-
Available online at www.sciencedirect.comAbstract
EMS is a tool for managing the interaction between the
organization and the environment. The aim of an EMS is to improve
the overallenvironmental performance of the organization. The
performance should be monitored through measurements, and managed
by indicators. In-dicators are variables that summarize or
otherwise simplify relevant information about the state of a
complex system. A correct evaluation ofenvironmental performance
arises from the choice of adequate raw data and from the
relationships among raw data.
This paper, after a short excursus concerning the rule of
indicators in environmental performance evaluation and the mean of
uncertainty,proposes an approach to the study and the evaluation,
through indicators and indices, of the environmental aspect
wastewater dischargesof a Local Authority who is involved in EMS
implementation. Particularly, the critical analysis of one of the
indices that has been used isreported. The role of the uncertainty
of measurements has been stressed. The results showed that
measurement uncertainty is essential foran efficient data
comparison and for a correct evaluation of environmental
performance, which, in turn, is essential to guarantee the
effectivenessof the EMS application. 2007 Elsevier Ltd. All rights
reserved.
Keywords: Environmental Management System; Environmental
performance; Indicators; ISO 14001; Uncertainty of measurements
1. Introduction
An Environmental Management System (EMS) is a part ofan
organizations management system (including all human,economical and
infrastructural assets) which aims to managethe environmental
aspects related to its activities, productsand services. Its main
and ultimate scope is to improve theenvironmental performance of
the organizations. The newISO 14001:2004 standard [1] defines the
environmentalperformance as measurable results of an
organizationsmanagement of its environmental aspects. To help
the
organizations in the process of performance measurement,
In-ternational Standard Organization (ISO) has developed
thespecific standard ISO 14031:00 [2]. Indicators are the main
toolsof this standard, and are defined as the specific expression
thatprovide information about an organizations
environmentalperformance. Their main scope is to make measurement
ofthe environmental performance easier for
organizations.Unfortunately, the measurement of environmental
perfor-mance remains one of the greatest difficulties for the
organiza-tions and for the certification/competent bodies [3e6].
Inparticular, a factor which is often neglected is the
uncertaintyEnvironmental performance, indicain EMS contex
Eleonora Perotto a,*, Roberto Canziana Technical University of
Milan, CQA, DIIAR, P
b Technical University of Milan, DIIAR, P.zac Technical
University of Milan, CQA, Department of Ene
d Technical University of Milan, TTO, P.za
Received 2 November 2006;
Available online
Journal of Cleaner Production* Corresponding author. Tel.:39 02
23996433/6522; fax:39 02 23996499.E-mail address:
[email protected] (E. Perotto).
0959-6526/$ - see front matter 2007 Elsevier Ltd. All rights
reserved.doi:10.1016/j.jclepro.2007.01.004tors and measurement
uncertaintyt: a case study
i b, Renzo Marchesi c, Paola Butelli d
.za Leonardo da Vinci 32, 20133 Milan, ItalyLeonardo da Vinci
32, 20133 Milan, Italy
rgetics, P.za Leonardo da Vinci 32, 20133 Milan, Italy
Leonardo da Vinci 32, 20133 Milan, Italy
accepted 20 January 2007
23 March 2007
16 (2008) 517e530www.elsevier.com/locate/jcleproof measurements
related to the indicators and indices. On thecontrary, the
uncertainty that affects raw data is a crucial issue,since an
indicator can yield a reliable picture of the environmen-tal
aspects or performance only if it is based on good-qualitydata
[7].
-
2. Environmental Management System
Environmental Management System (EMS) is a
problem-identification and problem-solving tool, based on the
conceptof continual improvement, that can be implemented in
anorganization in many different ways, depending on the sectorof
activity and the needs perceived by management [8]. In par-ticular,
standards for EMS have been developed by the Inter-national
Organisation for Standardisation (ISO 14001) andby the European
Commission e Eco-Management and AuditScheme (EMAS Regulation)
[9].
The standard ISO 14001:04 (and likewise the EMAS Regu-lation
761/2001) defines the EMS a part of an organizationsmanagement
system used to develop and implement its envi-ronmental policy and
manage its environmental aspects,where the environmental aspects
are element of an organiza-tions activities or products or services
that can interact with theenvironment. So, an Environmental
Management System isa method of incorporating environmental care
throughout thecorporate structure. It is a useful tool to improve
compliancewith legislation, address stakeholder pressure, improve
corpo-rate image and raise awareness of environmental issues
withinthe organization. Most EMSs are built on the Plan, Do,Check,
Act model. So, an EMS is a continual cycle of plan-ning,
implementing, reviewing and improving the processesand actions that
an organization undertakes to meet its environ-mental obligation
[10] and to permit the continuous improve-ment of the global
environmental performance. Following themodel, the organization
that will correctly have applied theprinciples of the standard will
come to be in a higher step ofthe virtual spiral in comparison to
the preceding cycle. Thestandard ISO 14001 (and likewise the EMAS
Regulation) de-velopments the path according to the phases shown in
Table 1( process approach). For more details see Refs.
[1,9,11e13].
3. Environmental performance
Many organizations are seeking ways to understand, dem-onstrate
and improve their environmental performances. An
Table 1
EMS process approach ex ISO 14001:04
Continual
improvement
Environmental
policy
Overall intentions and direction of an
organization related to its environmental
performance as formally expressed by top
management
Planning Establish the objectives and processes
necessary to deliver results in accordance
with the organizations environmental
policy
Implementation
and operation
implement the processes
Checking Monitor and measure processes against
environmental policy, objectives, targets,
legal and other requirements, and report
the results
Management Take actions to continually improve
518 E. Perotto et al. / Journal of Cleanreview performance of
the Environmental
Management Systemorganization with an EMS should assess its
environmental per-formance against its environmental policy,
objectives, targetsand other environmental performance criteria. In
fact, anEMS gives an organized and coherent scheme to properlydeal
with environmental issues in organizations, with themain purpose to
improve their environmental performances.
Many authors refer environmental performance and prob-lems
related to its evaluation (e.g. [14e19]). Therefore, in1999, ISO
published the standard ISO 14031 that gives guid-ance on the design
and use of environmental performanceevaluation within an
organization. However, this issue is stillmatter for discussion, as
reported in many papers [4e6,20,21].
Several definitions exist for the expression
environmentalperformance, e.g.:
measurable results of an organizations management of
itsenvironmental aspects (results can be measured against
theorganizations environmental policy, environmental objec-tives,
environmental targets and other environmental per-formance
requirements [1]); and
results of an organizations management of its environ-mental
aspects (results may be measured against the or-ganizations
environmental policy, objectives and targets)[2,9].
In any case, in order to evaluate the environmental perfor-mance
it is necessary to assess the environmental aspects(element of an
organizations activities or products or servicesthat can interact
with the environment [1]). Changes to the en-vironment, either
adverse or beneficial, resulting wholly orpartially from
environmental aspects, are defined as environ-mental impacts. The
relationship between environmentalaspects and impacts is one of
cause and effect.
Besides, a significant environmental aspect is an environ-mental
aspect that has or can have a significant environmentalimpact [1].
The organization shall ensure that the significantenvironmental
aspects are taken into account in establishing,implementing and
maintaining its EMS: identifying significantenvironmental aspects
and associated impacts is necessary inorder to determine whether
and where control or improvementis needed and to set priorities for
management action. In par-ticular, it is necessary to define some
significance criteria, thatshall be comprehensive, suitable for
independent checking, re-producible and verifiable, in order to
identify the significantenvironmental aspects of the organizations
activities, productsand services. The role of the significant
aspects and the relatedproblems are illustrated in the ISO
guidelines (ISO 14004:04[22]) and those of EMAS Regulation
(Recommendation 680/2001 [23] and Recommendation 532/2003 [24]) and
bysome authors (e.g. [3,25e30]).
Usually, to assist organizations in the management of
theirenvironmental significant aspects and impacts it is
necessaryto use a tool such as an environmental indicator. The rule
ofenvironmental indicators in the environmental
performanceevaluation is essential for many authors (e.g.
[16,31e35]). In-
er Production 16 (2008) 517e530dicators will support
organizations in quantifying and report-ing their environmental
performances: in fact, it is necessary
-
of the environmental performance easier for organizations. Ac-to
associate one or more indicators to each environmental as-pect.
Particularly, indicators allow to classify and summarizedata
concerning environmental aspects, returning an immedi-ate and
representative picture of the company situation in re-lation to its
environmental situation, comparable with theterritorial context of
the organization and with the objectivesthat have been stated.
Indicators should address those environ-mental impacts that are
most significant and which the com-pany can directly influence by
its operations, management,activities, products and services. They
should also be sensitiveenough to reflect significant changes in
environmental im-pacts. These values are essential, because they
represent theterm of reference for all future environmental
performanceevaluations.
4. Indicators and indices
4.1. Indicators, environmental indicators andenvironmental
performance indicators
The definitions of indicators are particularly confusing
[36].Some specific definitions of indicator in the literature
are:measure of system behaviour in terms of meaningful and
per-ceptible attributes [37]; measure that summarizes informa-tion
relevant to particular phenomenon, or to reasonableproxy for such
to measure [38]; parameter, or value derivedfrom parameters, which
points to/provides information about/describes the
phenomenon/environment/area with significanceextending beyond that
directly associated with parameter(property that is measured or
observed) value [39]; and var-iable that describes the system,
where to variable is an opera-tional representation of an attribute
(quality, characteristic,property) of the system and it represents
our image of an attri-bute defined in terms of the specific
measurement or observa-tion procedures [40].
In general, indicators should be able to [41]: (i) assess
con-ditions and trends; (ii) compare across places and
situations;(iii) assess conditions and trends in relation to goals
and tar-gets; (iv) provide early warning information; and (v)
anticipatefuture conditions and trends. So, it is possible to say
that de-sirable indicators are variables that summarize or
otherwisesimplify relevant information, make phenomena of
interestvisible or perceptible to the managing staff, and are able
toquantify, measure, and communicate relevant information.Some of
those properties are not universal requisites (e.g.qualitative
indicators may be used in some situations), buta matter of
convenience [41]. Most definitions of environmen-tal indicators
rule out the possibility of qualitative indicators,by restricting
the concept to numerical variables, either explic-itly or
implicitly [32,36,37,39,42]. Indeed, it is maintained thatone of
the essential functions of indicators is to quantify anitem.
Qualitative indicators may be preferred to quantitativeindicators
in at least three cases: (i) when quantitative infor-mation is not
available; (ii) when the attribute of interest is in-herently
non-quantifiable; and (iii) when cost is a crucial
issue,overwhelming all other considerations. In some cases,
qualita-
E. Perotto et al. / Journal of Cleative assessments can be
translated into quantitative notation.Only the more general
requirements or desirable propertiesare listed below [41]:
1. the values of the indicators must be measurable (or at
leastobservable);
2. data must be either already available or they should
beobtainable (through special measuring or
monitoringactivities);
3. the methodology for data gathering, data processing,
andconstruction of indicators must be clear, transparent
andstandardized;
4. means for building and monitoring indicators should
beavailable;
5. the indicators or sets of indicators should be cost
effective,an issue often overlooked;
6. political acceptability at the appropriate level (local,
na-tional, and international) must be fostered (indicatorsthat are
not acceptable by decision-makers are unlikelyto influence
decisions); and
7. participation of, and support by, the public in the use of
in-dicators is highly desirable, as one element of the
generalrequirement of participation of the broader society in
thequest for sustainable development.
As for the environmental indicators many definitions havebeen
proposed. For EPAs Report on the Environment(2003), an
environmental indicator is a numerical value de-rived from actual
measurements of a pressure, state or ambientcondition, exposure or
human health or ecological conditionover a specified geographic
domain, whose trends over timerepresent or draw attention to
underlying trends in the condi-tion of the environment [43]. The
Asian Development Bank(1999) tells that the environmental
indicators represent an ef-ficient way of measuring the environment
issues in a country:potentially, indicators can signal the health
of the environmentand can help in formulating actions to serve the
long-termneeds of the environment and the community [44]. TheUNEP
(2004) defines environmental indicators as a way toimprove the
delivery of information for decision-making [8],while OECD (2004)
defines them as an essential tools fortracking environmental
progress, supporting policy evaluationand informing the public
[45].
Regarding the performance indicators, they can representa finite
set of quantities chosen to reflect certain aspects in
anorganization. One possible definition of this type of
indicatorsis a number, absolute or relative, that facilitates
management,communication and follow-up of an organisations
perfor-mance [46]. Bartolomeo (1995) defines environmental
per-formance indicators as the quantitative and
qualitativeinformation that allow the evaluation, from an
environmentalpoint of view, of company effectiveness and efficiency
in theconsumption of resources [47]. The ISO 14031 [2] definesthe
environmental performance indicators as specific expres-sion that
provide information about an organizations environ-mental
performance and their scope is to make measurement
519ner Production 16 (2008) 517e530cording to ISO 14031
indicators should be divided as follows.
-
tion about the environmental performance of anorganizations
operations;
2. Environmental Condition Indicators (ECI): specific
ex-pression that provides information about the local, re-gional,
national or global conditions of the environment.
The ECls provide information about the condition of the
en-vironment. This information can help an organization to
betterunderstand the actual impact or potential impact of its
environ-mental aspects, and thus assist in the planning and
implemen-tation of EMS.
It is generally difficult to choose the suitable
performanceindicators, as well as to define their suitable number
whichcan describe thoroughly what one wants to know. Also,when
different specific needs for information are to be ful-filled, then
different indicators should be chosen, or built.
In EMS, the classification of indicators recommended bystandard
ISO 14031 and the examples of indicators providedshould be
considered first, even though they are not completeor comprehensive
[7,21,48,49]. Particularly, an organizationshould make a list of
indicators by following the generalguidelines of the ISO 14031
standard and linking them tothe corresponding environmental
aspects. Table 2 shows an ex-ample of a table that can be filled to
make it easier the connec-tion between an environmental aspect and
the correspondingindicators.
4.2. Indices
The distinction between indices and indicators is not clearyet.
Regarding this issue, there are two different opinions.Many authors
[32,50,51] put indices on a higher level of ag-gregation than
indicators (Information Pyramid ). Other au-thors [41] report that
indices and indicators differ because ofdifferent complexities of
the function by which they are ob-tained, not because of their
hierarchical level. In most cases,
Table 2
Example of a table for linking activities (products or services)
and their environ
Activity/product/service Environmental aspect Condition
Indica
OPI
Combustion Emission into atmosphere N, A, E Emiss
. . .
. . .N normal operating conditions, A abnormal conditions, E
emergency situaOPIOperational Performance Indicators; MPIManagement
Performance Ind(i) to reflect the state of an environmental
resource in orderto understand the dynamics of an environmental
systemor the relationship between different
environmentalcomponents;
(ii) to facilitate the analysis of trade-offs between
objec-tives (development and environmental protection,etc.);
and
(iii) to assist in making resource allocations and
policydecisions.
Once indicators have been chosen, they can be aggregatedinto
indices, which can return very concise and readily under-standable
information. This, in turn, can be used to comparethe evolution of
a situation over time, but also to compare dif-ferent situations.
Typically, aggregation involves indicatorswhich refer to the same
area (e.g. economical and environmen-tal) or compartments (in the
case of environment: air, water,soil, and noise). Aggregation of
data and indicators and theprocess of weighing is a very critical
point. Weighs shouldbe proportional to the importance assigned to
each single indi-cator. It is evident that subjectivity plays a
very important rolein assigning weights. Therefore it is crucial
that the selectionof weights should be highly transparent and
weighs should bedefined according to measurable criteria. During
the process ofelaborating raw data to produce indicators and
indices, infor-mation may be partly lost, since it is transformed
intoa more concise form; however, it gains in ease of
communica-tion as it should be understood even by non-experts [53].
Asfor the issue of aggregation Wall and others [54] notethat: .the
development of highly aggregated indicators isconfronted with the
dilemma that, although a high level of ag-gregation is necessary in
order to intensify the awareness ofproblems, the existence of
desegregated values is essential inorder to draw conclusion for
possible courses of action. Thisdilemma particularly affects highly
aggregated approaches
mental aspects to the corresponding indicators
tors
MPI ECI
ion NOX/unit product No. of calls for maintenance
per year
NOX concentration
in air
. .
. .1. Environmental Performance Indicators (EPI): specific
ex-pression that provides information about an
organizationsenvironmental performance, which are divided into:
Management Performance Indicators (MPI): that pro-
vide information about the management efforts to in-fluence an
organizations environmental performance;and
Operational Performance Indicators (OPI): environ-mental
performance indicator that provides informa-
indicators are variables representing complicated functionsof
the primary data, while indices are simple functions oflower level
variables (sometimes called subindices). For theAsian Development
Bank [44], an index combines a numberof variables into a single
value. The ability of an index to pro-vide information at a level
that encompasses information ona number of variables in the form of
a single value makesthe concept of an index attractive for a number
of functions.An environmental index is necessary:
520 E. Perotto et al. / Journal of Cleaner Production 16 (2008)
517e530tions and accidents.
icators, ECI: Environmental Condition Indicators.
-
which do not have a disaggregated substructure. Moreover,highly
aggregated systems still have substantial conceptualproblems. In
approaches that envisage an aggregation of indi-vidual elements, it
constitutes a methodological barrier. Dis-tance-to-target methods
only appear to bypass the problemsof valuation; in addition, they
are often dependent on the exis-tence of target values..
A big attention should be given to the choice of the
rela-tionships between data: aggregation should be made accordingto
the methods which should be as objective as possible, andthe
procedure should be repeatable. Particularly, for the crea-tion of
the point scale and for the choice of the indicatorsweights, it is
essential to be able to guarantee objectivity andtransparency. For
this reason it is important to consider [7]:
- data of the organization at a definite time;- literature
values;- values which refer to similar cases; and- statistical
analysis techniques.
Another important issue is related to the last point: the
assur-ance of primary-data quality, paying particular attention to
thechoice and to the metrological quality of the raw data
[44,52,53].
5. Uncertainty of measurement
When you can measure what you are speaking about, andexpress it
in numbers, you know something about it; butwhen you cannot express
it in numbers, your knowledge isof a meagre and unsatisfactory
kind. It may be the begin-ning of knowledge, but you have scarcely,
in your thoughts,advanced to the stage of science
(Lord Kelvin)
The knowledge of the uncertainty is very important becauseit
implies increased confidence in the validity of the result ofa
measurement.
Uncertainty, as defined in Guide to the Expression of
Uncer-tainty in Measurement (GUMe [55]) and in VIM
(InternationalVocabulary of Basic and General Terms in Metrologye
[56]), isa parameter, associated with the result of a measurement,
thatcharacterizes the dispersion of the values that could
reasonablybe attributed to the measurand The parameter may be,
forexample, a standard deviation,1 or the width of a
confidenceinterval; while the measurand is a particular quantity
subjectedto measurement that is a set of operations having the
object ofdetermining a value of a quantity [56].
The science of measurement, embracing both experimentaland
theoretical determinations at any level of uncertainty inany field
of science and technology, is the metrology (Interna-tional Bureau
of Weights and Measures e IBPM e [57]).
E. Perotto et al. / Journal of Clean1 The standard deviation of
the mean X of n values taken from a populationis given by: SX
S=
n
p.There are two type of uncertainty: standard uncertainty
andexpanded uncertainty.
The standard uncertainty, however, evaluated, is repre-sented by
an estimated standard deviation, termed standard un-certainty with
suggested symbol ui, and equal to the positivesquare root of the
estimated variance. The ISO Guide [55] re-fers that the uncertainty
can be evaluated by Type A o Type Bevaluation:
Type A: This uncertainty component is represented by a
statis-tically estimated standard deviation si, equal to
thepositive square root of the statistically estimated var-iance
S2i , and the associated number of degrees offreedom vi. For such a
component the standard uncer-tainty is ui si.
Type B: This uncertainty component is represented by a quan-tity
uj, which may be considered an approximation tothe corresponding
standard deviation; it is equal tothe positive square root of u2j ,
which may be consid-ered an approximation to the corresponding
varianceand which is obtained from an assumed
probabilitydistribution based on all the available
information.Since the quantity u2j is treated like a variance anduj
like a standard deviation, for such a componentthe standard
uncertainty is simply uj.
The expanded uncertainty is a quantity defining an intervalabout
the result of a measurement that may be expected to en-compass a
large fraction of the distribution of values that couldreasonably
be attributed to the measurand.
It should be born in mind that:
(i) the fraction of the distribution of values that could
rea-sonably be attributed to the measurand may be viewedas the
coverage probability or level of confidence of theinterval; and
(ii) one must define which is the probability distribution
ofmeasurement results, when a specific level of confidencehas to be
associated to the interval defined by the expandeduncertainty and
its combined standard uncertainty; thelevel of confidence that may
be attributed to this intervalcan be known only to the extent to
which the assumptionon the probability distribution may be
justified.
The coverage factor is a numerical factor that is used asa
multiplier of the combined standard uncertainty in order toobtain
an expanded uncertainty.
If the purpose of the uncertainty statement is to
providecoverage with a high level of confidence, an expanded
uncer-tainty is computed as:
U ku 1
where k is chosen to be the a/2 critical value from the
t-table(Students t-distribution) for v degrees of freedom. For
largedegrees of freedom, it is suggested to use k 2 to
approximate
521er Production 16 (2008) 517e53095% coverage.
-
Sometimes, the word uncertainty is interchanged withaccuracy,
but they are actually different. In fact, the Accu-racy of
measurement is the closeness of the agreement betweenthe result of
a measurement and a true value of the measur-and and it refers only
to systematic error [56]. Therefore,the word accuracy should not be
used for quantitatively de-scribing the characteristics of
measuring instruments or otherentities. Even ignoring this point,
the term accuracy is a par-tial contribute of the metrological term
uncertainty, whichrefers to both systematic and random errors.
6. Case study: the role of uncertainty of measurement
inenvironmental performance evaluation of municipalwastewater
discharges
Following the trend in the private sector, EMSs have
beenintroduced in several Local Authorities around the world
Table 3
Indicators that have been used to describe (i) the environmental
quality of the
organization [76]
Indicator
Hydrosphere Water Management
Watershed area (km2)
Main water bodies (No., km2)
Mean flow rate in main rivers (m3 s1)Artificial water basins and
capacity of reservoirs (No
Water supply sources and abstractions (L s1)River banks
preservation areas (No., % of watershed
Indicator of congruity of preservation areas with the
No. of works carried out on artificial reservoirs on a
No. of abstractions and flow-rate diversions (L s1)
Environmental qualityExtended Biotic Index (EBI)
Ecological State of the Water Body (according to Ita
Ammonium nitrogen concentration (mg L1)Dissolved Oxygen (mg
L1)E. coli (UFC in 100 mL)Conformity to regulations for bathing and
swimming
No. of complaints per yearthe study and the evaluation of a
specific environmental aspect(wastewater discharges) of a Local
Authority which is involvedin EMS implementation. The results of
the EnvironmentalAnalysis showed that wastewater discharges
negativelyaffected water quality of the receiving water body, and
thatthis aspect was significant. Therefore, it was decided to
reportthe environmental performance evaluation of
wastewaterdischarges.
A list of some possible indicators that have been used dur-ing
the initial step of EMS implementation (EnvironmentalAnalysis e EA)
is reported. Indicators and indices havebeen chosen by considering
the importance of monitoring per-formances in an EMS context. Also,
it has been consideredthat sustainability management tools like
benchmarking [63]are strongly recommended in the Aalborg Charter
(1994)[70] for the exchange of experience and best practices
amonglocal authorities. This issue has been considered as
crucial,since local authority actions play an essential role in
environmental compartment hydrosphere and (ii) how it is managed
by an
ECI MPI
., km2, m3)
area, km2)
Provincial Master Plan (%)
yearly basis
lian law n. 152/06, Part 3, Addendum 1)
(%)The expanded uncertainty defined above is assumed to pro-vide
a high level of coverage for the unknown true value of
themeasurement of interest, so that for any measurement result,
Y:
Y U True value Y UFor further information see Refs
[55,56,58e60].The evaluation of measurement uncertainty is
essential for
the metrological quality of the results. Without such
evaluationthe results of the measurements cannot be compared
neitherbetween themselves nor with literature or standard
values.
Another important application of the assessment of
theuncertainty is for benchmarking. Benchmarking should be atthe
base of EMSs. In fact, it is not only an important tool forboosting
improvements, as it allows to compare and rankorganizations
performances, but it also goes beyond theestablishment of
benchmarks, standards and norms, since itinvestigates the practices
that support the benchmark itself(e.g. [61e64]).
[65], at the national level [66] as well as the local
governmentlevel e municipal administrations [67,68].
In Italy, Local Authorities which most frequently apply forEMSs
are Municipalities (Sincert site [69]). Since an EMSshould ensure
the management of the environmental aspectsof the organization that
are under its direct control and influ-ence, then an EMS for a
Local Authority can help in approach-ing the goal of sustainable
development of the entire territory.Therefore, for a Municipality
the Environmental Analysis(EA) is often very important since it
should cover not onlythe environmental aspects related to its
specific activities,products and services, but also the
environmental aspects af-fecting the territory. For this purpose,
it is crucial to define in-dicators and indices which are able to
effectively depict boththe environmental conditions of the
territory and the relevantenvironmental aspects which can exert
negative effects onthe environment.
This paper proposes the use of indicators and indices for
522 E. Perotto et al. / Journal of Cleaner Production 16 (2008)
517e530
-
sary to assess which activities/products/services are involvedin
wastewater production and treatment and to evaluate the
en-vironment where this aspect takes place.
Here below, some examples of indicators that are used toassess
this aspect are reported, according to the ISO 14031classification.
The choice of indicators reflects some literatureguidelines:
[71e73]. Particularly, Table 3 shows some possibleindicators for
the assessment of the hydrosphere, that is, theenvironmental
compartment where the impact wastewaterdischarge takes place. In
this case:
- ECI are Environmental Condition Indicators which givea picture
of the quality and the state of the hydrosphere;and
- MPI describe how hydrosphere is managed by the localauthority,
municipality in primis.
Some of the proposed indicators are the result of
carto-graphical digital map elaborations based on
GeographicalInformation Systems (GIS). As an example, the
Indicatorof congruity of preservation areas with the Provincial
MasterPlan is expressed in terms of percent actually protected
Table 4
Examples of indicators that can be considered for the
environmental aspect define
sewers and wastewater treatment plant [76]
Environmental aspect: wastewater discharges
Activity Indicator
Management of sewers and
wastewater treatment plant
(WWTP)
Per capita wastewater discharge into sewers (
COD concentration at inlet/outlet from WWT
BOD5 concentration at inlet/outlet from WW
SST concentration at inlet/outlet from WWTP
Nitric/nitrous nitrogen concentration at inlet/o
Ammonium nitrogen concentration at inlet/ou
Phosphorus concentration at inlet/outlet from
Mass of biosolids that are disposed off yearly
Ratio of population equivalent served to total
Compliance to limits at sampling points (%)
Ratio of No. of actions to No. of sampling (y
Beaches where bathing was declared forbidde
Maintenance actions (No. per year)Complaints concerning
malfunctions or nuisaronmental impacts;- Management Performance
Indicators (MPI) give informa-
tion about management practices of the sewer system andthe
wastewater treatment plant.
By applying and evaluating the proposed indicators to
thespecific case of a Municipality, it appeared very clearly
thatthe compartment water presented some critical elements,mainly
related to the environmental aspect wastewaterdischarges.
Particularly, the indicators have shown the existence ofa
microbiological contamination of the water body, whichwas most
probably linked to the discharge of the wastewatertreatment plant.
In fact:
- indicator Concentration of Escherichia coli in river(ECI e
CFU/100 mL) (Fig. 1) shows that microbiologicalcontamination of
river is growing between 1999 and 2000:the limit stated by law
(700) is largely overcome (1300).Escherichia coli (usually
abbreviated to E. coli), in fact,is one of the main species of
bacteria that live in the lowerintestines of warm-blooded animals,
including mammals,
d as wastewater discharges for the activity/service defined as
management of
OPI MPI
L per capita and day)
P (mg L1)TP (mg L1)
(mg L1)utlet from WWTP (mg L1)tlet from WWTP (mg L1)WWTP (mg
L1)(t per year)
population (%)
early base, %)
n by ordinance (No. per year)improving the state of the
environment, not only as a generalpolicy issue, but also for
planning water quality objectives andproviding high-quality
services to the public.
Finally, the critical analysis of one of the indices that
havebeen adopted is presented. The role of the uncertainty of
mea-surements has been stressed, because in EMS context it is
es-sential to assess the uncertainty of the raw data and
correctlyinterpret the information given by indices.
6.1. Indicators for wastewater discharge as anenvironmental
aspect
Wastewater discharge is an environmental aspect whichexerts its
ultimate impact on the receiving water body, aswastewater
discharges can heavily affect the quality of naturalwaters. In
order to properly understand this aspect, it is neces-
land along the main water bodies compared with the require-ments
reported on the Master Plan.
Many indicators, instead, have been obtained by
actualmeasurements, such as the concentration of specific
elementsand pollutants in the water body (e.g.: dissolved oxygen
andammonium nitrogen concentrations). Actually, most indicatorsthat
are commonly used for the characterization of this envi-ronmental
aspect have been obtained through direct measure-ments. In Table 4
some examples of performance indicatorsreferred to the activity
management of a sewer system andthe related wastewater treatment
plant are reported. Theyare classified according to ISO 14031 as
follows:
- operational performance indicators (OPI) give informationabout
the efficiency of the sewer system and the wastewa-ter treatment
plant with particular care to the related envi-
523E. Perotto et al. / Journal of Cleaner Production 16 (2008)
517e530nce originated by the sewers/WWTP (No. per year)
-
for monitoring the state of wastewater treatment, which
couldtrace the trend of the performance of the municipal
wastewatertreatment plant over time, and, consequently to allow its
bettermanagement. This index was named State of WastewaterTreatment
Index (SWTI) and has been applied to the Munic-ipality
considered.
6.2.1. The index SWTIThe index has been developed aiming at a
better under-
standing of the performance of a wastewater treatment plantby
all stakeholders. In fact, it is important that the
informationgiven by this indicator is understandable not only to
techni-cians but also to decision-makers, so that they can
easilytake actions to deal with the problem. Particularly, the
scopeof such indicator should be to make more evident
whethersewerage and wastewater treatment are appropriate.
Directive 91/271/EEC [71], as amended by Directive 98/15/
phytodepuration systems, provided that they allow to meetthe
required effluent quality standards stated by the com-petent
Authority. Therefore, a definition of inappropriatetreatment should
also be given. Following the Europeanlegislation, inappropriate
treatment means a treatmentwhich does not allow to meet the
required discharge limits.For example, inappropriate WWTPs can be
all those whohave been sanctioned by the competent Authority.
However,by doing so, a rough approximation is made, as it
happensthat final effluent limits are exceeded not because the
plantis not adequately designed or built, but because of
improperdisposal practices (e.g. discharge of toxic substances
intosewers instead of proper disposal as special liquid wastes).In
this case, the discharge is inappropriate, not the plant.However,
the management staff of the WWTP should tracethe source of the
improper discharge and take technicaland/or administrative actions
to avoid other similarand its presence in water and groundwater is
a commonindicator of fecal contamination.
- indicator Conformity to regulations for bathing andswimming
(MPI e expressed as percentages) that con-siders the results of
conformity for the bathing and swim-ming, confirmed that
microbiological contamination in thereceiving water body was real:
in fact, the average ofthe last 5 years was as low as 50% and this
was due tothe fact that the conformity (ex DPR 470/82 e Italianlaw)
is not met for three parameters, all of them indicatorsof fecal
contamination, that are: Fecal Coliform bacteria,Total Coliform
bacteria and Streptococcus fecalis. Thepresence of those bacteria
in aquatic environments showsthat the water has been contaminated
by fecal material.
6.2. Definition of SWTI (State of Wastewater TreatmentIndex) and
its application as a possible descriptor of theenvironmental aspect
wastewater discharges
After finding that the environmental aspect wastewaterdischarges
was the main cause of the bad microbiologicalwater quality of the
river, it was devised to develop an index
Municipalities
1600
199920002001
Escherichia C
1400
1200
1000
800
600ufc/
100
ml
400
200
0
Fig. 1. Indicator E. coli for the Municipa
524 E. Perotto et al. / Journal of CleanEC [72], states that
Member States shall ensure that, by 31December 2005, urban waste
water entering collecting systemsshall before discharge be subject
to appropriate treatment inthe following cases:
for discharges to fresh-water and estuaries from agglomer-ations
of less than 2,000 P.E. (population equivalent),
for discharges to coastal waters from agglomerations ofless than
10,000 P.E.,
whereas for all discharges from agglomerations of more than2000
P.E., Member States shall ensure that urban waste waterentering
collecting systems shall before discharge be subject tosecondary
treatment or an equivalent treatment.
Furthermore, the European legislation defines an appro-priate
treatment as any process and/or system of disposalwhich enables the
waters receiving the discharges to meetthe specified quality
objectives and to comply with the relevantprovisions of Directive
91/271/EC and any other Communitydirectives.
A specific Italian regulation states that appropriatetreatment
is any simple biological treatment such as simpli-fied activated
sludge processes (as extended aeration), trick-ling filters,
rotating biological contactors, lagooning and
Law limit
oli
lity considered (shown by the solid arrow).
er Production 16 (2008) 517e530occurrences.
-
SWTI
Tot P:E: served by WWTP
Tot P:E: served by sewers
P:E: served by inappropriate WWTPTot P:E: served by WWTP
100 2
SWTI is calculated as the difference between the ratio ofthe
total population equivalent (P.E.) served by Waste WaterTreatment
Plants (WWTPs) to total P.E. served by the sewersystem and the
ratio of P.E. which are inadequately servedby a WWTP to total P.E.
served by WWTP (the P.E. representsthe unit of measure used to
describe the size of a waste waterdischarge).
If SWTI scores high and water quality remains poor, thencauses
other than inadequate municipal sewerage systems andwastewater
treatment should be investigated (e.g. diffuse pollu-tion such as
surface runoff, poor cattle-breeding techniques).
Moreover, this index expresses the combined overall effi-cacy of
the sewer system and the WWTP service and can beused to compare the
situation of each Municipality with othersin the same watershed.
This is extremely important becausethe contamination of the water
body could not only be causedby the Municipality under
investigation (implementing anEMS; from now on, named E), but also
from Municipalitieswhich are located in the same watershed.
Therefore, the geo-graphic scale should be wider than municipality
level in orderto identify and plan the most appropriate actions,
and also todetermine the role of each administrative body, from the
singlemunicipality level (low) to the regional level (high).
For
0 10 20 30 40
Municipality A
Municipality B
Municipality C
Municipality D
Municipality EFig. 2. SWTI for Municipality E (implementing an
EMSinstance, mapping the index on a watershed map over timemay be
very interesting for tracing the progress of implemen-tation of
Plans for Preservation of Waters Resources.
Population equivalent and the other data that are used
tocalculate SWTI are reported in Table 5. All data have beenfound
on the Provincial Report on Surface Water Quality.The calculated
values of SWTI for Municipality E and forneighbouring ones (that
have been named AeD) are shownin Table 6 and Fig. 2.
Municipalities AeD have been considered as neighbour-ing as they
belong to the same watershed. The neighbouringmunicipalities have
the same environmental, economic and so-cial characteristics of
Municipality under investigation, but arenot implementing an
EMS.
As one can see, the index SWTI has immediately evidenced(to
non-experts, too) which Municipalities could be responsi-ble for
the poor quality of the receiving water body. As a matterof fact,
SWTI has allowed the classification of treatment prac-tices in five
Municipalities, and allowed to point out thebenchmark in that area,
represented by Municipality B.Second ranks Municipality A, while
other Municipalities scorepoor to very poor index values.
In particular, SWTI for Municipality E shows that wastewa-ter
collection and treatment is not comparable to the standardsof
neighbouring Municipalities. Therefore, its sewerage/treat-ment
services should be improved and specific actions shouldbe planned.
However, the microbiological quality of the riveris not likely to
improve until Municipalities C and D greatlyimprove their
performances.
50 60 70 80 90 100 110The SWTI index is defined as [73]:
Table 5
Population equivalent (P.E.) in five Municipalities belonging on
the same
watershed
Municipality Sewered
P.E.
P.E. served
by WWTP
P.E. served by
inappropriate
WWTP
A 9073 8478 227
B 452 452 0
C 1355 186 0
D 997 997 686
E (implementing an EMS) 3764 3205 1100
Table 6
Values of the State of Treatment Index(SWTI) referring to data
reported in
Table 5
Municipality P.E. served by
WWTP/Sewered
P.E. (%)
P.E. served by
inappropriate
WWTP/P.E.
served by
WWTP (%)
SWTI (%)
A 93.4 2.7 90.8
B 100.0 0.0 100.0
C 13.7 0.0 13.7
D 100.0 68.8 31.2
E (implementing an EMS) 85.1 34.3 50.8
525E. Perotto et al. / Journal of Cleaner Production 16 (2008)
517e530) and for other Municipalities in the same watershed.
-
e6.2.2. Critical observations about SWTIThe index cannot not
directly provide any precise sugges-
tion about which are the best actions to be adopted, sincethe it
provides an aggregated information. Only an analysisof the
disaggregated data (in this case: absence of plants orthe presence
of inappropriate plants) can explain which isthe problem causing
low index scores. One of the first actionswhich can be devised as
necessary may be in-depth studiesabout the quality of the service.
For example, it may be foundadvisable to investigate which are the
causes of WWTP inad-equacy, by elaborating mass balances of
pollutants.
Other aspects involved in the definition of SWTI should
beanalysed more deeply, in order to prevent its improper use.
First of all we should define how reliable a measurement
is.Accuracy and precision are fundamental in order to
calculatereliable indicators and indices that give a correct
descriptionof reality. Just take the definition of population
equivalentas it is in the European Directive 91/271/EC [71]. It isa
unit of measurement of biodegradable organic pollution
rep-resenting a load of 60 g BOD5 produced on average per personand
day. The size of the agglomeration, expressed in P.E., cor-responds
to the organic load produced in the agglomerationduring an average
day during the week of the year with max-imum production. It is
calculated from the sum of the organicload produced by permanent
and seasonal residential estab-lishments and services and the
organic load produced on thesame day by the industrial wastewater
which must be collectedby a collecting system (European Commission,
2001 e [74]).Measuring BOD5 with precision and accuracy is a
challenge.BOD5 is a highly variable measure related to biological
activ-ity, which is difficult to standardize, since it relies on
bacterialseeding (see official method for BOD5 [75]), which can
varygreatly for different wastewaters. SWTI is affected by the
un-certainty of BOD5 measurements to evaluate the organic loadof a
plant and the corresponding population equivalent and thisshould be
considered.
6.2.3. Assessment of the uncertainty associated withthe
Index
It was decided to assess the effect of uncertainty
associatedwith the biological measurement (BOD5) on SWTI
numericalvalues.
In this specific case, for the assessment of the uncertainty
ofSWTI, we started from the definition of population
equivalent(P.E.):
Table 7
Characteristics of WWTPs which are present in Municipality E
WWTP Type BOD5 Load
(BL, kg d1)P.E.
1 A 66.00 1100
2 A 60.30 1005
3 NA 32.40 540
4 NA 18.00 300
5 NA 12.00 200
6 NA 3.60 60
526 E. Perotto et al. / Journal of CleanTotal P.E. served by
WWTPs 3764
A appropriate; NA not appropriate.P:E: BL0:06
3
where BL total BOD5 load, expressed as kgBOD5 per day,which is
fed to the WWTP; 0.06 kg of BOD5 produced dailyby one person (kg
per capita and day).
Variable: Municipality E, wc(BL) = 20%, PDF: Normal
Chi-squareTest = 15,45378, gl = 8 (adgiust.), p = 0,0592
10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850
500
1000
1500
2000
2500
3000
No.
of o
bs
Variable: Municipality E, wc(BL) = 10%, PDF: Normal
Chi-square Test = 44,51302, gl = 8 (adgiust.), p = 0,0586
5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 850
500
1000
1500
2000
2500
3000
No.
of o
bs
Variable: Municipality E, wc(BL) = 5%, PDF: Normal
Chi-square Test= 16,81930, gl = 8 (adgiust.), p = 0,06205
32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 62 64 66 680
500
1000
1500
2000
2500
3000
No.
of o
bs
SWTI (%)
SWTI (%)
SWTI (%)
r Production 16 (2008) 517e530Fig. 3. SWTI frequency
distribution in Municipality E according to differ-
ent relative standard combined uncertainties wc(BL) 5%, 10% and
20%.
-
3205 P.E. served by WWTPs (both appropriate and not
ap-propriate); and
1100 P.E. served by WWTPs which are not appropriate.
The study of uncertainty associated to STI has beenperformed
with the Monte Carlo Method (n 10,000; forfurther information:
[76e78]), by assuming the followinghypotheses:
BL is normally distributed, as it usual as far as experimen-tal
measurements are concerning,
values of 5%, 10% and 20% have been tested as relativecombined
standard uncertainty associated to BL e i.e.wc(BL); these values
are rather common in this field assupported by some references
(inter alii: [79]).
Referring to Municipality E, results are shown in Fig. 3(AeC),
where data from Monte Carlo simulation are representedas
histograms, overlayed with the best-fitting normal curve(pdf,
Chi-square test, p> 0.05). The three different picturesare
related to the value of relative combined standard uncer-tainty
associated to BL (wc(BL)), respectively, equal to 5%,10% and 20%
for each case A, B, and C.
Finally, the expanded uncertainty (U) associated to SWTIhas been
calculated according to the following expression:
U kw 5
0 10 20 30 40
Municipality A
Municipality B
Municipality C
Municipality D
Municipality EFig. 4. Representation of SWTIU, where U is the
expanded uncertainty that afaffect BOD5 measurements (5%, 10% or
20%).it is not certain whether Municipality E is better than D,
sinceresults can be mutually compatible.
Municipalities A and B are also in a very similar
situation.Finally, comparing Municipality B (optimum) with
Municipal-ity E (at wc(BL) 20%) it is clear that this is another
case ofcompatible measures.
Therefore, it appears that it is necessary that Municipality
Cshould plan and take actions to improve its wastewater treat-ment
performances, while for Municipalities E and D it be-comes
difficult to establish any priority for intervention.
Finally, the use of an index as an instrument for planningand/or
benchmarking appears quite ineffective when uncer-tainty is high
(third scenarios, wc(BL) 20%), while thesame index could be a good
descriptor of reality if it is basedon good-quality raw data.
It can be concluded that an index should not be used with-out
considering the uncertainty of the raw data used and theuncertainty
of the resulting index values.
7. Conclusions
In the case study described earlier, the number of
servedpopulation equivalent of the different Municipalities
whichhave been evaluated, can be highly affected by uncertaintywhen
based on BOD5 measurements, while it is often and
50 60 70 80 90 100 110
wc(BL) = 5%wc(BL) = 10%wc(BL) = 20%
STI U
fects SWTI, according to three scenarios on the uncertainty w
(BL) which mayThe BOD5 load (BL, kg per day), which is the
starting-point raw datum used to calculate P.E., is obtained
from:
BL BQ 4
where B BOD5 concentration in wastewater (kg m3);Qwastewater
flow rate (m3 per day).
They both are experimental measurements.In each Municipality the
number of plants, the total BOD5
load and the corresponding P.E. have been considered.
ForMunicipality E, the corresponding relevant data are the
fol-lowing (details are reported in Table 7):
3764 total sewered P.E.;
where k is the coverage factor; w is the relative combined
stan-dard uncertainty.
The choice of the factor k is based on the level of con-fidence
desired. For an approximate level of confidence of95%, k is 2. The
results are shown in Fig. 4.
As it can be clearly seen from Fig. 4, the classification of
thefive Municipalities is not as certain as it was without
consideringthe uncertainty which affects the index, especially
consideringcase C, which is referred to a relative combined
standarduncertainty associated to [BL ewc(BL)] equal to 20%.
In fact, if the combined relative standard uncertaintywc(BL) is
equal to 5%, the classification based on the averagevalue as in
Fig. 2 still holds. However, if wc(BL) is set to 20%,the
classification could not be taken as it appears: for instance,
527E. Perotto et al. / Journal of Cleaner Production 16 (2008)
517e530c
-
nimproperly considered as an absolute value unaffected
byuncertainty.
From data described before, Municipalities cannot be com-pared
significantly through the evaluation of SWTI, since theuncertainty
of measurements is high. Any decision about tak-ing or not remedial
actions and about which remedial action isappropriate becomes more
and more susceptible of criticismas uncertainty increases.
The importance of raw data in the field of
EnvironmentalManagement Systems is clear: environmental performance
in-dicators can be strongly affected by uncertainty of raw data
tosuch an extent that results could be meaningless, or even
mis-leading. Therefore raw data should be selected according tothe
following rules:
(1) as for indicators: (i) choose the lowest possible number
ofindicators which can adequately describe the situation un-der
investigation; (ii) avoid redundant information;
(2) as for metrological traceability: (i) clearly specify
refer-ence conditions, analytical methods and proper calibrationof
the instrumentation; (ii) assess the uncertainty of
themeasurements.
It is essential to assess the uncertainty of the raw data in
or-der to correctly interpret the information given by
indicatorsand indices in EMS context. In such a way, indices can
bevery useful to decision makers provided that the
uncertaintyrelated to index values is clearly stated and accounted
for.
Therefore, in general, environmental data and informationcan be
comparable only if they are obtained by following
strictmetrological specifications about both measuring
methodologyand instrumentation. Also, the nature and
characteristics of rawdata should be clearly considered when
estimating their uncer-tainty. In other words, metrological quality
of raw data shouldalways be considered as a basic requirement in
order to useraw data rationally for further elaborations in any
area [7,80].
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Environmental performance, indicators and measurement
uncertainty in EMS context: a case studyIntroductionEnvironmental
Management SystemEnvironmental performanceIndicators and
indicesIndicators, environmental indicators and environmental
performance indicatorsIndices
Uncertainty of measurementCase study: the role of uncertainty of
measurement in environmental performance evaluation of municipal
wastewater dischargesIndicators for wastewater discharge as an
environmental aspectDefinition of SWTI (State of Wastewater
Treatment Index) and its application as a possible descriptor of
the environmental aspect wastewater dischargesThe index
SWTICritical observations about SWTIAssessment of the uncertainty
associated with the Index
ConclusionsReferences
