Municipal wastewater systems are increasingly expected to support sustainable urban water management by improving pollutant removal while limiting carbon burdens, yet the plant–network structure behind system performance remains insufficiently understood. This study assessed nine prefecture-level cities in Fujian, China, during 2015–2024 using pollution–carbon accounting with Monte Carlo uncertainty analysis, a linked dual-subsystem network SBM model, a Global Malmquist–Luenberger (GML) index, and second-stage fractional regression. Treated wastewater volume, reclaimed water reuse, and COD removal increased substantially, while net GHG emissions rose from 36.41 × 104 t CO2-eq in 2015 to 49.84 × 104 t CO2-eq in 2024. However, net GHG intensity declined per treated wastewater volume and per COD removal, indicating improved carbon intensity despite rising total emissions. Mean overall efficiency was 0.690, with lower network-side than plant-side efficiency (0.558 versus 0.892), identifying collection and conveyance as the main bottlenecks. Dynamic performance was broadly stable (mean GML = 1.001). Fractional regression showed that sewer density was negatively associated with overall and network-side efficiency, especially under higher hydraulic loading. Wastewater-system improvement should therefore shift from capacity expansion alone toward coordinated plant–network optimization to support sustainable wastewater management.
Zhang et al. (Mon,) studied this question.
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