Eco-efficiency analysis of Spanish WWTPs using the LCA + DEA method

Conditional Order-m Efficiency of Wastewater Treatment Plants: The Role of Environmental Factors

“…Inputs (€/m 3 ): cost of the energy used, fixed and variable (Energy) [5,17,18,[20][21][22][24][25][26][27], total staffing costs (Staff), including salaries, taxes and social insurance and charges [5,17,18,21,22,[24][25][26][27], and other expenses (Other), which would include the cost of reagents, the maintenance for treatment facilities and infrastructure (such as equipment and machinery, even their replacement), waste management (including sludge) and other concepts (such as offices, laboratories, gardens, etc.) [5,17,18,[20][21][22][23][24][25][26][27].…”

“…Outputs: elimination levels of suspended solids (ESS) and chemical oxygen demand (ECOD) measured in terms of mg/l, which are the measures used by WWTPS to evaluate the output quality of their waters and which are also habitually accepted as outputs in wastewater treatment processes [5,18,[20][21][22][23][24][25]27]. Suspended solids (SS) represents the total amount of particles of solid pollutant that remains in suspension in water.…”

“…Although it is true that, for Spain, quite a few have been published in this regard over the last few years. See, for example, Molinos-Senante et al [17][18][19], Lorenzo-Toja et al [20], Hernández-Sancho et al [5,21,22], Sala-Garrido et al [23][24][25], Hernández-Sancho and Sala-Garrido [26,27]. On the international level, mention should be made of the research carried out by Mahmoudi et al [28] for Iran, or De Jong et al [8], Kemp [29] for the Dutch WWTPs and Gerrini et al [15] for the Danish water services and WWTPs.…”

“…Other studies use the influence of more specific aspects such as the effect of contextual factors on calculating the economic-environmental efficiency ratios [17,18,20], seasonal influences using Free Disposal Hull (FDH) or DEA and the Mann-Whitney test [5,25] or even the type of technology by using metafrontier approach with technological gap ratios [23].…”

“…The inputs used for the analyses range from purely economic data measured in euros per year, such as operation and maintenance costs, staffing, reagents, or energy costs, to technical data such as the water mass treated expressed as cubic meters. The studies by Hernández-Sancho et al [5,21,22], Hernández-Sancho and Sala-Garrido [26,27], Molinos-Senante et al [17][18][19], Sala-Garrido et al [23][24][25], or Lorenzo-Toja et al [20] include the elimination of contaminants from the treated water as output, calculating this on the basis of initial and final levels of solids in suspension (SS in mg/L), organic material expressed as a chemical demand for oxygen (COD, in mg/L) and nutrients. Apart from this, the last two studies mentioned also take into consideration non-desirable outputs such as sound, odor, and visual impact levels.…”