Improved phosphorus, nitrogen and metal removal in stormwater bioretention filters - A lab-scale study of biofilters added with arbuscular mycorrhizas and biochar

Examensarbete för masterexamen
Altenstedt, Carolina
Water pollution in lakes, rivers, oceans, groundwater, among others is a well-documented problem, resulting in deterioration of the natural water quality worldwide due to urbanization, use of harmful substances and chemical fertilizers. If not handled, the massive amounts of pollutants especially phosphorus and nitrogen can cause eutrophication, one of the leading concerns regarding water quality, which consequently can lead to, loss of biodiversity, dead seas and chemical environments as a direct threat to human health. In the year 2000, the water framework directive, a tool for protecting all waters within the E.U, was implemented. As a result, the city of Gothenburg created local directives, intending to reduce the massive amounts of pollutants reaching natural waters in the urban environment. Bioretention filters, a treatment technique composed of plants, soil and sand in different layers, are a growing technique within water management in urban environments. Nevertheless, there is a limitation regarding the reduction capacity of these techniques, and the outgoing water does not always reach target values in all aspects. In order to increase the purification rates of bioretention filters, different materials and microbes can be used in order to increase the efficiency further. In this study, four artificial bioretention filters are created in lab-scale with the additions of a fungi called arbuscular mycorrhizas and commercial biochar, with the aim of investigating if these additions can enhance the removal of the pollutants phosphors, nitrogen and metals. Also, the initial performance of a newly created bioretention filter are determinate. From the findings it could be concluded that biochar is a promising alternative for reduced leaching of phosphorous and nitrogen most likely due to sorption, denitrification and nitrifications processes. Fungi did not reduce the levels of nutrients, questioning if the symbiosis was established or not and the need for further research is essential. The metal reduction was varied from both biochar and fungi, where the reduction from the bioretention filter containing biochar was the highest. This result highlights the importance of choosing feedstock and pyrolysis temperature for biochar production carefully, as the production type can facilitate different characteristics of the biochar.
Biofilter, bioretention filters, arbuscular mycorrhizas, biochar, nitrogen removal, phosphorus removal, metal removal
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