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Title / 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.
Classification / Water Industry > Water Treatment
Available grade / Achieved
Explanatory 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.
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.
Outcomes and evidence requirements
Outcome 1
Describe hardness, pH, and alkalinity of water.
Evidence requirements
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 inter-relationships.
1.3 The characteristics of water are described in terms of hardness, pH, and alkalinity.
Outcome 2
Describe the factors that influence hardness, pH, and alkalinity of water undergoing treatment.
Evidence requirements
2.1 Chemicals present in untreated water are described in terms of their impact on water hardness, pH, and alkalinity.
Range includes but is not limited to – carbon dioxide, carbonate, bicarbonate, sulphates, chlorides, natural organic matter.
2.2 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.
Outcome 3
Describe the reasons for pH and alkalinity control as used in water treatment.
Evidence requirements
3.1 pH and alkalinity are described in terms of their effect on treatment processes and control, and the reasons for their variations.
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.
Outcome 4
Describe the processes used in water treatment to control pH and alkalinity.
Evidence requirements
4.1 Chemicals, pH and alkalinity, and related components are described in terms of adjustment techniques.
Range 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.
4.2 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.
Outcome 5
Describe the storage, handling, and preparation of chemicals, and chemical dosing systems used in pH and alkalinity control.
Evidence requirements
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.
Replacement information / This unit standard and unit standard 24956 were replaced by unit standard 29990.This unit standard is expiring. Assessment against the standard must take place by the last date for assessment set out below.
Status information and last date for assessment for superseded versions
Process / Version / Date / Last Date for Assessment /Registration / 1 / 19 September 2008 / 31 December 2018
Review / 2 / 16 March 2017 / 31 December 2018
Consent and Moderation Requirements (CMR) reference / 0101
This CMR can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
Please note
Providers must be granted consent to assess against standards (accredited) by NZQA, before they can report credits from assessment against unit standards or deliver courses of study leading to that assessment.
Industry Training Organisations must be granted consent to assess against standards by NZQA before they can register credits from assessment against unit standards.
Providers and Industry Training Organisations, which have been granted consent and which are assessing against unit standards must engage with the moderation system that applies to those standards.
Requirements for consent to assess and an outline of the moderation system that applies to this standard are outlined in the Consent and Moderation Requirements (CMR). The CMR 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.
Infrastructure ITOSSB Code 101813 / Ó New Zealand Qualifications Authority 2017 / / New Zealand Qualifications Aut