17895 version 2
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Level 3
Credits 5
Purpose People credited with this unit standard are able to demonstrate knowledge of: the purposes and principles of separation processes; gravity settlers; buoyant media clarifiers; and air-based flotation systems, in water treatment.
Subfield Water Industry
Domain
Status
Status date
Date version published
Water Treatment
Registered
19 September 2008
19 September 2008
Planned review date
Entry information
31 December 2013
Open.
Accreditation Evaluation of documentation by NZQA and industry.
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
None.
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New Zealand Qualifications Authority 2020

17895 version 2
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Element 1
Demonstrate knowledge of the purposes and principles of separation processes in water treatment.
Range separation processes – air-based flotation, gravity settler, buoyancy media clarifier.
Performance criteria
1.1 Separation processes are described in terms of settlement and flotation, and factors that affect their effectiveness.
Range factors that affect separation effectiveness include but are not limited to
– re-suspension, submerged density, buoyancy, rise rates, settlement rates, overflow rates.
1.2 Suspensions suitable for separation are described in terms of settling rates, and factors that affect suspension.
Range factors that affect suspension include but are not limited to
– floc suspensions, turbid suspensions, particle sizes, particle densities.
1.3 The effectiveness of separation processes in water treatment is described in terms of contaminant capture.
Range includes but is not limited to – unhindered settlement, laminar flow, compression, particle size ranges, floc size, viscosity and temperature effects.
Element 2
Demonstrate knowledge of gravity settlers in water treatment.
Performance criteria
2.1 Types of open and closed gravity settlers used in water treatment are described in terms of their flow paths and operation.
Range open gravity settlers – circular and rectangular horizontal clarifiers, centrifloc clarifiers, upflow clarifiers, floc blankets, sludge removal, gravi-lectric cones, super pulsator; closed gravity settlers – tube settlers, plate separators, sludge removal, super pulsator.
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New Zealand Qualifications Authority 2020

17895 version 2
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2.2 Gravity settlers are described in terms of the factors that affect their overall performance.
Range includes but is not limited to
– flow distribution, retention time, suspended solids loading, temperature, light, wind, short-circuiting, floc size, sun-floc.
Element 3
Demonstrate knowledge of buoyant media clarifiers in water treatment.
Performance criteria
3.1 Buoyant media clarifiers are described in terms of their operation.
Range includes but is not limited to – inflow, outflow, filtration, settlement, headloss, media flotation.
3.2 Buoyant media clarifiers are described in terms of the factors that affect their performance.
Element 4
Range includes but is not limited to – screen integrity, floc removal.
Demonstrate knowledge of air-based flotation systems in water treatment.
Performance criteria
4.1 Air-based flotation systems are described in terms of their flow path and operation.
Range bubble size, dissolved air, carry water, saturation vessel, air nozzles.
4.2 Air-based flotation systems are described in terms of the factors that affect their performance.
Range includes but is not limited to – air bubble attachment, particle rise rates, flow distribution, loading rates, float removal.
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.
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New Zealand Qualifications Authority 2020

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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.
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New Zealand Qualifications Authority 2020