Giovanni De Feo 1 , Sabino De Gisi 1 , Maurizio Galasso 2 A multicriteria technique for optimizing the management of personnel of small wastewater treatment plants Department of Civil Engineering, University of Salerno, Italy 1 Bierrechimica S.r.l., Fisciano (SA), Settore Ricerca e Sviluppo 2
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Giovanni De Feo 1 , Sabino De Gisi 1, Maurizio Galasso 2
A multicriteria technique for optimizing the management of personnel
of small wastewater treatment plants
Department of Civil Engineering, University of Sale rno, Italy 1
Bierrechimica S.r.l., Fisciano (SA), Settore Ricerc a e Sviluppo2
Framework
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
� The operation costs include such items as personnel, energy (typically,electrical energy), fuel, chemicals and sludge disposal;
� The maintenance costs are typically divided into ordinary maintenance(grass and vegetation cutting, machinery greasing, periodical painting,etc.) and extraordinary maintenance costs (replacement of machineryor machinery parts, fundamental interventions on parts of the plant,general reconstruction of masonry structures, etc.);
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Introduction
� The adoption of small-scale treatment becomes economically attractive if thecommunities to serve are far away (decentralized systems);
� While, one of the main problems of small wastewater treatment plants (SWWTPs)is the non-existence of a qualified operator as well as the non-existence of thefunds to operate and maintain the plants (Sarikaya et al., 2003);
� In order to solve the operational problems of SWWTPs, generally it is proposedthe joint operation of several plants in the same region by the same contractor orcompany.
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Introduction
� Moreover, Wilderer and Schreff (2000) suggested that closecollaboration between university researchers and industrial designers,manufacturers and marketing people is necessary in order to keepresearch and development of novel wastewater treatment methods inline with the actual field requirements;
� As a matter of fact, the present study is the result of a closecollaboration between university researchers and a water andwastewater management company (Alto Calore Servizi S.p.A.) thatmanage several SWWTPs in the same region in Southern Italy.
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Goals
The aim of the proposed research was to define and apply a
simple multicriteria technique useful for the optimization of
the management (and, obviously, costs) of personnel of
SWWTPs.
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
The wastewater treatment plants under study
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Alto Calore Servizi S.p.A. (ACS) is a public limited companyconstituted of 127 Municipalities from the Districts of Avellino andBenevento, in the Campania region in Southern Italy. ACS worksin the sectors of drinking water supplies, sewerage systems andwastewater treatment plants (Alto Calore Servizi, 2009).
SediAlto Calore Servizi S.p.A.
(Sito Web ACS, 2009)
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Some informations
i Municipality
This study involved 16municipalities and 31WWTPs correspondingto an equivalentpopulation (PE) ofapproximately 36000.While, 350, 2250 and7000 inhabitants are theminimum, medium andmaximum values of PEserved, respectively.
1, 1.9 and 5 are theminimum, medium andmaximum numbers ofplants managed for eachmunicipality,respectively.
Materials & Methods
As shown, the WWTPs under study are based on a flow chart without primary settlingand with prolonged aeration.
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Inlet Wastewater
Bar Screens
Grit Chamber
Denitrification
Oxidation / Nitrification Tank
Secondary Settling Tank
Disinfection
Effluent
Return Activated Sludge
Secondary Activated Sludge
Underflow to Plant Influent
Dewatered Biosolids Flow to Disposal
Drying
Flow chart of the WWTPs under study
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
WWTPs under study
Montella Stratola
Castelvetere sul Calore
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Montella Baruso WWTPs under study
Nusco Ponteromito
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Cassano Irpino WWTPs under study
Flumeri località Murge
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Castel San Giorgio WWTPs under study
Melito Irpino PEEP
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Melito Irpino WWTPs under study
Pietrastornina località Furno
Materials and Methods
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Construction of the PE (population equivalent) Load Matrix (PELM)
Normalization of the PE Load Matrix and calucation of the PLI1
Construction of the Plants Load Matrix (PLALM)
Normalization of the Plants Load Matrix and calucation of the PLI
Construction of the Personnel Absolute Matrix (PAM)
2
Calculation of the medium personnel load index (PLI )m
Modification of the PELM and construction of the (PELM ')
Construction of the PE (population equivalent) Load Matrix (PELM ')
Elaboration of the Personnel Absolute Matrix (PAM ')
Modification of the PLALM and construction of the (PLALM ')
Construction of the Plants Load Matrix (PLALM ')
Elaboration of the Personnel Absolute Matrix (PAM '')
2Elaboration of the Personnel Absolute Matrix (PAM )
mCalcolation of the averege Personnel Load Index (PLI ) 2
Flow chart of the proposed procedure
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Construction of the PE (population equivalent) Load Matrix (PELM)
Normalization of the PE Load Matrix and calucation of the PLI1
Construction of the Plants Load Matrix (PLALM)
Normalization of the Plants Load Matrix and calucation of the PLI
Construction of the Personnel Absolute Matrix (PAM)
2
Calculation of the medium personnel load index (PLI )m
Modification of the PELM and construction of the (PELM ')
Construction of the PE (population equivalent) Load Matrix (PELM ')
Elaboration of the Personnel Absolute Matrix (PAM ')
Modification of the PLALM and construction of the (PLALM ')
Construction of the Plants Load Matrix (PLALM ')
Elaboration of the Personnel Absolute Matrix (PAM '')
2Elaboration of the Personnel Absolute Matrix (PAM )
mCalcolation of the averege Personnel Load Index (PLI ) 2
Flow chart of the proposed procedure
1
2
3
Equivalent population
Number of plants
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Construction of the PE (population equivalent) Load Matrix (PELM)
Normalization of the PE Load Matrix and calucation of the PLI1
Construction of the Plants Load Matrix (PLALM)
Normalization of the Plants Load Matrix and calucation of the PLI
Construction of the Personnel Absolute Matrix (PAM)
2
Calculation of the medium personnel load index (PLI )m
Modification of the PELM and construction of the (PELM ')
Construction of the PE (population equivalent) Load Matrix (PELM ')
Elaboration of the Personnel Absolute Matrix (PAM ')
Modification of the PLALM and construction of the (PLALM ')
Construction of the Plants Load Matrix (PLALM ')
Elaboration of the Personnel Absolute Matrix (PAM '')
2Elaboration of the Personnel Absolute Matrix (PAM )
mCalcolation of the averege Personnel Load Index (PLI ) 2
Flow chart of the proposed procedure
1
2
3
Characterization of the starting (not modified)
scenario
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Table 1. Numbers of plants, PE, manager personnel, assistan t personnel, laboratory personnel and executive personnelfor each municipality involved in the study (Personnel Absolute Matrix, PAM).
The first step of the procedure is to construct a personnel absolute matrix (PAM) with 6 columns(Plants, PE, Manager, Assistant, Laboratory, Executive) and as many rows as the number ofmunicipalities (16 in this case).
The value 0.2000 forthe manager of themunicipality n. 1means that hespends 20% of hisworking time in theWWTP
A number between 0 and 1 has tobe specified for each of them. Ifthe number is “0”, this meansthat the personnel unit does notwork for the consideredmunicipality. On the contrary, ifthe number is “1”, this meansthat the personnel unit works allthe time (in a year) for theconsidered municipality.
Input Data
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
The second step consists of dividing the PE of each municipality by the corresponding valuesassigned to the four kinds of personnel units, thus obtaining a PE Load Matrix (PELM).
Table 1. Numbers of plants, PE, manager personnel, assistan t personnel, laboratory personnel and executive personnel for each municipality involved inthe study (Personnel Absolute Matrix, PAM).
10 Montemiletto 3500 0.83 0.35 0.48 0.35 2.01 Average 2250 0.00 0.00 0.00 0.00 0.00 Min 350 -0.17 -0.44 -0.48 -0.44 -1.53 Max 7000 0.83 0.56 0.52 0.56 2.01
[3]
The PLI1 for themunicipality number “i”(PLI1,i) is obtained byadding up the valuescorresponding to the fourpersonnel units taken intoaccount
The lowest values indicate the municipalities where the personnel do not work enough in terms ofPE managed.
On the other hand, the highest values indicate the municipalities where the personnel work toomuch (compared to the other municipalities).
The PLI1 indicates the personnel load in terms of equivalent polulation managed (PE).
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
The fourth step consists of dividing the number of plants of each municipality by the correspondingvalues assigned to the four kinds of personnel units, thus obtaining a Plants Load Matrix (PLALM).
N. Municipality Plants PE Manager Assistant Laboratory Executive 1 Bonito 1 1800 0.2000 0.0440 0.0050 0.0040 2 Buonalbergo 3 3000 0.2500 0.1320 0.0160 0.0120 Table 1. Numbers of plants, PE, manager personnel, assistan t personnel, laboratory personnel and executive personnel for each municipality involved in
13 Salza Irpina 1 0.11 0.73 0.75 0.73 2.33 Average 1.9 0.00 0.00 0.00 0.00 0.00 Min 1.0 -0.49 -0.27 -0.25 -0.27 -1.25 Max 5.0 0.51 0.73 0.75 0.73 2.33
∑=
=4
12
iixPLI
Table 5. Normalized PLALM and calculation of the Personnel L oad Index 2 (PLI2).
The lowest values therefore indicate the municipalities where the personnel do not work enough interms of number of plants managed.
The highest values indicate the municipalities where the personnel work too much (compared tothe other municipalities).
The PLI2 indicates the personnel load in terms of number of plants managed.
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
The sixth step is to calculate for each municipality the medium Personnel Load Index (PLIm)obtained by taking the average values of the corresponding PLI1 and PLI2. The municipality can belisted in an increasing order in terms of PLIm,i.
Table 6. Calculation of the medium Personnel Load Index (PLIm).
The lowest values therefore indicate the municipalities where the personnel do not work enough.
The highest values indicate the municipalities where the personnel work too much (compared tothe other municipalities).
The PLIm indicates the average personnel load in terms of equivalent population and number ofplants managed.
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Construction of the PE (population equivalent) Load Matrix (PELM)
Normalization of the PE Load Matrix and calucation of the PLI1
Construction of the Plants Load Matrix (PLALM)
Normalization of the Plants Load Matrix and calucation of the PLI
Construction of the Personnel Absolute Matrix (PAM)
2
Calculation of the medium personnel load index (PLI )m
Modification of the PELM and construction of the (PELM ')
Construction of the PE (population equivalent) Load Matrix (PELM ')
Elaboration of the Personnel Absolute Matrix (PAM ')
Modification of the PLALM and construction of the (PLALM ')
Construction of the Plants Load Matrix (PLALM ')
Elaboration of the Personnel Absolute Matrix (PAM '')
2Elaboration of the Personnel Absolute Matrix (PAM )
mCalcolation of the averege Personnel Load Index (PLI ) 2
The seventh step of the procedure consists ofmodifying the PELM (called PELM’) bysubstituting the values in the four columnsgreater than the medium plus standarddeviation (µ+σ) and lesser than the mediumminus standard deviation (µ−σ) with thecorresponding values of (µ+σ) and (µ−σ),respectively.
[7]
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Construction of the PE (population equivalent) Load Matrix (PELM)
Normalization of the PE Load Matrix and calucation of the PLI1
Construction of the Plants Load Matrix (PLALM)
Normalization of the Plants Load Matrix and calucation of the PLI
Construction of the Personnel Absolute Matrix (PAM)
2
Calculation of the medium personnel load index (PLI )m
Modification of the PELM and construction of the (PELM ')
Construction of the PE (population equivalent) Load Matrix (PELM ')
Elaboration of the Personnel Absolute Matrix (PAM ')
Modification of the PLALM and construction of the (PLALM ')
Construction of the Plants Load Matrix (PLALM ')
Elaboration of the Personnel Absolute Matrix (PAM '')
2Elaboration of the Personnel Absolute Matrix (PAM )
mCalcolation of the averege Personnel Load Index (PLI ) 2
[8]
The eighth step is to obtain a firstmodification of the PAM (called PAM’) bychanging the values of its elements in linewith the PELM’.
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Construction of the PE (population equivalent) Load Matrix (PELM)
Normalization of the PE Load Matrix and calucation of the PLI1
Construction of the Plants Load Matrix (PLALM)
Normalization of the Plants Load Matrix and calucation of the PLI
Construction of the Personnel Absolute Matrix (PAM)
2
Calculation of the medium personnel load index (PLI )m
Modification of the PELM and construction of the (PELM ')
Construction of the PE (population equivalent) Load Matrix (PELM ')
Elaboration of the Personnel Absolute Matrix (PAM ')
Modification of the PLALM and construction of the (PLALM ')
Construction of the Plants Load Matrix (PLALM ')
Elaboration of the Personnel Absolute Matrix (PAM '')
2Elaboration of the Personnel Absolute Matrix (PAM )
mCalcolation of the averege Personnel Load Index (PLI ) 2
[9]
The ninth step of the procedure consists ofmodifying the PLALM (called PLALM’) bysubstituting the values in the four columnsgreater than the medium plus standarddeviation (µ+σ) and lesser than the mediumminus standard deviation (µ−σ) with thecorresponding values of (µ+σ) and (µ−σ),respectively.
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Construction of the PE (population equivalent) Load Matrix (PELM)
Normalization of the PE Load Matrix and calucation of the PLI1
Construction of the Plants Load Matrix (PLALM)
Normalization of the Plants Load Matrix and calucation of the PLI
Construction of the Personnel Absolute Matrix (PAM)
2
Calculation of the medium personnel load index (PLI )m
Modification of the PELM and construction of the (PELM ')
Construction of the PE (population equivalent) Load Matrix (PELM ')
Elaboration of the Personnel Absolute Matrix (PAM ')
Modification of the PLALM and construction of the (PLALM ')
Construction of the Plants Load Matrix (PLALM ')
Elaboration of the Personnel Absolute Matrix (PAM '')
2Elaboration of the Personnel Absolute Matrix (PAM )
mCalcolation of the averege Personnel Load Index (PLI ) 2
[10]
The tenth step is to obtain a secondmodification of the PAM (called PAM’’) bychanging the values of its elements in linewith the PLALM’.
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Construction of the PE (population equivalent) Load Matrix (PELM)
Normalization of the PE Load Matrix and calucation of the PLI1
Construction of the Plants Load Matrix (PLALM)
Normalization of the Plants Load Matrix and calucation of the PLI
Construction of the Personnel Absolute Matrix (PAM)
2
Calculation of the medium personnel load index (PLI )m
Modification of the PELM and construction of the (PELM ')
Construction of the PE (population equivalent) Load Matrix (PELM ')
Elaboration of the Personnel Absolute Matrix (PAM ')
Modification of the PLALM and construction of the (PLALM ')
Construction of the Plants Load Matrix (PLALM ')
Elaboration of the Personnel Absolute Matrix (PAM '')
2Elaboration of the Personnel Absolute Matrix (PAM )
mCalcolation of the averege Personnel Load Index (PLI ) 2
[11]
The eleventh step is to obtain a new PAM(called PAM2) as the medium of PAM’ andPAM’’. The values of PAM2 can be used incase to modify the time that each personnelunit spends on the management of theplants of the considered municipality.
Materials & Methods
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Construction of the PE (population equivalent) Load Matrix (PELM)
Normalization of the PE Load Matrix and calucation of the PLI1
Construction of the Plants Load Matrix (PLALM)
Normalization of the Plants Load Matrix and calucation of the PLI
Construction of the Personnel Absolute Matrix (PAM)
2
Calculation of the medium personnel load index (PLI )m
Modification of the PELM and construction of the (PELM ')
Construction of the PE (population equivalent) Load Matrix (PELM ')
Elaboration of the Personnel Absolute Matrix (PAM ')
Modification of the PLALM and construction of the (PLALM ')
Construction of the Plants Load Matrix (PLALM ')
Elaboration of the Personnel Absolute Matrix (PAM '')
2Elaboration of the Personnel Absolute Matrix (PAM )
mCalcolation of the averege Personnel Load Index (PLI ) 2[12]
The twelfth and last step is to recalculatethe PLIm (called PLIm,2) and compare thenew values with those calculated during thestep number 6.
Results and Discussions
Results & Discussion
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
The municipalities with thelowest values of PLI 1,i havemore than one plants . While,those municipalities with thehighest values of PLI 1,i haveonly one plant .
Criteria 1 - Equivalent population
Work too much +
- Do not work enough
Results & Discussion
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
The municipalities with the lowest valuesof PLI 2,i have only one plant . While, thosemunicipalities with the highest values ofPLI2,i have more than one plant , exceptedmunicipality number 11 and 13.
Criteria 2 – Number of plants managed
Work too much +
- Do not work enough
Results & Discussion
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Ave
rage
Per
sonn
el L
oad
Inde
xPLIm
Work too much +
- Do not work enough
Results & Discussion
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
-1-0.8-0.6-0.4-0.2
00.20.40.60.8
11.21.41.61.8
L ION
I
ME
L ITO
IRP
INO
(2)
FRIG
EN
TO (
5)
CA
ST
ELV
ET
ER
EF LU
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RI (
3)
SU
MM
ON
TE (
2)S
TU
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BU
ON
ALB
ER
GO
(3)
TR
EV
ICO
(3)
MO
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L LA
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AS
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(4)
MO
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IRP
.
MO
NTE
MIL
ET
TOS
ALZ
A IR
PIN
A
PLI m
B efore After
Work too much +
- Do not work enough
Results & Discussion
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
-1-0.8-0.6-0.4-0.2
00.20.40.60.8
11.21.41.61.8
L ION
I
ME
L ITO
IRP
INO
(2)
FRIG
EN
TO (
5)
CA
ST
ELV
ET
ER
EF LU
ME
RI (
3)
SU
MM
ON
TE (
2)S
TU
RN
O
BU
ON
ALB
ER
GO
(3)
TR
EV
ICO
(3)
MO
NTE
L LA
OS
PE
DA
LET
TO
BO
NIT
O
PIE
TR
AS
TO
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(4)
MO
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FOR
TE
IRP
.
MO
NTE
MIL
ET
TOS
ALZ
A IR
PIN
A
PLI m
B efore After
Work too much +
-The difference between the maximum and minimum greatly decreased passing from PLIm(1.68+0.80=2.48) to PLIm,2 (0,89+0.71=1.50);
This suggests that the personnel load both in terms of PE and numbers on plants managed aredistributed better for the four kinds of personnel units after the application of the procedureproposed.
Do not work enough
Results & Discussion
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
The municipalities 7, 10 and 12 represent those where the personnel unit don’t work, incomparison with the municipalities number 9, 11 and 12.
This result in obtained both in terms of PE and numbers on plants managed.
Results & Discussion
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
7
10
00
i Plants Manager 1
i
i
i
i
i
i
i
i
2
18
8
4
1
9
11
14
3
1913
16
12
5 17
6
15
Before
Plants Manager 2
Plants Manager 3
Plants Manager 4
Plants Manager 5
Plants Manager 6
Plants Manager 7
Plants Manager 8
Plants Manager 9
Results & Discussion
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
00
2
18
8
4
1
9
11
14
3
1913
16
12
5 17
6
15
7
10
After
i Plants Manager 1
i
i
i
i
i
i
i
i
Plants Manager 2
Plants Manager 3
Plants Manager 4
Plants Manager 5
Plants Manager 6
Plants Manager 7
Plants Manager 8
Plants Manager 9
Conclusions
Conclusions
The following general outcomes can be stated:
� the PE Load Matrix (PELM) is a useful instrument to evaluate the specificwork load of the personnel in terms of equivalent population managed;
� the Plants Load Matrix (PLALM) is a useful instrument to evaluate thespecific work load of the personnel in terms of numbers of plants managed;
� the Personnel Load Index 1 (PLI1) is a useful indicator to compare thespecific work load of the personnel in terms of equivalent populationmanaged;
� the Personnel Load Index 2 (PLI2) is a useful indicator to compare thespecific work load of the personnel in terms of number of plants managed;
� the medium Personnel Load Index 2 (PLIm) is a useful indicator to comparethe specific work load of the personnel both in terms of PE and number ofplants managed;
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Conclusions
� the proposed procedure was able to redeploy the workforce (plantsmanagers, plants manager assistants, laboratory technicians andexecutives) both in terms of equivalent population and numbers of plantsmanaged;
� the procedure is particularly affordable for plants managers and plantsmanager assistants, while, it is less recommended for laboratorytechnicians and executives due to the difficulty in evaluating the percentageof the time that they expend for the considered municipality;
The following general outcomes can be stated:
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Activity in Progress
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
� The proposed procedure could be improved adding other criteria estimatingthe work effort in the considered municipality, such as the number ofpumping stations, the number of extraordinary maintenance interventions,etc.; and
� finally, adding other criteria it could be useful to introduce a weightingtechnique (and a corresponding sensitivity analysis).
References
� Alto Calore Servizi (2009). Alto Calore Servizi S.p.A. Chi siamo (Who we are).http://www.altocalore.it/chisiamo.asp (accessed 4 november 2009).
� Bode H. and Grünebaum T. (2000). The cost of municipal sewage treatment – structure, origin,minimization – methods of fair cost comparison and allocation. Water, Science and Technology41(9), 289–298.
� García J., Mujeriegoa R., Obisb J. M. and Boub J. (2001). Wastewater treatment for smallcommunities in Catalonia (Mediterranean region). Water Policy, 3, 341–350.
� Masotti L. and Verlicchi P. (2005). Depurazione delle acque di piccole comunità. Tecnichenaturali e tecniche impiantistiche (Treatment of wastewater of small community. Natural andplant-engineering techniques). Hoepli, Milano, Italy.
� Rowland I. and Strongman R. (2000). Southern Water faces the small works challenge. WaterScience and Technology, 41(1), 33–39.
� Sarikaya H.Z., Sevimli M.F., Koyuncu I. and Yuksel E.(2003). Joint operation of smallwastewater treatment plants in southern Turkey. Water Science and Technology, 48(11–12), 69–76.
� Tchobanoglous G., Burton F.L, and Stensel H.D. (2003). Wastewater engineering: treatment andreuse / Metcalf & Eddy, Inc. – 4th ed., McGraw-Hill, New York.
� Wilderer P.A. and Schreff D. (2000). Decentralized and centralized wastewater management: achallenge for technology developers. Water Science and Technology, 41(1), 1–8.
Eng. Sabino De Gisi, Department of Civil Engineerin g, University of Salerno, Italy
Thank you for your
attention!G. De Feo, Sabino De Gisi, M. GalassoUniversity of Salerno (ITALY)