Press
release
Chlorine dioxide as a disinfectant
An effective and reliable solution
Dipl.- Ing. Sven Müller
Disinfection is a particularly important subject area. It's important on the one hand that disinfectants protect humans from illness and prevent bacteria contaminating technical systems, but also that the disinfectant used does not itself harm the human organism or impair materials and process flows.
Numerous methods employing a whole range of substances and technologies are used for disinfection tasks. Experience and decades of research work have shown that many applications are better served through the addition of chlorine dioxide. ALLDOS Eichler GmbH has taken this fact into account and can supply chlorine dioxide treatment systems such as the Oxiperm 164 or Oxiperm 166 which employ this disinfection method and can be used for a whole range of disinfection applications.
The compact systems are easy to operate and suitable for almost any water chemistry application. With their flexible range of capacity levels, Oxiperm treatment systems can be used for a broad spectrum of disinfection tasks. Possible applications begin with the treatment of drinking water and extend to the treatment of process water, cooling water and waste water. Disinfection using chlorine dioxide is also becoming increasingly popular in sensitive areas such as the food and beverages industry, since these are applications where any lessening of product quality caused by the odour or taste of the disinfectant cannot be tolerated. The growing demand for chlorine dioxide treatment systems is particularly marked in Cleaning In Place (CIP) applications.
Benefits of chlorine dioxide
Regardless of the matrix of the water being treated, chlorine dioxide has a far greater disinfecting action than, for example, chlorine in the same concentration. This not only ensures that the disinfecting effect is faster and longer lasting (sustained-release effect), but also that the effect itself is more selective. This is particularly evident in the fact that chlorine dioxide does not form any toxic chloramines or haloforms (THM). The product quality is not affected in any way as regards odour or taste.
ABecause of its high redox potential, chlorine dioxide has a much more powerful disinfecting action against all kinds of germs and contaminants such as viruses, bacteria, fungi and algae than is the case with other biocides. The oxidation potential is higher than with chlorine, for example, so that far fewer chemicals are required. The longer dwell time is also particularly advantageous due to the selective disinfection. Even germs that are resistant to chlorine, for example Legionella, can be killed completely by chlorine dioxide. Special measures need to be taken to combat them since they can adapt to conditions that are fatal to many organisms and are, the most part, resistant to biocides. Humans can be infected simply by inhaling the very smallest droplet of water contaminated with Legionella. The risk areas extend from water outlets which produce aerosols (minute water droplets) in plumbing installations in private households, hotels, hospitals and swimming baths to industrial applications such as cleaning and humidification plants.
In the case of aquaculture, i.e. springs or ponds, treated water that is re-infected with bacteria can be a particular source of danger, especially at elevated temperatures. The organisms have the best conditions for growth at temperatures of 25°C to 45°C. The pH of value for optimum growth lies in the region of 6.9. A population over a temperature range of 30°C to 35°C requires only a few hours to double in size. Legionella live in biofilms where they are shielded from most chemical disinfectants and all disinfection technologies that do not make use of chemicals.
Thermal disinfection, in which pipes are flushed with hot water at 70°C, is the conventional method for combating Legionella. This cannot provide a satisfactory solution in the long term, however, due to the high energy costs and the need to take precautionary safety measures to prevent scalding during the disinfection and cooling down phases. The long-term use of biocides other than chlorine dioxide would be conceivable, but the doses required would have to be so high that they would be harmful to human health.
The major difference between chlorine dioxide and chlorine or hypochlorite is the gradual effect it has on degrading the biofilm at relatively low doses. A concentration of 1 ppm will kill virtually all Legionella in the biofilm within 18 hours. A marked reduction in the biofilm can be achieved within the same time for a concentration of 1.5 ppm. Furthermore, the disinfecting action of chlorine dioxide is virtually independent of the pH value, meaning that it can also be used without problems in alkaline environments.
Disinfecting action of chlorine dioxide compared to chlorine
Chlorine dioxide is a greenish gas with an ozone-like odour which is soluble in water. The chemical action is based on conversion to chlorite or chloride. The biochemical effect on bacteria and viruses, however, is based on causing damage to the cell membranes and disrupting and/or interrupting metabolic processes.
BNo chloramines are generated in reactions involving chlorine dioxide. This therefore makes chlorine dioxide particularly interesting when treating water containing nitrogen and/or ammonia. A further advantage of using chlorine dioxide lies in its preventive effect against the growth of algae in order to prevent deposits in pipes and system components, particularly in cooling tower systems. Since chlorine dioxide can be produced in many ways, Oxiperm systems from ALLDOS Eichler GmbH are available for two different treatment processes to meet the user's particular requirements. Both have become popular worldwide.
 |
|
The acid/chlorite method with dilute and concentrated sodium chlorite and hydrochloric acid solutions |
|
|
The chlorine gas/chlorite method with concentrated sodium chloride solution and chlorine gas dissolved in water Oxiperm 166 |
Both methods produce chlorine dioxide with a high yield (up to 95%).
Oxiperm 164
The newly developed Oxiperm 164 featuring precise dosing, deaeration and calibration technology with the proven P3 system produces a mixture of chemicals which is as precise as it is resource friendly. The yield is about 90%. The production of chlorine dioxide using this method is based on the following equation:
5 NaCIO2 + 4 HCI -> 4 CIO2 + 5 NaCI + 2 H2O
A particular feature of these automatic Oxiperm 164 systems are the dual viewing functions for monitoring the preparation process. Light diodes in a clearly arranged flow scheme allow possible errors to be identified quickly and precisely. Additionally, all operating states and error messages are shown on the plain-text display. A link to the process control systems (BUS interfaces) can be used to monitor and display workflows or error messages.
Particular importance has also been attached to ease of operation, monitoring and maintenance. All control elements are situated on the front of the unit. Sensitive system components are installed in a safe, protected position at the back of the unit. Components on the back of the unit which require regular maintenance are easy to access. All systems are equipped with extensive sensor technology and a whole range of safety elements.
Oxiperm 164 is available in three capacity levels: Oxiperm 164 D is suitable for 5 to 2,000 g/h, while Oxiperm 164 C has a capacity of 150 to 2.500 g/h. The third variation is the large Oxiperm 164 C with integrated chlorine dioxide buffer for large applications of 4000 – 10,000 g/h capacity. The Oxiperm 164 variations can be operated with various control types and therefore give the operator high flexibility. Batch dosing, direct control via proportional signals (contact / flow) and direct or remote monitoring are all supported.
 |
 |
 |
Oxiperm 164 D
5 to 2000 g/h |
Oxiperm 164 C
150 to 2500 g/h |
Oxiperm 164 C 4 to 10 kg/h |
Oxiperm 166
This liquid/gas system uses the proven chlorite/chlorine method. The yield in this case is approx. 5% higher than with the acid/chlorite method at around 95%. The formation of chlorine dioxide occurs on the basis of the following equation:
2 NaCIO2 + CI2 -> 2 CIO2 + 2 NaCI
In addition to cutting-edge sensor technology, Oxiperm 166 also features high-precision PLC control with plain-text display. 6 capacity levels for dosing quantities from 0.7 to 10 kg/h are available. As with the Oxiperm 164 systems, this unit was also developed with the focus on safety and ease of use. The systems are equipped with manual and automatic shut-off valves. The user-friendly, menu-controlled navigation showing the process messages plays a major part in ensuring the unit's high operating comfort. Operating logs are saved automatically and can be output as required. The password protection used for the display prevents unauthorised access.
Oxiperm 166
Both types of system enable containers to be changed without interruption and with automatic deaeration after each change.
The Oxiperm disinfection systems not only boast a whole range of technical highlights, they also feature ALLDOS entire expertise on efficient, reliable and highly cost-effective disinfection.
ALLDOS Eichler GmbH
Reetzstraße 85
D-76327 Pfinztal
Tel.: (+ 49) 7240 61-0
Fax: (+ 49) 7240 61-177
E-mail alldos.de@alldos.com
www.alldos.de
|
 DOWNLOAD |
