The removal of residual organics from manganese (Mn) electrochemical solution using combined Fenton oxidation process with adsorption over activated carbon (AC) was investigated. The effect of operating conditions such as dosage of H₂O₂, H₂O₂/Fe²⁺ ratio, initial pH value, reaction temperature, and reaction time on Fenton oxidation was studied. Experimental results indicated that a maximum chemical oxygen demand (COD) of 83.2% was obtained under the optimized set of conditions: H₂O₂ concentration of 0.15 mol/L, H₂O₂/Fe²⁺ molar ratio of 3, initial pH value of 3, reaction temperature of 50 °C, and reaction time of 90 min. The leaching solution was furthered treated over AC and COD removal rate increased to 93.1% under 3.75 g/L dosage of AC, adsorption temperature of 70 °C, and adsorption time of 120 min. The adsorption mechanism of Mn over AC was detailly investigated, while the porous texture of AC was studied by nitrogen adsorption isotherm.

This study used the integrated biomarker response (IBR) index approach to assess the ecological risks of heavy metals in different regions of Dianchi Lake, combined with active monitoring and passive monitoring. The contents of five heavy metals (Cu, As, Cd, Hg, and Pb) and six biomarkers (acetylcholinesterase, sodium-potassium ATPase, metallothionein, superoxide dismutase, glutathione peroxidase, and malondialdehyde) in the muscles of crucians (Carassius auratus) were measured to calculate the IBR value. The results indicate that the contents of heavy metal in the fish under active monitoring and passive monitoring were rather low and did not exceed the National Food Safety Standards of China. The IBR value of day 14 of active monitoring correlated with the heavy metal Cd content in the fish, suggesting a potential risk of Cd pollution in the aquatic environment of Dianchi Lake. The IBR values obtained for different regions of the lake on day 14 can be arranged in the following order: West S3 (9.24) > East S1 (3.97) > South S2 (2.39) > North S4 (0.36). These results suggest a potential risk of heavy metal contamination in the western part of Dianchi Lake.

In this study, partial nitrification algal-bacterial granular sludge system was cultivated when treating ammonium-rich wastewater. With 200 mg/L influent NH₄-N concentration, the effluent NH₄-N, NO₂-N and NO₃-N concentrations were maintained at 62.3 mg/L, 67.1 mg/L, and 7.8 mg/L, making it as an ideal influent for anaerobic ammonia oxidation (Anammox). The combined stress of algae growth and free nitrous acid (FNA) should be responsible for partial nitrification in algal-bacterial granular sludge system. The concentration of N-acyl-homoserine lactones (AHLs, quorum sensing molecule) in the effluent of RL was up to 772.5 ng/L, much higher than that (592.8 ng/L) in the effluent of control without light irradiation (RC), leading to enhanced EPS production and granulation in the partial nitrification algal-bacterial granular sludge system. Because of the growth of algae (Chlorella, Scenedesmus, and Navicula), the lipid content in the algal-bacterial granules was 57.4 mg/g-SS, which was about 1.7 times higher than that in the granules from RC, making the algal-bacterial granule a value-added biomass. The relative abundance of Nitrosomonadaceae (AOB) slightly decreased from 5.4% in RC to 3.8% in RL, while Nitrospiraceae (NOB) was completely inhibited in algal-bacterial granules.

Endogenous pollution is one of the most notable issues in drinking water reservoirs, since the sediment is a main sink of contaminants in the aquatic environment. In this work, we investigated the spatial distribution characteristics of heavy metals and different species of N and P and assessed the pollution risks of the sediments from the Chenhang Reservoir, which is the first drinking water reservoir supplied by Yangtze River in Shanghai, China. The results show that heavy metals, including Cu, Pb, Zn, Mn, and Fe, were mainly accumulated in the downstream, while most Ni and Cr were concentrated in the sediments from the central and western zones. Total N in the sediments was primarily distributed in the eastern reservoir, while ammonia N and most of total P were accumulated in the central and eastern areas. The geo-accumulation index (Igₑₒ) and potential ecological risk index (PERI) suggest that the sediments were polluted by combined heavy metals at minor to medium levels, posing a potential risk to ecosystem. Moreover, sediment quality guidelines (SQGs) indicate that Ni in all sites and Zn in the eastern reservoir would cause great negative biological response to benthic organisms. Additionally, the sediments were slightly polluted by N but not P, especially in the downstream. Multivariate statistical analyses revealed that Cu, Zn, Pb, and N mainly derived from industrial wastewater, domestic sewage and surface runoff from the Yangtze River, while Cr, Ni, and P mainly originated from natural erosion and nonpoint sources. Graphical Abstract .

The anaerobic decomposition of coconut endosperm waste (CEW), residue derived from cooking, has been insidiously spewing greenhouse gasses. Thus, the bioconversion of CEW via in situ fermentation by exo-microbes from commercial Rid-X and subsequent valorization by black soldier fly larvae (BSFL) was the primary objective of the current study to gain sustainable larval lipid and protein. Accordingly, various concentrations of exo-microbes were separately homogenized with CEW to perform fermentation amidst feeding to BSFL. It was found that 2.50% of exo-microbes was the threshold amount entailed to assuage competition between exo-microbes and BSFL for common nutrients. The presence of remnant nutrients exuded from the fermentation using 2.50% of exo-microbes was confirmed to promote BSFL growth measured as maximum larval weight gained and growth rate. Although the BSFL could accumulate the highest protein (16 mg/larva) upon feeding with CEW containing 2.50% of exo-microbes, more lipid (13 mg/larva) was stored in employing 0.10% of exo-microbes because of minimum loss to metabolic processes while prolonging the BSFL in its 5th instar stage.

The simulation-optimization method is widely used in the design of the groundwater pollution monitoring network (GPMN). The uncertainty of the simulation model will significantly affect the design results of GPMN. When the Monte Carlo method is used to consider the influence of model uncertainty on the optimization results, the simulation model needs to be invoked many times, which will cause a huge amount of calculation. To reduce the calculation load, the study proposed to use the support vector regression (SVR) method to construct the surrogate model to couple the simulation model and the optimization model in the optimal design of GPMN. The optimization goal is to maximize the accuracy of the spatial description of pollution plume in each monitoring period. The study also considered the dynamic changes in the migration and morphological of pollution plumes in the optimization of GPMN. Finally, the West Shechang coal gangue pile in Fushun of China was used as a case study to verify the effectiveness of the above method. The results demonstrate that the SVR surrogate model can fit the input-output relationship of the simulation model to a high degree with less computation. The optimized monitoring network can reveal essential and comprehensive information about pollution plumes. The study provides a stable and reliable method for the design of GPMN.

Ecosystems play critically important roles in supporting human society, while human activities seriously disturb their initial balance. Lots of researches on ecosystem services are conducted due to the increasing concern on ecological security worldwide. In order to provide valuable insights for understanding the primary performance of ecosystem services–related studies, a qualitative and quantitative analysis by using a bibliometric tool is performed in this study. Journal impact factor, CiteScore, and h-index are used for identifying influential journals, while h-index is used for recognizing productive countries/territories and institutions. Social network analysis of countries/territories and institutions is visualized, respectively, so that relationships among them can be uncovered. Citation analysis of publications and co-occurrence analysis of high-frequency keywords are also performed to explore hotspots and popular methods in this field. This study uncovers a holistic picture on the primary performance of ecosystem services–related literatures published from 1997 to 2016, including journals, countries/territories, and institutions. Results find that forest, agriculture, and wetland ecosystems attract lots of attention. Finally, major methods used for ecosystem services evaluation are identified and discussed. Research outcomes will provide valuable insights to stakeholders interested in ecosystem services.

The phenol removal by adsorption through the guava tree bark has been studied in this research. The surface characterizations of the guava tree bark were assessed through BET, FTIR, and SEM apparatus. The phenol removal percentage was investigated in batch experiments taking phenol content (30–150 mg/L), time (30–180 min), pH (4–9), adsorbent dose (1–6 g/L), and temperature (30–50 °C). The maximum percentage of phenol removal was obtained at 90.67% at the phenol concentration of 30 mg/L, the contact time of 120 min, pH of 7, adsorbent dose of 4 g/L, and temperature of 50 °C. The kinetic study indicated that the second-order was superior to the first order. The isotherm study exhibited that the Freundlich isotherm fitted best among the Langmuir, D-R (Dubinin-Radushkevich), and Temkin isotherms. The value of adsorption energy evaluated by the D-R isotherm supported physical adsorption; however, the mechanism seemed to be weaker since the correlation coefficient of the D-R model was found to be quite less than the correlation coefficients of other isotherm models. The adsorption mechanisms through film diffusion and chemisorption were well established as tested by the Reichenberg model, the Elovich model, the Fick model, the Furusawa and Smith model, and the Boyd model. The adsorption thermodynamics concluded that the adsorption method supported endothermic, random, and spontaneous. The scale-up design, the procedure for safe disposal of spent adsorbent, and the regeneration of the adsorbent were deliberated in this research. The research determined that the guava tree bark is suitable for the removal of phenol from wastewater.

The presence of phosphorus in water is a major cause behind the eutrophication of the aquatic environment. The growing trend focuses on the use of agriculture waste to fabricate biosorbents with higher removal capabilities for phosphate present in wastewater. Herein, a novel adsorbent named multifunctional biochar (MFBC) was applied for the decontamination of both phosphate and cadmium through two-stage adsorption. The as-prepared MFBC was characterized by TEM, BET, XPS, FTIR, and Raman spectroscopy techniques to confirm the successful grafting and presence of multiple functionalities with both amino and carboxylic functional groups on biochar (BC) surface after chemical modification route was applied. The saturated uptake capacity of phosphate that reached 57.50 mg P g⁻¹ for MFBC was noticed within 75 min at pH 5.0 and 20 °C. Based on the results obtained from adsorption kinetics and isotherm studies, as well as XPS analysis, it was interpreted that the phosphate removal was due to physical electrostatic interaction developed between protonated amino groups (–NH₃⁺) and anionic phosphate. The as-obtained multifunctional biochar loaded with phosphate (MFBC-P) demonstrated efficient cadmium ion (Cd²⁺) uptake up to 61.40 mg g⁻¹ when it was further applied for second-stage adsorption in aqueous solution. Both residual carboxylic group and phosphate loaded on MFBC-P surface were responsible for Cd²⁺ sorption. Further XRD analysis revealed that cadmium was immobilized in the form of Cd (H₂PO₄)₂ and CdCO₃. In the binary solution system, the synergistic effects between phosphate and Cd²⁺ ions were monitored such as phosphate removal increases from 91.25 to 95.40% in the presence of Cd²⁺ ions as well as the remarkable enhancement from 36.11 to 83.76% in Cd²⁺ ion uptake value noticed for coexisting phosphate ions when MFBC was tested. The study shows that BC incorporated with multiple functionalities can provide attractive applications for environmental purification.

In this study, a composite aerogel (WP-MMT) composed of wastepaper (WP) and montmorillonite (MMT) was prepared by ambient pressure drying technology to adsorb Cd²⁺. The study of compression performance indicated that the composite aerogel had ideal mechanical strength when the mass ratio of WP to MMT was 1:1. The specific surface areas of the aerogels modified by hydrogen peroxide (WP-MMT-H₂O₂) and sodium hydroxide (WP-MMT-NaOH) were increased greatly. The sorption isotherms and kinetics of Cd²⁺ sorption on WP-MMT-H₂O₂ and WP-MMT-NaOH were investigated. The Cd²⁺ sorption data could be well described by a simple Langmuir model, and the pseudo-second-order kinetic model best fitted the kinetic data. The maximum sorption capacity obtained from the Langmuir model was 232.50 mg/g for WP-MMT-NaOH. The adsorption mechanism of WP-MMT was chemical adsorption of a single-molecule layer. In general, it was proved that the composite aerogel with high adsorption capacity of Cd²⁺ could be synthesized from modified WP and MMT by ambient pressure drying. The composite aerogel fabricated by wastepaper and montmorillonite showed bright application prospect in the aqueous heavy metal pollution control.