Environmental impacts and nutrient distribution routes for food waste separated disposal on large-scale anaerobic digestion/ composting plants.

Centralized biological treatments, i.e., anaerobic digestion (AD) and in-vessel composting (IVC), were supposed to be the promising processes for the disposal of food waste (FW) after source separation, while the systematic benefits were unclear for FW with high water content, salt and oil and thus influenced the selection by the local decision-makers. In this study, two large-scale working AD and IVC plants were compared for environmental impacts, nutrient recovery and economic benefits. For unit amount of FW, 89.26 kg CO2-eq was released in IVC mainly due to 47.89 kWh electricity consumption, and 57.02 kg CO2-eq was produced in AD. With the application of compost and energy recovery, 26.88 and 93.55 kg CO2-eq savings were obtained in IVC and AD, respectively. NH3 emissions were the main contributor to acidification (0.35 kg SO2-eq) in IVC, while AD exerted less impact on acidification (0.09 kg SO2-eq) and nutrient enrichment (0.25 kg NO3-eq) attributed to the counteract of energy recovery. 2029 would be the inflection point for global warming potential in AD with more clean energy applied in electricity mix in China. For nutrient recovery, more C (8.3%), N (37.9%) and P (66.7%) could be recovered in compost, while those were discharged via leachate and biogas residue in AD. The cost of IVC was 16 CNY/t (2.40 USD/t) lower than AD. Combing the three key indexes and the sale routes of products, IVC was recommended to be used in areas dominated by agriculture and forestry industries, and AD was more suitable for large cities.

Living alone, social cohesion, and quality of life among older adults in rural and urban China: a conditional process analysis.

OBJECTIVES: To test the independent and combined impact of social cohesion and geographic locale (urban/rural) on quality of life (QoL) for older adults in China. Using conditional process analysis, we tested three hypotheses: (1) QoL will be lower for persons living alone than those who live with family; (2) social cohesion will mediate the association of living arrangement and QoL; and (3) geographic locale will moderate direct and indirect pathways in the mediation model. DESIGN: Cross-sectional data from WHO Study on Global Aging and Adult Health (SAGE) (China, Wave 1, 2007-2010). SETTING: National probability sample of 74 primary sampling units in China, 32 in urban, and 32 in rural areas. PARTICIPANTS: A total of 9,663 adults aged 50 years and older. MEASUREMENTS: We measured QOL with the 8-item version of the WHOQOL-Bref; living arrangement as alone versus with family; and social cohesion with an 9-item index of frequency of a range of social activities in the previous 12 months. We controlled for sociodemographic characteristics and health and mental health variables in multivariate analyses. RESULTS: Data supported the first two hypotheses; however, the mediating effects of social cohesion held only in urban areas. CONCLUSION: This study advances the large body of work on living arrangements and well-being of older adults in China. Social cohesion contributed to better QoL regardless of living arrangement, and cohesion mediated the association of living arrangement and QOL in urban but not rural areas. Programs and policies that strengthen social cohesion through older adults' community involvement, especially in urban areas, will help to enhance QoL.

Chemical and olfactive impacts of organic matters on odor emission patterns from the simulated construction and demolition waste landfills.

The explosive increase of construction and demolition waste (CDW) caused the insufficient source separation and emergency disposal at domestic waste landfills in many developing countries. Some organic fractions were introduced to the CDW landfill process and resulted in serious odor pollution. To comprehensively explore the impacts of organic matters on odor emission patterns, five CDW landfills (OIL), with organic matters/ inert CDW components (O/I) from 5% to 30%, and the control group only with inert components (IL) or organics (OL) were simulated at the laboratory. The chemical and olfactive characters of odors were evaluated using the emission rate of 94 odorants content (ERtotal), theory odor concentration (TOCtotal), and e-nose concentration (ERENC), and their correlations with waste properties were also analyzed. It was found that the main contributors to ERtotal (IL: 93.0% NH3; OIL: 41.6% sulfides, 31.0% NH3, 25.9% oxygenated compounds) and TOCtotal (IL: 64.1% CH3SH, 28.2% NH3; OIL: 71.7% CH3SH, 24.8% H2S) changed significantly. With the rise of O/I, ERtotal, TOCtotal, and ERENC increased by 10.9, 20.6, and 2.1 times, respectively. And the organics content in CDW should be less than 10% (i.e., DOC<101.3 mg/L). The good regressions between waste properties (DOC, DN, pH) and ERENC- (r=0.86, 0.86, -0.88, p<0.05), TOCtotal- (r=0.82, 0.79, -0.82, p<0.05) implied that the carbon sources and acidic substances relating to organics degradation might result in that increase. Besides, the correlation analysis results (ERENC-vs.TOCtotal-, r=0.96, p<0.01; vs.ERtotal-, r=0.86, p<0.05) indicated that e-nose perhaps was a reliable odor continuous monitoring tool for CDW landfills.

Urban and rural factors associated with life satisfaction among older Chinese adults.

OBJECTIVE: This study compared urban and rural factors associated with life satisfaction among older adults in mainland China. METHOD: Study data were extracted at random from 10% of the Sample Survey on Aged Population in urban/rural China in 2006 for 1980 participants aged 60 and older, including 997 from urban cities and 983 from rural villages. RESULTS: In this study, 54.6% of urban older adults and 44.1% of rural older adults reported satisfaction with their lives. Binary logistic regression analysis showed that financial strain, depressive symptoms, filial piety, and accessibility of health services were significantly associated with life satisfaction for both urban and rural participants, but age and financial exchange with children were only associated with life satisfaction among urban older adults. CONCLUSION: Findings are consistent with some previous studies that indicated the importance of financial strain, depressive symptoms, filial piety, and accessibility of health services to life satisfaction among the older adults in both urban and rural areas. This study also demonstrated the importance of age and family financial exchange to the life satisfaction of urban older adults.

Resourceful treatment of complex uranium-organic wastewater by a hybrid tandem photocatalytic fuel cell with SnS2 nanoplate modified carbon felt cathode.

Resourceful treatment of wastewater is a promising way to facilitate sustainable development. Recently, photocatalytic fuel cells (PFCs) have attracted widespread attention as the method that can synchronously achieve wastewater treatment and clean energy production only depend on light. However, few PFCs focused on treating complex uranium (U(VI))-organic wastewater. This study prepared a SnS2 nanoplate decorated carbon felt (SnS2/CF) material by facile hydrothermal method and used as the cathode to construct a hybrid tandem photocatalytic fuel cell (HTPFC) system. Compared to the CF-HTPFC, the removal efficiencies of U(VI) and tetracycline hydrochloride (TCH) increased to 3.4 and 1.8 times in the SnS2/CF-HTPFC system, accompanied with the reaction rate (kobs) values increased to 30.39 and 3.78 times, respectively. More importantly, under real sunlight irradiation (From 10:00 to 16:00), the removal efficiencies of U(VI) and TCH respectively reached 92.49 % and 97.96 %, and the Pmax reached 6.49 mW·cm-2. HTPFC also displayed satisfactory performances in treating radioactive wastewater containing different organic compounds, with the removal efficiencies of U(VI) and organic compounds both exceeded 93.35 %. The loading of SnS2 nanoplates enhanced electrochemical performance and introduced abundant S active sites, allowing more U(VI) to be adsorbed and reduced, and simultaneously promoting the removal of organic matter by improving the charge separation efficiency.

Exploring into a light-avoided environment: Mechanical-thermal coupled conditions responsible for the aging behavior of plastic waste in landfills.

Plastics in landfills undergo a unique micronization process due to multi-factor and light-avoided conditions, but their aging process in such a typical environment remains unexplored. This study investigated the aging behavior of polyethylene plastics, representative of landfills, under simulated dynamic mechanical forces and high temperature-two prevalent environmental factors in landfills. The study explored the individual and combined contributions of these factors to the aging process. Results indicated that high temperature played a primary role in aging plastics by depolymerization and degradation through ·OH production, while mechanical forces contributed mainly to surface structure breakdown. The combined effect leads to more serious surface damage, creating holes, cracks, and scratches that provide access for free radical reactions to plastic bulk, thereby accelerating the aging and micronization process. The resulting microplastics were found to be 14.25 ± 0.53 µg L-1. Aged plastics exhibit a rapid aging rate of depolymerization and oxidation compared to virgin plastics due to their weak properties, suggesting a higher potential risk of microplastic generation. This study fills a knowledge gap regarding the aging behavior of plastics under complex and light-avoided landfill conditions, emphasizing the need for increased attention to the evolution process of microplastics from aged plastic waste in landfills.

Booming microplastics generation in landfill: An exponential evolution process under temporal pattern.

Landfills are the main plastic sinks and microplastics (MPs) sources in the anthropogenic terrestrial system. Understanding the dynamic process of generating MPs is a prerequisite to reducing their potential risk, which remains unexplored because of the complex stabilization process of landfills. In this study, we investigated the evolution process of MPs generated in a partitioned landfill, with well-recorded disposal ages of over 30 years. Considering the initial plastic proportions in fresh landfilled waste, the occurrence of MPs increased exponentially with the disposal age. A booming generation of MPs occurred from 71.3 ± 17.7 items/(g plastic) to 653.1 ± 191.5 items/(g plastic). The generation rates of MPs varied greatly depending on the individual polymer types, with polyethylene (PE) having the highest generation rate of 28.4 items/(g plastic) per year at 31 years, compared to that of polypropylene (PP) and polystyrene (PS) at 15.0 and 9.6 items/(g plastic) per year, respectively. The variation in the carbonyl index indicated that environmental oxidation might facilitate the fragmentation of plastic waste. The relative abundance of plastic-degrading microbes increased more than three times in the plastisphere after 30 years of landfilling, indicating that the potential biodegradation might be a nonnegligible driver for plastic fragmentation after long-term natural acclimatization. This study revealed the dynamic evolution process of MPs in landfills and predicted the booming stage, which might provide an important guideline for reducing the leakage risk of MPs during the reclamation of old landfills or dumping sites.

Variations and environmental impacts of odor emissions along the waste stream.

Odor nuisance related to municipal solid waste (MSW) disposal is one of the main incentives to counter the Not-In-My-Backyard Syndrome. Moreover, integrated odor management contributes to specific odor control at different waste treatment stages. In this study, odor emissions along typical MSW streams were categorized based on their olfactive and environmental impacts after a field investigation of the residential district (RD), transfer station (TS), and landfill (LF) in the Chongming Eco-island. It was found that odorants, especially NH3 and sulfides, increased along the MSW stream, with total chemical concentration increasing from 1241.5 ± 235.6 to 6947.2 ± 1726.8 µg/m3. Source separation and co-landfill system, which premixes the MSW with bottom ash (BA) at a ratio of 5:1, were speculated to efficiently attenuate odorants. Sulfides reduced owing to an increase in trace metal dissolution and carbon source consumption with the addition of BA at the LF, whereas NH3 in the leachate pond increased due to enhanced biodegradation and alkalinity. Photochemical ozone formation (6.7 × 10-8-8.6 × 10-5 personal equivalent, PE), nutrient enrichment (5.4 × 10-8-4.6 × 10-5 PE), and acidification (4.8 × 10-8-4.1 × 10-5 PE) were the major environmental impact categories. The priority odor pollutants screened using ternary fuzzy synthetic system could reflect the impact of olfaction and environment and greatly varied along the waste stream.

Improved understanding of dissolved organic matter transformation in concentrated leachate induced by hydroxyl radicals and reactive chlorine species.

Concentrated leachate (CL) is commonly featured with high salt and dissolved organic matters (DOM). In this study, molecular transformation of DOM was revealed to identify the reactive mechanisms with (non-) radical reactive species in ozonation, electrolysis and E+-ozonation processes. Chlorine ions were efficiently activated into non-radical reactive chlorine species (RCS) with 245.7 mg/L, which was more dominant in electrolysis. Compared to ozonation, C•OH was increased from 2.6 × 10-4 mg/L into 5.8 × 10-4 mg/L and the generation of Cl•/ClO• could be concluded according to the decline of non-radical RCS in E+-ozonation process. For chromophoric and fluorescent DOM, aromatic compounds and polymerization degree dramatically decreased in E+-ozonation. Lipid-like and CRAM/lignin-like compounds were substantially degraded, as •OH and ClO•/Cl• shows an affinity towards oxygen-containing organic compounds via single electron transfer by attracting OH bonds. Especially, carbon/hydrogen/oxygen (CHO-containing) compounds were readily to be degraded with the removal efficiency of 92.5 %, 97.0 % and 98.4 % in electrolysis, ozonation and E+-ozonation, respectively. Moreover, nitrogen atoms have a negative effect on DOM degradation, and thus, carbon/hydrogen/nitrogen and carbon/hydrogen/nitrogen/sulfur (CHN- and CHNS-containing) compounds were considered as refractory compounds. This paper is expected to shed light on the synergetic effect in E+-ozonation and transformation of refractory DOM in CL treatment.

Molecular insight into variations of dissolved organic matters in leachates along China's largest A/O-MBR-NF process to improve the removal efficiency.

Dissolved organic matter (DOM) is a critical component of high-strength organic wastewater, and the study of them from molecular perspective could improve the removal efficiency. Leachate samples were collected from China's largest two stage anaerobic/aerobic membrane bioreactor and nanofiltration (A/O-MBR-NF) process, with the treatment capacity of 5000 t/d, and characterized by electrospray ionization (ESI) coupled with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) from molecular perspective. High molecular weight (m/z > 500) compounds with 40-50 carbon atoms and 15-20 double bond equivalence (DBE) were biodegraded into medium molecular weight compounds with 10-20 carbon atoms and ∼10 DBE. Contribution of lipids and unsaturated hydrocarbons compounds in DOM turned into 42.1% and 2.5%, respectively, while contribution of condensed aromatics in DOM dramatically increased to 15.4% in leachates along the A/O-MBR process. Most of DOM was converted into higher polymerization degree and accumulated in concentrated leachate (CL). Sulfur-containing compounds, whose relative peak ratio accounted for 56.4%, were regarded as recalcitrant DOM in CL. Increase of retention time in anaerobic unit for raw leachate might be useful for decomposing the long-chain organic compounds, which could also reduce loadings for the following A/O-MBR process. Well-focus techniques such as sulfur-oxidation bacteria could be introduced into the MBR unit for better removing organo-sulfur compounds. Advanced oxidation processes for CL degradation would be efficiency for the removal of recalcitrant DOM. Thus, leachate could be disposed in a zero-discharge way based on the practical experience of such a typical working treatment process.

Occurrence of banned and commonly used pesticide residues in concentrated leachate: Implications for ecological risk assessment.

Amounts of banned and current pesticides have been used in domestic and agricultural pest control, and their residues have accumulated along the waste stream. In this work, pesticides were characterized in concentrated leachates (CLs) from 5 municipal landfill sites, 2 incineration plants and 1 composting plant in six provinces. A total of 31 pesticides were detected which included 8 organochlorine pesticides (OCPs, 303-2974 ng/L), 16 organophosphorus pesticides (OPPs, 1380-13,274 ng/L) and 7 synthetic pyrethroids (SPs, 319-5636 ng/L). Despite the ten years ban of hexachlorocyclohexane, methamidophos and parathion-methyl, they were still in CL at a mean value of 320 ng/L and 88 ng/L, respectively. The average Σ8OCPs, Σ16OPPs and Σ7SPs in CL from landfill sites were approximately 2.8, 1.1 and 4.5 times higher than those from incineration plants, which might have been influenced by pH, moisture and/or HRT. Additionally, it was found that CL from incineration plants and composting plant with lower pesticide contents posed a much higher acute and chronic eco-risk. Methamidophos was the dominant pesticide in CL from incineration plants, which was much higher than any other pesticides detected. The annual emissions of Σ8OCPs, Σ16OPPs and Σ7SPs discharged from landfill-CL were estimated to be 2370, 10,357 and 2994 g, respectively. It was evident from the study that long-term release of CL after waste disposal could cause potential risk of ecological pollution.

The identification and health risk assessment of odor emissions from waste landfilling and composting.

Odor nuisance is the main incentive for Not In My Back Yard campaigns around municipal solid waste (MSW) waste disposal facilities, and the odor identification is of significance for the understanding of the odor properties from MSW with different disposal methods. In this study, odor emissions from different stages at two large-scale working MSW disposal facilities, i.e., landfill (LF) and compost plant (CP), were distinguished with the same MSW feedstock in one city. It was found that CP suffered the heavier odor pollution and the characteristics of odorants changed significantly, especially the pile-turning workshop. Sulfides and aromatics were the main concentration contributors for LF, while that for CP were NH3 and oxygenated compounds. Significant correlations between odor concentration and halogenated compounds, sulfides (r2 = 0.945, 0.898, p<0.05, n = 12) were merely observed in CP. The priority odor pollutants of LF were H2S, benzene and NH3, while that of CP was NH3, ethyl acetate and benzene with a descending order. With regarding to their contributions for occupational exposure, the carcinogenic risk was negligible for these facilities, but H2S of LF might bring non-carcinogenic risk to on-site workers.

Ex situ simultaneous nitrification-denitrification and in situ denitrification process for the treatment of landfill leachates.

The objective of this research was to investigate the ex situ simultaneous nitrification-denitrification (SND) and in situ denitrification process and to evaluate its application for treating landfill leachates at long-term operations. Based on the predicted contaminant concentrations, two sets of laboratory-scale bioreactor landfill systems (an ex situ nitrification and in situ denitrification bioreactor as well as an ex situ SND and in situ denitrification bioreactor) were operated continuously for about 48 weeks. The recirculated leachate quantity and effluent characteristics of leachates were regularly monitored and analyzed by using the standard method. The ex situ SND and in situ denitrification process obtained a better leachate removal performance compared with the ex situ nitrification and in situ denitrification process, while the ex situ SND process can reduce the energy costs. However, the leachate treatment performance of this process was generally unsatisfactory as the contaminant concentrations do not meet the discharge standard within the forecasted time. These results further proved that the effectiveness of the treatment decreases along with an increasing landfill age. Therefore, further research must be performed to optimize the treatment efficiency of the bioreactor.

Use of bioreactor landfill for nitrogen removal to enhance methane production through ex situ simultaneous nitrification-denitrification and in situ denitrification.

High concentrations of nitrate-nitrogen (NO3--N) derived from ex situ nitrification phase can inhibit methane production during ex situ nitrification and in situ denitrification bioreactor landfill. A combined process comprised of ex situ simultaneous nitrification-denitrification (SND) in an aged refuse bioreactor (ARB) and in situ denitrification in a fresh refuse bioreactor (FRB) was conducted to reduce the negative effect of high concentrationsof NO3--N. Ex situ SND can be achieved because NO3--N concentration can be reduced and the removal rate of ammonium-nitrogen (NH4+-N) remains largely unchanged when the ventilation rate of ARB-A2 is controlled. The average NO3--N concentrations of effluent were 470mg/L in ex situ nitrification ARB-A1 and 186mg/L in ex situ SND ARB-A2. The average NH4+-N removal rates of ARB-A1 and ARB-A2 were 98% and 94%, respectively. Based on the experimental data from week 4 to week 30, it is predicted that NH4+-N concentration in FRB-F1 of the ex situ nitrification and in situ denitrification process would reach 25mg/L after 63weeks, and about 40weeks for the FRB-F2 of ex situ SND and in situ denitrification process . Ex situ SND and in situ denitrification process can improve themethane production of FRB-F2. The lag phase time of methane production for the FRB-F2 was 11weeks. This phase was significantly shorter than the 15-week phases of FRB-F1 in ex situ nitrification and in situ denitrification process. A seven-week stabilizationphase was required to increase methane content from 5% to 50% for FRB-F2. Methane content in FRB-F1 did not reach 50% but reached the 45% peak after 20weeks.

Effect of low aeration rate on simultaneous nitrification and denitrification in an intermittent aeration aged refuse bioreactor treating leachate.

Three intermittent aeration aged refuse bioreactors (ARBs), A, B, and C, with aeration rates of 670, 1340, and 2010L/m3 aged refuse·d in stage 1, and 670, 503, and 335L/m3 aged refuse·d in stage 2 were constructed to evaluate the effect of low aeration rate on leachate treatment by simultaneous nitrification and denitrification (SND). Results show that SND can be achieved and improved by reasonably adjusting the aeration rate of the ARB. In stage 1, the average chemical oxygen demand (COD) removal rates of ARBs A, B, and C were 91%, 92%, and 93%, respectively. The ammonia nitrogen (NH4+-N) removal rate of the three ARBs approached 100%. The total nitrogen (TN) average removal rates were 68%, 59%, and 57%. The average SND efficiency values were 73%, 66%, and 65%. In stage 2, the COD removal rates of ARBs A, B, and C decreased from the original values of 85%, 92%, and 93% to 84%, 81%, and 80%. The NH4+-N removal rate decreased from above 99% to 90%-92% in ARB B and from above 99% to 87%-91% in ARB C. The TN removal rates of ARBs B and C increased to 59% and 53% on day 15 from the initial values of 49% and 43% and were maintained at 49%-61% and 50%-60%. The SND efficiency of ARBs B and C improved, and the average values were 68% and 70% after day 15. These values were higher than the 66% of ARB A during the same period. Comprehensively considering the COD, NH4+-N, TN removal rate, and SND efficiency, the optimal aeration rate of 670L/m3 aged refuse·d is therefore suggested in this study.

The typical MSW odorants identification and the spatial odorants distribution in a large-scale transfer station.

Odorants from municipal solid waste (MSW) were complex variable, and the screening of key offensive odorants was the prerequisite for odor control process. In this study, spatial odor emissions and environmental impacts were investigated based on a large-scale working waste transfer station (LSWTS) using waste container system, and a comprehensive odor characterization method was developed and applied in terms of the odor concentration (OC), theory odor concentration (TOC), total chemical concentration (TCC), and electric nose (EN). The detected odor concentration ranged from 14 to 28 (dimensionless), and MSW container showed the highest OC value of 28, EN of 78, and TCC of 35 (ppm) due to the accumulation of leachate and residual MSW. Ninety-two species odorants were identified, and H2S, NH3, benzene, styrene, ethyl acetate, and dichloromethane were the main contributors in the container, while benzene, m,p,x-xylene, butanone, acetone, isopropanol, and ethyl acetate were predominant in the compression surface (CS) and compression plant (CP). Side of roads (SR) and unload hall (UH) showed low odorous impact. Based on this odor list, 20 species of odor substances were screened for the priority control through the synthetic evaluation method, considering the odorants concentrations, toxicity, threshold values, detection frequency, saturated vapor pressure, and appeared frequency. Graphical abstract.