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Describe abstraction and pre-treatment processes for potable water
Level
5
Credits
8
Purpose
People credited with this unit standard are able to describe: abstraction and
pre-treatment processes for surface water sources of potable water;
abstraction and pre-treatment processes for groundwater sources of potable
water; and processes affecting water quality, and management techniques
for raw water reservoirs; and identify critical points, hazards, preventive
actions, and corrective actions of processes and management points.
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 and unit standard 24897 replaced unit
standard 18448.
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
References
Legislation relevant to this unit standard includes but is not limited to the Health Act
1956, and Resource Management Act 1991.
Ministry of Health Public Health Risk Management Plan Guides for Drinking-Water
Supplies (PHRMPGs):
S1.1, Surface and groundwater sources;
S2, Development of new supplies;
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24898 version 1
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P11, Surface water abstraction – rivers, streams and infiltration galleries;
P4.2, Destratification.
Drinking-Water Standards for New Zealand 2000 and 2005, Ministry of Health,
Wellington.
Guidelines for Drinking-Water Quality Management for New Zealand, Ministry of
Health, Wellington, 2000, Chapter 3.4.2.
Proposed/National Environmental Standard for Human Drinking-water Sources,
Ministry for the Environment, available from http://www.mfe.govt.nz.
2
Definitions
Water quality – the suitability of water for use as drinking-water, with or without water
treatment.
Critical points – points in a process or in equipment where failure to function correctly
can lead to a public health hazard.
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.
Elements and performance criteria
Element 1
Describe abstraction and pre-treatment processes for surface water sources of potable
water.
Performance criteria
1.1
Design features of hardware for surface water abstractions are described in
terms of their function.
Range
1.2
Pre-treatment processes are described in terms of their purpose in relation to
raw water quality, and the effects they may have on water quality.
Range
1.3
six design features from – river intake types, weirs, pumps and wet
wells, mechanical and fixed screens, infiltration galleries, rough
filtration, intake towers, spillways, spring head, fish passes, raw
water pipelines.
raw water quality variations, aeration, consent limits, flow control;
control of – pathogens, pollutants, suspended matter, turbidity,
algae, taste and odour, aeration, iron and manganese.
Roof water is described in terms of the factors which cause contamination, and
control measures.
Range
includes but is not limited to – possums, birds, lead flashing, gutter
debris, spray drift;
control measures include but are not limited to – first flush
diverters, tank design.
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Element 2
Describe abstraction and pre-treatment processes for groundwater sources of potable
water.
Performance criteria
2.1
The construction of a well is described in terms of physical structures, their
placement for effectiveness, and processes.
Range
2.2
Groundwater aeration for pH, carbon dioxide, manganese, iron, and ammonia is
described in terms of process efficiency and plant operations.
Range
2.3
physical structures – screen types, pump, power cables, pipework,
check valves;
processes – developing, drawdown.
aerators – cascade, spray;
process efficiency – head losses, equipment footprints.
Groundwater chemical treatment for pH, carbon dioxide, manganese, iron, and
ammonia is described in terms of process chemistry, and plant operations.
Range
process chemistry – oxidation, alkali addition;
plant operation – dosing systems.
Element 3
Describe processes affecting water quality, and management techniques for raw water
reservoirs.
Performance criteria
3.1
The changes in water quality due to raw water storage in reservoirs are
identified in terms of features, physical, chemical, and micro-biological
parameters.
Range
includes but is not limited to –
features – water movement, turnover;
control – turbidity reduction, mixing, inflow dilution, depth
selection, multiple depth take-offs, multiple take-offs, ‘point’ and
linear aerators, circulation, retention time, chemical dosing and
mixing;
physical parameters – stratification, temperature, sunlight, tastes,
odours;
chemical parameters – nutrients, algal and cyanobacterial growth,
tastes, odours, toxicity;
microbiological parameters – cyanobacterial growth, tastes,
odours.
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3.2
Assessment of the effectiveness of raw water reservoir management tools
determines their effectiveness in controlling deterioration of raw water, and
corresponding improvement processes required.
Range
tools include but are not limited to – multiple outlets, multidepth
outlets, point source aeration, linear aerators, monitoring;
deterioration processes – thermocline formation, formation of an
anoxic hypolimnion and buildup of dissolved manganese, algal
and cyanobacterial blooms;
improvement processes – sedimentation, oxidation, ultraviolet
irradiation, circulation, aeration, dilution;
control – turbidity reduction, mixing, inflow dilution, depth
selection, multiple depth take-offs, multiple take-offs, ‘point’ and
linear aerators, circulation, retention time, chemical dosing and
mixing.
Element 4
Identify critical points, hazards, preventive actions, and corrective actions of processes
and management points.
Range
groundwater management and abstraction processes, surface raw water
management and abstraction processes.
Performance criteria
4.1
The critical points of processes and management points 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.
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.
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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