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Medium-low temperature pyrolysis is an effective method of retaining active components in sludge char. However, we found that incomplete cracking reactions resulted in residues of microplastics (MPs) remaining in the char; moreover, high levels of environmentally persistent free radicals (EPFRs) were detected in these MPs. Here, we investigated the temperature-dependent variations in the char-volatile products derived from sludge and MPs under different pyrolysis scenarios using multiple in situ probe coupling techniques and electron paramagnetic resonance spectroscopy, thereby identifying the sources of EPFRs and elucidating the corresponding formation-conversion mechanisms. The temperature was the key factor in the formation of EPFRs; in particular, in the 350-450 °C range, the abundance of EPFRs increased exponentially. Reactive EPFR readily formed in MPs with conjugated aromatic-ring structures (polyethylene terephthalate and polystyrene) at a temperature above 350 °C; EPFR concentrations were 5-17 times higher than those found in other types of polymers, and these radicals exhibited half-lives of more than 90 days. The EPFR formation mechanism could be summarized as solid-solid/solid-gas interfacial interactions between the polymers and the intermediate products from sludge pyrolysis (at 160-350 °C) and the homolytic cleavage-proton transfer occurring in the polymers themselves under the dual action of thermal induction and acid sites (at 350-450 °C). Based on the understanding of the evolution of EPFRs, temperature regulation and sludge components conditioning may be effective approaches to inhibit the formation of EPFRs in MPs, constituting reliable strategies to diminish the environmental risk associated with the byproducts of sludge pyrolysis.

This study aimed to develop a multistage treatment system for highly toxic wastewater named reverse osmosis concentrates (ROC) of landfill leachate (LL). Therefore, a combination of the ammonia stripping process (ASP), catalytic ozone oxidation process (COP) and Heterotrophic Nitrification Aerobic Denitrification process (HNADP) was proposed and the quality of effluent was evaluated for the concentration of Chemical Oxygen Demand (COD), ammonia nitrogen (NH4+-N) and total nitrogen (TN). ASP had moderate removal efficiency of NH4+-N, and TN in the effluent. COP was catalyzed by cerium supported activated carbon (Ce-AC) achieved good performance in disposal of COD. The effluent of HNADP had the most significant removal efficiency of COD, NH4+-N, and TN. As a result, the effluent of combined process successfully met the discharge standards for NH4+-N and TN according to Table 2 of GB 16889-2008 in China. To investigate the microbial mechanism of pollutant removal in HNADP, 16S rRNA high-throughput sequencing was performed and the results suggested that the relative abundance and diversity of microorganisms fluctuated with the changes of COD/TN ratio(C/N) in HNADP. Truepera and Halomonas were identified as the key genera involved in the simultaneous degradation of COD and nitrogen-containing pollutants, the functional genes (hao, amoA, nirS and nirK) were predicted in nitrification and denitrification process. Overall, this study demonstrates a feasible multistage system for treatment of ROC and propose that further explorations of combined techniques may lead to even more satisfactory removal efficiencies.

The relationship between the migration process and speciation distribution of Cr is important for the risk assessment in the underground environment. In this work, soil columns were collected from the chromate production site, with a 40-year operation, in the groundwater depression cone area of North China plain. The relationship between chromium pollution features and the geochemical properties of soil was established, and the migration risk of Cr(VI) was assessed based on the Nemerow composite index and Hydrus-1D model. The maximum total Cr concentration in the chromium slag dumping site reached 907 mg/kg, and that in the chromate production workshop was more than 200 mg/kg across the depth. The migration of Cr might be accelerated in the soil with abundant Mn (236-1461 mg/kg) but scarce organic matters ( 0.45%). The Hydrus simulation indicated that Cr(VI) would reach a cumulative flux of 300-729 mg/cm

The effect of interactions between different components in sewage sludge on the thermochemical transformation of nitrogenous species is usually neglected, which is important to explain the generation mechanism of some key nitrogenous by-products. Here, we investigated the distribution, form, and chemical properties of the products from sludge-extracted protein (PR) under different pyrolysis scenarios using several in-situ probe techniques, to elucidate the critical role of typical sludge organics/inorganics on the evolution of nitrogenous intermediates and by-products. The results suggested that Ca/Fe/Si/Al-containing inorganics significantly affected the pyrolytic behavior of PR and the thermal transformation of nitrogenous species, while sludge organics, including humic acids and polysaccharides, had limited effects on the temperature-dependent evolution of nitrogenous species in PR. Among them, calcium oxide catalyzed the ring-opening reaction of heterocyclic-N with aromatic-like structures, resulting in a 21.1 %-68.8 % reduction in nitrogen fixation efficiency in the char. At lower temperatures (350-450 °C), calcium oxide caused more nitrogen to be transferred to the gas/tar phases in the form of NH

Low-molecular-weight dissolved organic nitrogen (LMW-DON) is an emerging issue in concentrated leachate (CL). Ozonation is crucial to remove LMW-DON, but selectivity mechanisms of different reactive oxygen species were unknown. Here, reactions of O

Pyrolysis carbonization of sewage sludge is employed to achieve carbon sequestration and access carbon resources, while the quality of the obtained sludge-based carbon (SBC) is poor due to high ash contents and volatile organic matter. Here, carbonization in KOH/Na

Forced aeration is one of the promising ways to accelerate landfill reclamation, and understanding the relation between aeration rates and waste properties is the prerequisite to implementing forced aeration under the target of energy saving and carbon reduction. In this work, landfill reclamation processes with forced aeration were simulated using aged refuses (ARs) of 1, 4, 7, 10, and 13 disposal years, and the potential of field application was also investigated based on a field project, to identify the degradation rate of organic components, the O2 consumption efficiency and their correlations to microbes. It was found that the removal rate of organic matters declined from 20.3% (AR1) to 12.6% (AR13), and that biodegradable matter (BDM) decreased from 5.2–2.4% at the set aeration rate of 0.12 L O2/kg DM/day, respectively. A linear relationship between degradation rate constant (K) of BDM and disposal ages (x) was established: K=-0.0002193x + 0.0091 (R2 = 0.854), suggesting that BDM might be a suitable indicator to reflect the stabilization of ARs. The cellulose/ lignin ratio decrease rate for AR1 (18.3%) was much higher than AR13 (3.1%), while the corresponding humic-acid/ fulvic-acid ratio increased from 1.44 to 2.16. The dominant bacteria shift from Corynebacterium (9.2%), Acinetobacter (6.6%), and Fermentimonas (6.5%), genes related to the decompose of biodegradable organics, to Stenotrophomonas (10.2%) and Clostridiales (3.7%), which were associated with the humification. The aeration efficiencies of lab-scale tests were at the range of 5.4–11.8 g BDM/ L O2 for ARs with disposal ages of 1–13 years, and in situ landfill reclamation, ARs with disposal age of 10–18 years were around 1.9–8.8 g BDM/ L O2, as the disposal age decreased. The increased discrepancy was observed in ARs of lab-scale and field scale, indicating that the forced aeration rate should be adjusted based on aged refuses and the unit compartment combined, to reduce the operation cost.

A novel nanocomposite, named as nZVI@LH, was prepared by nanoscale zero-valent iron (nZVI) supported on lignin hydrogel and was used in the remediation of Cr(VI)-contaminated soil collected from an industrial site. Meanwhile, scanning electron microscopy with energy dispersive X-ray (SEM-EDX) and X-ray diffractometry (XRD) results determined that nZVI nanoparticles disperse uniformly on hydrogel. After the 14 days remediation, the immobilization efficiency of Cr(VI) could reach over 87% in the treatment of 3% (w/w%) nZVI@LH and 26% in the treatment of bare-nZVI. Leaching experiment results showed that the treatment group with 3% (w/w%) nZVI@LH was up to the national leaching toxicity identification standard, and there was no threat in simulation of acid rain over the long term. The water-soluble (WS) fraction in 3

Influent loading determines the performance of leachate treatment plant (LTP) facing the dynamic conditions, but enzyme expression in microbial community is unclear. Here, six nitrogen-metabolizing enzymes were detected during nitrification failures (NF), high loading (HL), low loading (LL), and low carbon/nitrogen (LCN) in a 500 m

The effectiveness and feasibility of the three biochar materials for remediation of arsenic (As) and lead (Pb) contaminated soil were explored in this study. Significant reduction of bioaccessibility and migration risks of both heavy metals have been explained mechanistically by incubation, column experiments and numerical simulation. Langmuir equation fitted As and Pb sorption isotherms better in the control and biochar (BC) amended soils, while Freundlich model was more suitable for iron modified biochar (Fe-BC) and sulfur/iron modified biochar (S/Fe-BC) amended soils, indicating that modified biochar promoted chemical adsorption process for As and Pb. For the three biochar materials, S/Fe-BC showed the best effects on reducing the bioavailability of As and Pb, with a decrease of 40.42%-64.21%. The reduction in bioaccessibility by metal portioning into available and non-available fractions was better for illustrating the mechanisms including adsorption, precipitation/coprecipitation and As(III) oxidation behind S/Fe-BC efficacy. Moreover, S/Fe-BC can effectively inhibit the leaching behavior of As and Pb under acid rain, which increased by 99.89% and 90.18%, respectively, compared with the control. The HYDRUS-1D modeling indicated that S/Fe-BC could continuously treat As (100 mg/L) and Pb (1000 mg/L) contaminated water for 16.22 years and 40.86 years, respectively, and ensure the groundwater quality criteria being met. Based on these insights, we believe that our study will provide meaningful information about the potentials of biochar derived materials for soil heavy metals' remediation.

Anaerobic digestion (AD) is a promising technology to treat waste-activated sludge, previous study proved that methane production could be enhanced with the addition of choline, this work aimed to solve the problem of rapid biodegradability of choline in the AD process by changing its dosing method. With 0.75 g/L as the optimal choline dosing concentration, experimental results showed that successive choline dosing during the first 3-6 days of AD (experimental groups, EGs) performed better than the single dosing. The accumulative biogas production in EGs was increased by 35.55-36.73%, which could be caused by the simultaneous promotion of hydrolysis-acidification and methanogenesis processes. Especially, the electron exchange capacity of digested sludge in EGs was increased by 16.71-34.58%. In addition, the surface Gibbs free energy (△G

As an important Energy Internet technology, energy router (ER) can implement energy routing and information interconnection for the electrical grid within a certain geography range. However, multi-energy supply allocation between multi-energy routers (MERs) has to be resolved, which can connect isolated area networks and expand the scale of the energy Internet. In this paper, equipment capacity and network routing are planned for multi-area multi-energy system (MAMES), which integrates multiple MERs with a virtual multi-energy router (VMER). Firstly, based on the VMER, the concept of MAMES is proposed. Then, the correlation model of multi-energy networks in VMER is constructed, based on MER energy transmission conversion extension model and hybrid power flow model. And the novel routing algorithm is proposed to determine the energy candidate set of the integrated energy networks. During planning, the random scenario generation based on Latin hypercube sampling (LHS) and scenario reduction based on k-means clustering are applied. Finally, the simulation shows that the planning method based on the routing algorithm can effectively obtain the capacity of energy equipment inside MERs and the routing layout between MERs in the MAMES. Proposed routing algorithm and operation scenarios reduction greatly improve the efficiency of planning. Correlated planning helps improve energy efficiency, environment protection, and economic benefits of MAMES.