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991.
Treatment wetlands have a finite period of effective nutrient removal after which treatment efficiency declines. This is due to the accumulation of organic matter which decreases the capacity and hydraulic retention time of the wetland. We investigated four potential solutions to improve the soluble reactive P (SRP) removal of a municipal wastewater treatment wetland soil including; dry down, surface additions of alum or calcium carbonate and physical removal of the accreted organic soil under both aerobic and anaerobic water column conditions. The flux of SRP from the soil to the water column under aerobic conditions was higher for the continuously flooded controls (1.1 ± 0.4 mg P m−2 d−1), dry down (1.5 ± 0.9 mg P m−2 d−1) and CaCO3 (0.8 ± 0.7 mg P m−2 d−1) treatments while the soil removal and alum treatments were significantly lower at 0.02 ± 0.10 and −0.07 ± 0.02 mg P m−2 d−1, respectively. These results demonstrate that the two most effective management strategies at sequestering SRP were organic soil removal and alum additions. There are difficulties and costs associated with removal and disposal of soils from a treatment wetland. Therefore our findings suggest that alum addition may be the most cost effective and efficient means of increasing the sequestering of P in aging treatment wetlands experiencing reduced P removal rates. However, more research is needed to determine the longer term effects of alum buildup in the organic soil on the wetland biota, in particular, on the macrophytes and invertebrates. Since alum effectiveness is time limited, a longer term solution to P flux may favor the organic soil removal. 相似文献
992.
The initial step in the analysis of contaminant transport in fractured rock requires the consideration of groundwater velocity. Practical methods for estimating the average linear groundwater velocity (vˉ) in fractured rock require determination of hydraulic apertures which are commonly calculated by applying the cubic law using transmissivity (T) values and the number of hydraulically active fractures in the test interval. High-resolution, constant-head step injection testing of cored boreholes in a 100 m thick fractured dolostone aquifer was conducted using inflatable packers to isolate specific test intervals from the rest of the borehole. The steps in each test interval were gradually increased from very low to much higher injection rates. At smaller injection rates, the flow rate vs. applied pressure graph projects through the origin and indicates Darcian flow; non Darcian flow is evident at higher injection rates. Non-Darcian flow results in significantly lower calculated T values, which translates to smaller hydraulic aperture values. Further error in the calculated hydraulic aperture stems from uncertainty in the number of hydraulically active fractures in each test interval. This estimate can be inferred from borehole image and core logs, however, all of the fractures identified are not necessarily hydraulically active. This study proposes a method based on Reynolds number calculations aimed at improving confidence in the selection of the number of active fractures in each test interval. 相似文献
993.
van der Ploeg MJ Baveco JM van der Hout A Bakker R Rietjens IM van den Brink NW 《Environmental pollution (Barking, Essex : 1987)》2011,159(1):198-203
Effects of C60 nanoparticles (nominal concentrations 0, 15.4 and 154 mg/kg soil) on mortality, growth and reproduction of Lumbricus rubellus earthworms were assessed. C60 exposure had a significant effect on cocoon production, juvenile growth rate and mortality. These endpoints were used to model effects on the population level. This demonstrated reduced population growth rate with increasing C60 concentrations. Furthermore, a shift in stage structure was shown for C60 exposed populations, i.e. a larger proportion of juveniles. This result implies that the lower juvenile growth rate due to exposure to C60 resulted in a larger proportion of juveniles, despite increased mortality among juveniles. Overall, this study indicates that C60 exposure may seriously affect earthworm populations. Furthermore, it was demonstrated that juveniles were more sensitive to C60 exposure than adults. 相似文献
994.
Armitage HF Britton AJ Woodin SJ van der Wal R 《Environmental pollution (Barking, Essex : 1987)》2011,159(1):140-147
The potential of alpine moss-sedge heath to recover from elevated nitrogen (N) deposition was assessed by transplanting Racomitrium lanuginosum shoots and vegetation turfs between 10 elevated N deposition sites (8.2-32.9 kg ha−1 yr−1) and a low N deposition site, Ben Wyvis (7.2 kg ha−1 yr−1). After two years, tissue N of Racomitrium shoots transplanted from higher N sites to Ben Wyvis only partially equilibrated to reduced N deposition whereas reciprocal transplants almost matched the tissue N of indigenous moss. Unexpectedly, moss shoot growth was stimulated at higher N deposition sites. However, moss depth and biomass increased in turfs transplanted to Ben Wyvis, apparently due to slower shoot turnover (suggested to result partly from decreased tissue C:N slowing decomposition), whilst abundance of vascular species declined. Racomitrium heath has the potential to recover from the impacts of N deposition; however, this is constrained by the persistence of enhanced moss tissue N contents. 相似文献
995.
Pujol Pereira EI Chung H Scow K Sadowsky MJ van Kessel C Six J 《Environmental pollution (Barking, Essex : 1987)》2011,159(2):401-407
We investigated the influence of elevated CO2 and O3 on soil N cycling within the soybean growing season and across soil environments (i.e., rhizosphere and bulk soil) at the Soybean Free Air Concentration Enrichment (SoyFACE) experiment in Illinois, USA. Elevated O3 decreased soil mineral N likely through a reduction in plant material input and increased denitrification, which was evidenced by the greater abundance of the denitrifier gene nosZ. Elevated CO2 did not alter the parameters evaluated and both elevated CO2 and O3 showed no interactive effects on nitrifier and denitrifier abundance, nor on total and mineral N concentrations. These results indicate that elevated CO2 may have limited effects on N transformations in soybean agroecosystems. However, elevated O3 can lead to a decrease in soil N availability in both bulk and rhizosphere soils, and this likely also affects ecosystem productivity by reducing the mineralization rates of plant-derived residues. 相似文献
996.
Fall C Espinosa-Rodriguez MA Flores-Alamo N van Loosdrecht MC Hooijmans CM 《Water environment research》2011,83(11):2036-2048
Activated sludge modeling technology is maturing; however, currently, there exists a great need to increase its use in daily engineering practice worldwide. A good way for building the capacities of the practitioners is to promote good modeling practices and standardize the protocols. In this study, a systematic procedure was proposed to calibrate the Activated Sludge Model No. 1 (ASM1) at a large wastewater treatment plant, by which the model adequately predicted the quality of the effluent and the sludge quantities. A hydraulics model was set up and validated through a tracer test. The Vesilind settling constants were measured and combined with the default value of the flocculent zone settling parameter, to calibrate the clarifiers. A virtual anoxic tank was installed in the return activated sludge to mimic the denitrification occurring in the settlers. In ASM1, the calibrated parameters were only two influent chemical oxygen demand fractions and one kinetic constant (oxygen half-saturation coefficient). 相似文献
997.
998.
Mehmet Berkun Egemen Aras Tugce Anılan 《Journal of Material Cycles and Waste Management》2011,13(4):305-313
As an economically developing country, Turkey has very well operated integrated solid waste management applications structured
on modern facilities, besides over 2,000 scattered open dump areas in the country. Integrated waste management applications
seem eligible for the metropolitan cities like Istanbul and Izmit (Kocaeli). Attempts have not been encouraging for the scattered
regional settlements using central storage sites due to financial shortages and received rejections from nearby settlements.
Small-scale compact solid waste management systems with materials recycling and composting can be more suitable alternatives
in the small-scale regional settlements. The major constituents of municipal solid waste are organic in nature and approximately
a quarter of municipal solid waste is recyclable. Although paper, including cardboard, is the main constituent, the composition
of recyclable waste varies strongly by the source or the type of collection point. Solid wastes need primary treatment in
order to be suitable for incineration and composting. Turkey needs to give more emphasis on the usage of modern solid waste
removal technologies to overcome the overgrowing solid waste disposal problems. 相似文献
999.
The circular economy has been developing rapidly in recent years in China. A legislative system has been created to provide
legal protection for the development of a circular economy, including a series of price and tax measures in the waste management
area. These measures form the basic foundation for promoting better waste management under the circular economic model. Many
challenges, however, remain. For instance, the legal system needs to incorporate more sophisticated science, and China lacks
key waste treatment technology that could support the further development of a circular economy. There is also a need to educate
the public about the concept of the circular economy and its benefits. Specific suggestions are made for the development and
implementation of the circular economic model. 相似文献
1000.
Hisanori Watanabe Hidekichi Yoshino 《Journal of Material Cycles and Waste Management》2011,13(2):113-117
Since hydrogen is a renewable energy source, biohydrogen has been researched in recent years. However, data on hydrogen fermentation
by a leachate from a waste landfill as inoculum are scarce. We investigated hydrogen production using a leachate from an industrial
waste landfill in Kanagawa Prefecture. The results showed no methane gas production, and the leachate was a suitable inoculum
for hydrogen fermentation. The maximum H2 yield was 2.67 mol of H2 per mol of carbohydrate added, obtained at 30°C and an initial pH of 7. The acetate and butyrate production was significant
when the H2 yield was higher. Oxidation–reduction potential analysis of the culture suggested that hydrogen-producing bacteria in the
leachate were facultative anaerobic. Scanning electron microscope observations revealed that the hydrogen-producing bacteria
comprised bacilli about 2 μm in length. 相似文献