Disinfection levels

Maximum Residual Disinfectant Level (MRDL) - The highest level of a disinfectant allowed in drinking water. There is convincing evidence that addition of a disinfectant is necessary for control of microbial contaminants. 

Maximum Residual Disinfectant Level Goal (MRDLG) - The... 

Please indicate which six of the following issues are the most important when considering the comfort and well-being of users and staff. (Air temperature, bacteria, chloramine levels in the water, chlorinous smells, clear water, fresh air, humidity, pH, residual disinfectant level, trihalomethanes, water temperature, water balance)... 

Chlorine Inorganic chemicals Maximum residual disinfectant level (MRDL) 4.0 mg/L Eye/nose irritation, stomach discomfort... 

OSHA regulates the level of chlorine dioxide in workplace air. The occupational exposure limit for an 8-hour workday, 40-hour workweek is 0.1 parts per million (0.28 milligrams per cubic meter [mg/m ]). The EPA has set a maximum contaminant level of 1 milligram per liter (mg/L) for chlorite in drinking water and a goal of 0.8 mg/L for both the maximum residual disinfectant level for chlorine dioxide and the maximum contaminant level for chlorite in drinking water treated with chlorine dioxide as a disinfectant. 

As regulated by EPA (as of January 1, 2002), the maximum residual disinfectant level (MRDL) for chlorine dioxide is 0.8 mg/L (EPA 2002g) the maximum contaminant level (MCE) for its oxidation product, chlorite ion, in drinking water is 1.0 mg/L (EPA 2002e). The levels of chlorite ion in distribution system waters have been reported as part of the Information Collection Rule (ICR), a research project used to support the development of national drinking water standards in the United States (EPA 2002d). 

Maximum residual disinfectant level 0.8 mg/L ERA 2002g 40CFR141.65(a)... 

EPA. 2002g. National primary drinking water regulations. Maximum residual disinfectant levels. U.S. Environmental Protection Agency. Code of Federal Regulations. 40 CFR 141.65(a). http //ecffback.access.gpo.gov/. April 24, 2002. 

UV can also be used in water reclamation and reuse. An example is the reclamation of swimming pool water. Usually, the swimming pool water reuse process includes coagulation, filtration, clarifier, disinfection, and pH adjustment. The conventional swimming pool disinfection chemical is chlorine however, high concentrations of residual chlorine can be harmful to human health. The UV technology can be placed between the filters and chlorine disinfection unit as a pre-disinfection unit and remove pathogens. Hence, much less amount of chlorine (compared with the process without UV unit) is needed for residue disinfectant level. 

EPA has also established maximum residual disinfectant levels (MRDLs) to limit the applied dose of chlorine, chloramines and chlorine dioxide during drinking water treatment ... 

MRDL = maximum residual disinfectant level. Measured as free chlorine. 

Describe in your own words the three CDC-defined disinfecting levels. 

Code of Federal Regulations (CFR). 2000. National Primary Drinking Water Regulations Maximum Contaminant Levels and Maximum Residual Disinfectant Levels. 40 CFR 141, Title 40, Part 141, as amended, Washington, DC. 

Maximum residual disinfectant level goal (MRDLG)—The level of a drinking water disinfectant below which there is no known or expected risk to health. 

The total concentration of HOCl + OCl , expressed as the equivalent CI2 concentration in ppm or mg/L, is called free chlorine. The free chlorine disinfection level in residential swimming pools is maintained between 0.5 and 3 ppm and is usually controlled by simple colorimetric analysis. The biocidal activity of the acid form, HOCl or active chlorine, is more than 20 times stronger than the activity of the ionized OCl— form [2]. It is therefore critical to maintain a pH lower than 7.6-7.8 where the HOCl form is significant (see Fig. 1). The minimum recommended pH is 7 for bather comfort and pool material compatibility reasons. 

Disinfectants, for example at laundry, may be applied by the customer himself The method of sanitizing substance application for carpets, which is spraying or dispensing of a disinfectant on the surface of floor covers during operation is known. The acceptable disinfection level may be obtained during laundry of textile products by such detergents, which may create residual fungal and bacteriostatic activity [58-60],... 

Table 1 provides a sununaiy of the maximum residual disinfectant level of the different disinfectants as listed in the EPA Alternative Disinfectants and Oxidants Guidance Manual [5]. 

---