Fluoride removal by a continuous flow electrocoagulation reactor

Long-term consumption of water containing excessive fluoride can lead to fluorosis of the teeth and bones. Electrocoagulation (EC) is an electrochemical technique, in which a variety of unwanted dissolved particles and suspended matter can be effectively removed from an aqueous solution by electrolysis. Continuous flow experiments with monopolar aluminium electrodes for fluoride removal were undertaken to investigate the effects of the different parameters such as: current density (12.5-50A/m(2)), flow rate (150-400 mL/min), initial pH (4-8), and initial fluoride concentration (5-25mg/L). The highest treatment efficiency was obtained for the largest current and the removal efficiency was found to be dependent on the current density, the flow rate and the initial fluoride concentration when the final pH ranged between 6 and 8. The composition of the sludge produced was analysed using the X-ray diffraction (XRD) spectrum. The strong presence of the aluminium hydroxide [Al(OH)(3)] in the above pH range, which maximizes the formation of aluminium fluoride hydroxide complex [Al(n)F(m)(OH)(3n-m)], is the main reason for defluoridation by electrocoagulation. The results obtained showed that the continuous flow electrocoagulation technology is an effective process for defluoridation of potable water supplies and could also be utilized for the defluoridation of industrial wastewater.     

Assessment of electrocoagulation for the treatment of petroleum refinery wastewater

Batch electrocoagulation experiments were carried out to evaluate the removal of sulfate and COD from petroleum refinery wastewater using three types of electrodes: aluminum, stainless steel, and iron. The effects of current density, electrode arrangement, electrolysis time, initial pH, and temperature were investigated for two wastewater samples with different concentrations of COD and sulfate. The experimental results indicated that the utilization of aluminum, as anode and cathode, was by far the most efficient arrangement in the reduction of both the contaminants. The treatment process was found to be largely affected by the current density and the initial composition of the wastewater. Although electrocoagulation was found to be most effective at 25°C and a pH of 8, the influence of these two parameters on the removal rate was not significant. The results demonstrated the technical feasibility of electrocoagulation as a possible and reliable technique for the pretreatment of heavily contaminated petroleum refinery wastewater.     

Blue space: The importance of water for preference,affect, and restorativeness ratings of natural and built scenes

Although theorists have suggested that aquatic environments or “blue space” might have particular restorative potential, to date there is little systematic empirical research on this issue. Indeed the presence of water has, unintentionally, been a confounding factor in research comparing people’s reactions to built and natural environments. Whereas aquatic features (rivers, lakes, coasts) are frequently present in visual stimuli representing natural environments they are rarely incorporated in stimuli portraying built environments. As many towns are, for good reason, located near water this is a potentially significant oversight. The current research collated a set of 120 photographs of natural and built scenes, half of which contained “aquatic” elements. Proportions of “aquatic”/“green”/“built” environments in each scene (e.g. 1/3rd, 2/3rds) were also standardised. Two studies investigated preferences (attractiveness, willingness to visit and willingness to pay for a hotel room with the view), affect and perceived restorativeness ratings for these photographs. As predicted, both natural and built scenes containing water were associated with higher preferences, greater positive affect and higher perceived restorativeness than those without water. Effect sizes were consistently large. Intriguingly, images of “built” environments containing water were generally rated just as positively as natural “green” space. We propose a number of avenues for further research including exploration of the mechanisms underlying these effects.     

Environmental quality criteria: Some considerations

The physicochemical characteristics of the recipient environment into which chemical contaminants are deposited may influence their chemical speciation, mobility, bioavailability, and toxicity. In formulating Water Quality Criteria, the Environmental Protection Agency of the United States (EPA) considered the modifying effect of abiotic environmental factors on pollutant toxicity in an innovative regulatory approach. Scientific knowledge of the interactions and correlations between pollutant toxicity and abiotic factors remains limited. Recognition of the influence of the physicochemical characteristics of the recipient environment on pollutant toxicity has implications for the eventual formulation of regional, rather than uniform and national, criteria. In addition, in developing Water Quality Criteria that incorporate the effects of pollutants on aquatic life, EPA primarily focused on toxicity to aquatic animals and plants (including unicellular algae). The effects of pollutants on microbe-mediated ecological processes that are necessary for maintaining the state and quality of the ecosphere (such as biogeochemical cyclings, litter decomposition, and mineralization) were not included in the formulation of the Water Quality Criteria. To facilitate the recognition and quantification of adverse effects of pollutants on these ecological processes, the development of a computation, termed the ecological dosage 50% (EcD₅₀) is recommended. Such a formulation could also be applied to setting environmental quality criteria for terrestrial ecosystems.     

Reforming small-scale mining in sub-Saharan Africa: Political and ideological challenges to a Fair Trade gold initiative

In sub-Saharan Africa, artisanal and small-scale mining (ASM) has caused a range of environmental, social and economic problems. Most of the donor support pledged to improve conditions in the sector to date, however, has failed to facilitate marked improvements, in large part because emphasis has been placed on technical interventions; at the same time, impoverished miners’ needs and concerns have been seriously overlooked. It is against this background that this paper critically examines the underpinnings and potential of “Fair Trade gold” as a solution to many of the problems plaguing the ASM sector and a mechanism for alleviating the hardships of its operators. Unlike the majority of ASM-support support measures implemented in the past, “Fair Trade gold” is entrenched in the discourse of “partnership” and “participation”. To ensure its effectiveness initiatives must be adapted according to the specificities of ASM.     

水处理无机混凝剂的研究进展

概略评述了国内外无机混凝剂的研究进展。无机混凝剂可分为铝盐类、铁盐类、铁铝复合类、活化硅酸等,聚合氯化铝（简称ＰＡＣ）是目前水处理中广泛应用的无机高分子混凝剂。无机复合类混凝剂是近来年发展十分迅速的水处理剂,聚硅酸铝盐类是其中的代表。文中对无机混凝剂今后的研究工作提出了建议,认为在无机混凝剂的研制开发中,要加强应用基础性研究,产品多样化、专门化,要降低生产成本,提高产品质量,进行优化研究。     

饮用水絮凝剂的应用现状与发展趋势

针对饮用水絮凝剂存在的问题，本文就国内外饮用水絮凝剂的研究，发展及应用情况进行了概述，并对絮凝剂今后的研究工作提出了建议。     

LIGNIN SEPARATION BY CONTINUOUS ION FLOTATION: INVESTIGATION OF PHYSICAL OPERATIONAL PARAMETERS1

ABSTRACT: Ion flotation is the term used to describe a process in which there is an initally homogeneous solution which becomes heterogeneous after the addition of an oppositely charged surfactant due to the reaction between the surfactant and specific ion(s); thus, insoluble complexes are formed. These insoluble complexes will then attached to the bubbles passing through the solution and thus leave in the foam phase. The performance of the continuous ion flotation process for the removal of haft lignin from water was investigated intensively using liquid flow rates, gas flow rates, feed locations and solution height as operational variables. The interrelationships among these physical parameters were studied and discussed. A dimensionless operational chart was established for process control. Results demonstrate that ion flotation is an effective process for removing lignin from water, provided that a quaternary ammonium salt, such as cetyldimethylbenzyl-ammonium chloride or the like, is used as a collector. At optimum operational conditions, higher than 0.95 fractional removal of lignin can be achieved.     

“Horizontal” and “vertical” diffusion: The cumulative influence of Impact and Benefit Agreements (IBAs) on mining policy-production in New Caledonia

The scale, duration and intensity of conflicts over mineral resources vary greatly. However, they always involve, in varying proportions, the triad stakeholder model—corporation, state, community—each element of which is internally heterogeneous. Increasingly, new players are entering the scene: international non-governmental organizations (NGOs), environmental grassroots groups, indigenous transnational networks, international aid and development agencies. Nevertheless, conflicts and arrangements around access to and control over mineral resources can take the apparent form of dyadic relationships between companies and local communities, resulting in negotiated company-community agreements, often called “Impact and Benefit Agreements” (IBAs). In our analysis, local agreements on mineral resource governance are seen as building blocks in the production of mining policy “from below”, even though they seem at first sight to exclude the state. This paper argues that these agreements, and the negotiations surrounding them, inform debates around mining through both “horizontal diffusion” (influence on other localities facing similar situations) and “vertical diffusion” (influence on policy design and implementation at upper political and administrative levels). This diffusion may occur in a “positive” sense, effecting further change in line with the intent of the original agreement, or in a “negative” one, actually making substantive change less likely, whether at a community or policy level. We build this argument through two case studies from New Caledonia, in the south-west Pacific, where mining has long been a key issue, especially in the current context of “negotiated decolonization” launched by the 1998 Nouméa Accord.     

The removal of lignin and phenol from paper mill effluents by electrocoagulation

This study aims to investigate the treatment of paper mill effluents using electrocoagulation. Removal of lignin, phenol, chemical oxygen demand (COD) and biological oxygen demand (BOD) from paper mill effluents was investigated at various current intensities by using different electrodes (Al and Fe) and at various electrolysis times (1.0, 2.5, 5.0 and 7.5min). It was observed that the experiments carried out at 12V, an electrolysis time of 2min and a current intensity of 77.13mA were sufficient for the removal of these pollutants with each electrode. The removal capacities of the process using an Al electrode were 80% of lignin, 98% of phenol, 70% of BOD, and 75% of COD after 7.5min. Using an Fe electrode the removal capacities were 92%, 93%, 80% and 55%, respectively. In addition, it was found that removal of lignin, phenol, BOD and COD increased with increasing current intensity. In the experiments carried out at different current intensities, higher removal can be explained through a decrease in intra-resistance of solution and consequently an increase at the transfer speed of organic species to electrodes. It was also found that Al electrode performs higher efficiency than Fe electrode except for COD removal. However, the time required for removal of BOD was more than that of COD. The results suggest that electrocoagulation could be considered as an effective alternative to paper mill effluents treatment.     

Determinants of noise annoyance in teachers from schools with different classroom reverberation times

A high proportion of school teachers report that they are disturbed by noise during teaching. The aim of the study was therefore to identify determinants of self-reported noise exposure and disturbance attributed to noise among secondary school teachers (n = 419) in 10 schools in Copenhagen, Denmark. The schools were selected to show contrasts in classroom reverberation times (RT), and were classified as “Short RT” (3 schools, mean RT 0.41–0.45 s), “Medium RT” (3 schools, mean RT 0.51–0.55 s) and “Long RT” (4 schools, mean RT 0.62–0.73 s). Significant determinants of self-reported noise exposure were a high number of children in the class, young age of the children, and low teacher seniority. “Long RT” classification was of borderline significance. Significant determinants of disturbance attributed to noise from children in the class were teacher seniority and “Long RT” acoustic classification of the school. The associations between work characteristics and noise disturbance measures were attenuated by low self-rated work capacity, suggesting that the consequences of noise and poor acoustics may not be limited to disturbance attributed to noise, but may have a wide negative impact on the perceived working environment.     

WATER USE AND WATER CONSERVATION BY THE COPPER MINING INDUSTRY1

ABSTRACT: This paper examines the use of water by copper mines for treating low grade ores. The froth flotation process for treating sulphide ore and the heap leaching process for treating oxide ore are described, and ways of reducing the amount of water used in these processes are discussed. Estimates of the costs reducing water consumption are given. Finally, the circumstances in which it would be desirable for a copper mine to reduce its level of water consumption are considered.     

Historic preservation,significance, and age value: A comparative phenomenology of historic Charleston and the nearby new-urbanist community of I'On

While the age of physical environments is the central tenet of historic preservation, there is a lack of empirical evidence about how everyday people actually value, perceive, and experience age as an intrinsic part of an urban environment. In order to ameliorate this knowledge deficit, this study employs phenomenology to understand the lived experience of being in a “new” versus an “old” or “historic” urban residential environment. The new environment is the I'On new urbanist development in Mt. Pleasant, South Carolina, and the old environment is the location of the United States' first historic district in Charleston, South Carolina. These locations are approximately within five miles of each other. In both places, the physical characteristics of the built environment are remarkably similar in density, form, layout, and design, but the age is dramatically different. Through photo elicitation techniques and interviews, the results of this study reveal that residents of historic Charleston and I'On value their built environments in remarkably similar ways. Surprisingly, elements that evoke a strong sense of attachment tend to be landscape features, such as gates, fountains, trees, and gardens rather than buildings. The informants valued the “mystery” that they felt was part of the landscape and which consisted of layered elements such as fences, gates, and paths, such that these features (including buildings) had to be “discovered.” Lastly, the informants strongly valued landscapes that showed “people care” through regular maintenance. The essential difference in people's experience and valuation of the new environment (I'On) and the old environment (historic Charleston) is in the older environment's ability to instill creative fantasies in the minds of the informants based on a hypothetical past of their own creation. The informants in I'On did not share these kinds of meanings.     

Environmental assessment of different management options for individual waste fractions by means of life-cycle assessment modelling

Several alternatives exist for handling of individual waste fractions, including recycling, incineration and landfilling. From an environmental point of view, the latter is commonly considered as the least desirable option. Many studies based on life-cycle assessment (LCA) highlight the environmental benefits offered by incineration and especially by recycling. However, the landfilling option is often approached unjustly in these studies, maybe disregarding the remarkable technological improvements that landfills have undergone in the last decades in many parts of the world.This study, by means of LCA-modelling, aims at comparing the environmental performance of three major management options (landfilling, recycling and incineration or composting) for a number of individual waste fractions. The landfilling option is here approached comprehensively, accounting for all technical and environmental factors involved, including energy generation from landfill gas and storage of biogenic carbon. Leachate and gas emissions associated to each individual waste fraction have been estimated by means of a mathematical modelling. This approach towards landfilling emissions allows for a more precise quantification of the landfill impacts when comparing management options for selected waste fractions.Results from the life-cycle impact assessment (LCIA) show that the environmental performance estimated for landfilling with energy recovery of the fractions “organics” and “recyclable paper” is comparable with composting (for “organics”) and incineration (for “recyclable paper”). This however requires high degree of control over gas and leachate emissions, high gas collection efficiency and extensive gas utilization at the landfill. For the other waste fractions, recycling and incineration are favourable, although specific emissions of a variety of toxic compounds (VOCs, PAHs, NO_x, heavy metals, etc.) may significantly worsen their environmental performance.     

Is Russia suffering from Dutch Disease? Cointegration with structural break

This paper examines whether Russia suffers from “Dutch Disease” by investigating the real appreciation of the Russian ruble and the relative de-industrialization in the post Soviet Union-era. According to UNDP Russia Report (2009) the Russian economy has indeed exhibited some typical symptoms of “Dutch Disease” in recent years as upward movements in oil prices are accompanied by a reduction in the share of manufacturing output and an increase in service prices. Furthermore, the report claims that these developments may trigger a recession in Russia in the future. Using Gregory and Hansen (1996a, 1996b) and Arai and Kurozumi (2007) structural break cointegration frameworks, our results indicate that the Russian economy exhibits some typical symptoms of “Dutch Disease”. Although the diagnosis is not certain, the risk is evident. Hence, policies that would make the Russian economy more robust to shocks in the oil price need to be carefully designed and implemented.     

Modeling the Effects of Extreme Drought on Pollutant Transport Processes in the Yangtze River Estuary

Water resources in the Yangtze River Estuary (YRE), which is the vital water supply for Shanghai, decreased by approximately 2.45 Gm³ in 2006, the second‐worst recorded drought year. A numerical model was developed to investigate the effects of this extreme drought on pollutant transport processes in the YRE. The model was calibrated against observations and displayed good agreement. Residence time, a critical hydrodynamic indicator, was implemented to indicate pollutant transport processes. Numerical experiments were conducted to examine the possibly drought‐induced influences. The model results demonstrated that the influences on pollutant transport processes varied spatially and temporally, and these influences could partly explain the observed temporal and spatial variations of total nitrate in 2006. The area most susceptible to drought is in the north branch with 2‐11 days' extension of residence time. As the drought occurred in both the high and normal water periods, its influences were more significant during the normal water period with saltwater intrusion into the north branch. The drought also introduced a pollutant transport lag in timescale of approximately five days by diminishing the seaward advection flux with freshwater discharge. In 2006, the magnified tidal influence during the drought contributed more than usual to structuring pollutant transport, as the pollutant transport processes were intensely associated with tidal flow and tidal cycle.     

Designing of an environmental assessment algorithm for surface mining projects

This paper depicts the method used to quantify the environmental impact of mining activities in surface mine projects. The affected environment was broken down into thirteen components, such as Human health and immunity, Surface water, Air quality, etc. The effect of twenty impacting factors from the mining and milling activities was then calculated for each Environmental Component. Environmental assessments are often performed by using matrix methods in which one dimension of the matrix is the “Impacting Factor” and the other one is the “Environmental Components”. For the presented matrix method, each Impacting Factor was first given a magnitude between −10 and 10. These factors are used to set up a matrix named Impacting Factor Matrix, whose elements represent the Impacting Factor values. The effects of each Impacting Factor on each Environmental Component were then quantified by multiplying the Impacting Factor Matrix by Weighting Factor Matrix. The elements of the weighting factors matrix reflect the effects of each Impacting Factor on each Environmental Component. The outlined method was originally developed for a mining and milling operation in Iran, but it can successfully be used for mining ventures and more general industrial activities in other countries in accordance to their environmental regulations and laws.     

Exploring insideness in urban children’s sense of place

This study, informed by phenomenology and ethnography, explores urban children’s relationship with their urban environment: In what ways do urban children exhibit “insideness” in their sense of place? This study proposes “insideness” as a conceptual construct to understand urban children’s sense of place in its ecological and dynamic nature. Employing qualitative research methods, the study explores place stories of urban children who live in low-income, immigrant neighborhoods in New York City. The study finds that as children cultivate their sense of place, they construct “insideness” in their sense of place including 1) environmental understanding (i.e., contextualized, comprehensive, and critical understanding of a place), 2) environmental competence (i.e., knowing how to navigate and engage in a place), and 3) diverse, strong affective relationships with a place. Using “insideness” as a conceptual tool, this study discusses children’s emplaced understanding and active and dialogical positionality in the development of their sense of place.