To highlight the continuing need to ensure that the integrity of
data quality obtained for the purpose of establishing and
publishing meaningful information for investment purposes,
performance assessment and beneficial changes to the environment
and public health is fit for purpose.
When reporting upon the quality and sufficiency of potable water
supplies, associated discharges to the aquatic environment, the
disposal of wastes arising from the production of drinking water,
the collection and treatment of domestic sewage (including trade
waste discharges), water used for a variety of industrial and food
product purposes, data must be of the requisite standard to
• corporate and executive management of associated
• water industry, food and environmental regulators
• customers, and
• relevant stakeholders, particularly those responsible for
public health and future investment planning.
The correct use of such data, taking full account of the
specific purpose for which the data was originally obtained is of
critical importance. Although most comments derive from
laboratory testing and water quality, they are equally applicable
to measurements of flow rates and quantities. Establishing
data quality is also important when, for example, assessing general
performance levels; Health and Safety records and complaints.
CIWEM's Position on Data Quality
- A significant proportion of the data assembled by water
utilities relate to water quality. Carefully designed monitoring
programmes should be maintained to establish water quality at
appropriate critical and sequential points in:-
- the abstraction, production and distribution stages of potable
- the collection and treatment of domestic sewage, industrial and
commercial trade wastes, and their subsequent discharge to
- environmental waters that may be used for leisure,
recreational, irrigation, industrial and transportation
- Such monitoring programmes should have three fundamental but
- Regulatory - programmes to demonstrate compliance with the
conditions of potable water regulations, product quality standards,
process permits, aqua-environment standards and statutory
- Operational or process control - wide-ranging variable
programmes aimed at observing and as appropriate, facilitating
effective control of the various stages of treatment processes that
influence potable water, sewage and trade effluents product and
- Investigative - specifically designed initiatives and projects
to identify causes of ineffective or spasmodically problematic
performance levels of treatment processes, the variability of
product quality, influent and effluent quality, adverse trends in
water resources, environmental damage, customer complaints and
"incidents" concerning public health.
- The objective of the monitoring programme must influence the
selection of both the frequency and location of sample collection
including the secure and recorded delivery of samples to receiving
laboratories. This is also of critical importance in choosing
either manual or automatic sampling methods - particularly with
regard to the latter when due consideration must be given to
utilising time; volume; or flow -proportional collection
methodology. Details of sample collection must be included in
the purpose codes that identify each sample with the result(s)
obtained from its subsequent examination or analysis.
- The variable(s) of interest or concern must be clearly defined,
to subsequently establish the analytical methodology that will
yield meaningful data. This may need full discussion between those
responsible for implementing the monitoring programme and the
provision of analytical services - particularly when the latter are
procured externally. Likewise, distinctions between dissolved
and "particulate" forms of relevant determinands must be delineated
- The choice of analytical methodology must reflect the
anticipated ranges of concentrations of determinands that are
likely to be encountered.
- The analytical methodology used by laboratories to determine
product, effluent and general water quality, must be fully
described in the Quality Control Manual that is specific to
individual laboratories. Details should be provided of:
- the principles and performance characteristics of each
analytical method used to determine chemical, microbiological,
biological, microscopic and radiological content;
- the analytical procedures;
- the reagents, apparatus and equipment;
- the collection, preservation and storage of samples;
- explanation of how the analytical result is expressed;
- An assessment of the variability of the results obtained and
published by reviewing the sources and types of errors that may
influence the said results.
The Quality Control (QC) procedures applicable to specific batches
of samples and determinants must be published in this Manual
together with any relevant published references to the protocol of
- Laboratories must have in place an Analytical Quality Control
system that is capable of determining the quality of its published
water quality and associated data. This is demonstrated by
continually monitoring the reliability of the results obtained
having regard to the use of reliable, effective equipment,
high-quality reagents and, properly trained competent
analysts. All such laboratories must have precise knowledge
of the accuracy and precision of their analytical data.
- 'Responsible' analysts must manage all fields of enumeration
that lead to the publication of water quality data.
Being appropriately qualified and able to demonstrate competencies
in the water examination techniques used, especially method
development and the ability to effectively investigate errors is
crucial to the production of reliable data. Furthermore,
laboratory personnel supervised by the 'Responsible' analyst must
be trained and experienced in the correct use of relevant
laboratory equipment, instrumentation, the application of
appropriate laboratory techniques, with proficiency in data
- Representation of accuracy, precision, repeatability and
reproducibility must remain self-evident. A well-defined Analytical
Quality Control (AQC) regime incorporating the use of suitable
control charts is essential in obtaining reliable water quality
data. The responsibility for managing the AQC programme should
ideally rest with a competent scientist who is wholly independent
of the management structure of the laboratory.
- Random audits are essential to confirm that all laboratory
generated data are recorded, with errors correctly identified (when
they occur), acknowledged and signed.
- A quality control, maintenance and calibration programme must
be implemented for process instrumentation yielding "on-line"
measurements for process control and observation purposes. Scale
length, drift and concentration spans are important aspects of the
calibration and operational control of such instrumentation to
enable the ensuing data to be meaningful. It is important to
understand the manufacturers' specifications for such
instrumentation and to fully acknowledge operating protocol for the
validity of the instrumentation to be verified, or justified, as
- It is essential that manufacturers and suppliers of analytical
and process (on-line) instrumentation be alerted to any anomalies
that may be experienced particularly if deviations from specified
operating characteristics are observed.
- The comparison of data sets derived from different analytical
techniques requires care and attention. It should not be
assumed that new analytical methodology will display lower or less
errors than well used and practised "traditional" methods.
The newer methods may be preferred on the basis of ease of
automation, speed, cost and possibly, lower limits of
- Data assembled for purposes other than water quality must also
be subject to critical scrutiny. Typical examples where data
are recorded for specific reasons are:
- Performance indicator systems
- Health and Safety trends and records.
All data should be confidence graded. Both the reliability of
the source and the accuracy of the data should be assessed and
specified. Whereas the accuracy accounts for uncertainty in
the acquisition or measurement of input data, the reliability will
take account of the extent to which the data sources yield
consistent, stable and uniform results, from repeated observations
or measurements made under the same conditions each time.
Document BS ISO 24510:2007 gives examples of bands of both the
accuracy and reliability of data, highlighting the ever present
need to assess data source reliability and data accuracy for each
- The forgoing paragraphs emphasise the ongoing need to use data
with care. Data produced for different purposes must not be
used indiscriminately. Purpose codes that accompany data
acquisition must be respected, otherwise misleading or erroneous
information will ensue.
The Chartered Institution of Water and Environmental Management
(CIWEM) is the leading professional body for the people who plan,
protect and care for the environment and its resources, providing
educational opportunities, independent information to the public
and advice to government. Members in 97 countries include
scientists, engineers, ecologists and students.
Note: CIWEM Policy Position Statements (PPS) represent the
Institution's views on issues at a particular point in time. It is
accepted that situations change as research provides new evidence.
It should be understood, therefore, that CIWEM PPS's are under
constant review, and that previously-held views may alter and
lead to revised PPS's.