Treat your water in two steps!
Posted: Thu Dec 07, 2006 8:30 pm
The following post is from AvianFluTalk preparedness forum:
Treat your water in two steps!
https://www.avianflutalk.com/forum_posts.asp?TID=963&PID=20904&title=water#20904
The following is an explanation of why you should filter your water FIRST, using one of the filters noted in other posts, and THEN use your chlorine to complete the purification process of your water:
Note: THis guideline will be cross-posted in the appropriate Chlorine threads. -Admin
It may be a good idea, if you are planning on using chlorine or other chemical disinfectants, to use an activated carbon filter prior to use to filter out the resultant chlorine and carcinogenic THM's.
Please see below:
Disinfection
Disinfection with aggressive chemicals like chlorine or ozone is normally the last step in purifying drinking water. Water is disinfected to destroy any pathogens which passed through the filters. Possible pathogens include viruses, bacteria including Escherichia coli and Shigella, and protozoans including Giardia lamblia and Cryptosporidium. Many water systems intentionally leave residual disinfection agents in the water after exiting the plant so it travels throughout the distribution system. The most common disinfection method is some form of chlorine such as chlorine gas, sodium hypochlorite, chloramine or chlorine dioxide. The water and chemical mix are allowed to sit in a large tank, called a clear well. The water must sit in the clear well to ensure that the water is in contact with the disinfectant for a minimum amount of time because it takes time to inactivate the harmful microbes. Chlorine is a strong oxidant that kills many microorganisms and remains in the water to provide continuing disinfection. Other disinfection methods include using ozone which acts very rapidly or Ultra Violet light that is almost instantaneous also inactivate pathogens.
Chlorine gas and sodium hypochlorite are the most commonly used disinfectants, because they are inexpensive and easy to manage. They are effective in killing bacteria, but have limited effectiveness against protozoans that form cysts in water (Giardia lamblia and Cryptosporidium, both of which are pathogenic). Chlorine gas and sodium hypochlorite both have strong residuals in the water once it enters the distribution system.
The main drawback in using chlorine gas or sodium hypochlorite is that these react with organic compounds in the water to form potentially harmful levels of the chemical by-products trihalomethanes (THMs) and haloacetic acids, both of which are carcinogenic and regulated by the U.S. EPA. The formation of THMs and haloacetic acids is minimized by effective removal of as many organics from the water as possible before disinfection and/or by adding ammonia immediately after chemical disinfection is completed. Formerly, it was common practice to chlorinate the water at the beginning of the purification process, but this practice has mostly been abandoned to minimize the production of THMs.
Chloramines are not as effective disinfectants compared to chlorine gas or sodium hypochlorite, but do not form THMs or haloacetic acids. They are typically used only in stored and distributed treated water. An example of this sort is proceeses using ozone for primary disinfection which is very quickly accomplished then using monochloramine to create a residual level of disinfectant in the water. Chlorine dioxide is another rapid acting disinfectant against bacteria but unlike ozone it leaves a long lasting residual in the water. Despite these beneficial characteristics, it is rarely used because it may creates excessive amounts of chlorate and chlorite, both of which are regulated to low allowable levels.
Treat your water in two steps!
https://www.avianflutalk.com/forum_posts.asp?TID=963&PID=20904&title=water#20904
The following is an explanation of why you should filter your water FIRST, using one of the filters noted in other posts, and THEN use your chlorine to complete the purification process of your water:
Note: THis guideline will be cross-posted in the appropriate Chlorine threads. -Admin
It may be a good idea, if you are planning on using chlorine or other chemical disinfectants, to use an activated carbon filter prior to use to filter out the resultant chlorine and carcinogenic THM's.
Please see below:
Disinfection
Disinfection with aggressive chemicals like chlorine or ozone is normally the last step in purifying drinking water. Water is disinfected to destroy any pathogens which passed through the filters. Possible pathogens include viruses, bacteria including Escherichia coli and Shigella, and protozoans including Giardia lamblia and Cryptosporidium. Many water systems intentionally leave residual disinfection agents in the water after exiting the plant so it travels throughout the distribution system. The most common disinfection method is some form of chlorine such as chlorine gas, sodium hypochlorite, chloramine or chlorine dioxide. The water and chemical mix are allowed to sit in a large tank, called a clear well. The water must sit in the clear well to ensure that the water is in contact with the disinfectant for a minimum amount of time because it takes time to inactivate the harmful microbes. Chlorine is a strong oxidant that kills many microorganisms and remains in the water to provide continuing disinfection. Other disinfection methods include using ozone which acts very rapidly or Ultra Violet light that is almost instantaneous also inactivate pathogens.
Chlorine gas and sodium hypochlorite are the most commonly used disinfectants, because they are inexpensive and easy to manage. They are effective in killing bacteria, but have limited effectiveness against protozoans that form cysts in water (Giardia lamblia and Cryptosporidium, both of which are pathogenic). Chlorine gas and sodium hypochlorite both have strong residuals in the water once it enters the distribution system.
The main drawback in using chlorine gas or sodium hypochlorite is that these react with organic compounds in the water to form potentially harmful levels of the chemical by-products trihalomethanes (THMs) and haloacetic acids, both of which are carcinogenic and regulated by the U.S. EPA. The formation of THMs and haloacetic acids is minimized by effective removal of as many organics from the water as possible before disinfection and/or by adding ammonia immediately after chemical disinfection is completed. Formerly, it was common practice to chlorinate the water at the beginning of the purification process, but this practice has mostly been abandoned to minimize the production of THMs.
Chloramines are not as effective disinfectants compared to chlorine gas or sodium hypochlorite, but do not form THMs or haloacetic acids. They are typically used only in stored and distributed treated water. An example of this sort is proceeses using ozone for primary disinfection which is very quickly accomplished then using monochloramine to create a residual level of disinfectant in the water. Chlorine dioxide is another rapid acting disinfectant against bacteria but unlike ozone it leaves a long lasting residual in the water. Despite these beneficial characteristics, it is rarely used because it may creates excessive amounts of chlorate and chlorite, both of which are regulated to low allowable levels.