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Assess the optimisation of a drinking-water treatment plant
Level
6
Credits
12
Purpose
People credited with this unit standard are able to: assess the raw water
source of a drinking-water treatment plant; describe the overall operation of a
drinking-water treatment plant; describe how processes in the plant interact;
and assess plant processes and responses to determine drinking-water
treatment plant optimisation.
Subfield
Water Industry
Domain
Drinking-Water
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 18457.
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
Definitions
Drinking-water supply – the supply catchment, treatment plant, and distribution. The
drinking-water supplier has responsibility for managing the public health risks of the
drinking-water supply.
On site – on the site of a full scale operating drinking-water treatment plant.
Optimisation – adjusting plant input variables to make the process as effective as
possible in order to achieve the desired output, taking into account the constraints of
cost, human input, water quality, and water demand.
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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.
2
Assessment
The treatment plant used to demonstrate competence for this unit standard must
include at least filtration and disinfection processes, and have a variable raw water
surface source.
This unit standard is to be assessed against on site. It is accepted that the range of
raw water conditions set out in elements one and two are unlikely to occur at the time
of the assessment which will thus need to be by way of explanation rather than actual
demonstration.
Elements and performance criteria
Element 1
Assess the raw water source of a drinking-water treatment plant.
Performance criteria
1.1
The range in raw water quality is described on site in terms of source type,
climate, topography, catchment land use and geology, seasonal variations, and
human activity.
1.2
Assessment of the treatment options appropriate to the characteristics of a
given raw water supply identifies water quality and flow.
Range
1.3
includes but not limited to – variations in amount and type of
turbidity, organic loading, temperature, alkalinity, contaminants.
The rate of change of key variables is described relative to the ability of the
treatment system to adjust.
Range
one of – turbidity or colour versus coagulant dosing; filter loading
versus backwash initiation, chlorine demand versus dosing.
Element 2
Describe the overall operation of a drinking-water treatment plant.
Performance criteria
2.1
The water flow paths through a water treatment plant are physically identified on
site.
Range
inflow, outflow, storage, flow distribution in tanks.
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2.2
The flow control elements are identified and explained on site.
Range
2.3
The individual plant process sections are identified and described in terms of
their functions.
Range
2.4
controls – chemical pipework, dosing pumps, speed control, stroke
control, flow rate, calibration tests, tank dilution, instrumentation
for automatic control.
Description of final water quality monitoring and plant automatic controls
adjustment is in accordance with organisational procedures.
Range
2.6
process objective, inflows, outflows, physical identification, water
quality changes.
Chemical dosing systems components are identified on site in terms of the
controls of each chemical dosing system.
Range
2.5
includes but is not limited to – float switches, level measurements,
pump runs, pressure switches, valves, flow meters.
includes but is not limited to – level and dose settings, instrument
calibration.
Manual control or intervention controls that are carried out are described in
accordance with organisational procedures.
Range
may include but is not limited to – alarm response, manual pump
control, valve operation, filter backwash operation, sludge transfer.
Element 3
Describe how processes in the plant interact.
Performance criteria
3.1
Plant flow rate is assessed in terms of its interaction with other plant processes.
3.2
The relationship and interaction between pairs of unit operations is described in
terms of the total plant performance.
Range
includes but is not limited to the relationship between –
coagulation and flocculation processes to clarifier performance;
clarifier performance to filter runtime and final turbidity; filter
performance to disinfection breakpoints and residual strength; final
turbidity to organics removal and aluminium residuals.
3.3
Plant water chemistry is assessed in terms of raw water quality variations.
3.4
Adjustment of the plant mechanical processes is assessed in response to raw
water quality variations.
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Element 4
Assess plant processes and responses to determine drinking-water treatment plant
optimisation.
Performance criteria
4.1
Plant processes are described and assessed in terms of their level of
optimisation.
Range
evidence is required for at least three plant processes.
4.2
Plant flow rate is assessed in terms of final water quality variations.
4.3
PH is assessed in terms of its effect on all plant processes.
4.4
Coagulation, flocculation, and clarification processes are assessed in terms of
their effects on final water quality, and potential problems that affect water
quality improvement.
4.5
Filtration processes are assessed in terms of their effects on final water quality,
and potential problems that affect water quality improvement.
4.6
Plant disinfection processes are assessed in terms of their effects on final water
quality, and potential problems that affect water quality improvement.
Range
4.7
one of – chlorine, ultraviolet, ozone.
The operation of the plant is assessed for level of optimisation.
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