分点进水A/O工艺处理低碳源生活污水的脱氮性能研究

针对低C/N比污水脱氮的难点问题,在缺氧段不同点设置进水口,采用分点进水A/O工艺处理校园生活污水.考察了在污泥回流比为100%,硝化液回流比为200%,分流比为1∶1,缺氧池水力停留时间(HRT)分别为2、2.4和3 h情况下,分点进水A/O工艺的反硝化性能,并与传统的A/O工艺进行比较.结果表明,当缺氧池的水力停留...     

垃圾渗滤液的加载磁絮凝预处理工艺研究

垃圾渗滤液是一种成分复杂多变的高浓度难处理有机废水。采用加载磁絮凝技术对垃圾渗滤液进行预处理,以提高其可生化性,便于后续生化处理的进行。研究了适宜的磁载体种类、凝聚剂和絮凝剂的加入量,以及不同pH值和药剂投加顺序的影响,并进行了磁絮凝与常规絮凝工艺的对比实验。得到的最优组合工艺为：PAC投加量5.5 g/L,磁载体投加...     

湿法脱硫装置效率不高原因分析

分析了石灰石—石膏湿法烟气脱硫系统脱硫效率不高的原因,提出了查找方法和程序。     

欠发达地区农户生产效率研究——以西藏自治区为例

以西藏自治区为例,在2009年农户抽样调查数据基础上,利用数据包络法(DEA)探讨西藏不同区域农户生产效率,认为西藏农户生产效率差异与农业生产中自用价值的计算有关,若考虑自用价值,在固定生产规模报酬(CRS)假设下,平均生产效率为0.653,其中拉萨市最高(0.784),日喀则市最低(0.277);若不计入自用价值,山南与那曲地区呈现最高生产效率。表明西藏农户收入中自用价值占了较大比例,扣除自用价值,收入大幅减少,影响生产效率。因此,提高农牧户生产商品率是增加农牧民收入的有效途径。     

Sexual difference in mercury concentrations of lake trout (Salvelinus namaycush) from Lake Ontario

We determined total mercury (Hg) concentrations in 50 female lake trout (Salvelinus namaycush) and 69 male lake trout from Lake Ontario (Ontario, Canada and New York, United States). Results showed that, on average, males were 8% higher in Hg concentration than females in Lake Ontario. We also used bioenergetics modeling to determine whether a sexual difference in gross growth efficiency (GGE) could explain the observed sexual difference in Hg concentrations. According to the bioenergetics modeling results, male GGE was about 3% higher than female GGE, on average. Although the bioenergetics modeling could not explain the higher Hg concentrations exhibited by the males, a sexual difference in GGE remained a plausible explanation for the sexual difference in Hg concentrations of the lake trout. In an earlier study, male lake trout from Lake Ontario were found to be 22% higher in polychlorinated biphenyl (PCB) concentration than females from Lake Ontario. Thus, although males were higher in both Hg and PCB concentrations, the degree of the sexual difference in concentration varied between the two contaminants. Further research on sexual differences in Hg excretion rates and Hg direct uptake rates may be needed to resolve the disparity in results between the two contaminants.     

Phosphorus flows and use efficiencies in production and consumption of wheat, rice, and maize in China

Increasing fertilizer phosphorus (P) application in agriculture has greatly contributed to the increase of crop yields during the last decades in China but it has also increased P flows in food production and consumption. The relationship between P use efficiency and P flow is not well quantified at national level. In present paper we report on P flows and P use efficiencies in rice, wheat, and maize production in China using the NUFER model. Conservation strategies for P utilization and the impact of these strategies on P use efficiency have been evaluated. Total amounts of P input to wheat, rice, and maize fields were 1095, 1240, and 1128 Gg, respectively, in China, approximately 80% of which was in chemical fertilizers. The accumulation of P annually in the fields of wheat, rice, and maize was 29.4, 13.6, and 21.3 kg ha⁻¹, respectively. Phosphorus recovered in the food products of wheat, rice, and maize accounted for only 12.5%, 13.5%, and 3.8% of the total P input, or 3.2%, 2.6%, and 0.9% of the applied fertilizer P, respectively. The present study shows that optimizing phosphorus flows and decreasing phosphorus losses in crop production and utilization through improved nutrient management must be considered as an important issue in the development of agriculture in China.     

The Links Between Resource Dependency and Attitude of Commercial Fishers to Coral Reef Conservation in the Red Sea

The imperative to further constrain extractive uses of natural resources will strengthen as resources degrade through over-use or exposure to climate changes. Here, we explore an approach to increase the support for marine conservation among coral reef fishers. We explore the proposition that resource dependency in the Egyptian Red Sea can act as a barrier to conservation. We administered face-to-face surveys to 49% of the fishing industry to: (i) identify the level of compliance to the local marine protected area (MPA), (ii) assess the level of dependency on marine resources in the region and (iii) examine the relationship between resource dependency and conservation attitudes. Only 11.4% of fishers were aware of the MPA. Fishers were mostly limited in their social flexibility and livelihood options. Results suggest that resource dependency is highly and negatively correlated with conservation attitudes suggesting that management efforts need to seriously focus on reducing dependency if conservation goals are to be met.     

Anthropogenic NOx emissions alter the intrinsic water-use efficiency (WUEi) for Quercus cerris stands under Mediterranean climate conditions

We investigated the effect of N deposition (Ndep) on intrinsic water-use efficiency (WUE_i), the ratio of photosynthesis (A) to stomatal conductance (g_s), for two Quercus cerris stands at different distances to an oil refinery in Southern Italy. We used δ¹³C in tree rings for assessing changes in WUE_i; while the influence of climate and NO_x emission was explored through δ¹⁸O and δ¹⁵N, respectively. Differences in WUE_i between the two sites were significant, with trees exposed to different degrees of NO_x emissions showing an abrupt increase with the onset of pollution. Assuming similar g_s at the two sites, as inferred through δ¹⁸O, the higher N availability at the polluted site caused the shift of the A/g_s ratio in favour of A. Overall, our result suggests that an increase of Ndep may enhance tree WUE under a scenario of reduction of precipitation predicted for Mediterranean area.     

An approach to tackling the environmental and health impacts of municipal solid waste disposal in developing countries

Indiscriminate disposal of municipal solid waste in developing countries poses severe environmental and health threats. The study proposes a new method for dealing with these problems. The hybrid structural interaction matrix (HSIM) was used to prioritise major identifiable environmental health factors arising from improper solid waste disposal. The simplistic resource allocation model was adopted to ensure optimality in the allocation of resources to prioritised factors. The study indicates that tackling environmental health impacts from the most prioritised negative disposal factors through optimal allocation of resources, will either reduce or eliminate the impacts associated with subsequent less prioritised factors that are direct consequences of the highly prioritised negative factors. The method proposed will aid decision makers in knowing which set of systemic factors are to be given preference and to what extent at given periods in time.     

The removal of Polycyclic Aromatic Hydrocarbons in the wastewater treatment process: experimental calculations and model predictions

The removal of PAHs during the wastewater treatment process was examined in an activated sludge mode conventional facility. Concentrations reported are taken from an earlier measuring campaign. Removals of PAHs ranged between 28 and 67% in the primary, <1-61% in the secondary stage, and 37-89% in the whole process. Significant positive relationships were observed for removal efficiencies and the log K(ow) of PAHs in the primary and the log K(H) of PAHs in the secondary stage. Experimental removals were compared to those obtained from the FATE model. In the primary stage, predicted removals were lower than those experimentally calculated while in the secondary stage were higher. Predicted removals were apportioned mainly to sorption with negligible contribution from volatilization and biodegradation. Remarkable consistency between experimental and modeled removal efficiencies (-20-+20%) was observed for almost all PAHs in the whole treatment process.