SESSION 32 HANDOUT 4 MONITORING OF CHLORINATION

0 ECOSV026 95E PLENARSESSIONEN 3–4 MAJ 2012
0 ECOSV051 105TH PLENARY SESSION 3031 JANUARY
0 ENVEV029 102ND PLENARY SESSION 34 JULY

0 NATV021 97TH PLENARY SESSION 810 OCTOBER
0 NATV036 106TH PLENARY SESSION 2 AND
10 T HIRTYEIGHTH REGULAR SESSION OEASERP JUNE

Session 3.2 - Handout 4 - Monitoring of chlorination

MONITORING CHLORINATION

The simplest and surest way of monitoring the effectiveness of chlorination of drinking water is to measure the Free Residual Chlorine (FRC).

The presence of FRC in water after30 or 60 mn contact time, proves that enough chlorine has been added to satisfy the chlorine demand or in other terms to react on all matter present in the water, including micro organisms, and leaving an excess of chlorine available to deal with possible recontamination (in the distribution system, during handling etc.)

Condition of water	Contact time	FRC
pH< 8	30 minutes	0.2 – 0.5 mg/l
pH > 8	60 minutes	0.4 – 1.0 mg/l
Temperature< 10 ^oC	60 minutes	0.2 – 0.5 mg/l

The measurement of FRC and pH is most easily done using a comparator also commonly called a « Pool tester ».

There may have two brands of tablets available in the field: Palintest and Lovibond. Sometimes other names are printed on the tablets. (E.g. Cifec on Lovibond tablets). If in doubt, contact your head office.

How to use the pool tester

Rinse the Pool tester 3 times with the water to be tested, including the cover. If a syringe is used to fill the pooltester, it should be rinsed inside and outside thoroughly with the water to be tested.
Fill the 3 compartments to the top with the water to be tested.
Put one Phenol Red tablet in the left hand compartment (measurement of pH)
Put one DPD 1 tablet in the right hand compartment (measurement of Free Residual Chlorine)
Replace the cover tightly (it is normal that some liquid is pressed out) with the arrows pointing towards the coloured reference scale.
Shake until the tablets are completely dissolved (about 20 seconds).
Read the results in natural day light, comparing the colours in the outside compartments (sample) with those in the central compartment (reference).
After testing, empty pool tester and syringe and rinse again.

KEY

1 Cover

2 Central compartment

3 pH compartment (Phenol Red tablet)

4 FRC compartment (DPD1tablet)

5 pH reading scale

6 pH reference scale

7 FRC reading scale

8 FRC reference scale

INPUTS

1 Pool tester with cover

1 Phenol Red tablet (Phenol Red marked in green on packaging)

1 DPD1 tablet (DPD1 must be marked in green on packaging)

- Water to be tested

IMPORTANT

For step 1 and 2 always make sure that you will not change the quality of the water you’d like to test: let water flow for a few moments before taking it from a tap. Be carrefull when pouring water out of a container: let it flow before taking your sample or use a thoroughly rinsed 50 ml syringe. Never put the tester into the container. If using jerry cans, fitted with a tap, do not use the tap to fill the pool tester, as the taps being placed next to the ground are often soiled (leading to false results).
Never touch the tablets, the inside of the pool tester or the inside part of the cover with your fingers: this could affect the results. Never use tablets that have fallen on the ground.
For use in a pool tester, the printing « DPD1 » on the packaging must be in green (fast dissolving). The other DPD1 tablets with printing in black should never be used in this pool tester.
Only whole tablet must be used. Do not use broken tablets (while opening packaging or because of bad storage).

Tablets have a shelf life of 5 years. The expiry date is written on the outside of the 500 tablets cardboard boxes.

If tablet strips are separated from their cardboard boxes the manufacturing date of the Lovibond tablets can be determined using the batch number: the first capital letter is the year of production; “M” is 1990, “N” is 1991 etc. “V” is not used, thus “A” is 2003 again. The two numbers after the capital letter is the month.

To determine manufacturing date of Palintest tablets contact your head office.

Do not use tablets, which have lost their colour (dull grey/brown instead of bright white for DPD1, and dull brown instead of bright orange for Phenol Red) or disintegrate on opening.
Expired/ damaged tablets can be disposed off with normal waste.
Both brands of tablets can be used in the standard pool tester.
Read the results within 60 seconds of the tablets dissolving to be sure of a reliable measurement. Results are not guaranteed after this time.
Read the results in good lightning conditions (day light but not in direct sun light; do not wear sun glasses to read the results). Ideally, the reading should be made on a white surface (ex: a tent wall)
It is not necessary to measure the pH every time. However, it must systematically be measured before starting chlorination as a pH >8 requires higher contact time and a higher residual chlorine (see TB Chlorination of drinking water). pH of a given water may vary with time due to seasonal changes, so it needs to be controlled from time to time.
Comments on pH of water:

pH = 7: neutral

pH < 7: acidic

pH > 7: alkaline (or = basic)

WARNING: In case of residual chlorine above 10 mg/l, the tablet will not develop any colour, wrongly indicating zero residual chlorine.

WASH cholera / AWD EP&R training – session 3.2 – handout 4 Page 1 of 3

2 Q UARANTETROISIEME SESSION ORDINAIRE OEASERP 4
3 ECAC25(SP)WP2 TWENTYFIFTH PLENARY SESSION (SPECIAL) OF
3 Q UARANTIÈME DEUXIEME SESSION ORDINAIRE OEASERP

Tags: chlorination monitoring, tb chlorination, session, handout, monitoring, chlorination