Synthesis of Hybrid Gas Permeation Membrane/Condensation Systems for Pollution Prevention

ABSTRACT

Pollution prevention is a major economic and environmental issue in the chemical processing industries. This paper addresses the design of cost-effective recovery systems for vaporous emissions, systems that allow environmentally sound recycling of the recovered components for re-use within the process as a means of pollution prevention. A methodology is proposed to design optimal hybrid systems that involve gas permeation membranes and vapor condensation systems. The design methodology is presented as a mixed-integer, nonlinear program. Based on a fixed structure of the system, a short-cut formulation is derived. Additionally, the incorporation of the system into the emerging mass integration methodology is presented. It is demonstrated, through an industrial case study, that hybrid membrane/condensation systems possess advantages over either separation technique alone.     

On the Occurrence of Transient Puffs in a Rotary Kiln Incinerator Simulator II. Contained Liquid Wastes on Sorbent

The generation of transient puffs resulting from the batch introduction of liquid waste into a 73 kW (250,000 Btu/h) rotary kiln incinerator simulator was investigated. The liquid was added onto a sorbent, enclosed in cylindrical cardboard containers that were introduced into the combustion chamber one at a time. A statistically designed parametric investigation determined the effects of liquid mass, liquid composition, kiln temperature, and kiln rotation speed on the total magnitude and instantaneous intensity of the pollutant puff leaving the kiln. Liquid "wastes" investigated included toluene, methylene chloride, carbon tetrachloride, and No. 5 fuel oil. Transient puffs from these wastes were monitored using on-line measurements for FID-measurable hydrocarbons, CO, and integrated particulate filter loadings, although the suitability of any one of these indicators depended on the chemical nature of the waste involved.

Results demonstrate that puffs formed during transient conditions are generated easily, even with small quantities of wastes and with the kiln operating at 100 percent excess air. High kiln temperatures and increased kiln rotation speeds exacerbated the generation of puffs, due to increased liquid evaporation rates. Transient puffs may contain hazardous products of incomplete combustion (PICs) even though adequate destruction and removal efficiencies are achieved. Mixtures of chlorinated and nonchlorinated principal organic hazardous constituents (POHCs) in the waste can lead to the formation of more diverse chlorinated compounds than are formed from a single chlorinated POHC such as carbon tetrachloride alone.

This paper is the second of a series. Its companion paper, Part I, which has been published previously,¹ is concerned with solid plastic wastes.     

Modelling the dispersion of treated wastewater in a shallow coastal wind-driven environment,Geographe Bay,Western Australia: implications for environmental management

Numerical models are useful for predicting the transport and fate of contaminants in dynamic marine environments, and are increasingly a practical solution to environmental impact assessments. In this study, a three-dimensional hydrodynamic model and field data were used to validate a far-field dispersion model that, in turn, was used to determine the fate of treated wastewater (TWW) discharged to the ocean via a submarine ocean outfall under hypothetical TWW flows. The models were validated with respect to bottom and surface water current speed and direction, and in situ measurements of total nitrogen and faecal coliforms. Variations in surface and bottom currents were accurately predicted by the model as were nutrient and coliform concentrations. Results indicated that the ocean circulation was predominately wind driven, evidenced by relatively small oscillations in the current speeds along the time-scale of the tide, and that dilution mixing zones were orientated in a predominantly north-eastern direction from the outfall and parallel to the coastline. Outputs of the model were used to determine the ‘footprint’ of the TWW plume under a differing discharge scenario and, particularly, whether the resultant changes in TWW contaminants, total nitrogen and faecal coliforms would meet local environmental quality objectives (EQO) for ecosystem integrity, shellfish harvesting and primary recreation. Modelling provided a practical solution for predicting the dilution of contaminants under a hypothetical discharge scenario and a means for determining the aerial extent of exclusion zones, where the EQOs for shellfish harvesting and primary recreation may not always be met. Results of this study add to the understanding of regional discharge conditions and provide a practical case study for managing impacts to marine environments under a differing TWW discharge scenario, in comparison to an existing scenario.     

Connectedness, social support and internalising emotional and behavioural problems in adolescents displaced by the Chechen conflict

The study investigated factors associated with internalising emotional and behavioural problems among adolescents displaced during the most recent Chechen conflict. A cross-sectional survey (N=183) examined relationships between social support and connectedness with family, peers and community in relation to internalising problems. Levels of internalising were higher in displaced Chechen youth compared to published norms among non-referred youth in the United States and among Russian children not affected by conflict. Girls demonstrated higher problem scores compared to boys. Significant inverse correlations were observed between family, peer and community connectedness and internalising problems. In multivariate analyses, family connectedness was indicated as a significant predictor of internalising problems, independent of age, gender, housing status and other forms of support evaluated. Sub-analyses by gender indicated stronger protective relationships between family connectedness and internalising problems in boys. Results indicate that family connectedness is an important protective factor requiring further exploration by gender in war-affected adolescents.     

A test of the mismatch hypothesis: How is timing of reproduction related to food abundance in an aerial insectivore?

In seasonal environments, vertebrates are generally thought to time their reproduction so offspring are raised during the peak of food abundance. The mismatch hypothesis predicts that reproductive success is maximized when animals synchronize their reproduction with the food supply. Understanding the mechanisms influencing the timing of reproduction has taken on new urgency as climate change is altering environmental conditions during reproduction, and there is concern that species will not be able to synchronize their reproduction with changing food supplies. Using data from five sites over 24 years (37 site-years), we tested the assumptions of the mismatch hypothesis in the Tree Swallow (Tachycineta bicolor), a widespread aerial insectivore, whose timing of egg-laying has shifted earlier by nine days since the 1950s. Contrary to the mismatch hypothesis, the start of egg-laying was strongly related to food abundance (flying insect biomass) during the laying period and not to timing of the seasonal peak in food supply. In fact, food abundance generally continued to increase throughout the breeding season, and there was no evidence of selection based on the mistiming of laying with the seasonal peak of food abundance. In contrast, there was selection for laying earlier, because birds that lay earlier generally have larger clutches and fledge more young. Overall, initial reproductive decisions in this insectivore appear to be based on the food supply during egg formation and not the nestling period. Thus, the mismatch hypothesis may not apply in environments with relatively constant or abundant food throughout the breeding season. Although climate change is often associated with earlier reproduction, our results caution that it is not necessarily driven by selection for synchronized reproduction.     

Different food preferences in four sympatric deep-sea Macrourid fishes

Feeding habits of the four most abundant deep-sea demersal trawl-caught macrourids on Chatham Rise, New Zealand, were examined from stomach contents. Two species were predominantly benthic foragers: Coelorinchus bollonsi on infaunal and epifaunal polychaetes, and C. aspercephalus on epifaunal crustaceans; and two species were predominantly mesopelagic foragers; C. oliverianus on calanoid copepods, and Lepidorhynchus denticulatus on mesopelagic crustaceans. The most important predictors of diet variability were identified using distance-based linear models and included areal predictors in all four species, fish size in C. aspercephalus, C. bollonsi and L. denticulatus, and sample year in C. bollonsi. Cluster analyses showed that the diets of C. aspercephalus and C. bollonsi were most distinct. There was a greater interspecific similarity in diet in the spatial and fish size subgroups of C. oliverianus and L. denticulatus, than at the species level. Failing to account for areal, temporal, and ontogenetic variability in diets may bias evaluations of resource competition.     

AN EXPERIMENT IN DETERMINISTIC WATERSHED MODELING1

An experimental three-dimensional finite-difference watershed model in the form of a Fortran IV program was constructed. The model was an oversimplified one which divided the watershed volume into layers of cells which represented the overland flow, the vadose, and the phreatic zones. Water budget equations which utilized such formulas as Darcy's law and Manning's equation were applied to each interior cell. The resulting set of simultaneous equations was solved for heads at the end of successive time increments. This information was transformed to streamflow and other hydrologic output. Input was weather data, which effected appropriate adjustments in the cells representing the surface-water and vadose zones. After testing the model, it was concluded that this type of model is undesirably sensitive to cell size and length of time increment. In spite of the deficiencies of this primitive model, this general kind of approach to modeling seems promising, but it may be necessary to devise new transport equations which apply to more natural divisions of watersheds.     

Responding to Pressure on Local Natural Resources: the Story of Three Villages in South-Eastern Nigeria

There has been a recent move by development professionals away from formal “scientific” attempts to address problems caused by changing environmental conditions, towards a greater reliance on the innovative ability and indigenous knowledge of local people. This has necessitated a greater understanding of the way in which communities respond to environmental and socio-economic change. Using a model that predicts community responses to pressure on local natural resources, and data collected in three villages in south-eastern Nigeria, an attempt is made to document the way in which people react and adapt to change. It is concluded that with sufficient time communities will usually develop new resource management and agricultural systems. However, where change is occurring rapidly, a facilitator is required to encourage and accelerate local innovation so that farming and natural resource management systems can be appropriately adjusted before severe environmental degradation takes place.     

Economic assessment of crop damages due to air pollution: the role of quality effects

Biological research has established that air pollution can affect the yield and quality of agricultural crops. Economic assessments of crop exposure to air pollution have focused on the yield effect. This study illustrates the implications of considering crop quality effects in addition to crop yield changes for the case of O3 impacts on soybeans. An economic model of US soybean, soybean oil, and soybean meal markets is used to simulate the impacts of increased soybean yields due to reduced O3 concentrations with and without changes in soybean quality. The simulations with quality effects are richer in their distributional implications and show larger increases in economic surplus than the simulations with yield effects only.     

Investigation of the concentration and isotopic composition of inputs and outputs of Pb in waters at an upland catchment in NE Scotland

As a consequence of the accumulation of anthropogenic Pb in upland catchments, there has been much recent concern about the potential mobilisation and transport of Pb from the soils to receiving waters and also the possible harmful effects that this might have on aquatic biota. This paper presents the findings of a two-year study of Pb behaviour in an organic-rich upland catchment at Glensaugh in NE Scotland. Pb inputs to the catchment were characterised by direct measurements of Pb concentration and (206)Pb/(207)Pb ratios in rain water and interception. Pb outputs from the catchment were calculated from measurements on stream water samples taken from the two main streams, the Cairn Burn and Birnie Burn. The relative contribution of Pb from groundwater and throughflow, under different flow conditions (base flow and high flow), to stream waters was investigated via analysis of springs sourced from groundwater and of waters flowing through the various soil horizons (S (surface), A, B, C, and D), respectively. The outcome of intensive sampling and analysis over the two-year time period was that, even with marked reduction in Pb inputs over the past two decades, the catchment was still acting as a net sink for the current atmospheric deposition. Although the Pb isotopic signature for stream water is very similar to that for the contemporaneous rain water ((206)Pb/(207)Pb approximately 1.15-1.16), only a small portion of the rain water is transferred directly to stream water. Instead, the Pb input is transferred to the stream waters mainly via groundwater and it was also confirmed that the latter had a similar Pb isotopic signature. From the Pb isotopic measurements on throughflow waters, however, Pb being removed via the streams contained some previously deposited Pb, i.e. mobilisation of a small portion of soil-derived anthropogenic Pb was occurring. These findings are important not only with respect to the source/sink status of the catchment but also for calculation of the extent of retention of the current atmospheric Pb inputs, which must take account of the release of previously deposited Pb from the catchment soils, a process occurring mainly under high flow conditions.