Anaerobic co-digestion of the organic fraction of municipal solid waste with FOG waste from a sewage treatment plant: Recovering a wasted methane potential and enhancing the biogas yield

Anaerobic digestion is applied widely to treat the source collected organic fraction of municipal solid wastes (SC-OFMSW). Lipid-rich wastes are a valuable substrate for anaerobic digestion due to their high theoretical methane potential. Nevertheless, although fat, oil and grease waste from sewage treatment plants (STP-FOGW) are commonly disposed of in landfill, European legislation is aimed at encouraging more effective forms of treatment. Co-digestion of the above wastes may enhance valorisation of STP-FOGW and lead to a higher biogas yield throughout the anaerobic digestion process. In the present study, STP-FOGW was evaluated as a co-substrate in wet anaerobic digestion of SC-OFMSW under mesophilic conditions (37 °C). Batch experiments carried out at different co-digestion ratios showed an improvement in methane production related to STP-FOGW addition. A 1:7 (VS/VS) STP-FOGW:SC-OFMSW feed ratio was selected for use in performing further lab-scale studies in a 5 L continuous reactor. Biogas yield increased from 0.38 ± 0.02 L g VS_feed^?1 to 0.55 ± 0.05 L g VS_feed^?1 as a result of adding STP-FOGW to reactor feed. Both VS reduction values and biogas methane content were maintained and inhibition produced by long chain fatty acid (LCFA) accumulation was not observed. Recovery of a currently wasted methane potential from STP-FOGW was achieved in a co-digestion process with SC-OFMSW.     

Appropriate combination of physico-chemical methods (coagulation/flocculation and ozonation) for the efficient treatment of landfill leachates

An integrated technique consisted of ozonation and coagulation/flocculation processes was studied, aiming to provide an efficient method for the treatment of stabilized/biologically pre-treated leachates, in order to reduce the organic pollutants' content to concentration values lower than the corresponding limits, imposed by the legislation. Leachates were collected from a municipal landfill site; samples containing around 1000 mg l(-1) COD and BOD(5)/COD ratio about 0.17 were treated by using two different processes or combinations between them, i.e. ozonation, coagulation-flocculation, ozonation followed by coagulation/flocculation and coagulation/flocculation followed by ozonation. The application of single ozonation resulted to the efficient removal of color and organic loading, due to the respective oxidation, induced by ozonation; however, COD values lower than 200 mg l(-1) could be only achieved after prolonged reaction times and for high ozone production rates. The coagulation of leachate samples was studied by the addition of ferric chloride or poly-aluminum chloride agents at various dosages. Maximum COD removal rates (up to 72%) were achieved by the addition of 7 mM Fe, or of 11 mM Al respectively. However, final COD values higher than 200 mg l(-1) were obtained indicating the requirement of an additional treatment step. Pre-ozonation followed by coagulation/flocculation was not found to be an efficient treatment approach for this aim, but coagulation/flocculation followed by ozonation, was proved to be an efficient process for the reduction of COD to lower than 180 mg l(-1).     

Chemical characterisation of PM episodes in NE Spain

The chemical composition of ambient particulate matter (PM) varies widely as a function of its main emission sources and of the chemical reactions which take place in the atmosphere. The aim of this study is to obtain the chemical profile of PM10 and PM2.5 during peak PM episodes, thus identifying the main emission sources and/or atmospheric processes which originate the PM episodes. To this end, cluster analysis was applied to a set of PM10 and PM2.5 data collected throughout 2001 in two urban and industrialised areas in NE Spain. As a result of this analysis, five clusters were identified for each site, and the interpretation of their chemical profiles lead to the identification of five types of peak PM episodes for each site: industrial, traffic and regional re-circulation episodes at both sites, plus crustal episodes in Barcelona, and peak traffic and industrial episodes (T+I) in Tarragona. Traffic episodes are characterised by daily means of 23 and 10 microg/m3 of OM+EC in Barcelona and Tarragona in PM10. Levels of secondary inorganic aerosols reach average daily means of 19 and 11 microg/m3 in Barcelona and Tarragona in PM10 during industrial episodes. High levels of sulphate (>5 microg/m3) and ozone (up to 77 microg/m3 daily mean) are good tracers of regional re-circulation episodes. During crustal episodes daily means of crustal elements reach up to 34 microg/m3 in Barcelona. Special attention has been drawn to the composition of the mineral matter during the different PM episodes.     

Biodegradation of polycyclic aromatic hydrocarbons in the natural waters of the Yellow River: effects of high sediment content on biodegradation

The contamination of polycyclic aromatic hydrocarbons (PAHs) has become one of the major problems in the Yellow River of China. As the Yellow River is the most turbid large river in the world, it remains unknown to which extent the high suspended sediment content in the river may affect the fate and effect of PAHs. Here we report the effect of sediment on biodegradation of chrysene, benzo(a)pyrene and benzo(g,h,i)perylene with phenanthrene as a co-metabolism substrate in natural waters from the Yellow River. Biodegradation kinetics of the PAHs in the river water with various levels of sediment contents were studied in the laboratory by fitting with a biodegradation kinetics model for organic compounds not supporting growth. The results indicated that the biodegradation rates of PAHs increased with the sediment content in the water. When the sediment contents were 0, 4 and 10 g/l, the biodegradation rate constants of chrysene with the initial concentration of 3.80 microg/l were 0.053, 0.084 and 0.111 d(-1), respectively. Further studies suggested the enhanced biodegradation rate in the presence of sediment was caused by the following mechanisms: (1) the population of PAH-degrading bacteria in the water system was found to increase with the sediment content; the bacteria population on sediment phase was far greater than that on water phase during the cultivation process; (2) the sorption of PAHs on the sediment phase was well described by the dual adsorption-partition model. Although the sorption capacity of PAH per unit weight of sediment decreased with the increase of the sediment content, the amount of sorbed PAH increased with the sediment content; and, (3) the desorption of PAHs from the solid phase led to a higher concentration near the water-sediment interface. Since the bacteria were also attached to the interface, this resulted in an increased contact chance between the bacteria and PAHs.     

Distribution of polycyclic aromatic hydrocarbons in soils at Guiyu area of China, affected by recycling of electronic waste using primitive technologies

The concentration, distribution, profile and possible source of polycyclic aromatic hydrocarbons (PAHs) in soil were studied in Guiyu, an electronic waste (E-waste) recycling center, using primitive technologies in Southeast China. Sixteen USEPA priority PAHs were analyzed in 49 soil samples (0-10 cm layer) in terms of individual and total concentrations, together with soil organic matter (SOM) concentrations. The concentrations of a sum of 16 PAHs ranged from 44.8 to 3206 microgkg(-1) (dry weight basis), in the descending order of E-waste open burning sites (2065 microgkg(-1))>areas near burning sites (851microgkg(-1))>rice fields (354 microgkg(-1))>reservoir areas (125microgkg(-1)). The dominant PAHs were naphthalene, phenanthrene and fluoranthene, which were mainly derived from incomplete combustion of E-waste (e.g. wire insulations and PVC materials), and partly from coal combustion and motorcycle exhausts. All individual and total PAH concentrations were significantly correlated with SOM except for naphthalene and acenaphthylene. Principal component analysis was performed, which indicated that PAHs were mainly distributed into three groups in accordance with their ring numbers and biological and anthropogenic source. In conclusion, PAH concentrations in the Guiyu soil were affected by the primitive E-waste recycling activities.     

Use of dolomite phosphate rock (DPR) fertilizers to reduce phosphorus leaching from sandy soil

There is increasing concern over P leaching from sandy soils applied with water-soluble P fertilizers. Laboratory column leaching experiments were conducted to evaluate P leaching from a typical acidic sandy soil in Florida amended with DPR fertilizers developed from dolomite phosphate rock (DPR) and N-Viro soil. Ten leaching events were carried out at an interval of 7 days, with a total leaching volume of 1,183 mm equivalent to the mean annual rainfall of this region during the period of 2001-2003. Leachates were collected and analyzed for total P and inorganic P. Phosphorus in the leachate was dominantly reactive, accounting for 67.7-99.9% of total P leached. Phosphorus leaching loss mainly occurred in the first three leaching events, accounting for 62.0-98.8% of the total P leached over the whole period. The percentage of P leached (in the total P added) from the soil amended with water-soluble P fertilizer was higher than those receiving the DPR fertilizers. The former was up to 96.6%, whereas the latter ranged from 0.3% to 3.8%. These results indicate that the use of N-Viro-based DPR fertilizers can reduce P leaching from sandy soils.     

Spatial distribution and vertical variation of arsenic in Guangdong soil profiles, China

Total of 260 soil profiles were reported to investigate the arsenic spatial distribution and vertical variation in Guangdong province. The arsenic concentration followed an approximately lognormal distribution. The arsenic geometric mean concentration of 10.4 mg/kg is higher than that of China. An upper baseline concentration of 23.4 mg/kg was estimated for surface soils. The influence of soil properties on arsenic concentration was not important. Arsenic spatial distributions presented similar patterns that high arsenic concentration mainly located in limestone, and sandshale areas, indicating that soil arsenic distribution was dependent on bedrock properties than anthropogenic inputs. Moreover, from A- to C-horizon arsenic geometric mean concentrations had an increasing tendency of 10.4, 10.7 to 11.3 mg/kg. This vertical variation may be related to the lower soil organic matter and soil degradation and erosion. Consequently, the soil arsenic export into surface and groundwaters would reach 1040 t year-1 in the study area.     

上海市旅游生态足迹分析

运用生态足迹的理论与方法,结合旅游者的生态消费及结构特征,借助现代地理信息技术,对上海市旅游生态足迹进行了分析。通过测算,2009年上海市旅游生态足迹为66 333 483.428hm2,人均旅游生态足迹为466.547×10-4 hm2;旅游生态承载力为1 900 029.08hm2,人均旅游生态承载力为146.908×10-4 hm2,人均生态赤字为319.692×10-4 hm2。从上海市旅游生态足迹结构来看,旅游交通和旅游购物足迹的比例最大,分别占71.79%和23.76%,旅游餐饮和休闲娱乐其次,分别为3.44%和0.14%,比例最小的是旅游观光和旅游住宿。这表明旅游活动正在过度消耗上海城市资源环境,旅游业目前处于生态赤字状态,因此应采取相关的改进措施,以实现资源保护与旅游发展的平衡,并着手调整旅游产业内部结构,发展环保节能的交通工具,大力推动低碳旅游发展,开发有特色的旅游商品,提高旅游购物消费,在保证生态资源可持续利用的同时保持旅游经济快速发展。     

锦州生态市建设生态环境保护指标的可达性分析

按照《生态县、生态市、生态省建设指标（修订稿）》要求,锦州市生态市建设从经济发展、生态环境保护和社会进步三个方面,设置了19项指标,结合锦州市实际情况,对其中的生态环境保护类11项指标作出达标情况分析,其中全部达标的有“空气环境质量”、“水环境质量”、“集中式饮用水源水质达标率”、“城市污水集中处理率”、“城市生活垃圾无害化处理率”5项,不达标的有“森林覆盖率”、“受保护地区占国土的面积比例”、“化学需氧量排放强度”、“噪声环境质量”、“城镇人均公共绿地面积”、“环境保护投资占GDP的比例”6项,并着重针对不达标指标结合《锦州市环境保护“十二五”规划》等内容进行可达性分析。     

Combining remote sensing imagery and forest age inventory for biomass mapping

Aboveground biomass (AGB) of forests is an important component of the global carbon cycle. In this study, Landsat ETM(+) images and field forest inventory data were used to estimate AGB of forests in Liping County, Guizhou Province, China. Three different vegetation indices, including simple ratio (SR), reduced simple ratio (RSR), and normalized difference vegetation index (NDVI), were calculated from atmospherically corrected ETM(+) reflectance images. A leaf area index (LAI) map was produced from the RSR map using a regression model based on measured LAI and RSR. The LAI map was then used to develop an initial AGB map, from which forest stand age was deduced. Vegetation indices, LAI, and forest stand age were together used to develop AGB estimation models for different forest types through a stepwise regression analysis. Significant predictors of AGB changed with forest types. LAI and NDVI were significant predictors of AGB for Chinese fir (R(2)=0.93). The model using LAI and stand age as predictors explained 94% of the AGB variance for coniferous forests. Stand age captured 79% of the AGB variance for broadleaved forests (R(2)=0.792). AGB of mixed forests was predicted well by LAI and SR (R(2)=0.931). Without differentiating among forest types, the model with SR and LAI as predictors was able to explain 90% of AGB variances of all forests. In Liping County, AGB shows a strong gradient that increases from northeast to southwest. About 64% of the forests have AGB in the range from 90 to 180 t ha(-1).