Biofilm formation and microbial community analysis of the simulated river bioreactor for contaminated source water remediation

Background, aim, and scope

The start-up pattern of biofilm remediation system affects the biofilm characteristics and operating performances. The objective of this study was to evaluate the performances of the contaminated source water remediation systems with different start-up patterns in view of the pollutants removal performances and microbial community succession.

Methods

The operating performances of four lab-scale simulated river biofilm reactors were examined which employed different start-up methods (natural enrichment and artificial enhancement viadischarging sediment with influent velocity gradient increase) and different bio-fillers (Elastic filler and AquaMats? ecobase). At the same time, the microbial communities of the bioreactors in different phases were analyzed by polymerase chain reaction, denaturing gradient gel electrophoresis, and sequencing.

Results and discussion

The pollutants removal performances became stable in the four reactors after 2 months?? operation, with ammonia nitrogen and permanganate index (COD_Mn) removal efficiencies of 84.41?C94.21% and 69.66?C76.60%, respectively. The biomass of mature biofilm was higher in the bioreactors by artificial enhancement than that by natural enrichment. Microbial community analysis indicated that elastic filler could enrich mature biofilm faster than AquaMats?. The heterotrophic bacteria diversity of biofilm decreased by artificial enhancement, which favored the ammonia-oxidizing bacteria (AOB) developing on the bio-fillers. Furthermore, Nitrosomonas- and Nitrosospira-like AOB coexisted in the biofilm, and Pseudomonas sp., Sphaerotilus sp., Janthinobacterium sp., Corynebacterium aurimucosum were dominant in the oligotrophic niche.

Conclusion

Artificial enhancement via the combination of sediment discharging and influent velocity gradient increasing could enhance the biofilm formation and autotrophic AOB enrichment in oligotrophic niche.     

几种腐殖填料生物滤池COD去除效能比较研究

分别采用腐殖垃圾、泥炭、煤炭等腐殖填料及河沙构筑生物滤池,处理模拟废水,比较研究其COD去除效能及降解特征,为工艺填料改性提供理论依据。几种填料的扫描电镜分析图显示腐殖垃圾及泥炭以团聚体三维空间结构为主;煤炭与河沙表面粗糙程度较小,且主要由颗粒状物质构成。稀释平板涂布法分离出各生物滤池中发挥主要作用的微生物共3种,各系统菌落数量有差异,但种类相同。3种腐殖填料生物滤池在进水有机物浓度为500 mg/L及1000 mg/L时均有较理想的有机物去除效率。3种腐殖填料生物滤池中泥炭构筑的腐殖填料生物滤池有机物比降解速率最小,因而微生物比增长速率最小,微生物增长和自身氧化最易趋向于动态平衡,对应的饱和水力渗透系数最大,滤池最不易发生堵塞,最有利于腐殖填料生物滤池长期稳定运行,证明泥炭是一种优良的生物介质。     

辉县市城区环境空气质量现状及污染防治对策

对辉县市城区2006—2011年间环境空气质量监测数据进行了评价，并对城区污染物浓度时空变化进行了分析。结果表明，辉县市城区大气污染主要表现为可吸入颗粒物污染严重，主要是能源结构不合理、锅炉废气污染严重、城区道路保洁方式落后等原因造成的，由此提出了合理规划城市布局、减少结构性污染等对策。     

WATCH

Abstract

The development of everthing follows its own law, which does not change at people's own sweet will. Therefore, we must study the development of things so as to grasp the essence of things in their deep meanings, explore the direction of their development, and make them better serve the people. As a part of the thought of sustainable development, city environment art will be of active significance to the perfection of the thought and will also be the concrete embodiment of the synthetic index of economic development. Such a thesis, starting from the macroscopic angle, and relying on the leading thought of sustainable development, takes hold of the development trend of city environment art, and explores the various problems that have arisen in city environment in the process of city management by combining thoughts on city planning, so as to guide urban harmonious development theoretically. The present paper expounds on the views comprehensively and, through the synthetic analysis on city planning, city environment, art esthetics and the thought of sustainable development, makes a detailed analysis of the effects of the present rapid city development on city environment.     

Emission factors and particulate matter size distribution of polycyclic aromatic hydrocarbons from residential coal combustions in rural Northern China

Coal consumption is one important contributor to energy production, and is regarded as one of the most important sources of air pollutants that have considerable impacts on human health and climate change. Emissions of polycyclic aromatic hydrocarbons (PAHs) from coal combustion were studied in a typical stove. Emission factors (EFs) of 16 EPA priority PAHs from tested coals ranged from 6.25 ± 1.16 mg kg^?1 (anthracite) to 253 ± 170 mg kg^?1 (bituminous), with NAP and PHE dominated in gaseous and particulate phases, respectively. Size distributions of particulate phase PAHs from tested coals showed that they were mostly associated with particulate matter (PM) with size either between 0.7 and 2.1 μm or less than 0.4 μm (PM_0.4). In the latter category, not only were more PAHs present in PM_0.4, but also contained higher fractions of high molecular weight PAHs. Generally, there were more than 89% of total particulate phase PAHs associated with PM_2.5. Gas-particle partitioning of freshly emitted PAHs from residential coal combustions were thought to be mainly controlled by absorption rather than adsorption, which is similar to those from other sources. Besides, the influence of fuel properties and combustion conditions was further investigated by using stepwise regression analysis, which indicated that almost 57 ± 10% of total variations in PAH EFs can be accounted for by moisture and volatile matter content of coal in residential combustion.     

Correlations between physicochemical properties of PAHs and their distribution in soil, moss and reindeer dung at Ny-Ålesund of the Arctic

Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in soil, moss and reindeer dung collected at Ny-Ålesund of the Arctic were measured to investigate their accumulation trends and distribution in the three compartments. Compared with the other regions, the proportions of 2 + 3 ring PAHs to the total PAHs were higher, whereas the proportions of 5 + 6 ring PAHs were lower in the three compartments at Ny-Ålesund. Significant log/log-linear relationship was observed between the sub-cooled liquid vapor pressure and the soil/moss quotient (Q_SM). The relation was similar to the relationship between the gas/particle partition coefficient (K_P) and of PAHs, implying Q_SM would be a “mirror image” of K_P. Excellent log/log-linear relationships were observed between Q_SM and K_OA as well as between the moss/dung quotient (Q_MD) and K_OW. The results presented here indicate the physicochemical properties are suitable for characterizing the distribution of PAHs in soil, moss and reindeer dung.     

A new direct thermal desorption-GC/MS method: Organic speciation of ambient particulate matter collected in Golden, BC

Particulate matter having an aerodynamic diameter less than 2.5 μm (PM2.5) is thought to be implicated in a number of medical conditions, including cancer, rheumatoid arthritis, heart attack, and aging. However, very little chemical speciation data is available for the organic fraction of ambient aerosols. A new direct thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) method was developed for the analysis of the organic fraction of PM2.5. Samples were collected in Golden, British Columbia, over a 15-month period. n-Alkanes constituted 33–98% by mass of the organic compounds identified. PAHs accounted for 1–65% and biomarkers (hopanes and steranes) 1–8% of the organic mass. Annual mean concentrations were: n-alkanes (0.07–1.55 ng m⁻³), 16 PAHs (0.02–1.83 ng m⁻³), and biomarkers (0.02–0.18 ng m⁻³). Daily levels of these organics were 4.89–74.38 ng m⁻³, 0.27–100.24 ng m⁻³, 0.14–4.39 ng m⁻³, respectively. Ratios of organic carbon to elemental carbon (OC/EC) and trends over time were similar to those observed for PM2.5. There was no clear seasonal variation in the distribution of petroleum biomarkers, but elevated levels of other organic species were observed during the winter. Strong correlations between PAHs and EC, and between petroleum biomarkers and EC, suggest a common emission source – most likely motor vehicles and space heating.     

Simulation of global warming potential (GWP) from rice fields in the Tai-Lake region,China by coupling 1:50,000 soil database with DNDC model

Quantifying greenhouse gas (GHG) emissions from wetland ecosystems is a relatively new issue in global climate change studies. China has approximately 22% of the world's rice paddies and 38% of the world's rice production, which are crucial to accurately estimate the global warming potential (GWP) at regional scale. This paper reports an application of a biogeochemical model (DeNitrification and DeComposition or DNDC) for quantifying GWP from rice fields in the Tai-Lake region of China. For this application, DNDC is linked to a 1:50,000 soil database, which was derived from 1107 paddy soil profiles compiled during the Second National Soil Survey of China in the 1980–1990s. The simulated results show that the 2.34 Mha of paddy soil cultivated in rice–wheat rotation in the Tai-Lake region emitted about ?1.48 Tg C, 0.84 Tg N and 5.67 Tg C as CO₂, N₂O, and CH₄ respectively, with a cumulative GWP of 565 Tg CO₂ equivalent from 1982 to 2000. As for soil subgroups, the highest GWP (26,900 kg CO₂ equivalent ha^?1 yr^?1) was linked to gleyed paddy soils accounting for about 4.4% of the total area of paddy soils. The lowest GWP (5370 kg CO₂ equivalent ha^?1 yr^?1) was associated with submergenic paddy soils accounting for about 0.32% of the total area of paddy soils. The most common soil in the area was hydromorphic paddy soils, which accounted for about 53% of the total area of paddy soils with a GWP of 12,300 kg CO₂ equivalent ha^?1 yr^?1. On a regional basis, the annual averaged GWP in the polder, Tai-Lake plain, and alluvial plain soil regions was distinctly higher than that in the low mountainous and Hilly soil regions. As for administrative areas, the average annual GWP of counties in Shanghai city was high. Conversely, the average annual GWP of counties in Jiangsu province was low. The high variability in soil properties throughout the Tai-Lake region is important and affects the net greenhouse gas emissions. Therefore, the use of detailed soil data sets with high-resolution digital soil maps is essential to improve the accuracy of GWP estimates with process-based models at regional and national scales.     

Optimization of hydrogen distribution systems with pressure constraints

Hydrogenation units are often operated at high pressure, requiring the use of compressors which are one of the most expensive chemical processing equipment. Optimizing a hydrogen network should therefore take into consideration not only purity and flowrate constraints but also pressure requirements. In this paper, based on the hydrogen surplus diagram approach, the average pressure profiles of hydrogen sources and sinks are proposed through the introduction of a system’s minimum pressure drop Δp. Combined with the traditional purity profiles, whether a source can meet a sink either for hydrogen concentration or for pressure requirements can be determined intuitively. In cases where the pressure of a source is not sufficient for a sink, installing a hydrogen compressor or using another source with higher purity and pressure could be potential solutions. A cost equation is established to determine which of the two solutions is economically more viable. For different matching situations between sources and sinks, strategies for optimum placement of compression equipment within a given hydrogen network are proposed. A case study is used to illustrate the application and effectiveness of the proposed method.     

Trip-Based Explanatory Variables For Estimating Vehicle Fuel Consumption and Emission Rates

The current state-of-practice in the US for estimatingvehicle emissions is based on a single traffic-relatedexplanatory variable, namely average speed. Research,however, has demonstrated that the use of average speed asa single traffic-related variable is insufficient for theestimation of vehicle emissions. For example, although theEnvironmental Protection Agency (EPA) MOBILE5 model wouldindicate that a slowing of traffic typically increasesemissions, empirical research indicates the opposite inmany cases.The objective of this paper is to identify criticalaggregate trip variables as potential explanatory variablesfor the estimation of a vehicle's fuel consumption andemissions. Subsequently, statistical models for estimatingfuel consumption and emissions of hydrocarbon (HC), carbonmonoxide (CO), and oxides of nitrogen (NO_x) aredeveloped using these critical variables that include theaverage speed, speed variability, the level ofdeceleration, and the level of acceleration. The proposedmodels are demonstrated to be consistent with microscopicenergy and emission model estimates that are based on thevehicle's instantaneous speed and acceleration levels(coefficient of determination ranges from 0.88 to 0.96).