# chlornation of drinking water guide



## abue tycer (8 نوفمبر 2010)

[SIZE=+1]Chlorination of Drinking Water
Guide






Commercial System

​[/SIZE]​
[SIZE=+0]Water used for drinking and cooking should be free of *pathogenic *(disease causing) microorganisms that cause such illnesses as typhoid fever, dysentery, cholera, and gastroenteritis. Whether a person contracts these diseases from water depends on the type of pathogen, the number of organisms in the water (density), the strength of the organism (virulence), the volume of water ingested, and the susceptibility of the individual. Purification of drinking water containing pathogenic microorganisms requires specific treatment called disinfection.[/SIZE] 
[SIZE=+0]Although several methods eliminate disease-causing microorganisms in water, chlorination is the most commonly used. Chlorination is effective against many pathogenic bacteria, but at normal dosage rates it does not kill all viruses, cysts, or worms. When combined with filtration, chlorination is an excellent way to disinfect drinking water supplies.[/SIZE] 
[SIZE=+0]This fact sheet discusses the requirements of a disinfection system, how to test the biological quality of drinking water, how to calculate the amount of chlorine needed in a particular situation, chlorination equipment, by-products of disinfection, and alternative disinfection methods.[/SIZE] 
*[SIZE=+0]Disinfection requirements[/SIZE]* 
[SIZE=+0]Disinfection reduces pathogenic microorganisms in water to levels designated safe by public health standards. This prevents the *transmission *of disease.[/SIZE] 
[SIZE=+0]An effective disinfection system kills or neutralizes all pathogens in the water. It is automatic, simply maintained, safe, and inexpensive. An ideal system treats all the water and provides residual (long term) disinfection. Chemicals should be easily stored and not make the water unpalatable.[/SIZE] 
[SIZE=+0]State and federal governments require *public *water supplies to be biologically safe. The U.S. Environmental Protection Agency (EPA) recently proposed expanded regulations to increase the protection provided by public water systems. Water supply operators will be directed to disinfect and, if necessary, filter the water to prevent contamination from _Giardia lamblia, _coliform bacteria, viruses, heterotrophic bacteria, turbidity, and _Legionella._[/SIZE] 
[SIZE=+0]Private systems, while not federally regulated, also are vulnerable to biological contamination from sewage, improper well construction, and poor-quality water sources. Since more than 30 million people in the United States rely on private wells for drinking water, maintaining biologically safe water is a major concern.[/SIZE] 
*[SIZE=+0]Testing water for biological quality[/SIZE]* 
[SIZE=+0]The biological quality of drinking water is determined by tests for *coliform group bacteria. *These organisms are found in the intestinal tract of warm-blooded animals and in soil. Their presence in water *indicates *pathogenic contamination, but they are not considered to be pathogens. The standard for coliform bacteria in drinking water is "less than 1 coliform colony per 100 milliliters of sample" (< 1/ 100ml).[/SIZE] 
[SIZE=+0]Public water systems are required to test regularly for coliform bacteria. Private system testing is done at the owner's discretion. Drinking water from a private system should be tested for biological quality *at least once each year, *usually in the spring. Testing is also recommended following repair or improvements in the well.[/SIZE] 
[SIZE=+0]Coliform presence ina water sample does not necessarily mean that the water is hazardous to drink. The test is a screening technique, and a positive result (more than 1 colony per 100 ml water sample) means the water should be retested. The retested sample should be analyzed for fecal coliform organisms. A high positive test result, however, indicates substantial contamination requiring prompt action. Such water should not be consumed until the source of contamination is determined and the water purified.[/SIZE] 
[SIZE=+0]A testing laboratory provides specific sampling instructions and containers. The sampling protocol includes the following:[/SIZE] 

[SIZE=+0]use sterile sample container and handle only the outside of container and cap;[/SIZE] ​
[SIZE=+0]run cold water for a few minutes (15 minutes) to clear the lines;[/SIZE] [SIZE=+0]upon collecting sample, immediately cap bottle and place in chilled container if delivery to lab exceeds 1 hour (never exceed 30 hours). Many laboratories do not accept samples on Friday due to time limits.[/SIZE]​
*[SIZE=+0]Chlorine treatment[/SIZE]* ​
[SIZE=+0]Chlorine readily combines with chemicals dissolved in water, microorganisms, small animals, plant material, tastes, odors, and colors. These components "use up" chlorine and comprise the *chlorine demand *of the treatment system. It is important to add sufficient chlorine to the water to meet the chlorine demand and provide residual disinfection.[/SIZE] 
[SIZE=+0]The chlorine that does not combine with other components in the water is *free *(residual) chlorine, and the *breakpoint *is the point at which free chlorine is available for continuous disinfection. An ideal system supplies free chlorine at a concentration of 0.3-0.5 mg/l. Simple test kits, most commonly the DPD colorimetric test kit (so called because diethyl phenylene diamine produces the color reaction), are available for testing breakpoint and chlorine residual in private systems. The kit must test free chlorine, not total chlorine.[/SIZE] 
*[SIZE=+0]Contact time with microorganisms[/SIZE]* 
[SIZE=+0]The *contact (retention) time *(Table 1) in chlorination is that period between introduction of the disinfectant and when the water is used. A long interaction between chlorine and the microorganisms results in an effective disinfection process. Contact time varies with chlorine concentration, the type of pathogens present, pH, and temperature of the water. The calculation procedure is given below.[/SIZE] 
[SIZE=+0]Contact time must increase under conditions of low water temperature or high pH (alkalinity). Complete mixing of chlorine and water is necessary, and often a holding tank is needed to achieve appropriate contact time. In a private well system, the minimum-size holding tank is determined by multiplying the capacity of the pump by 10. For example, a 5-gallons-per-minute (gpm) pump requires a 50-gallon holding tank. Pressure tanks are not recommended for this purpose since they usually have a combined inlet/outlet and all the water does not pass through the tank.[/SIZE] 
[SIZE=+0]An alternative to the holding tank is a long length of coiled pipe to increase contact between water and chlorine. Scaling and sediment build-up inside the pipe make this method inferior to the holding tank.[/SIZE] 

*[SIZE=+0]Table 1. Calculating Contact Time[/SIZE]* [SIZE=+0]*minutes required = K / chlorine residual (mg/l)*[/SIZE] 

*K values to determine chlorine contact time*​_*Highest*_

_*Lowest Water Temperature (degrees F)*_​_*pH*_
_*> 50*_
*45*
*< 40*
*6.5*
*4*
*5*
*6*
*7.0*
*8*
*10*
*12*
*7.5*
*12*
*15*
*18*
*8.0*
*16*
*20*
*24*
*8.5*
*20*
*25*
*30*
*9.0*
*24*
*30*
*36*

[SIZE=+0]*To calculate contact time, one should use the highest pH and lowest water temperature expected. *For example, if the highest pH anticipated is 7.5 and the lowest water temperature is 42 °F, the "K" value (from the table below) to use in the formula is 15. Therefore, a chlorine residual of 0.5 mg/l necessitates 30 minutes contact time. A residual of 0.3 mg/l requires 50 minutes contact time for adequate disinfection.[/SIZE] 

*[SIZE=+0]Chlorination levels[/SIZE]* 
[SIZE=+0]If a system does not allow adequate contact time with normal dosages of chlorine, *superchlorination *followed by *dechlorination *(chlorine removal) may be necessary.[/SIZE] 
[SIZE=+0]Superchlorination provides a chlorine residual of 3.0-5.0 mg/l, 10 times the recommended minimum breakpoint chlorine concentration. Retention time for superchlorination is approximately 5 minutes. Activated carbon filtration removes the high chlorine residual .[/SIZE] 
[SIZE=+0]*Shock chlorination *is recommended whenever a well is new, repaired, or found to be contaminated. This treatment introduces high levels of chlorine to the water. Unlike superchlorination, shock chlorination is a "one time only" occurrence, and chlorine is depleted as water flows through the system; activated carbon treatment is not required. If bacteriological problems persist following shock chlorination, the system should be evaluated. More information regarding shock disinfection can be found at Shock Well Disinfection Website.[/SIZE] 

 
​
[SIZE=+0]CHLORINATION GUIDELINES[/SIZE]
[SIZE=+0]Chlorine solutions lose strength while standing or when exposed to air or sunlight. Make fresh solutions frequently to maintain necessary residual.[/SIZE] ​
[SIZE=+0]Maintain a free chlorine residual of 0.3-0.5 mg/l after a 10 minute contact time. Measure the residual frequently.[/SIZE] 
[SIZE=+0]Once the chlorine dosage is increased to meet greater demand, do not decrease it.[/SIZE] [SIZE=+0]Locate and eliminate the source of contamination to avoid continuous chlorination. If a water source is available that does not require disinfection, use it.[/SIZE] ​
[SIZE=+0]Keep records of pertinent information concerning the chlorination system.[/SIZE] *[SIZE=+0]Types of chlorine used in disinfection[/SIZE]* ​
[SIZE=+0]Public water systems use chlorine in the gaseous form, which is considered too dangerous and expensive for home use. Private systems use liquid chlorine (sodium hypochlorite) or dry chlorine (calcium hypochlorite). To avoid hardness deposits on equipment, manufacturers recommend using soft, distilled, or demineralized water when making up chlorine solutions.[/SIZE] 
*Liquid Chlorine* 

 
household bleach most common form 
available chlorine range: 
5.25% (domestic laundry bleach) 
18% (commercial laundry bleach) 
slightly more stable than solutions from dry chlorine 
protect from sun, air, and heat 
*Dry Chlorine* 

 
powder dissolved in water 
available chlorine: 4% 
produces heavy sediment that clogs equipment; filtration required 
dry powder stable when stored properly 
dry powder fire hazard near flammable materials 
solution maintains strength for 1 week 
protect from sun and heat 

*[SIZE=+0]Equipment for continuous chlorination[/SIZE]* ​
[SIZE=+0]Continuous chlorination of a private water supply can be done by various methods. The injection device should operate only when water is being pumped, and the water pump should shut off if the chlorinator fails or if the chlorine supply is depleted. A brief description of common chlorination devices follows.[/SIZE] 
*[SIZE=+0]chlorine pump [/SIZE]*[SIZE=+0](see Fig. 1):[/SIZE] 

[SIZE=+0]commonly used, positive displacement or chemical-feed device,[/SIZE] ​
[SIZE=+0]adds small amount, of chlorine to the water,[/SIZE] ​
[SIZE=+0]dose either fixed or varies with water flow rates[/SIZE] ​
[SIZE=+0]recommended for low and fluctuating water pressure,[/SIZE] ​
[SIZE=+0]chlorine drawn into device then pumped to water delivery line[/SIZE] ​




[SIZE=+0]Figure 1. Pump type (positive displacement) chlorinator[/SIZE] [SIZE=+0]Figure 2. Injector (aspirator) chlorinator[/SIZE]​


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## مهندس المحبة (9 نوفمبر 2010)

شكرا أخي أبو تيسير على هذا الموضوع المميز .........


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## محمد محمود لبيب (16 نوفمبر 2010)

المو ضوع ممتاز


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## jassim78 (17 نوفمبر 2010)

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## خلوف العراقي (19 نوفمبر 2010)

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## hassanaki (6 ديسمبر 2010)

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