Disinfection systems

Salgot M, Folch M, Huertas E, Tapias J, Avellaneda D, Giros G, Brissaud F, Verges C, Molina J, Pigem (2002) Comparison of different advanced disinfection systems for wastewater reclamation. Wat Sci Tech/Wat Supply 02(03) 213-218... 

There is thus a requirement for a disinfection system which will assist in minimising the risk from Legionella in hot and cold water services without the problems associated with chlorination. 

Sometimes in the design of a BSL-4 facility, the full letter of health and safety codes/requirements for the protection of workers can not be met. This is where health and safety specialists must compromise and use their ingenuity to meet the intent of the requirements. For example, it is not always possible to provide a secondary means of egress from each area. Two change facilities are not cost effective or practical. A viable alternative is the use of airlocks with built-in liquid disinfection systems which are not hazardous to humans, but destroy the biohazard. These airlocks must be clearly identified as others are often used for transportation of equipment and other materials and contain hazardous disinfection systems. 

In the control of chlorine disinfectant systems, the effective use of the chlorine for its intended purpose is assumed if the treated water considerably downstream from the chlorinalor contains a residual of chlorine. Depending upon use. lull-contact tinte may be assumed alter len miuules. or the interval may be extended lo several hnurs. The systems also are usually carefully monitored by bacteriological testing. Normally a dose of I lo 2 milligrams of chlorine per liter is adequate lo destroy all bacteria and leave an effective residual. Residuals of 0.1 to 0.2 milligrams per liter are usually maintained in the diluent streams front water-treatment plants as a factor of safely for consumers. 

Wei C, Lin WY, Zainal Z, Williams NE, Zhu K, Kruzic AP, Smith RL, Rajeshwar K. Bactericidal activity of Ti02 photocatalyst in aqueous media toward a solar-assisted water disinfection system. Environ Sci Technol 1994 28 934-938. 

Biocidal applications. The use of quaternary ammonium salts in disinfecting systems for household and industrial cleaners has been known for many years [95, 96]. Alkyl-benzyldimethyl quaternaries, alkyltrimethyl quaternaries, and dialkyldimethyl quaternaries are the more commonly used biocidal quaternary ammonium salts [16]. Recently, dialkyldimethyl quaternary ammonium salts have received renewed attention as potential wood preservatives to replace the heavy metal types [97]. Metal-free wood preservative formulations containing dialkyldimethyl ammonium salts with non-halide anions, such as carboxylates, borates, and carbonates, have been developed [98, 99]. 

Residual action to avoid nonregular or jagged disinfections (advantage compared to not persistent effect of UV disinfection systems)... 

The aim of this section is to quantify the influence of some operating parameters such as flow rate, catalyst concentration, initial bacterial concentration, and reactor volume. These parameters affect reactor efficiency evaluation and therefore subsequent optimization of the disinfection system. 

Design a UV disinfection system that will deliver a minimum design dose of 100 mJ/cm2. Assume for the purpose of this example that the following data apply ... 

Configure the UV disinfection system. Typically, 2, 4, 8, or 16 lamps per module are available. For an 8-lamp module, eight modules are required per bank for a total of 64 lamps per bank. 

Both of these hydraulic loading rates fall within the acceptable range for the UV disinfection system provided by the manufacturer. 

Ho C-F H, Pitt P, Mamais D, Chiu C, Jolis D (1998) Evaluation of UV Disinfection Systems for Large-scale Secondary Effluent, Water Environ. Res. 70, No. 6 1142— 1150. 

Malley Jr JP (2000) Engineering of UV Disinfection Systems for Drinking Water, lUVA News 2, No. 3 8-12. 

WAR K (1994) Bactericidal Activity of Ti02 Photocatalyst in Aqueous Media Toward a Solar-Assisted Water Disinfection System, Environ. Sci. Technol. 28, No. 5 934-938. 

In contrast with all other electrically enhanced processes, electrochemical disinfection can be employed at low concentration of pollutants (in this case microorganisms). No highly conductive electrolyte is required for effective disinfection. Electrochemical disinfection will have to compete with chemicals normally used for water disinfection, such as chlorine, or ultrahltration membrane systems. In remote areas (such as rural village water supply) the electrochemical disinfection system, which does not necessarily need a pump, is competitive especially for small-scale processes [71]. 

Effectiveness of the physical cleaning of isolators applied in conjunction with gaseous or aerosol disinfection systems. 

At the end of the pilot plant trial period a series of four tests was carried out under comparable conditions. By providing a comparison between the two disinfection systems employed, these tests show the characteristics of each. 

UV can cause permanent inactivation of virus, bacteria, spores, fungi and other pathogens. UV irradiation disinfection requires no additional chemicals. Unlike chlorination disinfection, it does not produce odor it is usually deemed as the best choice with very low or no DBFs and no residual toxicity. In addition, it is able to kill some chlorine-resistant pathogens such as Cryptosporidium and Giardia. Compared with other disinfection alternatives, UV is a cost-effective, clean, and simple approach. UV disinfection system does not require the transportation, storage, and handling of regulated chemicals such as chlorine. 

In this chapter, the mechanisms of UV disinfechon will be presented. A mathematical description of microorganism killing by UV radiation is given. Design approaches of disinfection systems are demonstrated. Case studies will also be presented at the end of this chapter. 

UV germicide mechanisms are introduced. Basic principles of UV disinfection system design, installation, and operation considerations are presented. The concern about UV disinfection by-products is also discussed. In addition, the mechanisms of UV oxidation are addressed. Its applications on organic pollutants decomposing as an emerging water and wastewater treatment technology are discussed. 

Any ideal UV disinfection system should provide sufficient dose to kill pathogens in water and wastewater. Both closed and open UV systems can be used as shown in Figs. 7 and 8. Closed channel UV system is often used in drinking water disinfection, while open channel UV system is always adopted for wastewater disinfection. No matter... 

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