1. At the end of this lesson you will be able to:
Learning Objectives
At the end of this lesson you will be able to:
Understand the importance of chlorine testing
Demonstrate the chlorine testing procedures
Learning objectives.
At the end of this lesson you will be able to:
Describe the basic principles for the
operation of the HACH© pocket chlorine
colorimeter
Demonstrate the operation of the HACH pocket
chlorine colorimeter in accordance with the
manufacturer’s instructions 1

2. Introduction
The Water Corporation has a memorandum of understanding with the Department of Health to supply safe drinking water to consumers.
In simple terms, turbidity is a measure of how cloudy a water sample appears. 2

3. Check calibration of all chlorine meters regularly.
Introduction
Following a 2002 audit by the Department of Health the following changes were made:
Standardise all chlorine meters to HACH Pocket Colorimeters (also HACH DR 800 & 2000 series units).
Check calibration of all chlorine meters regularly.
Train all users to ensure competence.
12 months given to develop resources and train
everyone.
The ability of light to pass through water depends on how much suspended matter is present.
Turbidity may be caused by large amounts of silt, micro-organisms, plant fibres, sawdust, wood ash, chemicals and coal dust. 3

4. Introduction
Chlorine standards are difficult to make, preserve and store for field use.
(i.e. 1.0 mg/L chlorine).
The Water Corp settled on using HACH SpecCheck secondary standards – they can only be used for 2 years from date of manufacture. 4

5. Introduction
Having made all these changes we could ensure
that progress was made towards:
all staff using the chlorine meters being
competent.
all instruments kept in excellent working condition. 5

6. Why add chlorine to water?
Chlorine forms the main barrier against disease in the disinfection process which means that chlorine is the most important of all chemicals to test in the drinking water supply. 6

7. Importance of chlorine testing
Chlorine testing is an essential part of managing the water supply.
Results from your tests are recorded, checked and abnormal results investigated.
Incidents must be reported and action must
be taken immediately. 7

8. Disinfection processes used
Chlorination - most common method used.
Chloramination - sites along the Mundaring to
Kalgoorlie pipeline
Ultra violet irradiation - Leonora & some other
regional sites with RO systems (as a pre-treatment to protect the membranes). 8

9. Chlorine chemistry
The reaction between chlorine and water is shown as:
Cl H2O → HOCl H Cl-
chlorine water hypochlorous hydrogen chloride
acid ion ion
Note:
HOCl - free residual chlorine. 9

10. Chlorine also reacts with ammonia in water to
Do you know?
Chlorine also reacts with ammonia in water to
form the chloramines - monochloramine,
dichloramine and trichloramine.
The proportion of hypochlorous acid in water depends on the:
temperature pH
ratio of chlorine and ammonia. N H Cl
monochloramine
dichloramine
trichlroamine 10

11. Chemical hazards
Chemicals used are safe if handled with
care - DPD free chlorine and DPD total chlorine powder.
Always practice good hygiene habits – wash your hands after using the chemicals.
Click on the hot text for more information. 11

12. Chemical hazards
Chemicals required are safe if handled with
care- DPD free and DPD total chlorine.
Always practice good hygiene habits.
N,N - diethyl-p-phenylenediamine 11