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  • 1.
    Carlsson, My
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik. Veolia Water Technologies AB (AnoxKaldnes), Lund, Sweden.
    Lagerkvist, Anders
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Morgan-Sagastume, Fernando
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik. Veolia Water Technologies AB (AnoxKaldnes), Lund, Sweden.
    Energy balance performance of municipal wastewater treatment systems considering sludge anaerobic biodegradability and biogas utilisation routes2016Ingår i: Journal of Environmental Chemical Engineering, ISSN 2160-6544, E-ISSN 2213-3437, Vol. 4, nr 4, s. 4680-4689Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The energy balance of a municipal wastewater treatment (WWT) system was evaluated considering the influence of excess biological sludge anaerobic biodegradability (BDAn) and of biogas utilisation as either fuel for co-generation of heat and power (CHP) or for vehicle transport. Sludge thermal pre-treatment prior to anaerobic digestion and high-rate carbon removal were considered as modifications of a reference municipal WWT system to impact the sludge BDAn. Both thermal pre-treatment and a high-rate process with a short sludge retention time (SRT = 1-3d) led to ∼30% higher sludge BDAn than that of untreated sludge from a low-rate WWT system with long SRT ( > 8d), which enhanced methane yields and energy production correspondingly. An efficient separation (40% of CODin) of primary solids promoted biogas production by capturing a significant part of the incoming COD, and lowered aeration energy demands for carbon oxidation due to lower loads of particulate organics into the biological treatment. Thermal pre-treatment can most effectively increase the biodegradability of sludge originating from a low-rate WWT system with a long SRT. Sludge solubilization alone as an indicator of increase biodegradability by a pre-treatment is inadequate for sludge types with inherently high biodegradability. A WWT system with primary separation, sludge pre-treatment, and CHP from biogas can be a net electricity producer and self-sufficient in thermal energy, provided the thermal energy from CHP is available for the pre-treatment. With other types of energy carriers as inputs and outputs, the WWT performance also needs evaluation with respect to the energy economic and environmental value. 

  • 2.
    Menya, E.
    et al.
    KTH, School of Industrial Engineering and Management, Department of Energy Technology, Division of Heat and Power Technology, Stockholm.
    Olwa, Joseph
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Energivetenskap.
    Hagström, P.
    KTH, School of Industrial Engineering and Management, Department of Energy Technology, Division of Heat and Power Technology, Stockholm.
    Okure, M.
    Department of Mechanical engineering, College of Engineering, Design, Art and Technology, Makerere University.
    Assessment of pollution levels resulting from biomass gasification2014Ingår i: Journal of Environmental Chemical Engineering, ISSN 2160-6544, E-ISSN 2213-3437, Vol. 2, nr 3, s. 1228-1235Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In biomass gasification process the producer gas generated can be cleaned by water scrubbing. Some of the organic compounds generated are entrained together with other flue gas dust particles in to the cooling stream. The treatment/disposal of this waste stream remains a challenge because some of the compounds are toxic to humans and the environment. The objective of this study was to assess pollution levels resulting from organic constituents of flue gas filtration in a downdraft gasifier. The study involved assessment of the concentration of polycyclic aromatic hydrocarbons (PAHs) in the liquid effluence. The impacts on human health and environment are also discussed and recommendations on measures to minimize the pollution levels are provided. A downdraft gasifier fed with maize cobs was used and condensates were collected by cooling of producer gas. Samples were preserved in a cooler at about 2 °C for 24 hours before analysis using a capillary gas chromatographer connected to a mass spectrometer (GC-MS). The results were that concentrations of; naphthalene was 204.3 mg/m3, benzene 17.92 mg/m3, toluene 182.94 mg/m3, ethylbenzene 202.43 mg/m3, 1,2-dimethyl benzene 359.28 mg/m3 and 1,3 + 1,4-dimethyl benzene 1016.18 mg/m3. It was observed that the concentrations of naphthalene and xylene were considerably higher than the recommended permissible exposure limits (PEL) on both human health and the environment. On the other hand, the concentrations of benzene, toluene, and ethylbenzene were below the PEL. Generally this study indicated that the liquid effluent meets regulatory standards, but it would be interesting to carryout tests with different biomass fuel types which this study recommends

  • 3.
    Mäkitalo, Maria
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Lu, Jinmei
    Maurice, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Öhlander, Björn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Prediction of the long-term performance of green liquor dregs as a sealing layer to prevent the formation of acid mine drainage2016Ingår i: Journal of Environmental Chemical Engineering, ISSN 2160-6544, E-ISSN 2213-3437, Vol. 4, nr 2, s. 2121-2127Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    One of the mining industry's main concerns is the management of waste rock and tailings generated by sulfide ore extraction. Upon exposure of atmospheric oxygen, iron sulfides oxidize generating acidity. Infiltrating water form a metal-rich acidic leachate called acid mine drainage (AMD), that can cause serious environmental problems. Green liquor dregs (GLD) is a material that resists the passage of oxygen and water and could thus be used to seal mine wastes, preventing their oxidation and AMD formation. To enable its use in dry mine waste covers, the long-term efficiency of such GLD sealing layers must be evaluated. In this study, fresh GLD and GLD aged for 3 to 13 years was collected from two sites and analysed to determine how aging affects its chemical and physical properties. Aged and fresh GLD were very similar with respect to all the properties important in a sealing layer. In particular, there was no evidence of calcite dissolution in aged GLD samples. Aged GLD also exhibited high water saturation (>91%) and chemical stability, both of which are important for effective long-term sealing. The shear strength of GLD deployed in the field increased over time but not sufficiently to ensure the long-term physical integrity of a pure GLD sealing layer. The development of hybrid materials with improved shear strength will therefore be necessary.

  • 4.
    Vondolia, Godwin Kofi
    et al.
    Department of Economics, University of Gothenburg, Norwegian College of Fishery Science, University of Tromsø.
    Eggert, Håkan
    Department of Economics, University of Gothenburg.
    Navrud, Ståle
    Department of Economics and Resource Management, Norwegian University of Life Sciences.
    Stage, Jesper
    Department of Business, Economics and Law, Mid Sweden University, Sundsvall.
    What do respondents bring to contingent valuation?: A comparison of monetary and labour payment vehicles2014Ingår i: Journal of Environmental Chemical Engineering, ISSN 2160-6544, E-ISSN 2213-3437, Vol. 3, nr 3, s. 253-267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the contingent valuation method, both the goods being valued and the payment vehicles used to value them are mostly hypothetical. However, although numerous studies have examined the impact of experience with the good on the willingness to pay, less attention has been given to experience with the payment vehicles. This paper examines how experience with payment vehicles influence responses to a contingent valuation scenario on maintaining irrigation canals in a developing country. Specifically, the paper uses a split-sample survey to investigate the effects of experience with monetary and labour payment vehicles on the acceptance of a contingent valuation scenario, protest bids and mean willingness to pay. Using convergent validity tests, we found that the experience acquired from using both monetary and labour payment vehicles reduces the asymmetries in acceptance rates. These findings suggest that experience with payment vehicles reduces time/money response asymmetries in the contingent valuation method.

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