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Title
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A comprehensive framework for eco-environmental impact evaluation of wastewater treatment plants: Integrating carbon footprint, energy footprint, toxicity, and economic assessments
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Abstract
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The need for clear and straightforward guidelines for carbon footprint (CFP) and energy footprint (EFP) evaluations is critical due to the non-transparent and misleading results that have been reported. This study aims to
address this gap by integrating CFP, EFP, toxicity, and economic assessments to evaluate the eco-environmental
impacts of wastewater treatment plants (WWTPs). The results indicate that the total CFP was below 0.6 kg CO2/
kg COD removed, which is attributed to CO2 offset and biogas recovery. However, site-specific EFP varied
considerably from 482.7 to 2294 kgCO2/kWh due to design differences of WWTPs and their aeration and mixing
energy demand (46.96–66.1%). The use of crude oil and natural gas for electricity generation significantly
increased EFP, CFP, and carcinogenic human toxicity. In contrast, a combined heat and power (CHP) installation
enabled energy recovery ranging from 12.09% to 65.65%. Construction costs dominated the highest share of
total costs (85.43%), with indirect construction costs (42.9%) and operation labor costs (61.4%) being the primary elements in the total net costs. It is worth noting that site-specific CO2 emission factors were used in the
calculations to decrease model uncertainty. However, to improve modeling reliability, we recommend modifying
the regional CO2 emission factor and focusing on emerging technologies to recover energy and biogas.
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