Abstract The biological fate of species deposited on electrostatic collectors remains difficult to resolve because airflow, discharge behavior, and interfacial processes are strongly coupled in practical systems. Here, we establish a zero-flow in situ discharge model to isolate collector-side responses at MnOx/FTO and bare FTO interfaces. Under identical electrode geometry, MnOx/FTO exhibited a stronger electrical response than bare FTO, while matched 6 kV exposure experiments produced greater biological damage on MnOx/FTO at the same exposure durations. This disparity demonstrates that nominal voltage and time do not necessarily represent equivalent interfacial electrical exposure. We therefore integrated the measured nonsteady current of MnOx/FTO to define the cumulative interfacial charge dose, Q, as a condition-specific descriptor of the accumulated electrical input. Increasing Q was associated with progressively stronger membrane damage and apoptosis-associated signaling, progressing from clear biological perturbation at Q1 to more pronounced responses at Q2 and further amplification at Q3. Electrostatic simulations indicated collector-side field localization, while ex situ XPS revealed non-monotonic Mn/O surface-state reconstruction, with defect-related oxygen reaching a maximum at Q2. Together, these results establish a charge-defined framework linking material-dependent discharge behavior, interfacial evolution, and collector-side biological response.
Abstract The scaling behavior of boric acid during direct contact membrane distillation (DCMD) treatment of boron-containing low-level radioactive wastewater was investigated, and an adaptive pulse cleaning strategy to sustain long-term performance was developed. A two-stage scaling mechanism was identified: stage I is characterized by rapid flux decline due to concentration/temperature polarization and pore blocking; stage II involves progressive scaling growth, promoted by reduced hydrophobicity and porosity. Both stages fit well with the cake filtration model. A pulse cleaning strategy was developed by periodically increasing cross-flow velocities. Fixed-interval pulse cleaning improved average flux by over 40% and reduced scaling mass by more than 83% compared with the steady-flow operation. To enable real-time cleaning initiation, a mathematical model derived from cake-layer theory was established to simulate flux decline with the instantaneous slope of the fouling coefficient kc serving as the trigger for pulse cleaning. The adaptive strategy was validated over 720 min of operation (39 cleaning cycles). By contrast, the adaptive pulse cleaning strategy maintained the average relative permeate flux above 0.72 throughout the first 240 min, substantially higher than the value of 0.58 achieved with fixed 30 min pulse cleaning. Collectively, the mechanism-guided, real-time adaptive strategy offers a practical and scalable solution for stable long-term DCMD treatment operations.
Abstract Remediation of mercury (Hg)-contaminated sediments seeks to reduce Hg and methylmercury (MeHg) transport and exposure. Sorbent amendments like activated carbon (AC) mixed into sediments or applied as part of a thin cap can reduce porewater concentrations, benthic exposure, and flux to surface water. However, mixing AC into bulk sediments has sometimes increased the sediment MeHg levels. This study tested whether applying AC as a thin layer could prevent the increase in sediment MeHg associated with the mixing of AC into the active methylation zone. We compared four amendment strategies in Hg-contaminated sediment microcosms: a thin AC layer (5 wt % of sediment) beneath a 2 cm sand cap, sand cap alone, AC layer alone, and AC fully mixed into the sediment. Sediment and aqueous profiles were measured directly and with equilibrium-based passive samplers to evaluate the amendment effects. All amendments decreased MeHg porewater concentrations and potential fluxes to surface water, with the greatest effectiveness for thin-layer AC under a sand cap. As expected, mixing AC into sediments significantly increased the level of sediment MeHg. In contrast, application of the same AC dose as a thin-layer AC cap did not increase sediment methyl mercury. Additionally, surface water MeHg was lowest in microcosms with AC caps, providing a promising strategy for the reduction of MeHg flux from sediments. The use of passive samplers enabled high-resolution, integrative depth profiling at 0.5 cm intervals, providing new insights into MeHg dynamics within treatment layers.
Abstract Achieving carbon neutrality in the wastewater sector requires reconciling pollutant removal and degradation with greenhouse gas (GHG) emissions, positioning eco-efficiency assessment as a central task in sustainable wastewater treatment engineering. Existing methods based on data envelopment analysis (DEA) and efficiency evaluation trees are limited by the curse of dimensionality and step distortions caused by hard boundaries, making it difficult to simultaneously address the multisource heterogeneity of large-scale wastewater treatment plants (WWTPs) and the continuous nonlinear characteristics of biochemical reactions. This study proposes a hybrid analytical framework that integrates consensus matrix clustering with the Fuzzy-RFEAT (Fuzzy Random Forest Eco-Efficiency Assessment Tree), embedding a sigmoid-type fuzzy membership function into the random forest frontier estimation to replace the rigid binary splits of traditional tree models with a soft-boundary mechanism. An empirical evaluation based on 4999 municipal wastewater treatment plants in mainland China indicates that consensus clustering decomposes the samples into eight functional phenotypes with significant process and scale differentiation; Fuzzy-RFEAT consistently achieved the optimal fitting accuracy across all 8 phenotypes, with the lowest coefficient of variation (0.50) for the cross-cluster RMSE among the four comparison models, validating the global consistency of the soft-boundary strategy across different scenarios. Furthermore, through an importance analysis of efficiency scores, this study identified three types of eco-efficiency bottleneck structures─physical pretreatment-constrained, single-variable-dominated, and multivariable-synergistic-constrained─and proposed typology-based targeted intervention strategies accordingly. This framework provides a rigorous, data-driven benchmark to guide refined efficiency benchmarking and prioritize differentiated low-carbon retrofits in engineered wastewater treatment systems.
Abstract Desalination of hypersaline brines is garnering increasing interest, which demands novel technologies. To this effect, we report a comprehensive autopsy of pilot-scale ultra-high pressure reverse osmosis (UHPRO) membranes operated in batch mode harvested from a produced water beneficial reuse treatment plant in the Permian Basin, Texas. Physical-chemical alterations of membranes due to operation at 1,650 psi, including dissimilar embossment behavior on either side of the permeate spacer, were diagnosed. On one side, the ridge and valley morphology created by the knitted spacer filaments caused inelastic wavelike membrane deformation. On the other side, spacer filaments were in-plane with each other, which only embossed membranes and did not cause substantial or permanent deformation. Scalants appeared to be preferentially accumulated alongside imprints, suggesting this was an artifact of membrane deformation. In extreme cases, the membranes even developed microcracks. Inorganic scaling and (bio)organic fouling were low, which was attributed to effective pretreatment and judicious UHPRO operation. Aluminosilicates were the dominant inorganic scale, and iodine was evenly distributed across the membrane surfaces. Low amounts of chromium, calcium, magnesium, barium, and iron were heterogeneously deposited across the membranes. Results pointed to the need to develop novel spacers and membrane polymers and to update concentration polarization models, accounting for potential flow heterogeneities introduced by embossment.
