24964 version 1
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Demonstrate knowledge of hardness, pH, and alkalinity control
processes in water treatment
Level
4
Credits
8
Purpose
People credited with this unit standard are able to describe: hardness, pH,
and alkalinity of water; the factors that influence hardness, pH, and alkalinity
of water undergoing treatment; the reasons for pH and alkalinity control as
used in water treatment; the processes used in water treatment to control pH
and alkalinity; and the storage, handling, and preparation of chemicals, and
chemical dosing systems used in pH and alkalinity control.
Subfield
Water Industry
Domain
Water Treatment
Status
Registered
Status date
19 September 2008
Date version published
19 September 2008
Planned review date
31 December 2013
Entry information
Open.
Replacement information
This unit standard replaced unit standard 17898.
Accreditation
Evaluation of documentation and visit by NZQA, industry
and teaching professional in the same field from another
provider.
Standard setting body (SSB)
Primary Industry Training Organisation
Accreditation and Moderation Action Plan (AMAP) reference
0179
This AMAP can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Special notes
1
References
Legislation relevant to this unit standard includes but is not limited to the Hazardous
Substances and New Organisms (HSNO) Act 1996.
Drinking-Water Standards for New Zealand, Ministry of Health, Wellington, 2000 and
2005.
 New Zealand Qualifications Authority 2016
24964 version 1
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Standard Methods for the Examination of Water and Wastewater, prepared jointly by
American Public Health Association (APHA), American Water Works Assocation
(AWWA), Water Environmental Federation (WEF) (Washington: American Public
Health Association, 1998). ISBN 0-87553-235-7.
2
A person is required to have approved handler certification if handling substances
being transferred under the HSNO Act 1996. Information on approved handler
procedures can be obtained from http://www.erma.govt.nz.
Elements and performance criteria
Element 1
Describe hardness, pH, and alkalinity of water.
Performance criteria
1.1
Hardness, pH, and alkalinity are described in terms of their differences.
1.2
Hardness, pH, and alkalinity of water are described in terms of their interrelationships.
1.3
The characteristics of water are described in terms of hardness, pH, and
alkalinity.
Element 2
Describe the factors that influence hardness, pH, and alkalinity of water undergoing
treatment.
Performance criteria
2.1
Chemicals present in untreated water are described in terms of their impact on
water hardness, pH, and alkalinity.
Range
2.2
includes but is not limited to – carbon dioxide, carbonate,
bicarbonate, sulphates, chlorides, natural organic matter.
Standard water treatment chemicals are described in terms of their effect on pH
and alkalinity.
Range
includes but is not limited to – alum, hydrated lime, soda ash,
caustic soda, carbon dioxide, sulphuric acid.
Element 3
Describe the reasons for pH and alkalinity control as used in water treatment.
Performance criteria
3.1
pH and alkalinity are described in terms of their effect on treatment processes
and control, and the reasons for their variations.
 New Zealand Qualifications Authority 2016
24964 version 1
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3.2
The pH range of drinking water is identified and described in accordance with
the Drinking-Water Standards for New Zealand.
3.3
pH value and disinfection efficiency are described in terms of the relative impact
of pH on chlorination, ozonation, and ultra-violet methods.
3.4
pH and alkalinity in the water distribution system are described in terms of the
measurement of their effects.
Range
effects include but are not limited to – elevated heavy metal
content, asbestos cement deterioration, scale formation, concrete
lining deterioration, staining and dirty water, tuberculation, pitting,
corrosion;
measurement methods include but are not limited to – Langelier
Stability Index (LSI), plumbosolvency.
Element 4
Describe the processes used in water treatment to control pH and alkalinity.
Performance criteria
4.1
Chemicals, pH and alkalinity, and related components are described in terms of
adjustment techniques.
Range
4.2
includes but is not limited to – aeration, alkali addition, acid
addition, CO² addition;
components include but are not limited to – dry powder feeders,
mixing tanks, dosing pumps, carry water, solution strength.
pH control methods used in water treatment are described in terms of chemical
dosing.
Range
control methods – pH measurement, calibration, feedback control
loops.
4.3
pH, hardness, and alkalinity are determined using laboratory techniques in
accordance with Standard Methods for the Examination of Water and
Wastewater.
4.4
The components involved with pH and alkalinity control are described in terms
of their limitations.
Range
components include but are not limited to – dry powder feeders,
mixing tanks, dosing pumps;
limitations include but are not limited to – safety, line cleaning,
flushing.
 New Zealand Qualifications Authority 2016
24964 version 1
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Element 5
Describe the storage, handling, and preparation of chemicals, and chemical dosing
systems used in pH and alkalinity control.
Performance criteria
5.1
The storage, handling, and preparation of chemicals used in pH and alkalinity
control are described in terms of the Health and Safety in Employment Act
1992, and HSNO Act 1996 and regulations.
5.2
Chemical dosing systems used in pH and alkalinity control processes are
described in terms of the components, methods, and points of application.
Range
components – chemical pipework, dosing pumps, speed control,
stroke control, flow rate, tank of dilutant, instrumentation for
automatic control.
Please note
Providers must be accredited by NZQA, or an inter-institutional body with delegated
authority for quality assurance, before they can report credits from assessment against
unit standards or deliver courses of study leading to that assessment.
Industry Training Organisations must be accredited by NZQA before they can register
credits from assessment against unit standards.
Accredited providers and Industry Training Organisations assessing against unit standards
must engage with the moderation system that applies to those standards.
Accreditation requirements and an outline of the moderation system that applies to this
standard are outlined in the Accreditation and Moderation Action Plan (AMAP). The
AMAP also includes useful information about special requirements for organisations
wishing to develop education and training programmes, such as minimum qualifications for
tutors and assessors, and special resource requirements.
Comments on this unit standard
Please contact the Primary Industry Training Organisation standards@primaryito.ac.nz if
you wish to suggest changes to the content of this unit standard.
 New Zealand Qualifications Authority 2016