18449 version 3
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Level 5
Credits 4
Purpose People credited with this unit standard are able to describe: the purpose and effectiveness of separation processes used in water treatment; gravity settlers, and ways of optimising the performance of gravity settlers used in water treatment; buoyant media clarifiers, and air-based flotation systems; and identify critical points, hazards, preventive actions, and corrective actions of processes and systems.
Subfield Water Industry
Domain
Status
Status date
Date version published
Drinking-Water
Registered
19 September 2008
19 September 2008
Planned review date
Entry information
31 December 2013
Open.
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 Reference
Drinking-Water Standards for New Zealand,
2005.
Ministry of Health, Wellington, 2000 and
2 Definitions
Critical points
– points in a process or in equipment where failure to function correctly can lead to a public health hazard.
Separation processes include both settlement and flotation.
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New Zealand Qualifications Authority 2020

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Organisational procedures – instructions to staff, and procedures which are documented in memo or manual format and are available in the workplace. These requirements include but are not limited to – site specific requirements, manufacturers’ specifications, product quality specifications, and legislative or regulatory requirements.
Element 1
Describe the purpose and effectiveness of separation processes used in water treatment.
Performance criteria
1.1 The reasons for, and methods of, separation processes are described in terms of reduced particulate loading.
Range reasons include but are not limited to – contaminant removal, methods include but are not limited to – re-suspension, rise rates, settlement rates, overflow rates.
1.2 The types of suspensions suitable for separation are described in terms of the impact of settling rates.
Range includes but is not limited to – floc suspensions, turbid suspensions, air attachment.
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, settlement rate, compression, particle size ranges, viscosity and temperature effects.
Element 2
Describe gravity settlers, and ways of optimising the performance of gravity settlers used in water treatment.
Performance criteria
2.1 Gravity settlers used in water treatment are described in terms of their flow paths and operation.
Range circular and rectangular horizontal clarifiers, centrifloc clarifiers, upflow clarifiers, floc blankets, overflow weirs and launders, accelator pulsed clarifier, gravi-lectric cones; tube settlers, plate separators.
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2.2 Gravity settlers are described in terms of their performance factors.
Range includes but is not limited to – flow distribution, retention time, suspended solids loading, temperature, light, wind, short-circuiting, floc size, sun-floc, turbidity.
2.3 Improvements to sludge collection from gravity settlers are described in terms of minimising water losses.
Range includes but is not limited to – sludge cone weight, time, variable time, effluent turbidity.
Element 3
Describe buoyant media clarifiers, and air-based flotation systems.
Performance criteria
3.1 Buoyant media clarifiers are described in terms of their principles of operation.
Range includes but is not limited to
– inflow, outflow, solids removal, settlement, headloss, media flotation.
3.2 Air-based flotation systems are described in terms of their principles of operation.
Range includes but is not limited to – air bubble attachment, particle rise rates, flow distribution, loading rates, float removal.
Element 4
Identify critical points, hazards, preventive actions, and corrective actions of processes and systems.
Range gravity separation process, gravity settlers, buoyant media clarifiers, air-based flotation systems.
Performance criteria
4.1 The critical points in processes and systems are identified in accordance with organisational procedures.
4.2 The hazards at each critical point are identified in terms of the causes of the events leading to their appearance, and the risk factors.
4.3 The preventive and corrective actions for events related to each hazard are identified.
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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.
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New Zealand Qualifications Authority 2020