This document provides information on water quality parameters, chlorination techniques, and conducting a training on these topics. It discusses the importance of safe drinking water and outlines the objectives of water treatment. Key water quality parameters like turbidity, pH, and chlorine residual levels are explained. Proper chlorination methods including chlorine dosage, contact time, and monitoring free residual chlorine are described to effectively disinfect water sources. The training aims to educate participants on testing and maintaining water quality.

1. ACF - USA
Training on
Water Quality Parameters &
Chlorination Techniques
11th
December 2015
Venue: Regency Hotel, Juba
Prepared by: Dominic
INTRODUCTION:
Safe water is essential for life and health. People can survive longer without food
than without water. Water is universally essential for drinking, cooking and
personal and domestic hygiene. In extreme situation, there may not be enough
water available to meet physiological needs, and in these case a survival level of
potable drinking water is probably the most urgent and important priority of all. In
most cases however, the main health problem associated with inadequate water
supply are caused by poor hygiene due to lack of water, and by the consumption of
water that is contaminated at some stage.
Objective:
The object of water treatment is to provide potable i.e. pathogen free (and
chemically safe) water that is also aesthetically acceptable to the consumer. It is also
desirable in emergency situation to provide an extra level of protection in the water,
in the form of chlorine residual, to deal with potential contamination at a household
level, i.g. in water containers.
Safe Water:
Safe water means water free from :-
• Visible suspended matter

2. • Colour
• Test and Odour
• Bacteria indicative of pollution
• Objectionable dissolved matter
• Aggressive constituents.
Water Sources:
There are three main sources of natural water.
Ground Water : Shallow aquifer / Deep aquifer / Spring
- DTW / STW / Spring / Ring-Well
Surface water : Pond, River, Lake, Streams etc.
Rain water : Roof collection, etc
Water quality parameters:
Physical Characteristics:
Colour, Odour, Taste, Turbidity, Temperature, pH, Conductivity, Suspended and
setteable Solids ( surface water )
Turbidity/Suspended solids
This term is a measure of how much suspended matter such as organic
materials, bacteria, algae, clay, mud, lime or rust is carried in the water and
has a bearing on the number of pathogens in the water and on how easy it is
to disinfect water to kill off pathogens. Whilst there is not an exact correlation
between turbidity and suspended solids, it is easier to measure turbidity
using the turbidity tube.
pH ( acidity / alkalinity )
Usually between 5.5 and 9, readings outside this range may indicate
pollution by strongly acidic or alkaliner waste water with pH below 5 could
constitute a health risk due to solubilisation of toxic heavy metal if they are
present and it could be corrosive.
Chlorination is much less effective in water at a pH above 8. However, WHO
guideline value of pH is 6.5 - 8.5.
The pH value is important as it alters the effectiveness of two of the chemicals
commonly used in water treatment. Chlorination is considerably slowed
down when the pH value is higher (>8), and either contact time or initial dose
needs to be increased. The effectiveness of aluminium sulphate, commonly
used as a coagulant, is severely effected by low or high pH ( with a range of
about pH 6.5 - 7.5 being optimum )

3. Chemical Characteristics:
Alkalinity, Acidity, Hardness, Biological oxygen demand (BOD), Chemical oxygen
demand (COD), Amonia, Nitrate and Nitrate Nitrogen, Total Dissolved Solids
(TDS), and the ionic contents of Calcium, Megnesium, Sodium, Pottassium, Iron,
Chlorides, Sulphates, Carbonates, Bi carbonates, Flourides.
Bacteriological Characteristics:
Bacteriological count of total and faecal coliforms; (pathogenic bacteria)
Water disinfection:
The best way to prevent contamination of drinking water is to protect the storage
and distribution of the water as well as only using protected water sources although
sometimes these systems break down and therefore the quickest way to deal with
potential problems of contamination and prevent ill health in the consumers of this
water is to disinfect the water.
Chlorine is the most widely used chemical for drinking water disinfection for
several reasons:
1. It is readily available
2. It is relatively easy to use
3. It is cheap
4. It is effective for the majority of bacteria, viruses and parasites found in
drinking water
5. It has the ability to continue disinfecting after initial treatment if there
is a sufficient level of free residual chlorine available.
Chlorine does not kill all protozoa cysts or helminths eggs or larvae (parasites), it
can be a dangerous chemical if safety precautions are not adhered to and finally
disinfection with chlorine is dependant on the pH, water temperature and
turbidity of the water being disinfected.
The World Health Organisation have produced tables of guideline levels for various
organisms and chemicals in Drinking Water that are acceptable for maintaining the
health, or more importantly for preventing ill health, of the individuals consuming
water. See below guideline levels (Table 1).

4. WHO Water Quality Guidelines Table 1:
Parameter WHO level MAL* Comment
E.coli 0 CFU <10 CFU 0 CFU is ideal but in the field this
is impossible to achieve
pH 6.5-8.5 6.5-8.5 pH 7 is ideal but in the field this
is very difficult to obtain
Turbidity <1 NTU 5 NTU The ideal level to reduce the
amount of chlorine required is 1
NTU but in the field this is very
difficult to obtain
Chlorine
(Free Residual
Chlorine)
0.2-0.5mg/L 0.2-0.5mg/L This is the level at the
distribution tap, for storage
tanks it should be around
0.8mg/L
How does Chlorine work?
The precise way in which chlorine kills pathogens is not known. It is believed that
the compounds formed when chlorine is added to water interfered with the
chemical processes which ensure the pathogens survival.
When a suitable chlorine compound is added to water only a part of it becomes
effective at killing pathogens. This part is called “Free Active” or “Active chlorine”.
AC is very good at invading the cells of pathogens. It is therefore, a very efficient
killer of pathogens. As a result, only small amounts of chlorine are required to
disinfected polluted water.
What affects Chlorine’s Efficiency?
After it has been added the active chlorine needs a certain amount of time to kill the
pathogens in the water. This is called the “contact time” . How much contact time is
required for the active chlorine to be fully effective depends upon many factors.
However, the most important are pH and water temperature.
Most raw water sources have a pH value within the range 6.5 - 8. As pH level rise
the disinfecting properties of chlorine start to become weaker and at pH 9 there is
very little disinfecting power. WHO guideline recommended drinking water be in
the range pH 6.5 - 8.5 and so pH can have a significant influence on the performance
of chlorine in water we are likely to be working with for drinking water supplies.
The temperature of the water to be disinfected can have a significant effect on
chlorine efficiency. The time needed for disinfection becomes longer as the
temperature of the water gets lower. There is a noticeable difference in the kill rate
of bacteria between 2 and 20º C.

5. If the water to be disinfected has a lot of suspended solids and / or organic matter
in it ( i.e. is highly turbid ), it will have a high chlorine demand. It is therefore,
desirable to clean the water as much as possible before the chlorination process
begins. This will significantly reduce the amount of chlorine needed and improve
it’s efficiency as a disinfectant.
If iron and manganese are present in the water to be disinfected a substantial
amount of chlorine may combine with them to form compounds which are insoluble
in water. It is therefore, beneficial to remove the iron and manganese. This may not
always be possible although simple aeration systems may be appropriate. It is
important that the person responsible for disinfection is aware of the influence the
presence of these metals can have on chlorine demand.
How long does it take to kill the pathogens?
The disinfecting effect of chlorine in not instantaneous. The amount of pathogens
killed is dependent upon the “contact time” between the chlorine and the
pathogens. For our purpose, a minimum contact time of 30 minutes is essential.
However, when considering this, account must be taken of the pH, temperature and
turbidity of the water.
For an example - a turbide water with a pH 7.5 - 8 and a temperature of 10º C will
require a longer contact time than a clear water ( 0 - <5 turbidity) with pH 6.5 - 7
and a temperature of 20º C.
“MINIMUM CONTACT TIME MUST ALWAYS BE 30 MINUTES.”
How to measure and monitor the Free Residual Chlorine Levels in
water
The simplest way of monitoring the effectiveness of chlorination of drinking water
is to measure the Free Residual Chlorine levels. The presence of the FRC in water,
after the most appropriate contact time, proves that sufficient chlorine has been
added to oxidise all the organic matter therefore leaving excess chlorine available to
deal with possible re-contamination.
The measurement of the FRC in water is easily done by using a “Pooltester” or
Lovibond comparator. The following procedures should be followed:
1. Rinse the Pooltester 3 times with the water to be tested
2. Refill the 3 (sometimes only 2) compartments completely with the test water
3. Put 1 phenol red tablet in the appropriate compartment (measures pH)
4. Put 1 DPD No1 tablet in the appropriate compartment (measures FRC)
5. Replace the lid correctly
6. Shake the pooltester to ensure that the tablets are completely dissolved
(approx 20 seconds)

6. 7. Read the results by comparing the colour intensity in the test compartments
to the reference colours to get the results.
Important Notes:
- Never touch the tablets with your fingers as this could affect the results
- The DPD tablets MUST be No1
- Read the results within 60 seconds of the tablets being dissolved to ensure
reliable results
- The pH need not be measured every time. It is used to determine the amount
of chlorine product to add to the water initially or when the source of the water is
changed.
How to Chlorinate Water
The most important factor in chlorination is determining the concentration of
chlorine that is required by the water to give an end result of FRC between 0.2-
0.5mg/L at the final delivery point. This is known as the Chlorine demand of the
water. In order to obtain this it is necessary to obtain a FRC in the storage or holding
tank of approximately 0.8mg/L. This may mean that as much as 2-3mg/L of
chlorine is added initially to the storage tanks. Before testing the FRC levels it is
important to remember that contact time is required
The main method of determining the chlorine demand of the water is as follows:
1. Prepare a 1% Stock Solution of chlorine – see table 3 below
2. Fill 5 non-metal buckets with 20L of water to be treated each
3. Add an increasing volume of 1% stock solution of chlorine to each bucket e.g.
1st Bucket: 1ml of 1% Stock solution
2nd Bucket: 1.5ml of 1% Stock solution
3rd Bucket: 2ml of 1% Stock solution
4th Bucket: 2.5ml of 1% Stock solution
5th Bucket: 3ml of 1% Stock solution
4. Wait a minimum of 30 minutes contact time
5. Measure the levels of Free Residual Chlorine in each bucket
6. Choose the bucket which gives approximately 0.8mg/L FRC
7. Use this result to calculate the amount of 1% stock solution to add to the total
volume of water in the storage or holding tank.
8. Pour in the required volume of chlorine into the tank, mix well then wait 30
minutes contact time
9. Recheck the FRC level at the distribution point once the water has had a
chance to circulate the system then readjust if required
10. Always recheck the chlorine demand periodically and when the water source
is changed or known to vary. This will ensure that the FRC level is maintained.
***

7. WORKED EXAMPLE OF CHLORINE DEMAND OF WATER
e.g. chlorination of water in a 2,000L storage tank
Follow steps 1-5. The FRC levels of the water in the individual buckets after 30
minutes contact time were as follows:
1st Bucket: 1ml of 1% Stock solution = 0mg/L
2nd Bucket: 1.5ml of 1% Stock solution = 0.1 mg/L
3rd Bucket: 2ml of 1% Stock solution = 0.4 mg/L
4th Bucket: 2.5ml of 1% Stock solution = 0.8 mg/L
5th Bucket: 3ml of 1% Stock solution = 1mg/L
The dosing rate therefore will be that for bucket 4 (2.5ml of 1% Stock solution in
20L= 0.8 mg/L) So if 2.5ml of 1% stock solution added to 20L of water gives
0.8mg/L FRC then you need 100 times the amount of stock solution to correctly dose
the 2,000L storage tank.
2,000L storage tank
20L bucket volume
 100
so, 100 x 2.5ml 1% Stock solution
=> 250ml 1% Stock solution needs to be added to the 2,000L storage tank to give
0.8mg/L