A novel strategy for gas mitigation during swine manure odour treatment using seaweed and a microbial consortium

• Comprehensive mitigation of gas emissions from swine manure was investigated. • Additives addition for mitigation of gas from the manure has been developed. • Sargassum horneri, seaweed masking strategy controlled gas by 90%-100%. • Immediate reduction in emitted gas and improving air quality has been determined. • Microbial consortium with seaweed completely controlled gas emissions by 100%. Gas emissions from swine farms have an impact on air quality in the Republic of Korea. Swine manure stored in deep pits for a long time is a major source of harmful gas emissions. Therefore, we evaluated the mitigation of emissions of ammonia (NH₃), hydrogen sulfide (H₂S) and amine gases from swine manure with biological products such as seaweed (Sargassum horneri) and a microbial consortium (Bacillus subtilis (1.2 × 10⁹ CFU/mL), Thiobacillus sp. (1.0 × 10¹⁰ CFU/mL) and Saccharomyces cerevisiae (2.0 × 10⁹ CFU/mL)) used as additives due to their promising benefits for nutrient cycling. Overall, seaweed powder masking over two days provided notable control of over 98%-100% of the gas emissions. Furthermore, significant control of gas emissions was especially pronounced when seaweed powder masking along with a microbial consortium was applied, resulting in a gas reduction rate of 100% for NH₃, amines and H₂S over 10 days of treatment. The results also suggested that seaweed powder masking and a microbial consortium used in combination to reduce the gas emissions from swine manure reduced odour compared with that observed when the two additives were used alone. Without the consortium, seaweed decreased total volatile fatty acid (VFA) production. The proposed novel method of masking with a microbial consortium is promising for mitigating hazardous gases, simple, and environmentally beneficial. More research is warranted to determine the mechanisms underlying the seaweed and substrate interactions.     

Biogas from the organic fraction of municipal solid waste: Dealing with contaminants for a solid oxide fuel cell energy generator

The present work investigates electricity production using a high efficiency electrochemical generator that employs as fuel a biogas from the dry anaerobic digestion of the organic fraction of municipal solid waste (OFMSW).The as-produced biogas contains several contaminants (sulfur, halogen, organic silicon and aromatic compounds) that can be harmful for the fuel cell: these were monitored via an innovative mass spectrometry technique that enables for in-line and real-time quantification.A cleaning trap with activated carbons for the removal of sulfur and other VOCs contained in the biogas was also tested and monitored by observing the different breakthrough times of studied contaminants.The electrochemical generator was a commercial Ni anode-supported planar Solid Oxide Fuel Cell (SOFC), tested for more than 300 h with a simulated biogas mixture (CH₄ 60 vol.%, CO₂ 40 vol.%), directly fed to the anode electrode. Air was added to promote the direct internal conversion of CH₄ to H₂ and CO via partial oxidation (POx).The initial breakthrough of H₂S from the cleaning section was also simulated and tested by adding ～1 ppm(v) of sulfur in the anode feed; a full recovery of the fuel cell performance after 24 h of sulfur exposure (～1 ppm(v)) was observed upon its removal, indicating the reliable time of anode exposure to sulfur in case of exhausted guard bed.     

Differences in volatile methyl siloxane (VMS) profiles in biogas from landfills and anaerobic digesters and energetics of VMS transformations

The objectives of this study were to compare the types and levels of volatile methyl siloxanes (VMS) present in biogas generated in the anaerobic digesters and landfills, evaluate the energetics of siloxane transformations under anaerobic conditions, compare the conditions in anaerobic digesters and municipal solid waste (MSW) landfills which result in differences in siloxane compositions. Biogas samples were collected at the South District Wastewater Treatment Plant and South Dade Landfill in Miami, Florida. In the digester gas, D4 and D5 comprised the bulk of total siloxanes (62% and 27%, respectively) whereas in the landfill gas, the bulk of siloxanes were trimethylsilanol (TMSOH) (58%) followed by D4 (17%). Presence of high levels of TMSOH in the landfill gas indicates that methane utilization may be a possible reaction mechanism for TMSOH formation. The free energy change for transformation of D5 and D4 to TMSOH either by hydrogen or methane utilization are thermodynamically favorable. Either hydrogen or methane should be present at relatively high concentrations for TMSOH formation which explains the high levels present in the landfill gas. The high bond energy and bond distance of the Si–O bond, in view of the atomic sizes of Si and O atoms, indicate that Si atoms can provide a barrier, making it difficult to break the Si–O bonds especially for molecules with specific geometric configurations such as D4 and D5 where oxygen atoms are positioned inside the frame formed by the large Si atoms which are surrounded by the methyl groups.     

Performance of sequential anaerobic/aerobic digestion applied to municipal sewage sludge

A promising alternative to conventional single phase processing, the use of sequential anaerobic-aerobic digestion, was extensively investigated on municipal sewage sludge from a full scale wastewater treatment plant. The objective of the work was to evaluate sequential digestion performance by testing the characteristics of the digested sludge in terms of volatile solids (VS), Chemical Oxygen Demand (COD) and nitrogen reduction, biogas production, dewaterability and the content of proteins and polysaccharides. VS removal efficiencies of 32% in the anaerobic phase and 17% in the aerobic one were obtained, and similar COD removal efficiencies (29% anaerobic and 21% aerobic) were also observed. The aerobic stage was also efficient in nitrogen removal providing a decrease of the nitrogen content in the supernatant attributable to nitrification and simultaneous denitrification. Moreover, in the aerobic phase an additional marked removal of proteins and polysaccharides produced in the anaerobic phase was achieved. The sludge dewaterability was evaluated by determining the Optimal Polymer Dose (OPD) and the Capillary Suction Time (CST) and a significant positive effect due to the aerobic stage was observed. Biogas production was close to the upper limit of the range of values reported in the literature in spite of the low anaerobic sludge retention time of 15 days. From a preliminary analysis it was found that the energy demand of the aerobic phase was significantly lower than the recovered energy in the anaerobic phase and the associated additional cost was negligible in comparison to the saving derived from the reduced amount of sludge to be disposed.     

顶空气相色谱法测定土壤或底泥中挥发性苯系物

采用顶空气相色谱法测定了土壤或底泥中的挥发性苯系物,测定了苯系物在10%NaCl水溶液60℃时的分配常数,给出了加入土壤导致液相体积改变的校正方法。用10% NaCl水溶液作为提取剂在 60℃加热平衡60min, 对5个苯系物的平均回收率达到73.6%, 检出限为4.2~5.5ng/g。     

Experimental studies of removing typical VOCs by dielectric barrier discharge reactor of different sizes

This research conducted both lab-scale and pilot-scale tests by selecting toluene as the typical volatile organic compounds (VOCs) and by using the promising non-thermal plasma oxidation technology – dielectric barrier discharge (DBD). To develop baseline engineering data to demonstrate the feasibility of application of self-made DBD reactors, the peak voltage, gas flow speed, initial toluene concentration, discharge frequency and duty ratio were studied. The results showed that toluene removal efficiency improves with increase of electrical voltage, frequency and duty ratio, and declines with increase of polar distance, gas flow speed and toluene initial concentration. When the voltage increases, the energy efficiency rises first and then drops. The energy efficiency reaches the climax when the energy density reaches 150.8 J/L and 101.7 J/L in the lab-scale experiment and pilot-scale experiment respectively.     

Optimizing food waste hydrothermal parameters to reduce Maillard reaction and increase volatile fatty acid production

The occurrence of the Maillard reaction and melanoidins formation during the hydrothermal treatment of food waste can reduce the yield of volatile fatty acids (VFA); however, few studies have investigated the adverse effects of the Maillard reaction. This study identified the impact of hydrothermal treatment parameters on hydrolysis and melanoidins formation and optimized the hydrothermal treatment conditions to enhance VFA production by minimizing the impact of the Maillard reaction. A response surface methodology was employed to optimize the hydrothermal treatment parameters and VFA production was evaluated. Results showed that temperature, reaction time, and pH were significant interacting factors with respect to hydrolysis and melanoidins formation while the C/N ratio and moisture content of food waste had little impact. The optimal conditions for hydrothermal treatment (temperature of 132 °C, reaction time of 27 min, and a pH of 5.6) enhanced VFA production by 22.1%. Under optimal hydrothermal treatment conditions, a higher initial C/N ratio further increased VFA production.     

水环境中挥发性有机物的监测方法

挥发性有机物具有种类多、含量少以及毒性大等特点,已成为我国水质监测优先控制污染物。本文叙述了近年来水中挥发性有机物在环境监测中的研究现状,主要介绍了4种预处理技术和两种分析方法,同时简单介绍了水环境中挥发性有机物的发展方向。     

The levels, sources and reactivity of volatile organic compounds in a typical urban area of Northeast China

Air concentrations of volatile organic compounds (VOCs) were continually measured at a monitoring site in Shenyang from 20 August to 16 September 2017. The average concentrations of alkanes, alkenes, aromatics and carbonyls were 28.54, 6.30, 5.59 and 9.78 ppbv, respectively. Seven sources were identified by the Positive Matrix Factorization model based on the measurement data of VOCs and CO. Vehicle exhaust contributed the most (36.15%) to the total propene-equivalent concentration of the measured VOCs, followed by combustion emission (16.92%), vegetation emission and secondary formation (14.33%), solvent usage (10.59%), petrochemical industry emission (9.89%), petrol evaporation (6.28%), and liquefied petroleum gas (LPG) usage (5.84%). Vehicle exhaust, solvent usage and combustion emission were found to be the top three VOC sources for O₃ formation potential, accounting for 34.52%, 16.55% and 11.94%, respectively. The diurnal variation of the total VOCs from each source could be well explained by their emission characteristics, e.g., the two peaks of VOC concentrations from LPG usage were in line with the cooking times for breakfast and lunch. Wind rose plots of the VOCs from each source could reveal the possible distribution of the sources around the monitoring site. The O₃ pollution episodes during the measurement period were found to be coincident with the elevation of VOCs, which was mainly due to the air parcel from the southeast direction where petrochemical industry emission was found to be dominant, suggesting that the petrochemical industry emission from the southeast was probably a significant cause of O₃ pollution in Shenyang.     

新型针状二氧化锰的制备、表征及其对土壤中有机物氧化性能研究

由化学法合成了一种新型类针状的二氧化锰(MnO2)材料,通过X射线衍射(XRD)、透射电镜(TEM)、比表面积测试(BET)、傅里叶转换红外光谱(FTIR)和X射线光电子能谱(XPS)等手段表征其结构特性,由MnO2对酚类有机物和医药类污染物的去除实验来评价其活性.结果表明,此材料为典型的δ-MnO2,其比表面积相对较大,为41m2·g-1,MnO2以MnO6八面体结构存在,Mn以MnO2形式存在.从MnO2对2-氯酚(2-CP)的去除及中间产物分析可知,MnO2对2-CP有较强的脱氯作用.另外,pH对2-CP的去除有较大影响.对酚类有机物和医药类污染物的去除实验考察发现,2,4-二氯酚(2,4-DCP)和2,4,6-三氯酚(2,4,6-TCP)的去除效率明显大于苯酚(Ph)和2-CP,而环丙沙星的去除与安替比林、布洛芬、苯妥英和苯海拉明相比更加容易,经过96h反应,去除率可达74%.