Template-Type: ReDIF-Article 1.0
Author-Name: María Molinos-Senante
Author-Name: Trinidad Gómez
Author-Name: Rafael Caballero
Author-Name: Ramón Sala Garrido
Title:  Evaluación de la eficiencia económica de estaciones depuradoras de aguas residuales: Un enfoque basado en la metafrontera
Abstract: RESUMEN:
La implementación de la Directiva 91/271/CEE ha
supuesto un significativo incremento en el número de estaciones depuradoras de
aguas residuales (EDARs) en operación. Es por ello que la evaluación de su
eficiencia, como herramienta para reducir sus costes operacionales, ha
despertado un creciente interés. Sin embargo, los análisis tradicionales
únicamente permiten comparar unidades homogéneas desde el punto de vista del
proceso productivo. En este trabajo, haciendo uso del concepto de metafrontera,
se compara la eficiencia de tres grupos de EDARs cuyo influente presenta
diferente carga contaminante. Posteriormente, se estima la ratio de brecha
tecnológica como indicador del potencial ahorro económico en las EDARs. Las
conclusiones de este estudio son de especial interés para los reguladores del
ciclo urbano del agua ya que se evidencian las dificultades de realizar
procesos de benchmarking a nivel estatal cuando las instalaciones están
afectadas por distinta climatología.
ABSTRACT:
The implementation of the Directive 91/271/EEC has involved a
significant increase in the number of wastewater treatment plants (WWTPs).
Hence, the assessment of their efficiency, as a tool to save operational costs,
has awakened increasing interest. Nevertheless, the traditional assessment of
the efficiency only allows comparing homogeneous units from a production
process perspective. This limitation can be overcome by using the concept of
metafrontier which is the envelopment of the frontiers of each technology
evaluated. Therefore, the assessment of the efficiency of the units is
decomposed into two steps. Firstly, it is evaluated the efficiency using the
frontier of each technology as reference. Subsequently, all the units to be
analysed are integrated and they are assessed using the metafrontier. The
assessment of the units by considering their own frontier and the metafrontier
allows estimating the technological gap ratio (TGR). It informs about the
potential of saving inputs keeping the production of outputs. Nowadays, the
pollution load of the WWTPs´ influent is variable depending mainly on the
industrial contribution and also on the precipitation since most of the
sewerage networks are unitary. In this context, the aim of this paper is to
check the following hypothesis: the efficiency of the WWTPs is affected by the
pollution load of their influent. By using the concept of metafrontier, it was
compared the efficiency of three groups of WWTPs whose influent has different
pollutant load –low, moderate and high-. Each of the production frontiers and
the metafrontier were estimated using data envelopment analyisis (DEA)
methodology considering variable returns to scale. Since the objective of WWTPs
is to treat the influent minimizing economic costs, an input orientation was followed.
Subsequently, it was estimated the TGR as indicator of the WWTPs´ potential
economic savings. An empirical application was performed using a sample of 86
Spanish WWTPs. Three inputs (labour costs, energy costs and other costs) and
one output (treated water) were considered. The categorisation of the WWTPs was
done based on the concentration of suspended solids and chemical oxygen demand
in the influent. The main findings of this study are as follows: (i) there are
statistical significant differences in the efficiency of the three groups of
WWTPs; (ii) considering the frontier of each group, plants with high pollution
load are the best performed since 41% of them are efficient. Nevertheless, the
scores of efficiency of the three groups evaluated are quite similar; (iii)
when the efficiency is estimated using the metafrontier as reference, the group
of plants with low pollution load is the one with the largest scores of
efficiency; (iv) the assessment of the TGR evidenced that WWTPs with low
pollution load are the ones with the lowest potential for saving costs. In
particular, the potential economic savings of WWTPs with moderate and high
pollution load in the influent was around 30% of current costs. From a policy
perspective, results of this study illustrate the difficulties of performing
benchmarking at national level. Therefore, the conclusions of this study are of
special interest for the regulators of the urban water services. Future
research on this topic should be focused on isolate the major contribution of
the different pollutant loads in the influent. Hence, policy makers and WWTP
operators could take decisions aimed to improve the performance of the plants
contributing to save economic costs.
Classification-JEL: R1
Keywords: Análisis envolvente de datos, Depuraciónd de aguas residuales, Eficiencia, Metafrontera, Data envelopment analysis (DEA), Wastewater treatment, Efficiency, Metafrontier
Pages: 83-100
Volume: 2
Year: 2014
File-URL: http://www.revistaestudiosregionales.com/documentos/articulos/pdf-articulo-2440.pdf
File-Format: Application/pdf
Handle: RePEc:rer:articu:v:2:y:2014:p:83-100