Leaching behavior and gastrointestinal bioaccessibility of rare earth elements (REEs) from hospital waste incineration (HWI) fly and bottom ash samples collected from Beijing and Nanjing Cities were assessed. In the same ash sample, the leaching concentrations of individual REEs determined by the Toxicity Characteristic Leaching Procedure (TCLP) were higher than those detected by the European standard protocol (EN-type test), thereby suggesting that the low pH value of leaching solution was an important factor influencing the leachability of REE. The REE bioaccessibility results, which were evaluated using the physiologically based extraction test (PBET), indicated that REEs were highly absorbed during gastric phase by dissolution; and subsequently precipitated and/or re-adsorbed in small intestinal phase. The relative amounts of the total REEs extracted by the TCLP method, EN-type test and PBET test were compared. In addition to the pH value of extraction solutions, the chelating role of REEs with organic ligands used in the PBET method was also an important parameter affecting REE adsorption in human body. Additionally, this study showed that REEs were extracted by these methods as concomitants of heavy metals and anions (NO3–, F–, SO42–, and Cl–) from HWI ash, which probably caused the remarkably complex toxicity on human body by the exposure pathway.
Currently, increasing amounts of end-of-life (EoL) electronic products are being generated due to their reduced life spans and the unavailability of suitable recycling technologies. In particular, waste printed circuit boards (PCBs) have become of global concern with regard to environmental issues because of their high metal and toxic material contents, which are pollutants. There are many environmental threats owed to the disposal of electronic waste; off-gasses, such as dioxins, furans, polybrominated organic pollutants, and polycyclic aromatic hydrocarbons, can be generated during thermal treatments, which can cause serious health problems if effective off-gas cleaning systems are not developed and improved. Moreover, heavy metals will dissolve, and release into the ground water from the landfill sites. Such waste PCBs contain precious metals which are of monetary value. Therefore, it is beneficial to recover the metal content and protect the environment from pollution. Hydrometallurgy is a successful technique used worldwide for the recovery of precious metals (especially gold and silver) from ores, concentrates, and waste materials. It is generally preferred over other methods because it can offer high recovery rates at a relatively low cost. This article reviews the recent trends and developments with regard to the recycling of precious metals from waste PCBs through hydrometallurgical techniques, such as leaching and recovery.
Waste pickling liquors (WPLs) containing high concentrations of iron and acid are hazardous waste products from the steel pickling processes. A novel combined coprecipitation–oxidation method for iron recovery by Fe3O4 nanoparticle production from the WPLs was developed in this study. An oxidation–reduction potential monitoring method was developed for real-time control of the Fe2+/Fe3+ molar ratio. The key coprecipitation–oxidation parameters were determined using the orthogonal experimental design method. The use of promoters greatly improved the Fe3O4 nanoparticle crystallinity, size, magnetization, and dispersion. X-ray diffraction patterns showed that the produced Fe3O4 nanoparticles were single phase. The Fe3O4 nanoparticles were approximately spherical and slightly agglomerated. Vibrating sample magnetometry showed that the Fe3O4 nanoparticles produced from the WPLs had good magnetic properties, with a saturation magnetization of 80.206 emu·g–1 and a remanence of 10.500 emu·g–1. The results show that this novel coprecipitation–oxidation method has great potential for recycling iron in WPLs.
This work presents an overall introduction to the Station for Observing Regional Processes of the Earth System–SORPES in Nanjing, East China, and gives an overview about main scientific findings in studies of air pollution-weather/climate interactions obtained since 2011. The main results summarized in this paper include overall characteristics of trace gases and aerosols, chemical transformation mechanisms for secondary pollutants like O3, HONO and secondary inorganic aerosols, and the air pollution–weather/climate interactions and feedbacks in mixed air pollution plumes from sources like fossil fuel combustion, biomass burning and dust storms. The future outlook of the development plan on instrumentation, networking and data-sharing for the SORPES station is also discussed.
Bottom ash is an inevitable by-product from municipal solid waste (MSW) incineration plants. Recycling it as additives for cement production is a promising disposal method. However, the heavy metals and chlorine are the main limiting factors because of the potential environmental risks and corrosion of cement kilns. Therefore, investigating heavy metal and chlorine characteristics of bottom ash is the significant prerequisite of its reuse in cement industries. In this study, a correlative analysis was conducted to evaluate the effect of the MSW components and collection mode on the heavy metal and chlorine characteristics in bottom ash. The chemical speciation of insoluble chlorine was also investigated by synchrotron X-ray diffraction analysis. The results showed that industrial waste was the main source of heavy metals, especially Cr and Pb, in bottom ash. The higher contents of plastics and kitchen waste lead to the higher chlorine level (0.6 wt.%–0.7 wt.%) of the bottom ash. The insoluble chlorine in the MSW incineration bottom ash existed primarily as AlOCl, which was produced under the high temperature (1250°C) in incinerators.
Recycling of waste electrical and electronic equipment (WEEE) is crucially important since it handles hazardous waste according to ever tightening laws and regulations and it adds benefits to economy and sustainable environment. Disassembly is one of the most important processes performed during the recovery of WEEE. The overall goal of disassembly is to maximize the retrieval of various metals and plastics contained in WEEE in order to reduce their negative effects on human health and environmental sustainability and to increase economic gains. This study aims to evaluate alternative layout configurations for WEEE disassembly systems (WDS). In this context, various configurations were compared in terms of pre-defined performance criteria, such as the total number of disassembled WEEE and the total revenue from sales, using simulation models. The results of this study show that the performance of a WDS was significantly affected by output transfer systems along with the specialization of operators on certain types of WEEE.
Effect of different carbon sources on purification performance and change of microbial community structure in a novel A2N-MBR process were investigated. The results showed that when fed with acetate, propionate or acetate and propionate mixed (1:1) as carbon sources, the effluent COD, NH4+-N, TN and TP were lower than 30, 5, 15 and 0.5 mg?L–1, respectively. However, taken glucose as carbon source, the TP concentration of effluent reached 2.6 mg?L–1. Process analysis found that the amount of anaerobic phosphorus release would be the key factor to determine the above effectiveness. The acetate was beneficial to the growth of Candidatus Accumulibacter associated with biological phosphorus removal, which was the main cause of high efficiency phosphorus removal in this system. In addition, it could eliminate the Candidatus Competibacter associated with glycogen-accumulating organisms and guarantee high efficiency phosphorus uptake of phosphorus accumulating organisms in the system with acetate as carbon source.
Conventional biological removal of nitrogen and phosphorus is usually limited due to the lack of biodegradable carbon source, therefore, new methods are needed. In this study, a new alternative consisting of enhanced biological phosphorus removal (EBPR) followed by partial nitritationanammox (PN/A), is proposed to enhance nutrients removal from municipal wastewater. Research was carried out in a laboratory-scale system of combined two sequencing batch reactors (SBRs). In SBR1, phosphorus removal was achieved under an alternating anaerobic-aerobic condition and ammonium concentration stayed the same since nitrifiers were washed out from the reactor under short sludge retention time of 2–3 d. The remaining ammonium was further treated in SBR2 where PN/A was established by inoculation. A maximum of nitrogen removal rate of 0.12 kg N?m–3?d–1 was finally achieved. During the stable period, effluent concentrations of total phosphorus and total nitrogen were 0.25 and 10.8 mg?L–1, respectively. This study suggests EBPR-PN/A process is feasible to enhance nutrients removal from municipal wastewater of low influent carbon source.
Bdellovibrio-and-like organisms (BALOs) are a group of ubiquitous and obligate predatory bacteria and commonly used as biocontrol agents. In this study, an efficient, environmental-friendly, and convenient BALOs encouraged municipal waste sludge biolysis pretreatment technique was developed and investigated for dewaterability enhancement of excess waste sludge. The indigenous predatory BALOs were successfully isolated from the sludge for biolysis treatment. Without any chemical addition or pH adjustment, the sludge specific resistance (SRF) and capillary suction time (CST) were significantly reduced by as high as 53.4% and 23.8%, respectively within 24 h’s treatment, which would further be lowered with the increase of BALOs input dosage. However, the continuous extension of reaction time would worsen the sludge dewaterability. The decreases of SRF and CST accompanied with the increases of sludge disintegration degree and soluble chemical oxygen demand, nitrogen, and phosphorus concentrations all emphasized the contributions of BALOs’ predation activities to sludge disturbance, cell lysis, and consequently the release of sludge intracellular water to finally effectively improve the sludge dewaterability and disposal efficiency.
A novel microorganism embedding material was prepared to enhance the biological nitrogen removal through simultaneous nitrification and denitrification. Polyvinyl alcohol (PVA), sodium alginate (SA) and cyclodextrin (CD) were used to compose gel bead with embedded activated sludge. The effects of temperature, CD addition and concentrations of PVA and SA on nitrogen removal were evaluated. Results show that the gel bead with CD addition at 30°C contributed to the highest nitrogen removal efficiency and nitrogen removal rate of 85.4% and 2.08 mgL·(L·h)–1, respectively. Meanwhile, negligible NO3– and NO2– were observed, proving the occurrence of simultaneous nitrification and denitrification. The High-Throughput Sequencing confirms that the microbial community mainly contained Comamonadaceae in the proportion of 61.3%. Overall, CD increased gel bead’s porosity and resulted in the high specific endogenous respiration rate and high nitrogen removal efficiency, which is a favorable additional agent to the traditional embedding material.
Many studies have focused on environmental estrogen-related diseases. However, no consistent gene markers or signatures for estrogenicity have been discovered in mammals. This study investigated the estrogenic effects of 17β-estradiol on the prostate in immature male mice. Consistent U-shaped responses were seen in bodyweight, ventral prostate epithelial morphology, and miRNA expression levels. Specifically, most estradiol regulated miRNAs were downregulated at low doses of estradiol (0.2 and 2 mg·kg–1), and whose expression returned to the control level at a larger dose (200 mg·kg–1). The function of these regulated miRNAs is related to the prostate cancer and PI3K-Akt signaling pathways, which is consistent with the function of estradiol. Furthermore, the miRNA-processing machinery, Drosha, in the prostate was also regulated in a similar pattern, which could be a part of the U-shaped miRNA expression mechanism. All of these data indicate that the prostate is a reliable organ for evaluating estrogenic activity and that the typical nonmonotonic dose-response relationship could be used as a novel biomarker for estrogenicity.
Utilizing oil extracted from waste engine oil and waste plastics, by pyrolysis, as a fuel for internal combustion engines has been demonstrated to be one of the best available waste management methods. Separate blends of fuel from waste engine oil and waste plastic oil was prepared by mixing with diesel and experimental investigation is conducted to study engine performance, combustion and exhaust emissions. It is observed that carbon monoxide (CO) emission increases by 50% for 50% waste plastic oil (50WPO:50D) and by 58% for 50% waste engine oil (50WEO:50D) at full load as compared to diesel. Unburnt hydrocarbon (HC) emission increases by 16% for 50WPO:50D and by 32% for 50WEO:50D as compared to diesel at maximum load. Smoke is found to decrease at all loading conditions for 50WPO:50D operation, but it is comparatively higher for 50WEO:50D operation. 50WPO:50D operation shows higher brake thermal efficiency for all loads as compared to 50WEO:50D and diesel fuel operation. Exhaust gas temperature is higher at all loads for 50WPO:50D and 50WEO:50D as compared to diesel fuel operation.
In addition to maximizing economic benefits, reverse supply chains should further seek to maximize social benefits by increasing the quantity of waste electrical and electronic equipment (WEEE). The paper investigates cooperative models with different parties in a three-echelon reverse supply chain for WEEE consisting of a single collector, a single remanufacturer, and two retailers based on complete information. In addition, the optimal decisions of four cooperative models and the effect of the market demand of remanufactured WEEE products and the market share of two retailers on the optimal decisions are discussed. The results indicate that optimal total channel profit and recycle quantity in a reverse supply chain are maximized in a centralized model. The optimal total channel profit and recycle quantity increase with an increase in the market demand of remanufactured WEEE products. The three-echelon reverse supply chain consisting of duopolistic retailers maximizes total channel profit and recycle quantity in a reverse supply chain for WEEE.
The effect of microwave pretreatment on the anaerobic degradation of hyacinth was investigated using response surface methodology (RSM). The components of lignin and the other constituents of hyacinth were altered by microwave pretreatment. Comparison of the near-infrared spectra of hyacinth pretreated by microwave irradiation and water-heating pretreatment revealed that no new compounds were generated during hyacinth pretreatment by microwave irradiation. Atomic force microscopy observations indicated that the physical structures of hyacinth were disrupted by microwave pretreatment. The yield of methane per gram of the microwave-irradiated substrate increased by 38.3% as compared to that of the substrate pretreated via water-heating. A maximum methane yield of 221 mL?g-sub–1 was obtained under the optimum pretreatment conditions (substrate concentration (PSC) = 20.1 g?L–1 and pretreatment time (PT) = 14.6 min) using RSM analysis. A maximum methane production rate of 0.76 mL?h–1?g-sub–1 was obtained by applying PSC = 9.5 g?L–1 and PT = 11 min. Interactive item coefficient analysis showed that methane production was dependent on the PSC and PT, separately, whereas the interactive effect of the PSC and PT on methane production was not significant. The same trend was also observed for the methane production rate.
Biological synthesis of quantum dots (QDs) as an environmental-friendly and facile preparation method has attracted increasing interests. However, it is difficult to distinguish the roles of bio-thiols in QDs synthesis process because of the complex nature in organisms. In this work, the CdSe QDs synthesis conditions in organisms were reconstructed by using a simplified in vitro approach to uncover the roles of two small bio-thiols in the QDs formation. CdSe QDs were synthesized with glutathione (GSH) and L-cysteine (Cys) respectively. Compared with Cys at the same molar concentration, the CdSe QDs synthesized by GSH had a larger and broader particle size distribution with improved optical properties and crystal structure. Furthermore, quantum chemical calculations indicate that the stronger Cd2+ binding capacity of GSH contributed a lot to the CdSe QDs formation despite of the greater capability Cys for selenite reduction. This work clearly demonstrates the different roles of small thiols in the Cd2+ stabilization in the environment and biomimetic QDs synthesis process.
Sulfamethoxzole (SMX) and trimethoprim (TMP), two combined-using sulfonamide antibiotics, have gained increasing attention in the surface water, groundwater and the drinking water because of the ecological risk. The removal of TMP and SMX by artificial composite soil treatment system (ACST) with different infiltration rates was systematically investigated using K+, Na+, Ca2+, Mg2+ hydrogeochemical indexes. Batch experiments showed that the sorption onto the low-cost and commercially available clay ceramsites was effective for the removal of SMX and TMP from water. The column with more silty clay at high infiltration rate (1.394 m·d–1) had removal rates of 80% to 90% for TMP and 60% to 70% for SMX. High SMX and TMP removal rates had a higher effluent concentration of K+, Ca2+ and Mg2+ and had a lower effluent Na+ concentration. Removal was strongly related to sorption. The results showed that the removal of SMX and TMP was related to hydrogeochemical processes. In this study, ACST is determined to be applicable to the drinking water plants.
Cadmium (Cd) and lead (Pb) in water and soil could be adsorbed by biochar produced from corn straw. Biochar pyrolyzed under 400°C for 2 h could reach the ideal removal efficiencies (99.24%and 98.62% for Cd and Pb, respectively) from water with the biochar dosage of 20 g·L–1 and initial concentration of 20 mg·L–1. The pH value of 4–7 was the optimal range for adsorption reaction. The adsorption mechanism was discussed on the basis of a range of characterizations, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR) and Raman analysis; it was concluded as surface complexation with active sorption sites (-OH, -COO-), coordination with π electrons (C = C, C = O) and precipitation with inorganic anions (OH-, CO32–, SO42–) for both Cd and Pb. The sorption isotherms fit Langmuir model better than Freundlich model, and the saturated sorption capacities for Cd and Pb were 38.91 mg·g-1 and 28.99 mg·g–1, respectively. When mixed with soil, biochar could effectively increase alkalinity and reduce bioavailability of heavy metals. Thus, biochar derived from corn straw would be a green material for both removal of heavy metals and amelioration of soil.
Sulfamethoxazole (SMX) and trimethoprim (TMP) are two critical sulfonamide antibiotics with enhanced persistency that are commonly found in wastewater treatment plants. Recently, more scholars have showed interests in how SMX and TMP antibiotics are biodegraded, which is seldom reported previously. Novel artificial composite soil treatment systems were designed to allow biodegradation to effectively remove adsorbed SMX and TMP from the surface of clay ceramsites. A synergy between sorption and biodegradation improves the removal of SMX and TMP. One highly efficient SMX and TMP degrading bacteria strain, Bacillus subtilis, was isolated from column reactors. In the removal process, this bacteria degrade SMX and TMP to NH4+, and then further convert NH4+ to NO3– in a continuous process. Microbial adaptation time was longer for SMX degradation than for TMP, and SMX was also able to be degraded in aerobic conditions. Importantly, the artificial composite soil treatment system is suitable for application in practical engineering.
Denitrifying biofilter (DNBF) is widely used for advanced nitrogen removal in the reclaimed wastewater treatment plants (RWWTPs). Manual control of DNBF easily led to unstable process performance and high cost. Consequently, there is a need to automatic control of two decisive operational processes, carbon dosage and backwash, in DNBF. In this study, online control of DNBF was investigated in the pilot-scale DNBF (600 m3·d–1), and then applied in the full-scale DNBF (10 × 104 m3·d–1). A novel simple online control strategy for carbon dosage with the effluent nitrate as the sole control parameter was designed and tested in the pilot-scale DNBF. Backwash operation was optimized based on the backwash control strategy using turbidity as control parameter. Using the integrated control strategy, in the pilot-scale DNBF, highly efficient nitrate removal with effluent TN lower than 3 mg·L–1 was achieved and DNBF was not clogged any more. The online control strategy for carbon dosage was successfully applied in a RWWTP. Using the online control strategy, the effluent nitrate concentration was controlled relatively stable and carbon dosage was saved for 18%.
Methane production from low-strength wastewater (LSWW) is generally difficult because of the low metabolism rate of methanogens. Here, an up-flow biofilm reactor equipped with conductive granular graphite (GG) as fillers was developed to enhance direct interspecies electron transfer (DIET) between syntrophic electroactive bacteria and methanogens to stimulate methanogenesis process. Compared to quartz sand fillers, using conductive fillers significantly enhanced methane production and accelerated the start-up stage of biofilm reactor. At HRT of 6 h, the average methane production rate and methane yield of reactor with GG were 0.106 m3/(m3·d) and 74.5 L/kg COD, which increased by 34.3 times and 22.4 times respectively compared with the reactor with common quartz sand fillers. The microbial community analysis revealed that methanogens structure was significantly altered and the archaea that are involved in DIET (such as Methanobacterium) were enriched in GG filler. The beneficial effects of conductive fillers on methane production implied a practical strategy for efficient methane recovery from LSWW.
