Environmental Engineering and Management Journal [619164]

Environmental Engineering and Management Journal
August 2014, Vol.13, No. 8, 1847-1859
http://omicron.ch.tuiasi.ro/EEMJ/

“Gheorghe Asachi” Technical University of Iasi, Romania

CONVENTIONAL vs. VACUUM SEWERAGE SYSTEM IN RURAL
AREAS – AN ECONOMIC AND ENVIRONMENTA L APPROACH

Iulia Carmen Ciobotici Terryn, Iuliana Lazar, Valentin Nedeff, Gabriel Lazar

“Vasile Alecsandri” University of Ba cau, Faculty of Engineer ing, Calea Marasesti, 157, Bacau – 600115, Romania

Abstract

The aim of this study is to investigate ne w perspectives with respect to the greening of the wastewater co llection, subsequentl y
assessing the value of the vacuum over the conventional wastewat er collecting system in rural areas. The research was framed
from the perspective of policy makers to aid in making decisi ons about benefits on long term horizon in implementing eco-
innovative infrastructure technologies. The st udy postulates the hypothesis that the vac uum sewerage system is technologically,
environmentally, economically a nd socially more sustainable in comparison with the classical solutions for the wastewater
collection. Economics provides a powerful t ool for helping solve environmental problem s. A comparative analysis between two
variants of the same project considering vacuum and conventional sewerage technologi es was performed, by using as input for
current research the Cost-Benefit Analysis. Tracing costs and benefits sheds new light on the innovative technologies for
wastewater collection. The anal ysis of the case study provides evidence to suppor t the hypothesis that the vacuum technology ca n
succeed in overcoming the environmental crises by internalizing the externalities, having the capacity to improve environmental
factors, reduce energy and maintenance costs. Besides, this rese arch shows the need to provide a framework for further analysis
that is essential for the promotion of eco-innovation and reflexive institutions.

Key words: cost-benefit analysis, eco-innovation, rural area , vacuum sewerage system , wastewater collection

Received: February, 2014; Revised final : August, 2014; Accepted: August, 2014

 Author to whom all correspondence s hould be addressed: e-mail: [anonimizat] 1. Introduction

In spite of the literature on eco-innovation and
its economic analysis th ere are some unexplored
areas such as wastewater collection and the
environmental impact of eco-innovation (Abernathy
and Utterback 1978; Beise 2001; Beise and Rennings
2004; Damanpour and Wischnevsky 2006; Duncan
1996; Frondel, Horbach, and Rennings 2007;
Gouldson and Murphy 2000; Hegger et al. 2010;
Horbach 2008; Horbach 2012; Huber 2008a, 2008b;
Johnstone 2005). Eco-innovation brings about
increased eco-efficiency and improved metabolic
consistency, in line with reducing energy demand,
etc. (Huber 2008a), th erefore internalizing
externalities. Some authors insist on the positive role
played by costs reductions as a motivation of clean
technologies (Foxon and Pearson 2008). Collection and wastewater treatment have a
huge impact on the environment and economy,
considering that each co mmunity needs access to
basic utilities in sanitation sector. In this respect
increased attention has to be paid to the adoption of
eco-innovation for the reduc tion of the environmental
impact correlated with the reduction of the
construction, functioning and maintenance costs.
There are three major challenges the local
councils in rural areas are facing nowadays: obsolete
or lack of sewerage systems, limited access to
innovative technologies due to reduced transfer of
know-how and scarce financial resources for
wastewater infrastructure. Therefore, the investing
authorities, instead of investing in eco-innovative
technologies, are being forced to invest in less
efficient and sustainable t echnologies, focusing on

Terryn et al./Environmental E ngineering and Management Journal 13 (2014), 8, 1847-1859

1848 short-term social benefits related to the number of
connections.
In the context of social and economic
evolution of rural space corre lated with infrastructure
development, an important place is represented by
the preoccupation for the management of financial
funds. They must meet the requirements of satisfying
the individual and collective needs, of public and
private entities’ functioning in accordance with the
economic and social objectiv es, consistent with the
principles of sustainable development (Bulgariu et al.
2013).
The relation between the environment and
economic development has always been at odds,
thus, the development of vacuum sewerage as an eco-
innovative system or wastewater pumping stations
with solids separation is seen as a window of
opportunity for overcoming the environmental crisis.
Even if the need and urgency of sewerage are
recognized, adequate resources are not always
available to provide sewe rage immediately in all
populated areas, therefore se lecting the best option is
of paramount importance. Sewerage projects should
be prioritized by weighting costs and benefits for
each alternative (Rashid and Hayes 2011).
As environmental quality is acknowledged as
a social need, in the pro cess of decision making both
direct regulation instruments and market principles
are being used as a decision support tool in selecting
the best alternatives in wastewater planning.
Economics provides a powerful tool for helping solve
environmental problems.
The European Union Water Framework
Directive (WFD) and Urban Waste Water Directive
(WWD) pay considerable attention to economic
analysis to water planning. In this respect, WFD
requires that cost-benefit analyses (CBA) are made
with the aim of identifying cases in which the
adoption of measures to ac hieve a good ecological
status for water bodies implies disproportionate costs
(Molinos-Senate, Hernandez-Sancho, and Sala-
Garrido 2010). Cost- benefit analysis has been used
as an evaluation tool in private and public sectors
projects (Rashid and Haye s 2011; Molinos-Senate,
Hernandez-Sancho, and Sala-Garrido 2010; Pickin
2008; Van der Bruggen et al. 2009; Godfrey,
Labhasetwar, and Wate 2009; Papa, Casper, and
Moore 2013), whenever its application in sewerage
sector is limited.
The aim of this paper is twofold. First, a
comparative financial cost-benefit analysis is
carried out in order to quan tify the range of costs and
benefits associated with investment in two variants of
modern wastewater collecting systems. The paper
aims to obtain useful information of the financial
feasibility of the construction, operation and
maintenance of alternativ e wastewater collection
systems.
The main proxy for the two variants of
projects is the energy cons umption. Secondly, a new
method is developed to quantify environmental
benefits, associated in economic terms with avoiding the discharge of pollutants into the environment. In
this regard, the main criterion of comparison is the
security of the system in what concerns the leakage
of wastewater into soil and groundwater. In this
regard, the research seek s to highlight areas for
improving the comprehensiveness and adequacy of
assessing the externalities in the frame of CBAs of
infrastructure development projects.
The research postulates the hypothesis that on
long term the vacuum sewerage system is
technologically, environmentally, economically and
socially more sustainable and feasible in comparison
with the classical solutio ns for the wastewater
collection pumping stations with solids separation.
The analysis focuses on a simulation of a particular
territorial context, the case of flat land rural area in
Romania. It is expected that the results of the study
will provide the decision makers with
recommendations in making decisions about benefits
on long term horizon in implementing eco-innovative
infrastructure technologies in what concerns the
economic viability and sustainability.

2. Material and methods

2.1. Methodology

This section presents the analytical model of
data analysis and the arguments behind the hypothesis that is tested in this work. Due to the
exploratory character of the study, a qualitative and
quantitative research was used. A desk study was conducted in order to make an inventory of the main
innovations in wastewater collection technologies.
The cost-benefit analysis is a tool for
assessing the efficiency of alternative public choices
within set budgetary limitations. The present study
demonstrates how to tackle the decision making
questions regarding the disposal of wastewater from
an economic stand-point. It compares two different
wastewater collecting sy stems by computing in
Microsoft Excel the costs and benefits applied to a
specific case study in Romania. A financial cost-
benefit analysis was carried out to analyze the effect
of implementing the vacuum sewerage system vs.
classical solution alternative with pumping stations
with solid separation for wastewater collection. The
question in place is whether it is financially and also
environmentally beneficial to construct a vacuum
sewerage system in comparison with the classical
solution.

2.1.1. Stages of CBA
In any CBA, several stages must be
conducted: defining the proj ect, identifying impacts
which are economically relevant (estimating costs
and benefits), physically quantifying impacts,
calculating a monetary valuation, discounting,
weighting and sensitivity analysis (Hanley and
Splash 2003).
The economic evaluation compared the value
of all quantifiable benefits gained due to a specific

Conventional vs. vacuum sewerage system in ru ral areas – an economic and environmental approach

1849project variant with the costs of implementing the
same intervention.
2.1.1.1. Estimated costs and benefits
Data on costs and benefits came from primary
data collected from feasibility studies, from other
published studies, catalogues of products, statistics,
and from expert opinion. The analysis considers
resources costs and benefits associated with two
project alternatives. The study makes the proviso
that the analysis does not attempt to monetize all
costs and benefits, focusing on the competitive
advantages of both sewerage collecting technologies.
All different economic, social and
environmental costs for th e target group of the
project were taken into account including local
inhabitants, socio-economic activities, as well as impact on employment, health, tourism, and
environment. The study reflects mainly on two
categories of costs. Inform ation on the first category
of costs that concerns the wastewater collection and
treatment is the most precise. Information on the second category regarding prevention and
environmental management costs are more difficult
to determine, because it can overlap with the first category. Estimated costs (fi nancial outputs) include
those of investment/capital costs (planning,
supervision, hardware, machinery and equipment, civil works), recurrent or operating costs (energy
consumption, materials, services, technical and
administrative personnel, maintenance costs).
Benefits include financial benefits (financial
inflows) that comprise the taxes applied for wastewater connection and revenue earned from
sewer bill, quantifiable socio-economic benefits
associated with direct benefits of avoiding water-
borne infections, benefits from collateral activities as
new economic activities that will generate
employment, benefits from tourism development,
benefits from the increased value of properties and
land etc. Regarding the benefits, the environmental
ones are more difficult to quantify from a financial
point of view. All costs and benefits were evaluated
by converting them into financial impacts.
Cost-benefit analysis st arts from the premise
that a project is feasible only when the aggregated
benefits exceed all costs. Whenever, it is well known
that wastewater collection and treatment it is a
feasible process mainly from the point of view of
positive environmental externalities as we deal with
proving a public good. We pose that the most
efficient wastewater collection process is the one that
minimizes input consumption (energy) and
undesirable output generation (smell and pollution
generation, leakage) while minimizing the operating
and maintenance costs.

2.1.1.2. Financial quantification of environmental
externalities
CBA has few recognized limitations as
concerns the valuation of environmental and social
issues. Wastewater collection and treatment has
important environmental and public health benefits that are defined in economic terms as positive
externalities. Externalities as a whole are made up of
positive and negative impacts derived from the
project alternatives.
For small scale projects, these positive
externalities are not quantified according to the
Guide for cost-benefit analysis of investment projects
because they do not have a market value. In order to
capture the total economic value of environmental
risks associated with eac h project variant, the
monetary valuation of positive externalities is
important in order to justify the economic feasibility
of the projects in wastewater collection.
Environmental benefits result from avoiding
external environmental effect s. They reflect the value
of environmental damage avoided derived from
wastewater collection. In this regard, it was
considered the probability of sewer seepage
occurrence in both alternatives.
In financial terms, it was assessed the value of
the externalities generated by the wastewater seepage
into the soil and groundwater as the aggregated
amount of pollutant emission discharged into
environment without treatment with a direct effect on groundwater. The method proposed consists in
quantifying the cost of the damage avoided as a result
of each project variant implementation. The
difference between the parameters of NTPA 002
(Romanian Government 2005b) (Normative concerning the conditions for wastewater discharge
into urban collecting systems or directly into waste
water treatment plants) and NTPA 001 (Romanian Government 2005a) (Normative establishing the
pollutants limits for urban and industrial waste water
when discharged into natural receivers) and the probability of leakage occurrence was used in
calculating the amount of each individual pollutant
discharged into the environment that makes the difference between the two design variants of the
sewerage system. Both regulations transpose the
requirement of the Council Directive 91/271/EEC (1991) concerning the urban waste water treatment.

2.1.1.3. Time horizon and residual value
The time horizon for wastewater collection
and treatment projects is of 30 years and represent
the maximum number of years for which forecasts
are provided. The time horizon included the time for
design, construction, start-up and operation of the
sewerage system and wastew ater treatment plant. The
residual value of the investment is a liquidation value
calculated by considering the residual market value
of fixed capital (assets and liabilities) at the end of
considered time horizon. The residual value (set at
39.58%) is expressed at constant prices and not
distorted, and it is allocated in the last year of the
time horizon of the investment project.

2.1.1.4. Decision rule and discounting
The international methodology of financial
analysis of the project on a cash flow forecast basis
suggests conducting the financial analysis and the

Terryn et al./Environmental E ngineering and Management Journal 13 (2014), 8, 1847-1859

1850 calculation of the investment returns using the total
cost of the investment. In order to evaluate the
financial attractiveness of a project alternative
against the other, the Ne t Present Value (NPV) and
Internal Rate of Return (IRR) techniques were used.
Both techniques emphasize the importance of the
concept of the time value of money.
The discount rate recommended by the
European Union and applied within the two projects
is 5%, and it is used to discount the financial flows to
the present and calculate th e NPV. It represents the
rate at which future values are discounted to present,
and it is, in fact, the opportunity cost of the capital. In
order to calculate the NPV it was necessary to use a
discounted cash flow, including the annual inflows
and outflows over the 30 year time horizon,
considered the time of investment.
The IRR describes by how much the cash
inflows exceed the cash outfl ows on an annualized
percentage basis, taking into account the timing of
those cash flows (Parissis et al. 2011). The IRR of
the investment is calculated considering the total
investment costs as an outflow, together with the
operating costs and revenues as an inflow and
measures then capacity of operating revenues to
sustain the investment costs.
Finally, we calculated the benefit-cost ratio,
an important indicator of the relative efficiency of a
project defined as total benefits divided by the total
costs of the project. The time value of money it is
incorporated, therefore, th e present values of the
benefits and costs are incorporated. All calculations
were made on a yearly basis.

2.1.1.5. Sensitivity analysis
The impact of the most significant parameters
was estimated. It allowed the determination of the ‘critical’ parameters of the model. Such parameters
are those whose variations, positive or negative, have
the greatest impact on the project’s financial performance. The analysis was carried out by varying
one element at a time and determining the effect of
that change on IRR or NPV. We considered those parameters (discount rate, investment value and
electricity costs) for which an absolute variation of
1% around the best estimate gives rise to a corresponding variation of not more than 5% in the
NPV and 1% of RIR (i.e. elasticity is unity or
greater).

2.2. Area of the study

The case study presented herein is that of a
small community in Romania. The villages Siretu
and Rusi Ciutea (Letea Veche commune, Bacau
County, Romania) count together 1996 residents,
communities with no major economic activities. The
population is connected to the water supply system
with an average of 3.4 inhabitants per family and
nowadays does not dispose of a sewage system and
wastewater treatment plan t, the wastewater being
collected in septic tanks, privies or discharged untreated directly into soil. The role of the local
authorities is to provide the best alternative in what
concerns the financial and environmental concerns
on long term that is why a cost-benefit analysis helps
in the process of decision making. The topography of
the studied area is flat, allowing for the design of
vacuum sewerage system, but also for the classical
solution for wastewater collection with pumping
stations with solids separation.
The study includes the analysis of two
alternative projects for the construction of a sewerage system for two small sized suburban, rural
communities. The project includes in the first stage
the development of a sewerage system for Siretu Village and a wastewater treatment plant placed in
Rusi Ciutea village dimensioned for the entire
volume of wastewater for the two communities. The
meaning of the study is to offer a comparative
analysis of two alternate wastewater collection systems keeping the wastewater treatment plant as a
constant for the two altern atives. The objective of the
paper is not to get into details concerning the wastewater treatment plant, even though the financial
costs were included for both variants, but to look at
the competitive advantages of the two wastewater collecting systems.

3. Options analysis: Vacuum sewerage system vs.
classical solution alternative with pumping
stations with solid separation

3.1. Vacuum sewerage system scenario

Vacuum sewage system is an eco-innovative
solution for wastewater collection because it deals
mainly with environmental and health protection,
reduced seepage and odors, economies in energy consumption in the operational phase, therefore
internalizing the externalities (extra non- monetary
costs of pollution generation). The general conditions
conducting to the use of th e vacuum system include
especially terrain conditions as unstable soil, flat terrain, rolling land with small elevations, high water
table, sensitive eco-systems, and developed rural
areas (Airvac Inc. 2013; Deutsches Institut für Normung (DIN) 1996; Roediger 2013).
The system is based on the principle of using
the differential pressure in vacuum pipelines to collect the wastewater and transport it to a vacuum
station, then gradually to a centralized wastewater
treatment plant (Airvac Inc. 2013; Deutsches Institut für Normung (DIN) 1996; Roediger 2013; Buchanan
et al. 2010). Regarding the functioning principle, a
vacuum is generated at a single point in the sewerage system, thus requiring only one point of energy
consumption, simplifying power sourcing and
reducing construction and ongoing operational costs. The energy is used for the vacuum generators to
evacuate the vacuum pumps and pipelines and for the
discharge pumps to discharge wastewater out of the
vacuum system in an existing sewage system or a
wastewater treatment plant.

Conventional vs. vacuum sewerage system in ru ral areas – an economic and environmental approach

1851In the construction phase, the vacuum
sewerage brings savings by avoiding deep and large
excavations, a smaller diameter of the pipes, elimination of pumping stations etc. A number of
minimum 200 connections or more is necessary.
Thus, the entire investment including the vacuum station, connection chambers and monitoring system
justify the investment, and the investment costs are
recovered. It is reported that monthly power costs range from $1.66 to $3.34 per month per connection.
Larger stations typically have lower power
consumption per connection (Buchanan et al. 2010). The vacuum sewer system proved to be with 23.91%
cheaper than the gravity sewer system, from the
economical point of view while the pumping sewer system is only with 1.7% cheaper than the gravity
system (Panfil et al. 2013).
The solution proposed as a first alternative for
wastewater collection consists in dimensioning a
vacuum sewage system and of a wastewater
treatment plant to treat th e wastewater from Rusi
Ciutea and Siretu villages. The vacuum sewerage
system is represented by the pressure sewers, collecting chambers, vacuum station, bio-filter,
gravitational sewer from the vacuum station to a
pumping station, a pumping station that pumps the water into the wastewater treatment plant.
Vacuum mains are slightly sloped towards the
vacuum station (min 0.2%), excepting the lifts in the saw tooth profile that help in keeping the sewer lines
shallow. Diameters in vacuum sewers are in the
range of DN 90 and DN 250 mm (inner diameter) as can be seen in Table 1. HDPE pipes are applied in
vacuum systems due to their low costs of installation
and flexibility. DIN EN 1091 requires a thickness of at least PN 10; within the project the chosen
thickness is PN16. Leakages do not appear in
vacuum systems due to an absolute tightness of installations. The pipes are aligned on both sides of
the road, in comparison w ith the classical solution
when the sewers were planned to be aligned on the
axis of the road. Advantages of the solution arise
from the fact that the road infrastructure is not damaged during the works, also for further
interventions for maintenance and repairing.
The vacuum sewers are connected to a
vacuum station equipped with hydraulic, electrical,
ventilation and control unit installations. The vacuum
station consists of three rotary vane vacuum pumps that generate vacuum in the sewer lines (3 x 5.5 kW),
a collection tank made of steel dimensioned
according to the flow rate and vacuum suction capacity to 10 cubic mete rs (4.17 l/sec), and two
sewage pumps that discharge sewage away from the
collection tanks to a gravitational sewer (2 x 11 kW).
The vacuum pumps maintain a negative
pressure between -0.4 and -0.6 bar in the collection
tank. When the tank pressure falls under a preset limit, the vacuum pumps start working to restore the
pressure. As such, vacuum pumps run only for 2-3
hours a day. A monitoring system was designed to
indicate the status of the vacuum valves and collection chambers.
For a better functioning of the vacuum station
and for reducing air emissions from vacuum generators, a bio-filter was planned (2.5 square
meters). The filter media absorb odors and volatile
compounds from the airstream by oxidation to carbon, inorganic salts and water with the support of
micro-organisms in the filter media. Bio-filter
achieves a reduction of sulfuric acid of greater than 95%.

3.2. Conventional sewerage system with solid separation wastewater pumps scenario

Conventional gravity sewers convey sewage
through pipelines to the wa stewater treatment plant
with means of five pumping stations. The sewer lines
are installed on a specific a lignment, with interspaced
manholes placed at set intervals, at pipe intersections
and changes in pipeline direction. Construction of the
system on flat terrain requir es deep excavations (1.2
to 5 m below ground level) and proper preparation
and bedding materials are required in the pipeline trenches. Installation of pipe, manholes, pumping
stations, building connections, junction chambers or
boxes and terminal cleanouts, requires large amounts of excavation.
Due to efficiency reasons and environmental
aspects and in order to keep a balance between the two sewerage options, five pumping stations with
solids separation were selected to transport the
sewage by collecting pipes and send it further in a wastewater treatment station.
The wastewater treatment plant keeps the
same characteristics as in the previous analysis. The
sewers are designed to be installed on the axis of the
road due to configuration of the land and
impossibility to dig large trenches on the sides of the road. According to the producers (KSB Group 2013),
the solid separation wastewater pumping stations
bring few benefits:
– energy saving due to pumps with narrow ball
passage, which produces better efficiency than with conventional sewage pumping stations;
– considerably less susceptible to plugging as the
pumps do not come into contact with the solids in the wastewater;
– uninterrupted operation during maintenance or
repair work due to the station's double-pump design and individual shut-off of the solids separation
reservoirs;
– all parts are accessible from outside, so very
easy to maintain and hygienic;
– resistance to corrosion and long life due to
construction from PE-HD material.
This innovative technology separates the
solids from sewage and guides it into separate solids
separation tanks. Only pre-purified sewage is able to
continue through the pump into the large, combined
collection tank. The coarse solids are eliminated from
the sewage, and in the next step the sewage is
transported by the dry sump pumps and pumped

Terryn et al./Environmental E ngineering and Management Journal 13 (2014), 8, 1847-1859

1852 downward into the collection tank.
On the way to the outgoing pipeline, the
sewage flows through the solids separation tank, pressing the solids out. The pumps function with
higher efficiency since onl y purified sewage without
coarse solids flows through the pumps, leading to significant saving on energy and thus on operating
costs. Moreover, blockages are no longer a problem.
One outline of the classical sewerage system investment with solid separation pumping stations is
presented in Table 2.

4. Results and discussions

This section discusses the main findings and
implications obtained from the analysis with respect
to the selection of the best alternative in wastewater
collection in terms of financial implications,
environmental and social benefits.
As the average water consumption in
Romania in the rural areas is about 100 l per person
per day, the total demand for domestic use for
selected case study is 451.24 cubic meters a day. The
volume of wastewater to be collected and treated has
been estimated at 375.62 cu bic meters on the basis of
average daily water consump tion, taking into account
the reduction of volume of water for farms (livestock
consumption). The estimati on of wastewater demand
for new connections is based on data gained from
previous experience in the area based on the concept
of the consumer willingness to pay. The maximum
requirement for wastewater collection is taken into
account for the investment.
We presume that 100% of households in the
selected area will be connected to the sewerage until
the 20th year of the time horizon. Our assumption is
that the biggest connection rate will take place in the
first three years after the project implementation
(around 80%), then the co nnection rate will decrease
gradually until the 20th year, when the potential
development of new houses will end due to
construction land limitations. The investment cost for
vacuum sewerage system is 1,392,259.13 euro, while
for the conventional system is 1,358,797.06 euro.
Costs and benefits are presented assuming that
all the investment interventions are implemented
within the first two years. The costs associated with
wastewater collection and treatment has been
grouped in five groups: staff, energy for wastewater
collection, and energy fo r wastewater treatment,
costs for wastewater treatment (reagents, waste
management etc.), administrative costs and
maintenance.
Considering the two wastewater collection
technologies, the energy consumption for both
project variants represented a proxy for selecting the
alternative with less energy consumption . The major
cost is the investment cost, whereas the most
important operating cost is energy cost for
wastewater treatment. Staf f costs reflect wages,
social security charges, taxes, etc. The staff costs
were considered similar for the two projects, the
implementation of the projects employing a number
of two persons for the exploitation and maintenance
of the investment.

Table 1. Outline of the vacuum sewerage system investment

Sewers L
(m) Collecting
Chambers
(number) Vacuum
station + bio-
filter Pumping
stations (pcs.) River
crossing
Vacuum sewers HDP E, PE100, SDR11,
PN16, DN 90 x 8.2 mm 1268
Vacuum sewers HDP E, PE100, SDR11,
PN16, DN 110 x10 mm 24
Vacuum sewers HDP E, PE100, SDR11,
PN16, DN e 125 x 11.4 mm 17
Vacuum sewers HDP E, PE100,SDR11,
PN16, DN 140 x 12.7 mm 0
Vacuum sewers HDP E, PE100, SDR11,
PN16, DN 160 x 14.6 mm 450
Vacuum sewers HDP E, PE100, SDR11,
PN16, DN 200 x 18.2 mm 50
Vacuum sewers HDP E, PE100, SDR11,
PN16, DN 250 x 22.7 mm 400 50 (PVC)
-3 rotary vane
vacuum
pumps (3 x
5.5 kW), -a collection
tank made of
steel (10 cubic meters-4.17
l/sec),
-2 sewage pumps (2 x 11
kW)
Gravitational sewers HDPE, PE80,
SDR17.6, PN6, DN 125 x 7.1 mm (from
the vacuum station to pumping station) 2450
Gravitational sewers HDPE, PE80,
SDR17.6, Pn6, DN 160 x 9.1 mm (from
the pumping station to WWTP) 1350 1 pcs Pipe bridge
over UHE
OL125mm
(133 x 5.0
mm)
PVC, SN2, Ø 200 x 3.9 mm (from WWTP to emissary) 690
Connections to the connecting
chambers- PVC, SN2, Ø 200 x 3.9 mm 300
Sewers 6.999 50 1 1

Conventional vs. vacuum sewerage system in ru ral areas – an economic and environmental approach

1853Table 2. Outline of the classical sewerage system inve stment with solid separation pumping stations

Sewers L
(m) Collecting
Chambers Pumping stations Manholes River crossing
Sewers PVC, SN4, DN 200 x 4.9 mm 120
Sewers PVC, SN4, DN 250 x 6.2 mm 1540
Pressure pipe HDPE, PE80, SDR17,6,
PN6, DN 110 x 6.3 mm 1092
Pressure pipe HDPE, PE80, SDR17.6,
PN6, DN 140 x 8.0 mm 1967
PVC, SN2, Ø 200 x 3.9 mm (from
WWTP to emissary) 690
Connections (including connection
chamber, PVC pipes, SN2, DN 200 x
3.9 mm and DN 400 x 28.5 mm 300 (including
connection
chamber,
PVC pipes,
SN2, DN 200
x 3.9 mm and
DN 400 x
28.5 mm 5 pcs.
1. Q=6 m3/h,
P = 2 kW.
2. Q=9 m3/h,
P = 2 kW.
3. Q=13 m3/h,
P = 2 kW.
4. Q =16 m3/h,
P = 2 kW.
5. Q = 23 m3/h,
P = 2 kW. 48pcs. Pipe bridge
over UHE
OL125 mm
(133 x 5.0 mm)
Sewers 5.709 200 5 48 1

Table 3. Costs for wastewater collection and treatment

Costs Vacuum system (euro/m3) Classical system (euro/m3)
Staff 0.044 0.044
Energy for wastewater collection 0.020 0.036
Energy for WWTP 0.146 0.146
Reagents for WWTP 0.023 0.023
Administrative costs a nd maintenance 0.004 0.005
Total 0.237 0.254

In the case study, the energy costs for the
classical solution exceed with 0.016 euro/m3 the
vacuum sewage solution; also the administrative and
maintenance costs are higher for the classical
wastewater system (Table 3). The reason is the high
efficiency of the vacuum station and the reduced
hours of functioning (2.5 hours/day). Our point is
that efficient technologies are less intensive in energy
and environmental pollution. Energy saving and
significant carbon reduction are achieved within the
vacuum sewerage solution. As the same model of
wastewater treatment pl ant was considered, the
energy consumption for th e wastewater treatment
plant (WWTP) for both alternatives is constant.
Based on the energy cost saving alone, the
payback time for vacuum sewerage is smaller than
payback time for classical sewerage project. The
reagents include chemicals utilized for the
wastewater and sludge treatment. The cost of
reagents was considered 0.023 euro/m3 wastewater,
based on similar projects.
The maintenance costs in clude costs that incur
for the maintenance and replacement of sewerage
system and components of wastewater treatment
plant. The average operati ng costs were considered
as representing 2 % from energy and staff costs,
showing a smaller cost for the vacuum alternative.
Quantification of benefits, in monetary terms, poses
certain difficulties as time as benefits split in three
categories: financial, so cial and environmental
benefits. The last two cat egories are non-market
benefits. In both cases, according to the number of
connections and therefore, the willingness to pay, the
financial or market benefits include the total income
from the tariffs for wastewater collection and
treatment and vary from 21,921 €/year after the
implementation of the project to 40,233 €/year at the end of the time horizon.
Assigning a value in willingness to pay is one
potential approach to value the benefits derived from
the implementation of the project. Whenever, no
matter what technology is implemented, it was
considered that each variant has the same value
concerning the willingness to pay for the sewerage
infrastructure to avoid waterborne diseases,
supplementary costs for emptying the septic tanks,
etc. The project generates its own revenues from the
tariffs of the wastewater collection and treatment,
determined by the forecasts of the number of
connections to the wastewater network and relative
tariffs. The revenues generated by both alternatives
are equal, namely 11.28 € for a connection permit
and 0.29 € for the collection and treatment of 1 m3 of
wastewater.
Non-quantifiable socio-economic benefits
imply avoiding evacuating wastewater on the soil
with effects on the soil qua lity and agriculture use,
improved recreational opportunities, etc. The benefits
primarily include mitigation of the environmental
pollution by reduction of raw wastewater discharge
and seepage, improved health conditions due to
pollution abatement and other tangible and intangible
benefits that will be presented below. Moreover,
water-borne and water-washed diseases are
responsible for the greatest proportion of the direct-
effect water and sanitation-related disease burden.
Costs savings in health car e are associated mainly
with a reduced number of treatments for diarrheal
cases (Hutton and Haller 2004).
The benefits of environmental improvement
from pollution reduction contribute to environmental
quality, public health quality and affects society
welfare of the local communities (Rashid and Hayes
2011).

Terryn et al./Environmental E ngineering and Management Journal 13 (2014), 8, 1847-1859

1854 According to the Guide for Cost-Benefit
Analysis of Investment Projects of the European
Commission (2008), these types of socio-economic
benefits are defined as externalities incurring any cost or benefit that spills over from the project
towards other parties without monetary
compensation. Even though a second step of the
cost-benefit analysis is the economic cost-benefit
analysis, for projects whose investment value is
under 50,000,000 € only financial cost-benefit
analysis is required, which measures only the direct
financial implications of the intervention.
Even not a component of financial cost-
benefit analysis, the evalua tion of the socio-economic
benefits was financially quantified in order to
emphasize important economic benefits on
estimating the health e ffects associated with
groundwater quality improvement, budget revenues
due to income tax, corporate tax generated by the
increased economic activity and tourism
development, and value generated by the land and
property markets. The ap praisal of the impacts
mentioned above is relevant for society, but for
which a market value is not available. These effects
have been identified, quantified and given a realistic
monetary value based on average current prices. The
method of appraisal is either the number of infectious
diseases avoided or costs generated by
hospitalization, either the number of new companies
in the area of project an d income generated, and
willingness to pay approach which allows for the
estimation of a money value through user revealed
preferences in similar cases.
In the cost-benefit analysis, benefits were
converted into monetary amounts using assumptions
about the value of identified benefits such as number
of cases avoided. The value of financial costs gained
is due to less diarrhea or Hepatitis A illness, using the
minimum treatment costs as the measure of value.
Given the number of inhabitants and similar projects,
a number of two cases of Hepatitis A avoided were
considered, with a total number of hospitalization of
30 days and 34.76 €/day, according to the average
tariffs at national level charged by hospitals within
the Infectious Diseases Division. These prices
include the price of medication and hospitalization.
The estimated cost for a di arrheal case in Romania,
considering the cost of me dication and the cost of
lost work productivity due to live of absence is 67.43
€/2 days, with a maximum occurrence probability of
7 cases a year in the case study considering the target
group and similar projects.
Due to the huge margin al health impact of
collecting wastewater at the point of use, the annual
global value of costs avoided is 2,557.76 €, representing the number of cases avoided of Hepatitis
A and diarrheal illness multiplied with the number of
cases and cost of medication and hospitalization as specified previously.
Any variant of the project implementation will
have a significant social and economic impact on the
local community. The assu mption was that ten new small companies with four employees each of them,
will start a business until the last year of the time
horizon. The minimum gross basic salary guaranteed to be paid was set at 190 € per month. The income
tax payable by the employee (47.72 €/person/month)
generated by the increased economic activity will
bring contribution to the budg et of the local council,
therefore, more resources for further development of
infrastructure. The additional income to the state budget from the income tax is set at 19.80
€/person/month and minimum profit was
approximated according to pr evious projects in the
rural areas at 352.27 €/month per each new company
and the corporate tax (84.57 €/person/month).
Maximum socio-economic benefits derived from the further economic development as a result of
wastewater infrastructure project implementation is
estimated in monetary terms at 148,738 €/year at the end of the projection period and represents the sum
of net salary, net profit, the income tax payable by
the employee and corporation tax, according to the
maximum number of settled companies.
The benefits generated by new sewerage
infrastructure, have the potential to contribute to the
tourism development, increased tourism
infrastructure and number of tourists staying
overnight (varying from 3-12 days). It is also
forecasted that the amount spent by tourist would
increase. A minimum number of 40 tourists/year
were considered with a mi nimum cost for B&B of 34
€/day. The estimation of maximum benefits from
tourism development in monetary terms counts
16,253 €/year. On the other hand, the value generated
by the land and property markets would increase. A
price of 10.9 €/square meter was considered,
according to the average pri ce of land in the region.
Thus, an increase with 20% of the value of land
determines a supplementary income of 2.16 €/square
meter. According to the estimations, within a year the
transactions will consist in 12 acres of land, resulting
in a supplementary income of 26,004 €/year. Land
use is in terms of arable land, permanent cropland
and construction land, and it plays an important role
in the progress of economic development from an
agricultural economy to an industrialized economy.
Environmental benefits from a wastewater
project when compare the two types of wastewater
collecting technologies incl ude mainly the reduction
of raw sewage discharges because of seepage risks in
the wastewater network, the pollutants damaging the
environment, quality of drinking water in private
wells and public health. These benefits represent, in
fact, the avoided monetary losses expected to accrue
as a result of the implemen tation of one project, or
another. Moreover, the reduction in the energy
consumption of the sewerage system can be seen as
an environmental benefit as time as production of
energy contributes to the climate change. However,
in order to avoid double counting the energy is
considered an operating cost.
The environmental benefits, expressed in
monetary terms, have been calculated. They reflect

Conventional vs. vacuum sewerage system in ru ral areas – an economic and environmental approach

1855the value of environmental damage avoided derived
from wastewater collectio n or an environmental
benefit. In this regard, we considered the probability
of sewer seepage occurrence in both alternatives.
According to the expert opinion, in the classical
wastewater system the sewer leakage can reach 5%
or more of the total volume of raw wastewater, with
difficulties in decelerating the sewer line break,
manholes or pumping stations which allows
wastewater seepage. In the vacuum system, this
probability is much reduced due to negative pressure
in the system and possibility of detecting the leakage
because of monitoring sy stem, reaching 1% of the
total wastewater running into the system with rapid
intervention on the specific sector with sewer line
break.
The occurrence of a sewer leakage event was
quantified at 3 times a year counting a volume of
180.76 m3 a year for the classi cal system and 11.25
m3 for the vacuum system in relation with the entire
volume of wastewater and security of the system.
The quantity of biologic oxygen consumption
(BOD 5) and total suspended solids (SS) were
calculated and multiplied with the financial value of
the penalties for exceeding the maximum allowed
concentration according to NTPA, when considered
the entire volume of wastewater had to be treated.
The total volume of sewe r leakage can be easily
calculated by making the difference between the
volumes of wastewater calculated as a result of
metered water consumption and metered wastewater
entering the wastewater treatment plant.
In financial terms, we value the externalities
generated by the wastewater seepage into the soil and
groundwater as the aggregated amount of pollutant emission discharged into the environment without
treatment with a direct effect on groundwater. The
cost of the damage avoided as a result of two projects variant implementation was taken as a proxy.
Water quality is measured mainly in terms of
biochemical oxygen demand (BOD
5). Having a low
level of BOD 5 in wastewater is essential to avoiding
penalties and producing high-quality effluent. If the
amount of pollutants leaving a wastewater collecting system is too high, or the discharge endangers public
health or the environment, the facility may violate its
permit and can be fined or required to upgrade. Due to relatively reduced volume of wastewater to be
collected and the low financial value of penalties, the
level of penalties is reduced both for classical and
vacuum system.
According to the Government Decision no.
328 (Romanian Government 2010), the level of
penalty for exceeding the BOD
5 is 46.165 €/tons and
5.77 €/tons for SS.
The damage costs are based on the willingness
to pay for environmental quality, smaller in our case
on the vacuum sewerage alternative. The financial value of avoiding further pollution is emphasized in
Table 4. In conditions in which the level of penalties
would increase and the leakage at the classical system would keep a minimum level of 5% of the entire volume of collected wastewater, it is evident
that the level of penalties for classical system is 17
times higher in what concerns the BOD
5 and 14 times
for SS. Based on the damage costs the vacuum sewer
system is more efficient when analyze only two
quality parameters of wastewater.
The water and wastewater projects represent
the case of natural monopoly and that is why market
prices suffer considerable distortions focusing on the principle of total costs recovery, including financial
costs for providing wastew ater services, operating
and maintenance costs, environmental costs related to damage to environment.
Due to its character of public good, the
consumers cannot renounce in consuming water (Budds and McGranahan 2003) or produce
wastewater. This is one reason of the financial
intervention of the European Union. In this regard, water supply and sanitation represent natural
monopolies, case in which the costs of infrastructure
are so high that they are not profitable for a private
company to provide them. In order to evaluate the
financial attractiveness of a project against the other,
the Net Present Value and Internet Rate of Return
techniques were used. The most important indicators
for the two sewerage systems are presented in Tables 5 and 6. In the absence of funding constraints, the
best value for money projects is that with the highest
NPV
(vacuum system). For infrastructure projects,
financial rates of return are usually negative because
of the tariff structure and public good character, non-
exclusive and non-rivalry, where the main aim is to
satisfy social and environmental requirements.
Negative IRR is accepted for social projects due to
the fact that this kind of investments represents a
priority, without having the capacity to generate
revenues.
The negative values of NPV within the two
alternatives of sanitation projects draws on the
necessity the project is co-financed. The IRR is
smaller than 5% (the recommended discount rate).
The benefit-cost ratio (BCR) is higher than 1,
meaning both projects are viable. For each Euro
invested in the vacuum sewerage project, 1.36 € is
saved (BCR = 1.36). Whenever, for each Euro
invested in the classical sewerage project, 1.28 € is
saved (BCR = 1.28). On the other hand, as was
discussed before, when looking at externalities, the
vacuum sewerage system brings more savings due to
the reduction of raw sewage discharges because of
spillage in the wastewater network. These benefits
represent, in fact, the avoided monetary losses
expected to accrue as a result of the implementation
of one project, or another. Having estimated the
summary measures, we then studied the impact of
different input variables on the results of our analyses
by conducting a sensitivity analysis.
Sensitivity analysis takes into account the
uncertainty associated with the assumptions and parameters of CBA by studying how changes in
variable values impact the results. We take the
uncertainty into account by conducting a sensitivity

Terryn et al./Environmental E ngineering and Management Journal 13 (2014), 8, 1847-1859

1856 analysis (SA) and examining how "sensitive" the
analysis results are to a change in base-case
parameters (discount rate, increasing investment value and energy price).
The results are presented in Tables 7 and 8.
The sensitivity analysis for the vacuum sewerage project exposed to the risk factors shows that the
variation with 1% of the discount rate, cost of
investment or energy price generates a modification of NPV smaller than 5%, and the reduction of IRR is under the limit of 1% indicated by the European
Union.
For a variation with 5% of the investment
costs, the vacuum sewerage alternative is exposed to
risks resulting in a variation with 5.36% of NPV.
The sensitivity analysis for the classical
sewerage project shows that the variation of selected
risk factors with 1% generates a variation of NPV
smaller than 5% while the reduction of IRR is under the limit of 1% indicated by the European Union.

Table 4. Quantification of the wastewater seepage from the wastewater network

Quantity (tone/year) x va lue of penalty (€/tons) Parameter Vacuum system Classical system
BOD 5 0.003 x 46.165 = 0.138 € 0.050 x 46.165= 2.308 €
SS 0.004 x 5.77= 0.024 € 0.060 x 5.77 =0.346 €

Table 5. Key performance indicators for the vacuum sewerage alternative

Key performance indicators Value Permissible value
Investment costs 1,392,259.13
NPV -1,134,321.32 ≤0
IRR -6.90 % ≤5%
Cost-benefit ratio 0.73 <1
Cumulative cash flow Positive ev ery year Positive every year

Table 6. Key performance indicators for the classical sewerage alternative

Key performance indicators Value Permissible value
Investment costs 1,358,797.06
NPV -1,114,957.86 ≤0
IRR -7.07 % ≤5%
Cost-benefit ratio 0.78 <1
Cumulative cash flow Positive ev ery year Positive every year

Table 7. Sensitivity analysis for vacuum sewerage project

Increase with 1% of the discount rate Increase with 5% of the discount rate
Initial Adjusted Variation (%) Adjusted Variation (%)
NPV -1,134, 321.43 -1,134,592.32 0.02 -1,135,369.31 -0.09
RIR -6.90% -6.95% 0.05 -7.13% -0.23
Increase with 1% of the investment costs Increase with 5% of the investment cost
Initial Adjusted Variation (%) Adjusted Variation (%)
NPV -1,134,321.32 -1,146,471.30 1.07 -1,195,070.78 -5,36
RIR -6.90% -6.91% -0.01 -6.95% -0.05
Increase with 1% of the energy cost Increase with 5% of the energy cost
Initial Adjusted Variation (%) Adjusted Variation (%)
NPV -1,134,321.32 -1,135,710.92 0.12 -1,141,269.60 -0.61
RIR -6.90% -6.92% -0.02 -7,01% -0.11

Table 8. Sensitivity analysis for classical sewerage system

Increase with 1% of the discount rate Increase with 5% of the discount rate
Initial Adjusted Variation (%) Adjusted Variation (%)
NPV -1,114,957.86 -1,115,089.31 0.01 -1,115,334,56 0.03
RIR -7.07% -7.12% -0.05 -7.30% -0.23
Increase with 1% of the investment costs Increase with 5% of the investment cost
Initial Adjusted Variation (%) Adjusted Variation (%)
NPV -1,114,957.86 -1,126,796.14 1.06 -1,174,149.23 5.31
RIR -7.07% -7.08% -0.01 -7.11% -0.04
Increase with 1% of the energy cost Increase with 5% of the energy cost
Initial Adjusted Variation (%) Adjusted Variation (%)
NPV -1,114,957.86 -1,116,231.70 0.11 -1,122,252.83 0. 65
RIR -7.07% -7.09% -0.02 -7.19% -0.12

Conventional vs. vacuum sewerage system in ru ral areas – an economic and environmental approach

1857
For a variation with 5% of the investment
costs the classical variant of the projects is sensitive, resulting in a variation with 5.31% of the NPV.
Moreover, the classical sewerage system is more
exposed to the risks in what concerns the variation in the price of electricity that has the greatest chance to
increase.
The research shows th e difference between
vacuum sewerage technology and conventional
technology, in terms of costs, environmental and social benefits. Even though there is a shortage of
published articles on the wastewater collection
technologies and their e nvironmental impact, the
analysis of the case study provides evidence to
support the hypothesis that the vacuum technology
can succeed in overcoming the environmental crises
by internalizing the externalities, having the capacity
to improve environmental factors, reduce energy and
maintenance costs.
On the one hand, the results showed in this
paper are based upon a technical analysis of energy
consumption. Despite the higher overall energy efficiency of both wastew ater collection solutions,
the vacuum technology brings more energy savings
(see Table 3) and consequently reduced greenhouse emissions. On the other hand, the environmental
externalities were estimated, and wastewater leakage
occurrence was used in calculating the amount of
main individual pollutants discharged into the
environment that makes the difference between the two design variants of the sewerage system, showing
greater benefits in implementing the vacuum
technology. Besides anal yzing the current and
potential developments and creating knowledge
about the environmental costs and benefits of a
sewage system construction and operation, this research shows the need to provide a framework for
further analysis to quantify the level of greenhouse
gases released as a result of functioning of alternative wastewater collecting system , that together with the
quantification of wastewater seepage into the soil and
groundwater, is essential for the promotion of eco-innovation and reflexive institutions.
In order to overcome some recognized CBA
limitations, a method to quantify the environmental impacts was developed. In our specific case, despite
commonly relied upon metrics to communicate
benefits to decision making, the CBA was used to
formulate economic arguments for investing in risk
reduction, rather than responding to the future impacts. The positive externalities associated with
avoiding the discharge of pollution into the
environment made the subject of the study. Moreover, life cycle assessm ent would help together
with cost-benefit analysis in delimitating the best
solution of investment.
By adopting more stringent and innovation
oriented regulations, environmentally proactive
bodies will be more capable of facing the challenge
of an accurate internalization of environmental
effects and reduce negative environmental impacts (Ferrón-Vílchez, de la To rre-Ruiz, and de Mandojana
2013). It may also be worthw hile to take the societal
perspective, which would include benefits to tax
payers for wastewater collection and improved quality of life. Unfortunately, the problem of tariff
setting for sanitation deviates from the optimum
economic, that is why the opportunity costs of the
service are not visible, being very small in relation
with the financial costs (Rogers, de Silva, and Bhatia
2002). Due to the public good character of sanitation this aspect creates ineffi ciencies in providing the
sanitation services.
A possible way of reaching the sustainable
development of wastewater collection is by using
shadow networks to insp ire innovation, encourage
institutional learning, and improve governance rules. This creates a new social reality that is more future-
responsive to problems and more hospitable to new
ways of thinking about water management (Medema
et al., 2013).

5. Conclusions

The approach described herein provides a
framework for deciding if the supplementary
investment costs for vacuum technology is
commensurate with the potential benefits. While the analysis is based on a simple methodology for cost-
benefit analysis, and somewhat uncertain data
concerning the willingness to pay, it is clear that some more benefits accrue when look from an
environmental perspective.
Research shows that the increase of the
additional benefits accruing from additional
provisions in the design and operation of
infrastructure is directly proportional with the technological improvements being brought to the
system.

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