2. You are asked to design a disinfection process using chloramine as yo The USE

Question

2. You are asked to design a disinfection process using chloramine as yo The USEPA regulati disinfection agent. The influent concentration of giardia is 100 100 ml. in the disinfection process. The chlorine contact tank is 30 meters long and has cross section of 10 meters and the flowrate is 150 cubic meters per hour and can be modeled as a plug flow reactor. The Ct value that needed is 1100 mg/L min. It is important to know that the chloramine concentration breaks down over time due environmental factors that are beyond your control. The decay is a first order process and has a decay coefficient of 0.1 hr, on requires a 3 log reduction in giardia concentration a. What is the effluent giardia concentration? b. In order to ensure disinfection occurs we often use the efluent concentration in our Ct calculation, what is the effluent concentration of chloramine? Given the decay behavior of chloramine described above concentration of chloramine should I dose this reactor with? Since the calculations above are conservative, what is the ao dose (assuming we can predict the chloramine concentration a And how much chloramine could we actually save per conservative? , what c. actual required d. )? day by notb

Explanation / Answer

Solution

a) Effluent Giardia Concentration

Giardia is the most common protozoa parasite isolated from the gastrointestinal tract.These parasites can pose a serious threat to immunocompromised people, for whom the symptoms are more severe and may include abdominal pain, watery diarrhoea, nausea, headaches, malaise, and fever. One of the sources of these parasites can be treated wastewater from wastewater treatment plants (WTPs).

b) Effluent Concentration of Chloramine

Chloramines are a group of chemical compounds that contain chlorine and ammonia. The particular type of chloramine used in drinking water disinfection is called monochloramine. Monochloramine is mixed into water in levels that kill germs but are still safe to drink.

Chloramine is used as a disinfectant for water because it is less aggressive than chlorine and more stable against light than hypochlorites.NH2Cl is commonly used in low concentrations as a secondary disinfectant.

In dilute aqueous solution, chloroamine is prepared by the reaction of ammonia with sodium hypochlorite:

NH3 + ClO NH2Cl + OH

C) Concentration of Chloramine dose

Giardia concentartion is 1000 Organisms for 100 ml.

Chlorianted tank 30m x 10m

Flow rate is 150 m3 per hour

Ct value is 1100mg /l

Decay co efficeient 0.1 ht-1

=150/10

= 15 m3 Per 1 Organisms

=(15*1000*300)/1100 = 1239 l per hour

=1.24 mg / l

For the given decay behaviour of Chloramine described concentrated Chloramine dose with the reactor levels up to 1.24 milligrams per liter (mg/L) .

d) Actual required dose

The above decay indicate that using or drinking water with small amounts of chloramine does not cause harmful health effects and provides protection against waterborne disease. Also we could save with chloramine levels of less than 50 mg/L.

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