Codisposal of municipal refuse, sewage sludge and marine dredgings for methane production

As marine disposal of sewage sludge and dredged sediments may impose serious adverse effects to marine ecosystems, landfilling seems to be the most feasible method for the final disposal of these wastes. A batch experiment was conducted to study waste degradation and gas production after sewage sludge and marine dredgings were mixed with municipal refuse at 13 different ratios for 36 days. The addition of sludge and dredgings to municipal refuse enhanced gas production, compared with the degradation of refuse or sludge alone. A proper mixing ratio of wastes can also shorten the time to reach the final phase of anaerobiosis. The highest gas production was obtained from the ratio of 75-20-5 (refuse-sludge-dredgings) (wet weight basis). Its average daily gas production rate was 1.42 l kg(-1) waste mixture; methane content was 68.3%. The results indicated that codisposal of the three wastes would be beneficial for energy recovery from landfill gas.     

Determination of solid-liquid partition coefficients (Kd) for the herbicides isoproturon and trifluralin in five UK agricultural soils

Isoproturon and trifluralin are herbicides of contrasting chemical characters and modes of action. Standard batch sorption procedures were carried out to investigate the individual sorption behaviour of 14C-isoproturon and 14C-trifluralin in five agricultural soils (1.8-4.2% OC), and the soil solid-liquid partition coefficients (Kd values) were determined. Trifluralin exhibited strong partitioning to the soil solid phase (Kd range 106-294) and low desorption potential, thus should not pose a threat to sensitive waters via leaching, although particle erosion and preferential flow pathways may facilitate transport. For isoproturon, soil adsorption was low (Kd range 1.96-5.75) and desorption was high, suggesting a high leaching potential, consistent with isoproturon being the most frequently found pesticide in UK surface waters. Soil partitioning was directly related to soil organic carbon (OC) content. Accumulation isotherms were modelled using a dual-phase adsorption model to estimate adsorption and desorption rate coefficients. Associations between herbicides and soil humic substances were also shown using gel filtration chromatography.     

Effect of soil properties on saturated and unsaturated virus transport through columns

Viruses from contaminant sources can be transported through porous media to drinking water wells. The objective of this study was to investigate inactivation and sorption of viruses during saturated and unsaturated transport in different soils. Bacteriophages phiX174 and MS-2, and Br- tracer in a phosphate-buffered saline solution were introduced into saturated and unsaturated soil columns as a step function under constant flow rate and hydraulic conditions. Results showed that significantly greater virus removal occurred in the unsaturated columns than in the saturated columns in the two soils containing high metal oxides content. However, the increase in virus retention under unsaturated conditions was not significant in two other soils having high phosphorus and calcium contents and high pH, and in another soil with high organic matter content. The results imply that the extent of water content effect on inactivation and sorption of viruses can range from significant to minimal depending on the properties of the transport medium. We found that the presence of in situ metal oxides was a significant factor responsible for virus sorption and inactivation. Therefore, soils with high metal oxides content may have the potential to be used as hydrological barriers in preventing microbial contamination in the subsurface environments. We also found that the water content effect on virus removal and inactivation strongly depended on solid properties of the testing medium.     

Enzymatic oxidative transformation of chlorophenol mixtures

Chlorinated phenols are major industrial and agricultural xenobiotics that pollute soil and ground water. It has been shown that laccases catalyze the oxidative coupling of phenolic compounds. Therefore, the transformation of one or a mixture of several chlorinated phenols by a laccase from the fungus Trametes villosa was studied. Generally, if more than one phenol was added, the transformation of chlorinated phenols decreased, and if the concentration of the laccase was increased, the transformation of the phenols was enhanced. There were exceptions to these observations: for instance, the transformation of 0.1 mM 4-chlorophenol incubated with 1 mM 2,4-dichlorophenol in buffered salt solutions was not enhanced if the concentration of the laccase was increased from 2 to 20 DMP units/mL. The reason for the reduced transformation of chlorinated phenols in the presence of additional phenols is still unknown. However, in spite of some limitations, the application of laccase to decontaminate wastewater polluted with chlorinated phenols appears feasible.     

Effects of biomass accumulation on microbially enhanced dissolution of a PCE pool: a numerical simulation

Recent studies have shown that dechlorinating bacteria can accelerate the dissolution rate of dense, nonaqueous phase liquids (DNAPLs) containing tetrachloroethene (PCE). We present an advection-dispersion-reaction model for a two-dimensional domain, with groundwater flowing over a pool of free-product PCE. PCE is converted to cis-1,2-dichloroethene (cDCE) and toxicity due to PCE or cDCE is neglected. We adopt previously published correlations relating biomass concentrations and hydraulic conductivity, accounting for biofilm growth and plug-like growth. The system of coupled equations is solved numerically. The high biotransformation rate of PCE increases the concentration gradient of PCE at the water-DNAPL interface, enhancing dissolution. The higher the electron donor (ED) concentration, the larger the dissolution enhancement. Based on the values of maximum specific rate we used, when the electron donor is unlimited, the active biomass accumulates adjacent to the water-NAPL interface and microbial reactions can significantly enhance the pool dissolution. The resulting steady-state dissolution rate can be approximated by a half-order solution when zero-order kinetics are suitable for representing the microbial reaction. However, bioclogging may significantly reduce local hydraulic conductivity; thus, it decreases the flow near the water-DNAPL interface, decreasing dissolution. When the ED is the limiting factor, active biomass accumulates away from the interface. This creates a no-flow zone between the active biomass and the interface. The enlargement of the no-flow zone, due to the donor limitation, diminishes the concentration gradient and the flushing around the water-DNAPL interface. Such adverse impacts may significantly decrease the enhancement predicted by models that do not consider the effects of bioclogging.     

Absorption and reaction kinetics of amines and ammonia solutions with carbon dioxide in flue gas

The removal system for the absorption of CO2 with amines and NH3 is an advanced air pollution control device to reduce greenhouse gas emissions. Absorption of CO2 by amines and NH3 solutions was performed in this study to derive the reaction kinetics. The absorption of CO2 as encountered in flue gases into aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), and NH3 was carried out using a stirred vessel with a plane gas-liquid interface at 50 degrees C. Various operating parameters were tested to determine the effect of these variables on the absorption kinetics of the reactants in both gas and liquid phases and the effect of competitions between various reactants on the mass-transfer rate. The observed absorption rate increases with increasing gas-liquid concentration, solvent concentration, temperature, and gas flow rate, but changes with the O2 concentration and pH value. The absorption efficiency of MEA is better than that of NH3 and DEA, but the absorption capacity of NH3 is the best. The active energies of the MEA and NH3 with CO2 are 33.19 and 40.09 kJ/mol, respectively.     

Organic contamination in the greenhouse soils from Beijing suburbs, China

Selected persistent organic pollutants including HCHs, DDTs and PAHs together with PAEs were determined in the greenhouse soils from Beijing suburbs. The total concentrations were 11.64-29.80 ng g(-1) for HCHs, 18.04-101.33 ng g(-1) for DDTs, 1.34-3.15 microg g(-1) for PAEs and 1.92-7.84 microg g(-1) for PAHs, respectively. Predominance of beta-HCH in all samples was obviously observed, suggesting a lack of new HCHs sources. High concentrations of DDE and DDD in comparison to their parents in the samples indicated that most of the DDT had been transformed into its metabolites. The contamination of PAHs was relatively serious and the most abundant compounds were 4-, 5- and 6-ring unsubstituted PAHs. The profiles reflect the important effect of traffic on the PAHs remaining in greenhouse soils. Three phthalate esters (DIBP, DnBP and DEHP) accounted for more than 97% of the phthalates studied. Analysis of n-alkanes was also performed in order to trace the natural or anthropogenic sources of hydrocarbons. Characterization and identification of these compounds in greenhouse soil may help in development of strategies to be used in monitoring organic pollutants in this region.     

环保型煤炭开采与利用技术--煤炭地下气化

介绍了煤炭地下气化技术的开发与应用，相比传统煤炭开采燃用技术，煤炭地下气化实现了煤炭清洁开采与利用，指出煤炭地下气化技术是环保型开采与利用技术，应用积极推广利用。     

含油污水乳化液微波分离实验研究

针对油气田乳化含油污水难分离的特点,利用微波技术进行的实验室研究结果表明,微波辐照温度与其后的静置时间都是影响其破乳率的重要因素,其分离效果随微波辐照后温度的增高而加强,而且在相同温度下乳液破乳率随静置时间加长而迅速增高。研究结果证实,微波辐射技术具有时间短、能耗少、效率高等特点,且经过微波处理后的含油污水易于进行油品回收再利用,有良好的应用前景。     

厌氧UASB-混凝沉淀法处理高浓度屠宰废水

应用UASB混凝沉淀法对高浓度屠宰废水的处理进行了试验研究。用UASB反应器处理屠宰废水,CODCr容积负荷可达6.8g(L·d),CODCr去除率达93%左右,并对UASB出水投加一定量的混凝剂PFS和助凝剂MZ,实验表明:系统出水达到《肉类加工工业水污染物排放标准》(GB1345792)二级标准。