and control.
Evidently, more and more manufacturers are turning to environment-friendly and physical water treatment methods to answer the call for less chemical addition in the final packaged water products through improved control of manufacturing process. One such trend is the use of medium-pressure ultraviolet, a type of disinfection system through physical process, which could reduce, and in some cases completely eliminate the use of ozone.
Over the years, the regulation on ultraviolet sterilisation has become more comprehensive. The US Grade-A Pasteurised Milk Ordinance clearly stipulates that ultraviolet disinfection is an accepted process to produce pasteurised equivalent water, with the premise of meeting certain technical standards. The specific requirements are as follows:
1) Monochrome ultraviolet irradiation of 253.7nm wavelength shall be 186mJ/cm2 and above 2) Dose of ultraviolet radiation from multi-spectral medium-pressure lamp shall be 120mJ/cm2 and above.
UV Can Effectively Address Issues On Pseudomonas Aeruginosa And Bromate
Ozone is widely used in many disinfection applications due to its strong oxidation power and good dispersion capability. Because it generates disinfection by-products and causes pollution in the filling room, its usage is restricted.
Bromide ions in water will react with ozone to form bromate:
Br- + O3 → BrO3-
Bromate is classified as class 2B carcinogen or possibly carcinogenic by the International Agency for Research on Cancer (IARC). In China, Drinking Natural Mineral Water Standard GB8537-2008 imposes strict limits on the content, which is not to exceed 10 ppb under any circumstances, and this is the same as WHO regulations. The amount of bromate formed is directly impacted by the concentration of ozone, contact time, pH, and concentration of bromide ions in water. The formation of bromate is directly proportional to the ozone concentration, contact time and bromide ion concentration, and is inversely proportional to the pH value in a certain pH range.
However, since the sterilisation effect of ozone is also proportional to the ozone concentration (C) and contact time (T), WTO stipulates that ozone treatment CT value should not be less than 1.6, therefore, the bromate and microbial control has become a difficult contradiction for beverage manufacturers to solve. Shifting to chemical-free disinfection has become the only option.
To control the microbial activities in the natural mineral water treatment process, Hanovia offers process and terminal control solutions aiming to reduce the concentration of ozone applied in the process, effectively controlling the formation of bromate as well.
For bottled water packaging processes, Hanovia offers similar solutions to prevent microbial contamination of RO systems, reduce cleaning frequencies, extend membrane lifespans, and control microorganism counts at various process points at satisfactory levels.
Control of Pseudomonas Aeruginosa Through A Medium-Pressure Ultraviolet System
Pseudomonas Aeruginosa (P. Aeruginosa) is a gram-negative bacillus found widely in nature, soil and water. The WHO HACCP assessment stipulates that P. Aeruginosa is a hazard indicator for bottled products for infants, which can cause diarrhoea in infants when infected. It can even cause secondary to chronic inflammation, infection or mixed infection leading to severe pneumonia, meningitis, sepsis, etc. On the other hand, growth of P. Aeruginosa will also increase the nitrite content in water.
The Chinese national standard GB19298-2014 and GB8537-2008 for drinking water stipulates that P. Aeruginosa should not be detected in every 250 ml of product samples. Because of its wide distribution in nature, P. Aeruginosa has posed many challenges to bottlers and packaging water producers. Cases of non-compliance are frequently reported. In generally, the presence of P. Aeruginosa in products that have just been manufactured is hardly detectable during final product sampling and testing. However, since most bottled products have rather long production-to-consumption cycle time, P. Aeruginosa could derive its nutrition from low organic environment and thrive. In fact, it was found the reproduction rate of P. Aeruginosa under such circumstances can reach 104 CFU/ml in a span of ten days or so. Complete removal of P. Aeruginosa is the only way to ensure the highest quality of finished products delivered, and it should be the sole measurable for evaluating the effectiveness of a disinfection system.
Based on current experience of the industry, the following are keys essential to microbial control:
1) Water source protection: Most manufacturers drawing groundwater as a source for water packaging production are known to have good knowledge in water source protection. Groundwater itself is anoxic in nature and not conducive for microbial growth. In most cases, secondary pollution in the water intake process contributes to microbial growth.
2) When surface water is used as the water source, it is important to continuously monitor and control microbial activities at source and critical points to minimise fouling at media filter and activated carbon filter.
3) Environmental control of the water production floor: the floor level should be kept dry at all times; ensure the water treatment system is properly concealed.
4) Pipeline CIP (Cleaning-in-place) and SIP (Sterilisation-in-place): Water tanks, media filter tanks and activated carbon tanks are usually equipped with bleeding valve, which is prone to become the channel for microbial intrusion. In-situ sterilisation using hot water, steam or ozone should be performed on an intermittent basis.
5) High-dose ultraviolet disinfection is used to continuously control microbial activities. To effectively control microbial load at various control points, different ultraviolet doses and technologies are often being used.
Selection Principle Of Ultraviolet Technologies
Ultraviolet light is a type of electromagnetic wave sandwiched between X-rays and visible light in the electromagnetic wave spectrum and has a wavelength in the range of 5 nm and 400 nm.
Ultraviolet radiation dose is akin to ozone concentration times contact time where disinfection is concerned, which is the only parameter that determines the sterilisation effect. The technology further divides into low-pressure ultraviolet and medium-pressure ultraviolet systems.
Low-pressure ultraviolet systems emit a single germicidal wavelength at 253.7 nm, which can only deactivate microorganisms through disruption of DNA base pairing, and inactivated microorganisms will again cause problems once they are photo-reactivated and dark repair themselves.
Medium-pressure ultraviolet systems emit multi-spectral lines, with germicidal wavelengths ranging from 240 nm to 280 nm. The wider germicidal range of wavelengths and higher ultraviolet intensity demonstrate better disinfection results when destroying DNA structure, enzymes and proteins in the microorganisms, causing irreversible damage and preventing reactivation of the microorganisms. In addition, medium-pressure ultraviolet systems are less affected by operating conditions and offer better monitoring accuracies over multi-lamp low pressure ultraviolet systems.
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