UGent campus Kortrijk, Department of green chemistry and technology, Laboratory of Industrial Water- and Ecotechnology
Abstract Bachelor Project 1 FBT 2020-2021: Removal and fate of microplastics in constructed wetlands
Microplastics are plastics smaller than 5 mm and occur in municipal wastewater that is treated in wastewater treatment plants (WWTP). Many studies have been done already on large-scale WWTP, but there is a lack of knowledge on what happens in small-scale WWTP such as constructed wetlands (CWs). This study aims to find out the role of horizontal subsurface flow CWs and vertical flow CWs on the removal and fate of microplastics. It is important to know the number of microplastics and contaminants that come into all different matrices of the environment via WWTPs for describing potential health risks and for finding solutions for this problem. Two small-scale WWTPs were studied. The first one was a WWTP in Aalbeke (Kortrijk), consisting of primary treatment, biorotors and a horizontal subsurface flow CW for polishing purposes. The second one was located in Zevergem (De Pinte) and consisted of primary treatment, two parallel vertical flow CWs and finally two parallel horizontal flow CWs. Digestion, density separation, filtration, staining and microscopic analysis were executed on raw wastewater samples, primarily treated wastewater samples and effluent samples, sediment and macroinvertebrates of the CWs. Attenuated total reflectance – Fourier transformed infrared spectroscopy (ATR-FTIR) was used for the identification of microplastics and Inductively coupled plasma – optical emission spectroscopy (ICP-OES) was used for the detection of heavy metals adsorbed on microplastics.
The horizontal subsurface flow constructed wetland of Aalbeke removes 96 % of the remaining microplastics. The vertical flow constructed wetlands and the horizontal subsurface flow constructed wetland of De Pinte remove together 92 % of the remaining microplastics. Fibres are the most present shape in every sample. Particles are more present than films. The size and shape distributions are approximately the same in every sample. The number of microplastics in the macroinvertebrates increased by 15 % at the outlet side compared with the inlet of the horizontal subsurface flow CW of Aalbeke. On the contrary, the number of microplastics in the sediment decreased by 17 % between the inlet and outlet side. The number of microplastics found in the macroinvertebrates of the horizontal subsurface flow CW of De Pinte increased by 33 % in comparison to the vertical flow CW of De Pinte. The number of microplastics in the sediment decreased by 38.5 %. Heavy metals adsorbed on microplastics collected in the raw wastewater are quantified. The heavy metals Fe, Zn, Cr, Cu, Mn, Pb and Ni are most present. Other heavy metals have a concentration under the detection limit of ICP-OES.
It can be concluded that CWs have an impact on the removal of microplastics. 96 % and 92 % of the microplastics are removed by the CWs of the WWTPs. In addition, heavy metals are adsorbed on the surface of microplastics, yet further research is needed to understand the fate of these heavy metals once the microplastics are trapped inside the CW sediment.
Abstract Bachelor Project 2 FBT 2020-2021: A study about the behavior of ink components used for plastic packaging in various media
The European Commission set a goal to be able to reuse or recycle all plastic packaging by 2030, which at the moment is not completely possible because of, among other thing, the impurities present in this post-consumer waste. Even though some research shows the benefits of dissolving adhesives and other components for delaminating multilayer packaging, still very little is actually known about extracting these impurities in order to regain the pure plastics.
Unlike other articles, this research will focus on the resins that are commonly used in the inks of plastic packaging and what the best methods are for dissolving these components. In this way, it might become possible to regain a colourless end product that can be reused or recycled more easily. Kinetic tests on a variety of resins in different media were performed by putting these mixtures on a shaking plate and extracting small amounts at different reaction times. These extracted samples and the necessary calibration curves were measured with either UV/VIS-spectroscopy or FTIR-spectroscopy (on potassium bromide pellets), depending on the selected media.
When the two different measurement methods are compared, it is clear that the calibration curves of the tests using the UV/VIS-spectroscopy have a higher regression coefficient, which suggests that this is a better method for quantifying the dissolution rates. One of the possible reasons can be the tendency of the samples to not spread evenly on the surface of the pellets that are used for the FTIR-spectroscopy. When the samples are compared to each other, it can be stated that there is a huge difference in the dissolution rate between different media. At the same time however, a medium that works well for one sample, doesn’t necessarily work well for the others. From the tested media, there is not a single one that works well for all the tested resins. Since the duration of the kinetics tests was only 30 minutes, it is uncertain that the samples that dissolved very well also have a higher maximum solubility than the other samples.
In conclusion, it can be stated that the choice of medium depends primarily on the specific resins present on the plastic packaging that needs to be reused or recycled. It is also important to keep in mind that the tests using UV/VIS-spectroscopy gave more stable calibration curves, indicating a more reliable quantification of the tested samples. For future research it could be interesting to test other media, other reaction times, vary the rotation speed of the shaking plate or even vary the temperature of the media.
Abstract Bachelor Project 2019-2020: Deodorizing the plastics polyethylene and polypropylene to optimize their recycling process
By 2030 there must be an increase in plastic recycling of post-consumer waste to 55 %. This must be the beginning towards the circular economy. But after all, there are some various impurities that complicate the recycling of the plastic waste such as inks/dyes, adhesive residues and odour. With the latter, the subject of the thesis begins; deodorize of the plastics polyethene and polypropylene to optimize their recycling. These plastics will be washed on lab-scale with solvents as sodium hydroxide, the surfactant CTAB, water, ethyl acetate and a combination of the surfactant and sodium hydroxide. The aim of the thesis is to find the washing-step with the highest removal efficiency.
But firstly there must be known which odours qualify these plastics. With headspace-solid phase microextraction the odours will be characterized. These scents will be checked at repeatability with the technique solvent desorption. When there’s a repeatability underneath relative standard deviations of 30 %, the compounds will be adopted in a (Selective Ion Mode-)method and analyzed with the GC-MS. In this way there’s a Selective Ion Mode method formed with 19 identified odours. The post-consumer waste of polyethene and polypropylene can now be washed. The remaining odours will be detected with the same technique solvent desorption based on the adsorbent capacity of carbon.
This research showed in the first place that the removal efficiency increases over the time that the plastics spend in the solvent with an exception of sodium hydroxide, where reabsorption took place. The odour removal with the aqueous liquids shows overall the lowest removal efficiency. Therefore there might be an outcome that these aqueous liquids only remove the superficial odours present on the water repellent plastics. But when CTAB is used, it showed the highest removal efficiency among the aqueous solutions, in combination of NaOH the removal efficiency increased. This can be explained by the arise of micelles that reduce the surface tension of water. This results in more moisturized water repellent and a better wettability of the plastics. Also the micelles help with the removal of non-polar odorous compounds. In contrast with the aqueous solvents, the organic solvent, ethyl acetate has the highest removal efficiency of 91 %. The washing procedure of these plastics can be seen as an solid-liquid extraction process, using solubility to transfer components from the solid phase to the liquid phase.
Besides the time and solvents also the influence of the temperature was tested. When the plastics were washed at a lower temperature, the removal efficiency was also lower. This can be explained by the solubility in the solid-liquid extraction process that increases with increasing temperature.
In the future the washed plastics could be transformed into granules and checked again on the formed or remaining odours. Eventually the regranules of polyethene and polypropylene can be used in high end recycling routes.
Abstract Bachelor Project 2017-2018: Leaching of heavy metals and polycyclic aromatic carbohydrates from building materials using pilot roofs
Due to the urbanization, more and more houses are being built. Many of these houses have flat roofs because of the energy saving capabilities in contrary to the houses with triangular roofs. When it rains the water on the flat roofs stays on it for a longer period of time than on triangular roofs. While the rainwater touches the roofing materials the phenomenon “leaching” occurs. Some bound components from the roofing materials get leached into the rainwater. The rainwater runoff contaminates the soil and the groundwater. This groundwater finally goes to rivers. The issue is that if there are high concentrations of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in the rainwater runoff due to the leaching from the roofing materials, this could be a problem for all aquatic environment in the first place. On the long term this would also affect humans. The purpose of this research is to observe the quantitative leaching of heavy metals and PAHs from certain roofing materials. The end goal is to determine which of the researched roofing materials are most polluting for the environment and if the pollution is severe or not.
The metals that are being researched are aluminium, chrome, iron, manganese, nickel, strontium, zinc, copper and lead. The PAHs that are being researched are naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluorantheen, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perlene.
The roofing materials that are researched in this experiment are bitumen green, ethylene-propylene-diene monomer (EPDM), bitumen grey, polyurethane (PU) and polyvinylchloride. At this moment not much is known about the leaching behaviour of these roofing materials. Nonetheless, these materials are used very often as roofing materials. That is why this research is so valuable to the community.
To collect rainwater runoff, there have been made several pilot roofs. Each pilot roof contains one square meter of a roofing material. There are also two blank’s. One blank is to research the total atmospheric deposition. The other blank is to research only the atmospheric deposition that comes with rainfall. At the bottom of each pilot roof there is a set up to collect the rainwater runoff. The first litre of rainwater runoff is collected in a separate 1 l bottle, this is called the first flush. The rest of the rainwater runoff gets collected in a 20 l bottle, this is called the bulk. During the sampling, there is both a first flush (FF) and bulk (B) sampling. Samples were measured for heavy metals with inductive coupled plasma – optical emission spectrometry (ICP-OES). For the research of PAHs, 300 ml of the sample is concentrated with solid phase extraction (SPE). The extract is then redissolved in 4 ml dichloromethane. The concentrated PAHs were analysed with gas chromatography/mass spectrometry (GC/MS).
For the metals, only bitumen grey and the EPDM roofing materials release higher concentrations over the whole period of the experiment. The following metals were measured for bitumen grey: aluminium (0 - 82 µg/l), iron (0 – 112 µg/l), manganese (87 – 338 µg/l), nickel (4 – 23 µg/l), strontium (8 – 34 µg/l) and copper (3 – 16 µg/l). EPDM only releases zinc, in concentrations of 161 – 2815 µg/l in each batch. Bitumen green, PU and PVC only release moderate to high concentrations of metals in the first rainwater runoff sample(s). After the first samples the bitumen green, PU and PVC materials only release very low concentrations of some metals and for some metals nothing.
For the PAHs, only phenanthrene, fluoranthene and pyrene have been detected. All phenanthrene and fluoranthene concentrations are attributed solely to the atmospheric deposition. Pyrene was only released from the EPDM roofing material in concentrations of 8 – 33 ng/l in each batch. For all the other roofing materials also pyrene came solely from atmospheric deposition.
When the results from the metal and PAHs leaching tests are taken together, there can be concluded that the bitumen green, PU and PVC roofing materials are harmless for the environment. Bitumen grey is more harmful for the environment because the copper concentration (3 – 16 µg/l) surpasses the maximum reference value of 7 µg/l in batch 1, 2, 5, 6, 7, 8 and 9. This is not coming from the bitumen but from the crushed stones in the surface finish. EPDM roofing shows more harmful leaching because the zinc concentration (161 – 2815 µg/l) surpasses the maximum reference value of 20 µg/l 8 to 140 times. The leaching of PAHs is in no way harmful to the environment.
Abstract bachelorproef 2016-2017: Arsenic contamination in water: phytoremediation and fish research
This research focusses on arsenic contamination in water of the industrial gold mine of Youga in Burkina Faso. Gold mining zones are often enriched in arsenic and other potentially toxic metals. A project was initiated at Ghent University Campus Kortrijk to study phytoremediation to reduce soil and water pollution by metals to rehabilate the mine after closing.
Leucaena leucocephala was the plant tested for phytoremediation. A germination test was performed, 100% of the seeds germinated in pure water and in 0,2 ppm arsenic, while only 94% germinated in 1 ppm and 2 ppm and only 72% in 10 ppm arsenic.
Plants were grown in a mixture of 50% soil of the mine site and 50% compost and received water containing arsenic: 0 ppm, 50 ppm, 100 ppm and 200 ppm. A microwave digestion procedure was optimized and an ICP-OES was used to analyze the samples. The plants all contained arsenic (till 1177 ppm for the plants who got 200 ppm) which means they can be used for phytoremediation of arsenic. When the different parts of the plant (roots, leaves and stem) are analyzed, the roots contain the most arsenic (1923 ppm), while the leaves contain the lowest amount of arsenic (11 ppm).
Fish samples were collected in pits and a river at the mine site. A microwave digestion procedure was optimized and the metals were determined by ICP-OES. From the four different fish types, one of them (Clarias anguillaris) clearly contains less heavy metals than the others, with a mean concentration of 1 ppm. The arsenic content in the fish from the river is lower than in the fish from the pits.
From these results can be concluded that Clarias anguillaris fish from the Nakambé River contains the least heavy metals. Leucaena leucocephala can be used to perform phytoremediation of arsenic.
Graaf Karel de Goedelaan 5