The application of footprints for assessing the sustainability of wastewater treatment plants: A review

Wastewater Treatment Plant Assessment by Quantifying the Carbon and Water Footprint

“…CF and WF Blue have a strong relationship with electricity consumption. Similar to the results reported by Gómez-Llanos et al [19] and Chen et al [5], the main factor in WF Blue assessment is electricity consumption. However, the primary emission source in CF assessment of the four WWTPs studied is CH 4 , with electricity consumption as the second factor, similar to Hospido et al [22].…”

“…For example, BOD5 ∆WFG,mef at Cuacos was 9.41 m 3 per cubic metre of water treated in 2014, versus to TN and TP with ∆WFG,mef values of 2.42 and 6.62 m 3 per cubic metre cubic of water treated, respectively. Therefore, TN and TP concentrations have a more limited reduction margin with regard to the values established by the standard, similar to what was observed by Chen et al [5].…”

“…If the operational grey water footprint indicator is related to the CF, the carbon footprint ratio (CFR) is defined by Equation (5). CFR indicates the purification function in a WWTP concerning the environmental impact in terms of GHG emissions.…”

“…where ∆WF G,mef is the operational grey water footprint (m 3 /time) and CF is the carbon footprint (kg CO 2 -eq/time), and K is equal to the unit kg CO 2 -eq per cubic meter and is used so that CFR is dimensionless. Figure 3 shows a scheme with the variation in the base indicators (∆WF G,mef , WF Blue and CF) of Equations (4) and (5) for the determined period of operation in a WWTP (OR t ) and an estimate of the life period. The range of variation of ∆WF G,mef in the life period of the WWTP with proper operation could cover from ∆WFG,mef with a value of zero, with effluent concertation equal to the maximum legal concentration (c ef ≈ c max , ∆WF G,mef ≈ 0), to ∆WF G,mef , with a value of effluent concentration equal to natural concentration (c ef ≈ c nat , ∆WF G,mef > 0) for a specific contaminant in the aqueous receiving medium.…”

“…The water footprint (WF) and the carbon footprint (CF) are the most commonly used indicators to assess the sustainability of WWTPs [5]. The concept of WF responds to the need for an indicator of freshwater consumption [6].…”