11,678 research outputs found

    Sustainable landfill leachate treatment using refuse and pine bark as a carbon source for biodenitrification

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    Raw and 10-week composted commercial garden refuse (CGR) materials and pine bark (PB) mulch were evaluated for their potential use as alternative and sustainable sources of carbon for landfill leachate bio-denitrification. Dynamic batch tests using synthetic nitrate solutions of 100, 500 and 2000 mg NO3 L−1 were used to investigate the substrate performance at increasing nitrate concentrations under optimal conditions. Further to this, sequential batch tests using genuine nitrified landfill leachate with a concentration of 2000 mg NO3 L−1 were carried out to evaluate substrates behaviour in the presence of a complex mixture of chemicals present in leachate. Results showed that complete denitrification occurred in all conditions, indicating that raw and composted CGR and PB can be used as sustainable and efficient media for landfill leachate bio-denitrification. Of the three substrates, raw garden refuse yields the fastest denitrification rate followed by 10-week composted CGR and PB. However, the efficiency of the raw CGR was lower when using genuine leachate, indicating the inhibitory effect of components of the leachate on the denitrification process. Ten-week composted CGR performed optimally at low nitrate concentrations, while poor nitrate removal ability was found at higher nitrate concentrations (2000 mg L−1). In contrast, the PB performance was 3.5 times faster than that of the composted garden refuse at higher nitrate concentrations. Further to this, multi-criteria analysis of the process variables provided an easily implementable framework for the use of waste materials as an alternative and sustainable source of carbon for denitrification

    IMPACT OF LOW-RATE SUBSTRATE REMOVAL ON THE PERFORMANCE OF DENITRIFYING SYSTEMS

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    Strict effluent N criteria may also require the use of slowly biodegradable substrate as carbon source for denitrification. The paper draws attention to the fact that oxygen penetration through the surface of uncovered denitrification basins may significantly deteriorate the efficiency when substrate removal rate is low, whereas at high consumption rates this impact may prove to be negligible. Results of comparative lab-scale experiments carried out in both batch and continuous-flow operation revealed that the reason why denitrification rates are much more severely affected at low substrate consumption rates is the increased dissolved oxygen concentration that occurs due to the decreased ability of its removal. In the comparative batch experiments a zero-head-space reactor and a reactor with an open surface were applied using different samples of preclarified wastewater deriving from an existing treatment plant. In the continuous-flow experiment two differently arranged activated sludge systems were operated simultaneously, fed by a model wastewater containing peptone as carbon source. The total reactor volume serving predenitrification was identical in both arrangements; however, in one of the systems it was compartmentalized into three reactors. None of the reactors were covered in this experiment. The dissolved oxygen concentration raised significantly in both of the batch and continuous-flow experiments when the readily biodegradable substrate had been depleted. The results supported that in cases when readily denitrifiable carbon source is not in a pronounced excess, staging of anoxic reactors may significantly improve the efficiency of denitrification through maintaining relatively high substrate removal rate and thereby low oxygen concentration in the first basins

    Key Parameters of Pulsed Laser Deposition for Solid Electrolyte Thin Film Growth

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    The pulsed laser deposition (PLD) technique has been a common method to grow thin films such as solid electrolyte (SE). The effects of substrate temperature and laser fluence on the thin film properties and the device performance are analyzed. For the first time, a quantitative analytical model dealing with the energy conversion in the process when laser hits the target is presented, which provides a solution that is crucial in correlating the formation of high quality and uniform thin films to the experimental design. The migration speed of the ablated particles, which determines the quality of the deposited films, is found to be directly related with the laser fluence. Specifically, a threshold fluence is required to generate high purity single form thin film. This model provides the opportunities to improve experimental design and quality control

    Environment Agency review of methods for determining organic waste biodegradability and municipal waste diversion.

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    The Environment Agency is required to regulate the landfilling of biodegradable organic wastes and their diversion from landfilling. Simple, cost effective, reliable and widely applicable methods for the measurement of organic waste and its biodegradability are needed for this activity. A review of such methods was carried out in order to select promising methods for an experimental screening exercise. The review considered both biological and non-biological methods including simple methods that may provide a surrogate measurement of waste biodegradability instead of the time-consuming biological methods. The biological methods selected for further evaluation were the aerobic specific oxygen uptake rate (SOUR) and dynamic respiration index (DRI) tests, and the anaerobic biochemical methane potential (BMP) test. The non-biological methods selected for further evaluation were dry matter (DM), loss on ignition (LOI), total organic carbon (TOC), total nitrogen (TN), water extractable dissolved organic carbon (DOC), BOD and COD, the lignin and cellulose content and the cellulase hydrolysis method. These tests are being evaluated on a wide variety of typical organic materials that might be found in municipal solid waste (MSW) such as newspaper corrugated paper, compost, kitchen waste (vegetable and animal), garden wastes (grass and twigs), nappies, cotton and wool textiles

    Predicting the effects of biochar on volatile petroleum hydrocarbon biodegradation and emanation from soil: a bacterial community finger-print analysis inferred modelling approach

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    We investigated the response of the dominant bacterial taxa in gravelly sand to the addition of biochar and/or mixtures of volatile petroleum hydrocarbons (VPHs) using denaturing gradient gel electrophoresis (DGGE) and sequencing of cut bands. Biochar addition alone had only weak effects on the soil bacterial community composition in batch study samples, while VPH addition had strong effects. Indirect effects of biochar on soil bacterial communities were apparent in column study samples, where biochar-enhanced sorption affected VPH spreading. Following VPH addition, cell abundance increased by no more than a factor of 2 and several Pseudomonas spp. became dominant in soil with and without biochar. We present a VPH fate model that considers soil bacterial biomass dynamics and a nutrient limited soil biomass carrying capacity. The model simulates an apparent lag phase before the onset of a brief period of intensive VPH biodegradation and biomass growth, which is followed by substantially slower VPH biodegradation, when nitrogen needs to be recycled between decaying and newly formed biomass. If biomass growth is limited by a factor other than the organic pollutant bioavailability, biochar amendment may enhance VPH attenuation in between a VPH source below ground and the atmosphere by reducing the risk of overloading the soil's biodegradation capacity
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