Chlorine Monitoring and Dechlorination Techniques Handbook

Chlorine Monitoring and Dechlorinating Techniques Handbook
20.3 g of sodium thiosulphate pentahydrate per litre of water. A 3,000 gallon
tank holds 13,650 litres of water. Therefore, one would need:
20.3g/L * 13,650 L = 277,095 grams or 277.1 kg 8 of sodium thiosulphate
pentahydrate to make up one tank of solution.
Step 5 - The flow rate was given as 5,000 m 3 /day. It would be easier to know the flow
rate in litres per day. In order to convert, use the following:
Since 1 m 3 = 1,000 L, the flow rate of water leaving the site is:
1000 x 5,000 = 5,000,000 L/day.
There are 1,440 minutes in one day. Therefore the flow rate of water in litres
per minute would be: 5,000,000 L/day divided by 1,440 minutes/day = 3,472
L/minute.
Step 6 - Determine the dosing rate. Using Table 3-5, cross-reference a 2% stock
solution with a TRC of 1 mg/L. The quantity of sodium thiosulphate
pentahydrate 2% stock solution is 708 mL for every 10,000 litres of water
discharged.
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Since the flow rate is known, the dosing rate of dechlorinating solution can
be determined as follows:
It will take:
3,472 L/minute * 708 mL/10,000 L = 245.8 mL of solution/minute to
dechlorinate the discharge water.
If the 13,650 L tank of dechlorinating solution is used, it will last for:
13,650 L * (1000 mL/L) 9 divided by 245.8 mL/minute = 55,533 minutes or
925 hours, or approximately 1 month, assuming that the plant is in operation
24-hours a day.
Remember that there are 1,000 grams in a kilogram.
There are 1,000 mL in 1 Litre.
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