Browsing by Author "Kirkelund, Gunvor M."
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- Characterization of particulate residues from Greenlandic municipal waste incineration to evaluate potential use as secondary resources in local constructionPublication . Kirkelund, Gunvor M.; Ferreira, Célia; Jensen, Pernille ErlandIn Greenland, waste incineration is used in the larger towns to treat the municipal solid waste. The incineration reduces the amount of waste, but produces particulate incineration residues such as fly and bottom ash that are disposed of. Most construction materials are imported to Arctic areas. The focus in this study is a characterisation of Greenlandic incineration residues to assess the potential as local secondary resources. In this study, fly ash samples from all the incinerators and bottom ash from two incinerators were collected and investigated for several physical-chemical properties. The fly ash samples consisted of very fine-grained particles, with different grading for each incinerator. High water solubility due to high salt concentrations was seen for all fly ash samples along with high concentrations of leachable heavy metals, thus pretreatment is recommended before use as secondary material. The bottom ashes consisted of coarser particles and exhibited lower heavy metal leaching than the fly ash. All residue samples were different and evaluation of reuse should be made individually, however the fly ash shows potential as cement replacement and bottom ash as sand replacement for construction purposes.
- Electrodialytic remediation of heavy metal polluted soil: treatment of water saturated or suspended soilPublication . Ottosen, Lisbeth M.; Jensen, Pernille E.; Kirkelund, Gunvor M.; Ferreira, Célia; Hansen, Henrik K.Electrodialytic soil remediation is a method for removal of heavy metals. Good results have previously been obtained with both treatment of a stationary, water saturated soil matrix and with remediation of a stirred suspension of soil in water. The two different setups have different uses. The first as in-situ or on-site treatment when there is no requirement for fast remediation, as the removal rate of the heavy metals are dependent on the distance between the electrodes (everything else equal) and in such application the electrode spacing must have a certain distance (often meters). In the stirred setup it is possible to shorten the transport route to few mm and to have a faster and continuous process. The present paper for the first time reports a direct comparison of the two options. The remediation of the stirred suspension showed faster than remediation of the water saturated soil even without a short distance between the membranes. The acidification of the suspended soil was fastest and following the mobilization of heavy metals. This may indicate that water splitting at the anion exchange membrane is used more efficiently in the stirred setup.
- Electrodialytic upgrading of MSWI APC residue from hazardous waste to secondary resourcePublication . Jensen, Pernille E.; Kirkelund, Gunvor M.; Viader, Raimon Parés; Magro, Catia; Pedersen, Kristine B.; Ferreira, Célia; Ottosen, Lisbeth M.
- Electrodialytic upgrading of three different municipal solid waste incineration residue types with focus on Cr, Pb, Zn, Mn, Mo, Sb, Se, V, Cl and SO4Publication . Jensen, Pernille E.; Kirkelund, Gunvor M.; Pedersen, Kristine B.; Dias-Ferreira, Célia; Ottosen, Lisbeth M.Handling of air pollution control (APC) residues from municipal solid waste incineration (MSWI) is a challenge due to its toxicity and high leaching of toxic elements and salts. Electrodialysis (ED) of the material has shown potential for reduction of leaching of toxic elements and salts to produce a material feasible for substitution of cement in mortar. In this work results of 23 pilot-scale experiments (5–8 kg APC residue each) in electrodialysis stack designed to investigate the leaching properties as a function of time and current density for APC residue from semi-dry and wet flue-gas cleaning systems, as well as MSWI fly ash without flue-gas cleaning products are reported. Significant leaching reduction of the critical elements Pb, Zn and Cl was obtained. The final leaching, however, depended mostly on the initial leaching, thus as leaching from fly ash and residue of wet flue-gas cleaning was lower before treatment compared to residues from semidry flue-gas cleaning, both Pb and Zn leaching could be reduced to lower levels in those materials, and they therefore appear more suitable for use in construction materials. The leaching reduction of Zn and to some degree Pb decreased with longer retention times and higher current densities. Cr and SO4 leaching increased during ED treatment, with lower increase at higher current. Washing or carbonation in combination with ED significantly reduced leaching of Pb and Zn from semidry residue. An indication of a similar effect to carbonation by simultaneous aeration with ED was observed and should be investigated further. While Mn and Mo leaching did not, Se, V and Sb leaching exceeded threshold values in semidry residue. The leaching of V seemed to increase while Se and Sb remained more or less constant during ED treatment.
- Improving the energy efficiency of an electrodialytic process to extract phosphorus from municipal solid waste digestate through different strategiesPublication . Oliveira, Verónica; Kirklund, G.; Horta, Carmo; Labrincha, João; Ferreira, Célia; Kirkelund, Gunvor M.This work assesses the possibility of energy optimisation during the electrodialytic extraction of phosphorus from the municipal solid waste digestate. Strategies tested for energy optimisation consisted in (i) using a dualstage extraction approach; (ii) replacement of continuous stirring by pulse stirring and; (iii) utilisation of pulse electric current as an alternative to a constant current. Experiments were carried out using different stirring profiles (continuous stirring, pulsed stirring, manual stirring and no stirring) and different profiles for generating the electric field (continuous current and pulsed current). Dual-stage approach decreased the energy consumption by 30%. Energy was mainly used in the stirring operation (80%). Applying this strategy caused a faster acidification of the waste suspension and reduced the time required for the extraction. As for the second strategy, use of pulse stirring, it is possible to save energy by operating the stirrer 25% of the time, without compromising the phosphorus extraction values, which are close to 90%. Corresponding energy savings reached 70%. The third strategy tested, use of pulse current, had as side-effect a significant decrease of the phosphorus extracted, so the implementation of pulse current is not recommended. Overall, the energy efficiency of the electrodialytic extraction of phosphorus can be improved by 80% through the use of the dual-stage approach and the use of stirring for 25% of the time. There is also a potential in further reducing the energy use by further improving the stirring system.
- Mercury levels in fly ash and APC residue from municipal solid waste incineration before and after electrodialytic remediationPublication . Ferreira, Célia; Kirkelund, Gunvor M.; Jensen, Pernille E.Fly ash (FA) and Air Pollution Control (APC) residues collected from three municipal solid waste incinerators (MSWI) in Denmark and Greenland were treated by electrodialytic remediation at pilot scale for 8 to 10 h. The original residues and the treated material were analysed for mercury (Hg) in order to assess the influence of the electrodialytic treatment on the concentrations of this element. Mercury levels varied with the MSWI residue, ranging from 0.41 mg kg−1 in FA sample from electrostatic precipitator (ESP) to 8.38 mg kg−1 in MSWI residues from a semi-dry system with lime and activated carbon. Two distinct behaviours were observed for mercury as a result of the electrodialytic treatment. This element became enriched in the MSWI residues from the semi-dry system with activated carbon, whereas it decreased in ESP’s and cyclone’s FA. This work presents for the first time information about the effect of electrodialytic treatment on mercury levels and discusses the valorisation options for these MSWI residues.
- Recycling of MSWI fly ash in clay bricks: effect of washing and electrodialytic treatmentPublication . Chen, W.; Klupsch, E.; Kirkelund, Gunvor M.; Jensen, P. E.; Ottosen, Lisbeth M.; Ferreira, Célia
- Struvite quality assessment during electrodialytic extractionPublication . Oliveira, V.; Kirkelund, Gunvor M.; Labrincha, J.; Ferreira, CéliaStruvite recovered from anaerobically digested sludge can be conducted by a two – step process. The first step consists of electrodialytic extraction of phosphorus and heavy metals from the waste. The second step comprises the chemical precipitation of phosphorus as struvite. This work studied if the quality of phosphorus recovered as struvite is affected by the reduction of energy on the electrodialytic extraction step. Four electrodialytic experiments were carried out to assess the effect of the energy reduction through stirring time. This was followed by four struvite-precipitation experiments. The efficacy of the electrodialytic extraction of heavy metals is not affected by reducing the stirring from continuous mode to just 25% of the time. XRD analysis confirmed that the precipitates were constituted by pure struvite, while no significant accumulation of heavy metals was found in produced struvite. The struvite meets the requirements for use as phosphorus-based fertiliser.
- Testing new strategies to improve the recovery of phosphorus from anaerobically digested organic fraction of municipal solid wastePublication . Oliveira, Verónica; Ferreira, Célia; Labrincha, João; Rocha, Joana; Kirkelund, Gunvor M.BACKGROUND: This work is focused on phosphorus (P) recovery from the anaerobically digested organic fraction of municipal solid waste (referred to as ‘digestate’) as a fertilizer. The main purpose was to propose and test modifications to the electrodialytic process that increase P extraction, improve the quality of the fertilizer by removing contaminants, and reduce hydraulic retention time to allow for smaller system footprints. Strategies tested were: (i) lowering the pH of the digestate suspension to <4.5 using the electrochemical reactions and enhance P solubilization from the waste; (ii) changing the configuration of the electrodialytic cell from three to two chambers; and (iii) stirring the sample to shorten the duration of the extraction. RESULTS: Results show that the acidification of digestate by the electrochemical reactions was effective to enhance P extraction yield. Three-chamber electrodialytic experiments enabled the removal of heavy metals from the digestate, producing P-rich solutions with low metal concentrations. This resulted in the production of high-quality fertilizer which can be used for agricultural applications. The modification of the electrodialytic cell set-up from three- to two-chamber neither resulted in an increase of the P extraction yields, nor contributed to the removal of metals from the liquid phase of digestate. Reduction of the hydraulic retention time of electrodialytic extraction of P from 16 days to 9 days was attained by the use of stirring and by electrodialytic acidification. CONCLUSIONS: An increase of P recovery was accomplished by modification of electrodialytic extraction, resulting in 90% of Pbeing successfully extracted from the digestate and transformed into struvite.
- The influence of electrodialytic remediation on dioxin (PCDD/PCDF) levels in fly ash and air pollution control residuesPublication . Ferreira, Célia; Kirkelund, Gunvor M.; Jensen, Pernille E.Fly ash and Air Pollution Control (APC) residues collected from three municipal solid waste incinerators in Denmark and Greenland were treated by electrodialytic remediation at pilot scale for 8e10 h. This work presents for the first time the effect of electrodialytic treatment on polychlorinated dibenzo-pdioxins (PCDD) and polychlorinated dibenzofurans (PCDF), and how these levels impact on the valorization options for fly ash and APC residue. PCDD/PCDF levels in the original residues ranged between 4.85 and 197 ng g1 , being higher for the electrostatic precipitator fly ash. The toxic equivalent (TEQ) varied ten fold, ranging 0.18e2.0 ng g1 ITEQ, with penta and hexa-homologs being most significant for toxicity. After the electrodialytic treatment PCDD/PCDF levels increased in the residues (between 1.4 and 2.0 times). This does not mean PCDD/PCDF were synthesized, but else that soluble materials dissolve, leaving behind the non-water soluble compounds, such as PCDD/PCDF. According to the Basel Convention, PCDD/ PCDF levels in these materials is low (<15 mg WHO-TEQ kg1 ) and the fly ash and APC residue could eventually be valorized, for instance as construction material, provided end-of-waste criteria are set and that a risk assessment of individual options is carried out, including the end-of-life stage when the materials become waste again.