Electrochemical degradation of per- and poly-fluoroalkyl substances using boron-doped diamond electrodes

Electrochemical degradation using boron-doped diamond (BDD) electrodes has been proven to be a promising technique for the treatment of water contaminated with per- and poly-fluoroalkyl substances (PFAS). Various studies have demonstrated that the extent of PFAS degradation is influenced by the composition of samples and electrochemical conditions. This study evaluated the significance of several factors, such as the current density, initial concentration of PFAS, concentration of electrolyte, treatment time, and their interactions on the degradation of PFAS. A 24 factorial design was applied to determine the effects of the investigated factors on the degradation of perfluorooctanoic acid (PFOA) and generation of fluoride in spiked water. The best-performing conditions were then applied to the degradation of PFAS in wastewater samples. The results revealed that current density and time were the most important factors for PFOA degradation. In contrast, a high initial concentration of electrolyte had no significant impact on the degradation of PFOA, whereas it decreased the generation of F− . The experimental design model indicated that the treatment of spiked water under a current density higher than 14 mA cm− 2 for 3–4 h could degrade PFOA with an efficiency of up to 100% and generate an F− fraction of approximately 40–50%. The observed high PFOA degradation and a low concentration of PFAS degradation products indicated that the mineralization of PFOA was effective. Under the obtained best conditions, the degradation of PFOA in wastewater samples was 44–70%. The degradation efficiency for other PFAS in these samples was 65–80% for perfluorooctane sulfonic acid (PFOS) and 42–52% for 6–2 fluorotelomer sulfonate (6-2 FTSA). The presence of high total organic carbon (TOC) and chloride contents was found to be an important factor affecting the efficiency of PFAS electrochemical degradation in wastewater samples. The current study indicates that the tested method can effectively degrade PFAS in both water and wastewater and suggests that increasing the treatment time is needed to account for the presence of other oxidizable matrices

Role of soil organic matter for immobilisation of metals : treatment of leachate from MSWI bottom ashes

In this thesis, the focus is laid on the ability of natural organic matter (OM) to serve as a metal stabilising agent. The metal contaminants investigated arise from the MSWI bottom ash leachate. Besides the high content of metals, elevated pH and salinity are characteristic for ash leachate that, in turn, can alter the functionality of OM. Batch and column leaching tests were used to study the retention capacity of substrates with different amount of OM. Also, field observations were made of the influence of ash leachate on soil and plants. In this case, ash leachate was generated under field conditions from an experimental road built on municipal solid waste incineration (MSWI) bottom ashes. It has been shown that copper, chromium, and lead retention is proportional to OM content of the substrates. Zinc retention showed to have the least dependence on OM. The metals were not leached in proportion to dissolved OM. Most probably several mechanisms were responsible for the retention of metals: (i) high concentration of Ca in ash leachate could lead to the formation of Ca-dissolved organic carbon (DOC) complexes that have the ability to precipitate some metals (ionic strength effect) and prevent metal transport; (ii) high solution pH could favour hydroxide formation and counteract the metal complexation with dissolved OM, as well as (iii) surface adsorption could contribute to metal retention. Despite the good metal retention capacity of OM, a continuous metal load will occupy binding sites of OM and therefore reduce its retention capacity. Metal retention capacity of rich in OM substrate could be improved by additional soil amendments and vegetation. Tolerant plant species that are capable to grow at high soil metal concentrations and immobilize pollutants within the root zone have a potential to be used for phytostabilisation of metal contaminated soil. Such plants are also associated with a low risk of the translocation of contaminants from soil through plant roots to shoots, i.e. from one media to another. Immobilization is not a technology for the removal of contaminants from soil but for the stabilization (inactivation) of potentially toxic metals. The aim of soil remediation is to reduce the contaminant exposure and spread. Then the reduced leaching, bioavailability, as well as ecotoxicity of metals as a result of phytostabilisation might be a proper solution. Development of suitable soil and amendment mixtures capable to retain broad range of metals and interaction of plants with stabilised matrix are the questions to be answered in the future research.Godkänd; 2003; 20070109 (mlk

Circular Economy and Sustainability: Management and Policy (Volume 2)

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Assessment of trace element stabilization in soil

The thesis deals with the remediation of trace element contaminated soil by the chemical stabilization technique. The objective is to complement the knowledge about possibilities of applying the stabilization either (1) as an alternate soil remediation method to excavation and landfilling or (2) for a pre-treatment of contaminated soil before landfilling. The work is based on two case studies of the stabilization of 1) Cr, Cu, As, and Zn contaminated soil using metallic iron and 2) Pb and Cu contaminated soil amended with coal fly ash and natural organic matter. The questions in focus were: How efficient the stabilization is in a multi-element contaminated soil? How to assess the soil stabilization efficiency? Is the technique sufficiently developed to be used in large scale applications? A literature review, laboratory and pilot scale field experiments were performed to answer the raised questions. A relevance of various methods for the stability evaluations, as well as environmental, regulatory and economic aspects managing the treated soil are discussed.Godkänd; 2005; 20061001 (ysko

Assessment of trace element stabilization in soil by short- and long-term leaching tests : results after 3 years assessment of trace element stabilization in soil with different types of amendments

Stabilization technique was applied to treat contaminated soils in laboratory and pilot scale field (lysimeter) experiments. Three types of amendments were tested for their abilities to reduce contaminant mobility in soil: zerovalet iron, coal fly ash from wood and coal combustion, and natural organic matter - peat. The stabilization of the soils contaminated with Pb and Cu (soil S) and wood impregnation chemical cremated copper arsenate (CCA) (soil R), as assessed by batch leaching tests, significantly reduced the leaching of all analyzed elements. Treatment efficiency decreased in the following order (%): Pb(>99)>Cu(98) in soil S and As(99)≈Zn(99)>Cu(93)>Cr(57) in soil R. The results obtained from the lysimeter experiments over a three-year observation period showed nearly as high treatment efficiency as that achieved in the laboratory experiments.Godkänd; 2007; 20080111 (ysko

Energy generation by waste incineration : the management of impregnated wood

Landfilling of organic waste is no longer allowed in Sweden. Instead, essentially all such waste is being recycled, and about half of it goes to incineration which accounts for about 10% of the total need for heating of buildings. Incineration implies destruction of potentially harmful constituents in the waste, but does not destroy contaminant elements such as arsenic which almost exclusively originates from impregnated wood. Methods for identification of chromium, copper and arsenic in such wood are analysed as well as techniques for sorting it into two categories. If incinerated separately, these can give rise to ash with Cr, Cu and As, and ash with only Cu. The former ash has a small volume and can be stabilized/landfilled at a qualified facility, and the latter ash might be used for beneficiation of Cu. In addition, the contamination by As, especially, in other fuels will be small and consequently also in the ash, thus facilitating its use. It is found that such sorting may be achieved using visual inspection as well as x-ray fluorescence (XRF), whilst use of reagents does not appear to offer any advantage over these two. Both methods are already in industrial use in Sweden, thus proving the feasibility of segregation and stabilization of contaminants in impregnated wood.Validerad; 2015; Nivå 1; 20150920 (rolsjo

Measurements of Flammable Gas Concentration in Landfill Areas with a Low-Cost Sensor

Global warming, as the result of the negative impact of humans on climate change, has been observed based on various data sources. Various measures have aimed to reduce anthropogenic factors, and also to lower carbon dioxide (CO2) and methane CH4 emissions. One of the main contributors to anthropogenic factors is organic waste in municipal solid waste landfills. There are many landfills where cost-effective rapid technologies for the identification and quantification of CH4 emission sites are not applied. There is still a need for the development of accessible and cost-effective methods that react in a real-time manner for the rapid detection and monitoring of methane emissions. This paper’s main goal is to create a prototype sensor suitable for operational measurement of the gas value, suitable for integration into geodetic equipment or an unmanned aerial vehicle system. A sensor system (device) was developed, which consisted of three semiconductor sensors—MQ2, MQ4, and MQ135—which aimed to capture flammable gases (CO2, CH4, O2 purity) and to evaluate the averages of the measured values from the components mounted on the board—the semiconductor sensors. The sensors were calibrated in a laboratory and tested in a closed landfill. The measurement data consisted of the read resistances (analog signal) from the MQ2, MQ4, and MQ135 sensors, and the relative humidity and the temperature (digital signal) of the DHT2 sensor with a timestamp calculated by the RTC module. The use of the method was confirmed because the sensors reacted as expected when placed in the vicinity of the gas collection well. Furthermore, the sensor will be tested and improved for field work in landfill sites

Mobility of redox sensitive elements due to organic matter in contaminated soil : bottom ash and residual waste fraction

Godkänd; 2012; 20120614 (ysko

Utilization of chemically stabilized soil in a landfill top cover

Godkänd; 2008; 20081015 (juku