Insights into chromium removal mechanism by Ca-based sorbents from flue gas.

Chromium is a typical toxic pollution in sewage sludge incineration flue gas. Cr removal from flue gas is a challenge due to the high toxicity and valence variability of chromium. Ca-based sorbents, including CG-CaO, CA-CaO, and CCi-CaO, were developed for Cr capture by calcining calcium D-gluconate monohydrate, calcium acetate hydrate, and calcium citrate tetrahydrate, respectively. CG-CaO, CA-CaO, and CCi-CaO exhibit better Cr removal performance than traditional CaO. CA-CaO shows superior Cr adsorption ability due to the large BET surface area and pore volume. The Cr adsorption efficiency of CA-CaO is up to 94.79 % at 1000 °C. XRD and XPS results reveal that the adsorbed Cr contains Cr(III) and Cr(VI), and exists in the form of CaCr2O4 and CaCrO4. Cr adsorption on Ca-based sorbents is mainly controlled by adsorption and oxidation mechanism. The adsorption process of Cr on different Ca-based sorbents was described by four typical adsorption kinetic models. For CaO and CG-CaO, pseudo-first order model and Elovich model are suitable for the description of Cr adsorption. For CA-CaO and CCi-CaO, pseudo-second order model, Elovich model and Weber and Morris model fit well with the experimental values of Cr adsorption, suggesting that Cr adsorption on CA-CaO and CCi-CaO is controlled by a combined mechanism of chemisorption and intraparticle diffusion. The saturated adsorption capacity of CaO, CG-CaO, CA-CaO and CCi-CaO are evaluated to be 39.77, 48.98, 102.22 and 104.52 mg/g, respectively. The effects of incineration flue gas components on Cr adsorption were also explored. O2 shows no obvious influence on Cr adsorption over CA-CaO. HCl, SO2, NO and CO2 can inhibit Cr adsorption because of the competitive adsorption, and the inhibitory effect of SO2 is the strongest.

Comparative study of high-performance mesophilic and thermophilic anaerobic membrane bioreactors in the co-digestion of sewage sludge and food waste: Methanogenic performance and energy recovery potential.

To support smart cities in terms of waste management and bioenergy recovery, the co-digestion of sewage sludge (SeS) and food waste (FW) was conducted by the anaerobic membrane bioreactor (AnMBR) under mesophilic and thermophilic conditions in this study. The biogas production rate of the thermophilic AnMBR (ThAnMBR) at the SeS to FW ratio of 0:100, 75:25, 50:50 and 100:0 was 2.84 ± 0.21, 2.51 ± 0.26, 1.54 ± 0.26 and 1.31 ± 0.08 L-biogas/L/d, inconspicuous compared with that of the mesophilic AnMBR (MeAnMBR) at 3.00 ± 0.25, 2.46 ± 0.30, 1.63 ± 0.23 and 1.30 ± 0.17 L-biogas/L/d, respectively. The higher hydrolysis ratio and the poorer rejection efficiencies of the membrane under thermophilic conditions, resulting that the permeate COD, carbohydrate and protein of the ThAnMBR was higher than that of the MeAnMBR. The lost COD that might be converted into biogas was discharged with the permeate in the ThAnMBR, which was partly responsible for the inconspicuous methanogenic performance. Furthermore, the results of energy recovery potential assessment showed that the energy return on investment (EROI) of the MeAnMBR was 4.54, 3.81, 2.69 and 2.22 at the four SeS ratios, which was higher than that of the ThAnMBR at 3.29, 2.97, 2.02 and 1.80, respectively, indicating the advantage of the MeAnMBR over the ThAnMBR in energy recovery potential. The outcomes of this study will help to choose a more favorable temperature to co-digest SeS and FW to support the construction of smart cities.

Enhanced digestion of sludge via co-digestion with food waste in a high-solid anaerobic membrane bioreactor: Performance evaluation and microbial response.

A 15 L high-solid mesophilic AnMBR was operated for the digestion of food waste, primary sludge and excess sludge. The digestion performance was evaluated from the perspective of methane generation, permeate quality and organic reduction. Furthermore, the change in the microbial community was investigated by 16S rRNA gene analysis. The results showed that the introduction of sludge decreased the H2S levels in biogas compared with the mono-digestion of food waste and the co-digestion with food waste increased biogas and methane production compared with the mono-digestion of sludge. A substitution ratio of 25 % became a turning point of permeate composition and reaction rates. The energy recovery ratios of the mesophilic AnMBR were over 75 % based on stoichiometric analysis. In reaction kinetics analysis, hydrolysis as the first step of anaerobic digestion was found to be most influenced by the composition of the substrate. Finally, the microbial community structures were stable under tested conditions while the evolutionary relationships within the dominant phyla were observed. In the archaea community, Methanosaeta was the dominant methanogen regardless sludge ratio in the substrate.

Treatment of fresh leachate by anaerobic membrane bioreactor: On-site investigation, long-term performance and response of microbial community.

This study proposed fresh leachate treatment with anaerobic membrane bioreactor (AnMBR) based on the on-site investigation of the characteristics of fresh leachate. Temperature-related profiles of fresh leachate properties, like chemical oxygen demand (COD), were observed. In addition, AnMBR achieved a high COD removal of 98% with a maximum organic loading rate (OLR) of 19.27 kg-COD/m3/d at the shortest hydraulic retention time (HRT) of 1.5 d. The microbial analysis implied that the abundant protein and carbohydrate degraders (e.g., Thermovirga and Petrimonas) as well as syntrophic bacteria, such as Syntrophomonas, ensured the effective adaptation of AnMBR to the reduced HRTs. However, an excessive OLR at 36.55 kg-COD/m3/d at HRT of 1 d resulted in a sharp decrease in key microbes, such as archaea (from 37% to 15%), finally leading to the deterioration of AnMBR. This study provides scientific guidance for treating fresh leachate by AnMBR and its full-scale application for high-strength wastewater.

Long term operation performance and membrane fouling mechanisms of anaerobic membrane bioreactor treating waste activated sludge at high solid concentration and high flux.

High solid anaerobic membrane bioreactor (HSAnMBR) is widely applied in biomass treatment and energy regeneration, while membrane operation performance and membrane fouling control remain critical issues. In this study, a HSAnMBR was utilized for waste activated sludge (WAS) treatment at organic loading rates of 3.69-3.72 gCOD/L·d and biogas yield was ranged in 0.38-0.39 L/gVSfed with the COD conversion efficiency of 40 %. The membrane operated stably when the average flux was 9.6, 4.5 and 1.2 L/m2/h at mixed liquor total solid of 25, 30 and 40 g/L with a filtration: relaxation of 4:1, 1:1 and 1:2, respectively. The distinctive characteristics of membrane fouling at high solid condition were that the polysaccharides and proteins had high fouling propensity and were the main composition of the foulant layer. Furthermore, phosphorus and magnesium were the predominant causes of inorganic fouling. The minerals precipitated on the membrane and were embedded into membrane pores, contributing to cake layer formation and pore blocking. This research provided a comprehensive analysis of the membrane operation characterization and fouling mechanisms of HSAnMBR, which was expected to push forward HSAnMBR applications to WAS treatment.

Study on the effect of income perception on cleaner-production fraud.

We investigated a single-cycle product supply chain in a game model, where a supplier is the leader. By innovatively introducing cleaner production fraudulent income perception factor into a game model, we studied the mechanism of the effect of enterprise social responsibility and environmental awareness on cleaner production fraud. The results showed that the income of retailers and suppliers changes under different perceptions of fraudulent income. That is, the value of cleaner production fraudulent income perception factor will affect the enterprise's choice of differentiation strategy. When the enterprise's sense of social responsibility is weak, it is more likely to choose cleaner production fraud. Conversely, under the constraints of high social responsibility, it more likely avoids production fraud. Regarding government supervision, the income of suppliers and retailers changes under different government penalties. Furthermore, a reasonable punishment for cleaner production fraud can reduce such violations. However, after the punishment reaches a level, the efficiency of supervision begins to decline. In views of that, improving enterprise social responsibility through institutional reform is a more effective way to reduce cleaner production fraud. To contribute to a healthy competitive market environment, government supervision should establish a feedback mechanism, and make timely adjustments.

Enhanced degradation and biogas production of waste activated sludge by a high-solid anaerobic membrane bioreactor together with in pipe thermal pretreatment process.

An integrated system combining in pipe thermal pretreatment with a high-solid anaerobic membrane bioreactor (AnMBR) was developed to promote the anaerobic digestion of waste activated sludge (WAS). Two different pretreatment methods investigated were the venturi nozzle treatment (VNT) and steam injector treatment (SIT), both at a low temperature of 70 °C. The biogas production after pretreatment was 23.5-30.5% higher than that of untreated WAS, and the VS based biogas yield was 0.46-0.47 L/g-VS when HRT was 15 days. The membrane operated smoothly when the average flux was 9.6 and 4.5 L/m2/h under an MLTS of 25 and 30 g/L, respectively. The calculations of the mass balance indicated that 44-45% COD was converted to methane with pretreatment and only 1% remained in the permeate. That is, high energy recovery and organic matter removal efficiency were achieved for the treatment of WAS using the high-solid AnMBR with in pipe thermal pretreatment.

Methanogenic performance and microbial community during thermophilic digestion of food waste and sewage sludge in a high-solid anaerobic membrane bioreactor.

The methanogenic performance and microbial community of the thermophilic anaerobic mono-digestion and co-digestion of food waste and sewage sludge in a high-solid membrane bioreactor were investigated by a continuous experiment. The methane recovery rate of the system reached 98.0% and 89.0% when the substrate was pure food waste and 25% sewage sludge substitution, respectively. Kinetics characterization showed that hydrolysis was the rate-limiting step in both mono-digestion and co-digestion while methanogenic performance and microbial community were significantly affected by feed condition. The dominant archaea for methane generation shifted from Methanothermobacter thermophilus (72.82%) to Methanosarcina thermophila (96.25%) with sewage sludge gradually added from 0% to 100% in the substrate. The relationships between digestion performance, such as the accumulation of soluble proteins in the reactor, and functional microbial groups were also carefully analyzed. Finally, reasonable metabolic pathways for mono-digestion and co-digestion were summarized.

Analysis of Farmland Abandonment and Government Supervision Traps in China.

Farmland abandonment has become relatively common in rural China. In the context of food security, the Chinese government has introduced policies for farmland abandonment supervision, but the effect of these policies has proven to be marginal. By constructing an evolutionary game model, our research explores the evolutionary logic during the supervision of farmland abandonment by governments and rural households. The results indicate that low food yield and high opportunity costs are the leading causes of farmland abandonment. The probable punishment administered by the central government for dereliction is a major motivation for the local government to practice farmland abandonment supervision. The low supervision avoidance cost for rural households leads local governments and households to form collaborations to jointly cope with central government supervision. When this occurs, local governments' supervision of farmland abandonment falls into a trap, as it leads to continued supervision practices that are costly and ineffective. Food security risk comes from the contradictory population and land resources demands. To improve food security while managing these contradictory demands, it is both necessary and feasible for the government to control population growth and focus on farmland protection, whereas it is unnecessary and unfeasible for the government to supervise whether or not farmland should be abandoned.

One-year operation of a 20-L submerged anaerobic membrane bioreactor for real domestic wastewater treatment at room temperature: Pursuing the optimal HRT and sustainable flux.

A 20 L hollow-fiber submerged anaerobic membrane bioreactor (SAnMBR) was used to treat real domestic wastewater at 25 °C with hydraulic retention times (HRTs) ranging from 4 to 12 h. The process performance was evaluated by organic removal efficiency, biogas production, sludge yield, and filtration behaviors during one-year's operation. For HRTs ranging between 6 and 12 h, the AnMBR showed good organic removal efficiency with chemical oxygen demand (COD) and biochemical oxygen demand (BOD) removal efficiencies of about 89% and 93%, respectively. The biogas yield was 0.26 L-gas/g-CODfed, with approximately 80% methane content, and the sludge yield was 0.07-0.11 g-VSS/g-CODrem. While at an HRT of 4 h, with the higher wastewater treatment capacity and organic loading rate (OLR), the biogas production was lower (0.17 L-gas/g-CODfed), and the sludge production was higher (0.22 g-VSS/g-CODrem). The organic removal performance (COD 84% and BOD 89%) at HRT of 4 h was acceptable due to the effective separation effect of the membrane filtration process. According to COD balance analysis, the low biogas yield and high sludge yield at HRT of 4 h were due to insufficient biodegradation under an OLR of 2.05 g-COD/L-reactor/d. Theoretical calculations based on Henry's law indicate that the ideal methane content in the biogas should be 82-85% when the operational temperature was 25 °C. To achieve a high flux and sustainable AnMBR operation, the impact of mixed liquor suspended solid (MLSS) and gas sparging velocity (GSV) on the filtration performance was analyzed. The critical flux increased with increase in the GSV from 24.2 to 174.3 m/h, but decreased with increase in the MLSS concentration from 8.2 to 20.2 g/L. Therefore, decreasing fouling rate to 0.8-1.2 kPa/d by efficiently controlling GSV and MLSS, sustainable operation could be achieved at a flux of 0.34 m/d.

Bioenergy recovery from methanogenic co-digestion of food waste and sewage sludge by a high-solid anaerobic membrane bioreactor (AnMBR): mass balance and energy potential.

To support smart city in terms of municipal waste management and bioenergy recovery, a high-solid anaerobic membrane bioreactor (AnMBR) was developed for sewage sludge (SeS) and food waste (FW) treatment in this study. COD mass balance showed that 54.1%, 66.9%, 73.5%, 91.4% and 93.5% of the COD input was converted into methane at the FW ratio of 0, 25%, 50%, 75% and 100%, respectively. The corresponding net energy balance was 13.6, 14.1, 17.1, 22.9 and 27.4 kJ/g-VS, respectively. An important finding of this investigation was that, for the first time, the relationship between net energy balance and carbon to nitrogen (C/N) ratio was revealed and the established sigmoid-type function was shown to be capable of predicting energy balance at different C/N ratios regardless of the region. The outcomes of this study show the potential of high-solid AnMBRs in SeS and FW treatment for supporting smart cities in the future.

Improvement of coffee grounds high solid thermophilic methane fermentation by co-digestion with in-situ produced waste activated sludge: Performance and stability.

The feasibility of in-situ stabilization in the co-digestion of coffee grounds (CG) and waste activated sludge (WAS) was investigated. Two lab-scale thermophilic continuous stirred tank reactors (CSTR), R1 and R2 were operated with substrates that contained different WAS ratios, S1 (WAS% = 20%) and S2 (WAS% = 30%). During the whole process, there was no external supply of ammonia and trace elements. The volatile solid (VS) removal efficiency of R1 and R2 was comparable, and the biogas yield of R1 (0.467 ± 0.100 L/g-VSin) was slightly higher than R2 (0.408 ± 0.020 L/g-VSin). The total ammonia nitrogen (TAN) of R1 and R2 was 482 ± 32 and 884 ± 24 mg/L, respectively. The stoichiometry formulas of co-digestion were established to calculate the theoretical microbial yield coefficients and the requirements of microorganism reproduction. A comparison between the theoretical requirements and experimental values showed that co-digestion with WAS could avoid supply for an external supply of minerals. For the net energy production, R1 and R2 could generate 6342 and 5069 kWh of electricity daily, respectively.

Knowledge, Behaviors, and Attitudes Regarding Venous Thromboembolism Prophylaxis: A Survey of Clinicians at a Tertiary Hospital of China.

BACKGROUND: In this study, we sought to assess knowledge, attitudes, and behaviors regarding venous thromboembolism (VTE) prophylaxis among clinicians at a tertiary hospital of China. METHODS: An electronic questionnaire was sent to clinicians to gather information regarding demographic data (5 items), knowledge about VTE prophylaxis (21 items), behaviors regarding VTE prophylaxis (8 items), and attitudes regarding VTE prophylaxis (7 items). Answers of "strongly agree" and "agree" on the behaviors and attitude items were defined as affirmative responses. Clinicians were also asked to provide suggestions regarding VTE prophylaxis. RESULTS: A total of 867 clinicians were included in this study. The overall correct response rate for knowledge items was 60.9%. The median affirmative response rate for behavior items was 48.6% (range 29.5-80.3%), and the median affirmative response rate for attitude items was 98.7% (range 96.9-99.3%). Clinicians were most concerned about the adverse effects triggered by chemical VTE prophylaxis (79.5%) and possibility of a financial penalty when a patient could not be treated with VTE prophylaxis (72.3%). Low patient compliance and low level of clinician knowledge and participation were identified most commonly as difficulties involved in VTE prophylaxis. A total of 78 suggestions were collected; these suggestions generally focused on improving the quality and frequency of staff training (n = 24) and enhancing learning opportunities (n = 22). CONCLUSIONS: Although the clinicians' overall attitude toward VTE prophylaxis was positive, the knowledge level was relatively poor, and the rate of affirmative responses regarding behaviors was low. Medical institutions should improve clinician training regarding VTE prophylaxis.

Advanced methanogenic performance and fouling mechanism investigation of a high-solid anaerobic membrane bioreactor (AnMBR) for the co-digestion of food waste and sewage sludge.

Disposal of the increasingly huge amounts of sewage sludge (SeS) has become an impending problem worldwide. To solve this problem, a high-solid anaerobic membrane bioreactor (AnMBR) was used for the anaerobic co-digestion (AcoD) of SeS and food waste (FW). This study investigated the effects of SeS ratio on the methanogenic performance of the AcoD with a gradual increase value from 0 to 25%, 50%, 75% and 100% (total solids based). The results showed that the highest methanogenic performance was achieved at mono FW digestion. As for the co-digestion, the optimal FW/SeS ratio for methanogenic performance was 75%:25% among all the mixing ratios. The COD based biogas yield and methane yield were 0.498 L-biogas/g-CODfed and 0.295 L-CH4/g-CODfed at this optimal mixing ratio, which were 67.7% and 67.6% higher than those of the mono SeS digestion, respectively. The upgraded values were attributed to the improved hydrolysis ratio (by 8.14%) and the balanced carbon-to-nitrogen (C/N) ratio by co-digestion with FW, which synergistically stimulated methanogenesis ratio by 81.0%. The continuous membrane filtration property was investigated and four typical trans-membrane pressure (TMP) variation curves at different fouling degrees were determined. The membrane could sustainably operate at a flux of 6 L/m2/h (LMH) at the mixed liquor total solids (MLTS) concentration of 25 - 30 g/L. The combination of continuous membrane filtration property, particle size distribution of the mixed liquor and the external forces analysis was firstly applied to unravel the membrane fouling mechanism of a high-solid AnMBR. The result of this study will contribute to the establishment of an efficient FW and SeS treatment strategy.

High solid mono-digestion and co-digestion performance of food waste and sewage sludge by a thermophilic anaerobic membrane bioreactor.

The performance of co-digestion of food waste (FW) and sewage sludge (sludge) by a thermophilic anaerobic membrane bioreactor (ThAnMBR) was firstly investigated. The long-term stable operation showed the feasibility of the utilization of ThAnMBR for mono- and co-digestion of FW and sludge at a high solid condition. Good permeate quality was obtained at all sludge ratios while the addition of sludge restricted the methane generation. For a sludge substitution with a 25% TS-based substrate, the biogas yield of 0.812 L/g-VSfed was at 91% and 158% that of the mono-digestion of FW and sludge, respectively. Membrane performance indicated that the ThAnMBR operated stably at a high flux of 5 LMH under the high solid (~27 g/L) condition. Furthermore, membrane filtration with a 0.1 µm pore size of hollow fiber not only completely removed suspended solids but also rejected about 70% of soluble COD, 80% of soluble carbohydrates and 17% of soluble proteins.

MARCKSL1 promotes the proliferation, migration and invasion of lung adenocarcinoma cells.

Lung cancer is the most common cancer in males and females and ~40% of lung cancer cases are adenocarcinomas. Previous studies have demonstrated that myristoylated alanine rich protein kinase C substrate (MARCKS) is upregulated in several types of cancer and is associated with poor prognosis in patients with breast cancer. However, its expression level and role in lung adenocarcinoma remain unknown. Therefore, the aim of the present study was to investigate the expression level and biological functions of MARCKS like 1 (MARCKSL1), a member of the MARCKS family, in lung adenocarcinoma. The expression level of MARCKSL1 was examined in human lung adenocarcinoma tissues and cell lines. MARCKSL1-specific small interfering RNAs effectively suppressed its expression level and significantly inhibited the proliferation, migration and invasion of lung adenocarcinoma cells. Additionally, the role of MARCKSLI in the regulation of metastasis was examined. Silencing MARCKSL1 decreased the expression of the epithelial-mesenchymal transition (EMT)-associated proteins E-cadherin, N-cadherin, vimentin and snail family transcriptional repressor 2, and decreased the phosphorylation level of AKT. The results obtained in the current study suggested that MARCKSL1 promoted the progression of lung adenocarcinoma by regulating EMT. MARCKSLI may have prognostic value and serve as a novel therapeutic target in lung adenocarcinoma.

Enhancement of sustainable flux by optimizing filtration mode of a high-solid anaerobic membrane bioreactor during long-term continuous treatment of food waste.

Membrane fouling or flux limitation is the major bottleneck that hinders anaerobic membrane bioreactor (AnMBR) application. An AnMBR with a working volume of 15 L was operated for 180 days to investigate the maximum sustainable flux at different high solid concentrations during the anaerobic treatment of food waste. A total of eight filtration-to-relaxation (F/R) ratios were incorporated, with a fixed filtration time of 3 min and varied relaxation times (decreased from 12 to 1 min). Besides, a total of five instantaneous fluxes were applied: 12, 14, 16, 18 and 20 L/m2/h (LMH). Results showed that sustainable flux was greatly enhanced by filtration mode optimization. The optimal F/R ratios were 3:1, 3:1, 3:1 and 3:6 at mixed liquor total solid (MLTS) concentrations of 10, 15, 20 and 25 g/L, respectively. The corresponding sustainable flux values were 13.2 ±â€¯0.3, 10.1 ±â€¯0.4, 9.3 ±â€¯0.2 and 4.0 ±â€¯0.3 LMH, respectively. These values were 29%, 35%, 52% and 21% higher than the critical flux determined by the flux-stepping technique. The results of this study were used to perform a mathematical simulation. The obtained regression equation between the maximum sustainable flux and MLTS concentration can be used to predict the sustainable flux at other MLTS concentrations. This work provides valuable insight into the design and operation of high-solid AnMBRs, and is expected to contribute to further advances in the application of AnMBRs in industry.

Environmental Benefit Assessment for the Carbonation Process of Petroleum Coke Fly Ash in a Rotating Packed Bed.

A high-gravity carbonation process was deployed at a petrochemical plant using petroleum coke fly ash and blowdown wastewater to simultaneously mineralized CO2 and remove nitrogen oxides and particulate matters from the flue gas. With a high-gravity carbonation process, the CO2 removal efficiency was found to be 95.6%, corresponding to a capture capacity of 600 kg CO2 per day, at a gas flow rate of 1.47 m3/min under ambient temperature and pressure. Moreover, the removal efficiency of nitrogen oxides and particulate matters was 99.1% and 83.2%, respectively. After carbonation, the reacted fly ash was further utilized as supplementary cementitious materials in the blended cement mortar. The results indicated that cement with carbonated fly ash exhibited superior compressive strength (38.1 ± 2.5 MPa at 28 days in 5% substitution ratio) compared to the cement with fresh fly ash. Furthermore, the environmental benefits for the high-gravity carbonation process using fly ash were critically assessed. The energy consumption of the entire high-gravity carbonation ranged from 80 to 169 kWh/t-CO2 (0.29-0.61 GJ/t-CO2). Compared with the scenarios of business-as-usual and conventional carbon capture and storage plant, the economic benefit from the high-gravity carbonation process was approximately 90 and 74 USD per ton of CO2 fixation, respectively.