排序方式: 共有26条查询结果,搜索用时 531 毫秒
11.
Membrane separation technology is increasingly becoming an important innovation in biological wastewater treatment. Biofouling of the membrane is a major factor affecting the efficient and economic operation of membrane separation bioreactors (MBRs). This review summarizes the state-of-the-art progress in understanding the mechanisms and factors affecting membrane biofouling and the strategies for biofouling control. Biofouling mechanisms include the adsorption of soluble and suspended extracellular polymers on membrane surfaces and in membrane pores, the clogging of membrane pore structure by fine colloidal particles and cell debris, and the adhesion and deposition of sludge cake on membrane surfaces. Design and operating conditions of membrane modules and materials, hydrodynamic conditions in MBRs, process and environmental conditions of activated sludge systems, and the physicochemical properties of the wastewater are the dominant factors determining membrane biofouling. Current strategies to control biofouling include periodic relaxation, backwashing, chemical cleaning, and possible manipulation of hydrodynamic conditions and sludge properties. Achieving full integration of MBRs in wastewater treatment technology requires further research and development. Fundamental information on the bacteria, colloid, and membrane interaction, developed through multimethod and multiscale approaches, is particularly needed. 相似文献
12.
13.
Watanabe M Adams RM Wu J Bolte JP Cox MM Johnson SL Liss WJ Boggess WG Ebersole JL 《Journal of environmental management》2005,75(2):93-104
This paper integrates economic, biological, and physical models to explore the efficient combination and spatial allocation of conservation efforts to protect water quality and increase salmonid populations in the Grande Ronde basin, Oregon. We focus on the effects of shade on water temperatures and the subsequent impacts on endangered juvenile salmonid populations. The integrated modeling system consists of a physical model that links riparian conditions and hydrological characteristics to water temperature; a biological model that links water temperature and riparian conditions to salmonid abundance, and an economic model that incorporates both physical and biological models to estimate minimum cost allocations of conservation efforts. Our findings indicate that conservation alternatives such as passive and active riparian restoration, the width of riparian restoration zones, and the types of vegetation used in restoration activities should be selected based on the spatial distribution of riparian characteristics in the basin. The relative effectiveness of passive and active restoration plays an important role in determining the efficient allocations of conservation efforts. The time frame considered in the restoration efforts and the magnitude of desired temperature reductions also affect the efficient combinations of restoration activities. If the objective of conservation efforts is to maximize fish populations, then fishery benefits should be directly targeted. Targeting other criterion such as water temperatures would result in different allocations of conservation efforts, and therefore are not generally efficient. 相似文献
14.
The potential impact on a variety of bioassay organisms when pulp-mill biosolids from a thermomechanical pulp mill (western Canada) were applied to a reference soil has been investigated in a laboratory setup. The current research assessed acute, chronic, and reproductive impacts using a battery of terrestrial and aquatic organisms. Terrestrial organisms were exposed to soil amended with different concentrations of biosolids, while aquatic organisms were used to assess the impact of biosolids' runoff into receiving waters. The former bioassays showed that an application rate of 20 tonneshectare(-1) (tha(-1)) "bone-dry" biosolids applied to reference soil produced no observable adverse impact on the terrestrial organisms. In the latter assays, undiluted (100%) and 50% diluted biosolids' runoff into receiving water had a detrimental impact on the aquatic organisms. However, concentrations not exceeding 25% (environmentally relevant concentrations) had neither an acute nor chronic impact compared to reference populations. The organisms' abilities to reproduce were also unaltered. While this study only examined the biosolids from one mill, there is the potential that land-application of characteristically well-defined pulp mill biosolids may constitute an acceptable way of disposing of pulp and paper mill biosolid residues. However, the biosolids coming from different mills, with differing processes, must be dealt with on a case-by-case situation. Each series of biosolids must be rigorously tested for toxicological impact in the laboratory under tightly controlled conditions. Subsequently, field experimentation must be conducted before definitive conclusions can be made. 相似文献
15.
Brood guarding animals face many critical trade-offs. Sand goby males (Pomatoschistus minutus) build nests with larger openings during low oxygen conditions, presumably to enhance ventilation. However, this may make
the nest easier for egg predators to detect and harder for guarding males to defend. Manipulating oxygen level and predator
presence (a small crab) for small and large males, we found support for a parental trade-off between fanning and nest defense.
An increased fanning activity resulted in less time for guarding. Small males and males in low oxygen showed a higher fanning
expenditure than large males and males in high oxygen, but surprisingly, filial cannibalism did not differ between these groups.
Males built larger nest openings in low than high oxygen. However, males in both high and low oxygen treatments reduced their
nest opening size in the presence of a predator, again indicating an important trade-off between ventilation and nest defense. 相似文献
16.
17.
Roland von Glasow Tim D. Jickells Alexander Baklanov Gregory R. Carmichael Tom M. Church Laura Gallardo Claire Hughes Maria Kanakidou Peter S. Liss Laurence Mee Robin Raine Purvaja Ramachandran R. Ramesh Kyrre Sundseth Urumu Tsunogai Mitsuo Uematsu Tong Zhu 《Ambio》2013,42(1):13-28
Megacities are not only important drivers for socio-economic development but also sources of environmental challenges. Many megacities and large urban agglomerations are located in the coastal zone where land, atmosphere, and ocean meet, posing multiple environmental challenges which we consider here. The atmospheric flow around megacities is complicated by urban heat island effects and topographic flows and sea breezes and influences air pollution and human health. The outflow of polluted air over the ocean perturbs biogeochemical processes. Contaminant inputs can damage downstream coastal zone ecosystem function and resources including fisheries, induce harmful algal blooms and feedback to the atmosphere via marine emissions. The scale of influence of megacities in the coastal zone is hundreds to thousands of kilometers in the atmosphere and tens to hundreds of kilometers in the ocean. We list research needs to further our understanding of coastal megacities with the ultimate aim to improve their environmental management. 相似文献
18.
WJ. Muller V.H. Sehaeffer 《Journal of the Air & Waste Management Association (1995)》2013,63(9):808-812
Abstract Sensory and pulmonary irritation are physiological responses to chemical exposure which result in characteristic, measurable changes in respiratory activity in mice. A standard method has been applied to the estimation of sensory irritation associated with a specific chemical exposure. This method has been correlated with human responses to these chemicals. Symptoms associated with chemical irritants are consistent with complaints due to problems with indoor air quality, which may include eye and upper respiratory tract irritation, headaches, and nausea. A stepwise strategy for assessing the contribution of indoor products to sensory and pulmonary irritation is discussed in the current paper. The strategy includes product emissions testing using dynamic environmental chambers, the selection of suspected irritants for respiratory irritation testing, respiratory irritation testing of individual compounds and representative mixtures using synthesized atmospheres, and the evaluation of test data to determine those compounds which may contribute to sensory and pulmonary irritation in humans. The current strategy is being applied to evaluate carpet system materials and their constituent chemicals. 相似文献
19.
20.
Ola Svensson Maria Lissåker Kenyon B. Mobley 《Behavioral ecology and sociobiology》2010,64(8):1325-1331
When parental care is costly, parents should avoid caring for unrelated young. Therefore, it is an advantage to discriminate
between related and unrelated offspring so that parents can make informed decisions about parental care. In the present study,
we test the hypothesis that male sand gobies (Pomatoschistus minutus) recognize and differentially care for their own offspring when given a choice between a nest with sired eggs and a second
nest with eggs sired by an unrelated male. The sand goby is a species with exclusive and costly paternal care. Male parasitic
spawnings (e.g., sneaking) as well as nest takeovers by other males are common. Our results show that nests containing sired
eggs were preferred and received significantly more care, as measured by nest building and nest occupancy, than nests with
foreign eggs even when males cared for both nests. These findings suggest that males respond to paternity cues and recognize
their own clutches. Relative clutch size also had a significant effect on male parental care. When sired clutches were larger
than foreign clutches, males preferred to care for their own nest. In the few cases where males chose to take care of foreign
nests, the foreign clutch was larger than their own clutch. Taken together, our results provide evidence that both paternity
cues and clutch size influence parenting decisions among male sand gobies. 相似文献