Completed degree projects
Master Thesis on blackwater treatment and nutrient recovery
Lisa Gren, who has studied Natural Resources Engineering with a focus on Environment and Water, has recently published her Master Thesis The mass balance of compounds in source-separated blackwater treatment at RecoLab, Helsingborg. The purpose of the work was to investigate the treatment and nutrient recovery of source-separated blackwater at RecoLab through the calculation of mass balances. The mass balances showed that the biogas production at RecoLab was functioning well, with a production of approximately 150 m³ CH₄/week or 88 kWh/PE/year. A large fraction of the COD was reduced during anaerobic digestion. Nutrient recovery in the form of sludge and struvite (a recovery of 27% of total phosphorus and 2.5% of total nitrogen) was affected by the struvite precipitation process, which had a low separation rate. The mass balances indicated significant losses of total phosphorus and total solids during the struvite precipitation process. To achieve a satisfactory nutrient recovery, the separation and collection of struvite should be improved. The thesis also showed that both the sludge and the struvite had low metal content (13 and 0.68 mg Cd/kg P, respectively).
PFAS in wastewater and sewage sludge at Uddebo wastewater treatment plant, Luleå
Jonatan Forsberg who has studied civil engineering natural resource technology with specialization in environment and water has now completed his thesis "PFAS in a Swedish wastewater treatment plant: An analysis of the effectiveness of major treatment steps on 33 PFAS".
The work is the initial part of a year-long study where the levels of 33 PFAS contaminants are tracked in wastewater and sewage sludge during the treatment process at Uddebo treatment plant.
The results showed that there was no clear variation in PFAS levels between the different treatment steps. However, there was a clear difference between the PFASs detected in wastewater and sewage sludge, where sewage sludge only had detectable levels of PFASs with a perfluorinated carbon chain longer than 6. A clear difference in the level of detected PFASs could also be seen between the different sampling occasions, indicating a possible link between larger amounts of meltwater and certain PFASs. However, all results require further investigation to see if they are true for the whole of 2022 or only the first winter months.
Supervisor and examiner at LTU were Kelsey Flanagan and Jurate Kumpiene respectively. The degree project was carried out in collaboration with Luleå municipality.
Link to the degree project
External link.
Green roofs for runoff reduction in subarctic climate?
How well do green roofs work to reduce runoff in subarctic climate? This is the question that Dag Schéele, who has studied civil engineering Architecture at LTU, examined in his thesis "Stormwater management with green roofs in subarctic climate".
By analyzing data from green roofs in Kiruna and Umeå, retention could be quantified. Even in a subarctic climate, the different roofs were able to reduce runoff by 60 to 70 percent annually. For the roof in Umeå, a model was also built to further study which design factors were important for the roof's hydrological performance. It turned out that the depth of the roof substrate has a large effect on the retention capacity of the roof, while the slope of the roof or the length of the flow path over the roof was of less importance. This indicates that one has quite a lot of freedom to design the roof based on, for example, aesthetic considerations without negatively affecting the function of the roof.
The measurements in Umeå were carried out in cooperation with VAKIN and in Kiruna in cooperation with Tekniska verken and NCC. Ico Broekhuizen and Joel Lönnqvist have been supervisors for the thesis and Godecke Blecken examiner.
Link to the thesis External link.
Methods for flow measurement in small watercourses
Linus Nyström who has studied civil engineering Natural Resources Engineering tested in his thesis "Acoustic Doppler Current Profiling for streamflow measurements in subarctic climate" different methods for flow measurement in several small streams in Norrbotten.
Bland annat testade han Acoustic Doppler Current Profiling (ADCP), där en liten båt mäter flödeshastighet på olika djup och över hela bredden av vattendraget. This method has been used on larger rivers but not small streams. The performance during different seasons has also not been explored before. Therefore, flow measurements with ADCP, as well as traditional float and dilution methods, were carried out on different streams on several occasions during winter and spring. Resultat från studien visade att ADCP metoden hade svårt att mäta under vinterperioder, men däremot fungerade denna metod bra när flödet blev lite högre och det inte fanns is kvar på vattendraget.
The thesis was carried out in cooperation with SWECO in Kiruna. Supervisor for the work was Ico Broekhuizen and examiner was Godecke Blecken from Luleå University of Technology.
Link to the thesis External link.
Thesis on the purification capacity of different biofilter materials in Swedish climate
Anna Träff has completed her studies in the Master Programme in Natural Resources Engineering with a focus on Environment and Water at Luleå University of Technology.
Within the framework of her thesis "Evaluation of pollutant removal performance of stormwater biofilters in a Swedish climate; Comparison of three different filter media designs", she investigated the removal performance of total and dissolved heavy metals, phosphorus, nitrogen and total suspended solids (TSS) of three stormwater biofilters in Malmö, with different configurations of the filter section. It had either sand-based filter material without a submerged zone or a sand-based filter material with a water-saturated zone; the third type had a filter material consisting of equal parts of sand-based material and pumice.
The results showed good treatment capacity in the current climate of the sand-only biofilters, especially for metals and TSS. A reduction of total phosphorus and nitrogen could generally also be achieved to some extent. For the biofilter containing a mixture of sand and pumice, the treatment capacity was lower for all parameters compared to the other two biofilters.
The supervisor for the thesis was Godecke Blecken; Maria Viklander was the supervisor.
Link to the thesis External link.
Degree project on the cost-effectiveness of different stormwater management systems
Abdullah Noorhussin Ali, who has studied Master of Science in Natural Resources Engineering with a focus on environment and water, has recently published his thesis "Lifetime Cost-Effectiveness of Constructed Wetland and Rain Garden Facilities in Relation to Expected Treatment Performance".
The aim of the study was to compare the overall cost-effectiveness (including both construction and maintenance costs) of different stormwater management facilities for different parameters, such as the volume of stormwater treated, phosphorus and nitrogen removal and suspended particles.
The results, which were based on expected costs and maintenance measures for two real facilities, showed that maintenance costs accounted for a significant part of the total costs (42% of the constructed wetland system and 50% of the biofilter), emphasizing the importance of planning to anticipate these costs at an early stage. Furthermore, the wetland system was shown to be more cost effective in terms of treated stormwater volume and phosphorus removal, while the biofilter was more cost effective in terms of nitrogen removal and TSS removal, which is consistent with the Stormtac model. Although the results of the study, which are based on a limited number of case studies and an expected cost and treatment efficiency, are not universal, the study has developed a useful approach to more accurately account for total costs and different design objectives during the planning phase.
The study was conducted in collaboration with SWECO in Luleå. Supervisor was Kelsey Flanagan and examiner Lian Lundy from Urban Water Engineering at Luleå University of Technology.
Link to the thesis work External link.
Thesis on wastewater from the pulp and paper industry
Hodda Shariatmadari has now completed her thesis "Wastewater Treatment at Kraft Pulp Mills - Effect of temporary effluents and mitigation measures". She has studied Environmental and Water at the Master of Science in Natural Resources Engineering program.
Pulp and paper industries use large amounts of water in their production, which in turn leads to a large amount of wastewater produced. One of the main environmental aspects of the pulp and paper industry is the amount of wastewater and the quality of the wastewater that reaches the recipient. The effluent contains organic matter, nutrients (nitrogen and phosphorus), suspended particles, and chlorine compounds. Abnormal discharges from the various processes at the mills, which occur under abnormal operating conditions, can overload the treatment plants, which in turn causes elevated levels of these discharges and also risks discharging other more toxic substances into the receiving waters. To detect and prevent these abnormal emissions is therefore of great importance to reduce the environmental impact.
The purpose of the degree project was to investigate the effect of the abnormal emissions from the processes in the sulphate pulp mill at the treatment plant, with the aim of developing an action plan with measures to avoid and reduce the impact when incidents occur in order to be able to handle them in the best possible way. This has mainly been done through interviews with employees at different kraft pulp mills around Sweden, focusing on their experiences of abnormal emissions in order to best compile and analyse these.
The results of the study (the interviews) showed a total of 16 different types of abnormal process emissions, where the most common were emissions in the form of lye from the processes and chlorate from the bleaching plant. The most common types of incidents that occur were found to be incidents resulting from planned and unplanned shutdowns. Measures for all releases have been compiled in both Swedish and English. When applying measures, it is important to keep in mind that the measures can vary significantly depending on the type of incident that occurs as well as the type of treatment plant implemented in the mill. The measures must therefore be adapted to each specific mill.
Supervisor for the thesis was Inga Herrmann and examiner was Annelie Hedström from LTU, in collaboration with AFRY with Thérèse Johansson and Åsa Sivard as external supervisors. After the studies, Hodda Shariatmadari has started working at the consulting company AFRY with other exciting projects.
Link to the thesis External link.
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