The assessment of economic and technical efficiency is a useful tool to select the most appropriate technology for wastewater treatment. However, traditional models require that the units being assessed
operate with the same technology. To overcome this limitation, we investigate the viability of using a
non-concave metafrontier approach that is based on data envelopment analysis (DEA) to calculate the
techno-economic efficiency and technological gap ratios (TGRs) of wastewater treatment plants (WWTPs)
operating with non-homogeneous technologies. The model is applied to a sample of 99 Spanish WWTPs,
encompassing four alternative technologies: activated sludge; aerated lagoon; trickling filter; and rotating biological contactor. The results indicate that mean efficiencies are relatively high and uniform across
the different technologies. Furthermore, analysis of TGR values shows that techno-economic efficiency
is optimal for WWTPs operating with activated sludge in comparison with the other technologies. Our
study shows the importance of quantitatively comparing the efficiency of WWTPs that use different
technologies in order to help managers make informed decisions when selecting the most appropriate
technology.
