24904 version 1
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Describe process control, P and I drawings, and SCADA, for a water or
wastewater treatment plant
Level
5
Credits
5
Purpose
People credited with this unit standard are able to: describe the factors that
impact on a process, and process control system variables; describe the
specifications and calibration of the constituent parts of process control;
describe the differences between process control methods; describe the
operational sequence of information contained in piping and instrumentation
(P and I) drawings; describe the legislative requirements for reports that are
produced by Supervisory Control and Data Acquisition (SCADA); and identify
critical points of automated process control equipment, and identify hazards,
preventive actions, and corrective actions, for a water or wastewater
treatment plant.
Subfield
Water Industry
Domain
Water - Generic
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 and unit standard 24913 replaced unit
standard 17872, and unit standard 17873.
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.
 New Zealand Qualifications Authority 2016
24904 version 1
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Special notes
1
References
Legislation relevant to this unit standard includes but is not limited to the Resource
Management Act 1991.
Drinking-water standards for New Zealand, Ministry of Health, Wellington, 2000 and
2005.
2
Definitions
Critical points – points in a process or in equipment where failure to function correctly
can lead to a public health hazard.
Wastewater includes stormwater and sewage systems.
Elements and performance criteria
Element 1
Describe the factors that impact on processes, and process control system variables for a
water or wastewater treatment plant.
Performance criteria
1.1
The factors that impact on processes are described for a water or wastewater
treatment plant.
Range
1.2
two of – dead-band, process delays, external influences,
instrument calibration, power surges; upstream process – precoagulation, pH control, streaming current detectors for
coagulation control.
Process control is described in terms of the variables associated with the
process.
Range
process variable, set point, manipulated variable, output, process
control times, dead band, disturbances, striction.
Element 2
Describe the specifications and calibration of the constituent parts of process control for a
water or wastewater treatment plant.
Performance criteria
2.1
The constituent parts of water or wastewater treatment plant process control are
described in terms of their specifications.
Range
constituent parts – digital sensors, analog sensors.
 New Zealand Qualifications Authority 2016
24904 version 1
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2.2
The constituent parts of water or wastewater treatment plant process control are
described in terms of the methods and standards for calibration in order to
comply with legislation.
Range
constituent parts – dedicated PLCs, actuators, signal process;
evidence is required for at least two;
standards and legislation – Drinking-Water Standards 2000 and
2005, Resource Management Act 1991;
evidence is required for at least one.
Element 3
Describe the differences between process control methods for a water or wastewater
treatment plant.
Range
one-off, proportional (P), integral (I), derivative (D), compound (PID).
Performance criteria
3.1
Process control methods are described in terms of their methods of operation
and effects on the treatment plant.
3.2
Process control methods are described in terms of their differences.
Element 4
Describe the operational sequence of information contained in P and I drawings for a
water or wastewater treatment plant.
Performance criteria
4.1
P and I drawings are described in terms of their operational sequence.
Range
instrumentation symbols, process lines; electrical, pneumatic,
hydraulic, data lines, tags, interconnection references, symbol
standards, critical points, fail-safe measures, interlocks, alarms.
Element 5
Describe the legislative requirements for reports that are produced by SCADA for a water
or wastewater treatment plant.
Performance criteria
5.1
SCADA is described in terms of the legislative requirements for reports that are
produced.
Range
one of – Drinking-Water Standards 2000 and 2005, Resource
Management Act 1991.
 New Zealand Qualifications Authority 2016
24904 version 1
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Element 6
Identify critical points of automated process control equipment, hazards, and preventive
and corrective actions, for a water or wastewater treatment plant.
Performance criteria
6.1
The critical points in automated process control are identified.
6.2
The hazards, the causes of the events leading to their appearance, and the
factors that affect risk are identified at each critical point.
6.3
The preventive and corrective actions for events related to each hazard 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.
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