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Describe wastewater activated sludge treatment processes, and critical
points
Level
5
Credits
10
Purpose
People credited with this unit standard are able to: describe the type and
design; describe the microbiology; describe and interpret tests; describe
performance optimising; and identify critical points, adverse effects,
preventive actions, and corrective actions, of activated sludge processes.
Subfield
Water Industry
Domain
Wastewater 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 19181.
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
Definitions
Optimising – adjusting plant input variables to make the process as effective as possible to
achieve the desired output, taking into account the constraints of cost, human input,
effluent quality, and resource consent requirements.
Critical points – points in a process or in equipment where failure to function correctly can
lead to a public health hazard adverse effects which may affect the treatment process or
other processes in the treatment plant.
 New Zealand Qualifications Authority 2016
24934 version 1
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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.
Wastewater includes stormwater and sewage systems.
In the context of this unit standard, activated sludge treatment includes the separation
process.
Elements and performance criteria
Element 1
Describe the type and design of activated sludge processes.
Performance criteria
1.1
Activated sludge processes are described in terms of their type and design.
Range
1.2
The recycling of solids is described in terms of solids concentrations.
Range
1.3
conventional activated sludge, extended aeration, biological
nutrient removal.
mixed liquor suspended solids, the return of activated sludge,
sludge volume index, sludge age during the process.
The introduction of dissolved oxygen into the process is described in terms of
process operation.
Range
process types – surface aeration, diffused aeration.
Element 2
Describe the microbiology of activated sludge processes.
Range
loading rates, sludge volume index.
Performance criteria
2.1
The micro-organisms in activated sludge wastewater treatment are identified
and described in terms of their functions and effects.
Range
2.2
functions – sludge bulking, burnout, filamentous bacteria,
biological and physical processes;
food to micro-organism ratio.
Microbiological activity which affects process parameters is described.
Range
oxidation, sludge volume and density indices, sludge age, enzyme
addition, pH effects.
 New Zealand Qualifications Authority 2016
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Element 3
Describe and interpret tests of activated sludge processes.
Performance criteria
3.1
Activated sludge processes are described in terms of the timing and types of
tests to be undertaken.
Range
3.2
tests include but are not limited to – pH, suspended solids,
phosphorus, nitrogen, Biochemical Oxygen Demand (BOD),
temperature, dissolved oxygen, microscopic evaluation, mixed
liquor, sludge volume index, settleability.
Test results are interpreted in relation to process variations.
Range
loading, time, environmental manipulation.
Element 4
Describe performance optimising of activated sludge processes.
Performance criteria
4.1
Results of monitoring are described in terms of the adjustments that may be
carried out.
Element 5
Identify critical points of activated sludge processes, adverse effects, preventive actions,
and corrective actions.
Performance criteria
5.1
The critical points in activated sludge processes are identified in accordance
with organisational procedures.
5.2
The adverse effects at each critical point are identified in terms of the causes or
the events leading to their occurrence.
5.3
The preventive and corrective actions for problems or events related to each
adverse effect are identified.
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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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