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Modified Fenton technique has been widely used to remediate soils contaminated with crude oil but significantly limited to soil organic matter (SOM) consuming oxidants. In this study, soils with developed SOM inactivation by FeOOH formed in situ were created and spiked with crude oil (total petroleum hydrocarbons (TPH): 19453 mg/kg), then treated by modified Fenton reagents. The reaction activity of hydroxyl radicals (•OH) relative to TPH (K) notably increased to 0.65 when the degree of developed inactivation of the SOM (β) was 100% (DIS-100), which was 1.45, 2.03 and 2.83-fold than that of DIS-50, DIS-15 and control (CK), respectively. Meanwhile, the higher the K, the more •OH transferred, which realized the efficient oriented oxidation of TPH. Moreover, improving the transfer of •OH from SOM to TPH was more important than increasing •OH production in soil remediation. With the β increasing to 100%, the ratio of invalid H 2 O 2 decomposition to produce O 2 decreased to 22%, equal to 25% reduction compared to CK. Therefore, when β was 100%, the utilization efficiency of H 2 O 2 was improved to 1.48 mg/mmol, which was approximately 1.39, 3.35 and 5.43-fold higher than the efficiency got by DIS-50, DIS-15 and CK, respectively, achieving the cost-effective dedicated oxidation of TPH. In addition, the FeOOH cross-linked with SOM via Fe–O–C and Fe–N bonds to develop inactivation of SOM. In general, this study highlighted a new insight into the effect of developed inactivation of SOM on soil remediation. [Display omitted] • Soil organic matter can be inactivated by cross-linking with FeOOH formed in situ. • FeOOH can cross-link with soil organic matter though Fe–O–C and Fe–N bonds. • The higher degree of developed inactivation SOM, the more.•OH was transferred. • Promoting.•OH transfer to TPH was more important than increasing •OH production. [ABSTRACT FROM AUTHOR]

There are a large number of simple landfills in hilly areas, and the results of previous studies have shown that pollutants in landfills can spread via interflow and cause surface source pollution. The hybrid activated sludge-membrane aerated bioreactor (H-MABR) developed in a previous study can be used for the treatment of interflow with a low chemical oxygen demand (COD)/total nitrogen (TN) ratio, and it has been shown to be effective in laboratory simulations. To investigate the effectiveness of the H-MABR in treating interflow around landfills in real-world applications, an in-situ pilot-scale evaluation of the effectiveness of H-MABR operation was conducted at a landfill. The results indicated that the removal efficiencies of COD, TN, and ammonia nitrogen in interflow by H-MABR were 87.1 ± 6.0%, 80.9 ± 7.9%, and 97.9 ± 1.4%, respectively. The removal rate of TN reached 148.6–205.6 g-N/m3·d. The concentration of each pollutant in the effluent was in accordance with China's "Standard for pollution control on the landfill site of municipal solid waste (GB16889-2008)," wherein the COD, TN, and ammonia nitrogen of effluent should be less than 100 mg/L, 40 mg/L, and 25 mg/L, respectively. The results of community composition analysis and PICRUSt analysis based on 16S rRNA gene sequencing showed that there were different dominant functional bacteria between the inner and outer rings, but functional genes involved in the nitrification-denitrification, assimilated nitrate reduction, and dissimilated nitrate reduction pathway were all detected. Furthermore, except for the nitrite oxidation gene narG , the abundance of which did not significantly differ between the inner and outer rings, the abundance of the other functional genes was higher in the outer ring than in the inner ring. An economic evaluation revealed that the operation cost of interflow treatment by the H-MABR was as low as ¥2.78/m3; thus, the H-MABR is a shock-load-resistant and cost-effective technology for interflow treatment. [Display omitted] • The performance of a H-MABR was studied under pilot-scale conditions. • The removal efficiencies of COD and TN reached 87.06 ± 6.04% and 80.86 ± 7.90%, respectively. • The TN removal rate of H-MABR reached 148.6–205.6 g-N/m3·d. • The operation costs of H-MABR were low (¥2.78/m3). [ABSTRACT FROM AUTHOR]

Nature-based solutions have been proven in recent decades as a reliable and cost-effective technology for the treatment of wastewaters. Different plant species have been studied for this purpose, but particular attention has been given to duckweeds, the smallest flowering plant in the world. Duckweed-based systems for simultaneous wastewater treatment and nutrient recovery have the potential to provide sustainable and cost-effective solutions to reduce water pollution and increase nutrient efficiency at catchment level. However, despite being considered a seemingly simple technology, the performance of wastewater treatment systems using duckweed depends on environmental and operational conditions not very well understood. For that reason, careful consideration must be given to such environmental factors controlling duckweed biomass growth but the evidence in published literature is scare and dispersed. This study employs a systematic review approach to conduct a meta-analysis of the effect of environmental conditions on duckweed growth by means of standardised IQ-scores. The results suggest that duckweed biomass growth rates reach a maximum within specific ranges for temperature (11.4–32.3 °C), daily light integral (DLI) (5–20 mol m−2), and nitrogen (>5 mg N L−1) and phosphorus (>1 mg P L−1) concentrations; DLI was found to be a better parameter to assess the overall effect of light (photoperiod and intensity) on duckweed growth and that the effect of nitrogen and phosphorus supply should consider the nitrogen species available for plant growth and its ratio to phosphorus concentrations (recommended N:P ratio = 15:1). By establishing the optimal range of culture conditions for duckweed, this study provides important insights for optimizing engineered wastewater treatment systems that rely on duckweed for nutrient control and recovery, which is primarily mediated by duckweed growth. [Display omitted] • A meta-analysis with standardised scores can help to compare duckweed growth studies. • Different duckweed genera have different temperature optima. • The daily light integral is a useful parameter for assessing the impact of light on duckweed growth. • There is no clearly defined preference for N source. • The ratio of N:P has important effects on growth rates. [ABSTRACT FROM AUTHOR]

Sediment hypoxia is a growing problem and has negative ecological impacts on the aquatic ecosystem. Hypoxia can disturb the biodiversity and biogeochemical cycles of both phosphorus (P) and nitrogen (N) in water columns and sediments. Anthropogenic eutrophication and internal nutrient release from lakebed sediment accelerate hypoxia to form a dead zone. Thus, sediment hypoxia mitigation is necessary for ecological restoration and sustainable development. Conventional aeration practices to control sediment hypoxia, are not effective due to high cost, sediment disturbance and less sustainability. Owing to high solubility and stability, micro-nanobubbles (MNBs) offer several advantages over conventional water and wastewater treatment practices. Clay loaded oxygen micro-nanobubbles (OMNBs) can be delivered into deep water sediment by gravity and settling. Nanobubble technology provides a promising route for cost-effective oxygen delivery in large natural water systems. OMNBs also have the immense potential to manipulate biochemical pathways and microbial processes for remediating sediment pollution in natural waters. This review article aims to analyze recent trends employing OMNBs loaded materials to mitigate sediment hypoxia and subsequent pollution. The first part of the review highlights various minerals/materials used for the delivery of OMNBs into benthic sediments of freshwater bodies. Release of OMNBs at hypoxic sediment water interphase (SWI) can provide significant dissolved oxygen (DO) to remediate hypoxia induced sediment pollution Second part of the manuscript unveils the impacts of OMNBs on sediment pollutants (e.g., methylmercury, arsenic, and greenhouse gases) remediation and microbial processes for improved biogeochemical cycles. The review article will facilitate environmental engineers and ecologists to control sediment pollution along with ecological restoration. [Display omitted] • OMNBs can mitigate eutrophication induced anoxia and sediment pollution. • Cost-effective technology for environmental remediation and ecological restoration. • Positive influence of OMNBs on microbial processes and geochemical cycle. • Reduced emission of GHGs and sustainable restoration of aquatic biodiversity. [ABSTRACT FROM AUTHOR]

Soil salinization is a widespread problem affecting global food production. Phytoremediation is emerging as a viable and cost-effective technology to reclaim salt-affected soil. However, its efficiency is not clear due to the uncertainty of plant responses in saline soils. The main objective of this paper is to propose a phytoremediation dynamic model (PDM) for salt-affected soil within the process-based biogeochemical denitrification-decomposition (DNDC) model. The PDM represents two salinity processes of phytoremediation: plant salt uptake and salt-affected biomass growth. The salt-soil-plant interaction is simulated as a coupled mass balance equation of water and salt plant uptake. The salt extraction ability by plant is a combination of salt uptake efficiency (F) and transpiration rate. For water filled pore space (WFPS) , the statistical measures RMSE , MAE , and R 2 during the calibration period are 2.57, 2.14, and 0.49, and they are 2.67, 2.34, and 0.56 during the validation period, respectively. For soil salinity, RMSE , MAE , and R 2 during the calibration period are 0.02, 0.02, and 0.92, and 0.06, 0.04, and 0.68 during the validation period, respectively, which are reasonably good for further scenario analysis. Over the four years, cumulative salt uptake varied based on weather conditions. At the optimal salt uptake efficiency (F = 20), cumulative salt uptake from soil was 16–90% for alfalfa, 11–70% for barley, and 10–80% for spring wheat. While at the lowest salt uptake efficiency (F = 40), cumulative salt uptake was nearly zero for all crops. Although barley has the highest peak transpiration flux, alfalfa and spring wheat have greater cumulative salt uptake because their peak transpiration fluxes occurred more frequently than in barley. For salt-tolerant crops biomass growth depends on their threshold soil salinity which determines their ability to take up salt without affecting biomass growth. In order to phytoremediate salt-affected soil, salt-tolerant crops having longer duration of crop physiological stages should be used, but their phytoremediation effectiveness will depend on weather conditions and the soil environment. [Display omitted] • Salt-soil-plant interaction is simulated in denitrification-decomposition model. • Salt uptake is complex function of transpiration flux, soil moisture and salinity. • The cumulative salt uptake in barley is smaller than alfalfa and spring wheat. • Biomass growth of alfalfa is smaller than spring wheat and barley in saline soil. • The longer crop physiological stages is a key for efficient phytoremediation. [ABSTRACT FROM AUTHOR]