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  • 1.
    Krustok, Ivo
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Communities of microalgae and bacteria in photobioreactors treating municipal wastewater2015Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Everyone who uses water produces wastewater. This inevitability creates several problems that increase with the growth of the population and industry. What to do with the wastewater, how to purify it and how to design the infrastructure are all important questions that each municipality has to deal with, taking into account ever growing demands to reduce environmental impact. In these conditions scientists and engineers have turned to biological processes to help treat the water. Currently the most commonly used wastewater treatment method known as the activated sludge process involves bacteria that help break down the pollutants. While it has been used successfully for around 100 years now, it has many limitations when faced with modern demands. As an alternative, microalgae reactors, commonly known as photobioreactors, have been suggested.

    Microalgae are microscopic water organisms that can use photosynthesis to form sugars from CO2 and water. To do this they require energy from light, hence the photo part of the photobioreactor. In addition to taking up CO2 from their environment, they take up nutrients such as nitrogen and phosphorous compounds. This is a reason why microalgae have great potential for use in wastewater treatment. When grown in wastewater together with the microorganisms already present, they are able to reduce the amount of pollutants by taking them up into their cells, effectively purifying the water.

    Since wastewater has its own microbial community, the biological processes taking place in a wastewater treating photobioreactor are more complex compared to growing a single species of algae in a sterile medium. With the work presented in this licentiate, we characterized the algae and bacterial communities present in photobioreactors treating wastewater in addition to finding the most optimal ways to grow algae originating from a local lake in a wastewater medium. We looked at the species found, most important metabolic pathways, growth dynamics for both algae and bacteria and water purification dynamics.

    Overall, we were successful in inoculating municipal wastewater from Västerås wastewater treatment plant with algae from Lake Mälaren. The dominant algae growing in our systems belonged to the genera Scenedesmus, Desmodesmus and Chlorella. We also saw that the bacterial community was involved in synthesis of vitamins essential for algae growth. The information presented in this thesis is another step towards a better design of control and monitoring systems in full-scale photobioreactor plants.

  • 2.
    Krustok, Ivo
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Microbiological analysis of municipal wastewater treating photobioreactors2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Microalgae reactors, commonly known as photobioreactors, have become increasingly popular as an alternative for wastewater treatment. These systems reduce pollutants and remove nutrients such as nitrogen and phosphorous compounds from wastewater utilizing microalgae and bacteria. The biomass produced in the reactors can potentially be used to produce biofuels and decrease some of the energy demands of the process.

    Wastewater treating photobioreactors are a relatively new technology and many aspects of their microbiology need further study. This thesis presents a broad overview of the algal and bacterial communities present in these systems by looking at the most important species, metabolic pathways and growth dynamics of both algae and bacteria.

    The experiments presented in this thesis were conducted using municipal wastewater from the Västerås wastewater treatment plant. The wastewater was inoculated with algae from Lake Mälaren and compared to non-inoculated reactors. Overall, the inoculated reactors demonstrated better algal growth than those that were not inoculated. The tested systems also removed much of the ammonium and phosphorous present in the wastewater.

    The dominant algae in the tested systems belonged to the genera Scenedesmus, Desmodesmus and Chlorella. In addition to algae, the systems contained a large number of bacteria, mostly from the phyla Proteobacteria and Bacteroidetes.

    The algal photobioreactors contained a lower abundance of genes related to nitrogen metabolism, virulence and antibiotic resistance compared to the initial wastewater, showing that a shift in the bacterial community had occurred. The bacteria found in the systems were shown to be involved in synthesis of vitamins essential for algae growth such as vitamin B12, suggesting cooperation between the bacteria and algae.

  • 3.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Diaz, J G
    Faculty of Science, Universidad Autónoma de Madrid, Ciudad Universitaria de Cantoblanco, Madrid, Spain.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Algae biomass cultivation in nitrogen rich biogas digestate.2015In: Water Science and Technology, ISSN 0273-1223, E-ISSN 1996-9732, Vol. 72, no 10, p. 1723-1729Article in journal (Refereed)
    Abstract [en]

    Because microalgae are known for quick biomass growth and nutrient uptake, there has been much interest in their use in research on wastewater treatment methods. While many studies have concentrated on the algal treatment of wastewaters with low to medium ammonium concentrations, there are several liquid waste streams with high ammonium concentrations that microalgae could potentially treat. The aim of this paper was to test ammonium tolerance of the indigenous algae community of Lake Malaren and to use this mixed consortia of algae to remove nutrients from biogas digestate. Algae from Lake Malaren were cultivated in Jaworski's Medium containing a range of ammonium concentrations and the resulting algal growth was determined. The algae were able to grow at NH4-N concentrations of up to 200 mg L(-1) after which there was significant inhibition. To test the effectiveness of the lake water algae on the treatment of biogas digestate, different pre-cultivation set-ups and biogas digestate concentrations were tested. It was determined that mixing pre-cultivated suspension algae with 25% of biogas digestate by volume, resulting in an ammonium concentration of around 300 mg L(-1), produced the highest algal growth. The algae were effective in removing 72.8 ± 2.2% of NH4-N and 41.4 ± 41.4% of PO4-P.

  • 4.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Diaz, Juan Guillermo
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Shabiimam, MA
    Indian Institute of Technology, Bombay, India.
    ALGAE BIOMASS CULTIVATION WITH AMMONIUM RICH WASTEWATERS AS SUBSTRATE: THE POTENTIAL FOR SIMULTANEOUS WASTEWATER TREATMENT AND ENERGY RECOVERY2014Conference paper (Refereed)
    Abstract [en]

    Ammonia rich wastewaters pose risk to recipient waters and the atmosphere, and can be difficult to treat in wastewater treatment plants (WTTP) due to toxicity to the microbes in conventional biological treatment systems. This article presents an idea on how to use a combination of bacteria and microalgae for efficient treatment of wastewaters with high ammonia concentrations (200-1400 mg/L). The challenge in this research is that most algae species are sensitive to high ammonia concentrations (>1 mM)(Abalde and Mezzamo, 2009). Despite the numerous wastewaters that contain high ammonia concentrations, i.e. landfill leachate, piggery manure, reject water and biogas digestate, the progress in finding sustainable treatment methods is taking time. This despite the fact that climate change, eutrophication and eco-toxicity is negatively affected by this commonly occurring component. Further, nitrogen is a valuable nutrient that in conventional WWTP is just released into the air without any recycling or recovery.

    In this article, we present a study where algae were cultivated as a mean for treatment of wastewater reject water and swine manure from a piggery farm. The algae inoculum was pretreated from lake water, sampled in mid Sweden during summer algae blooms. Lake Mälaren is a shallow lake with a rich algae consortia, optimized for the local climate. During seasonal algae blooms, the lake demonstrates the extremely rapid growth rate of the algae such as cyanobacteria, green algae and diatoms. Algae inoculum, wastewater substrate and dilution media (tap water) were mixed in various ranges of ammonium concentrations to evaluate the nutrient removal and algae biomass growth. During the algae cultivation experiment, chlorophyll, optical density and TS were used as indicators for algae biomass growth. Flow Injection System (FIA) was used for nutrient analysis.

    The two main findings in this research are that algae growth is inhibited by ammonia but that it is possible to grow algae in readily high ammonia concentrations. Moreover, significant amount of ammonium were removed by algae during the cultivation in the reactors.

  • 5.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering.
    Cultivation of microalgae for potential heavy metal reduction in a wastewater treatmet plant2012In: / [ed] Jinyue Yan, 2012Conference paper (Refereed)
    Abstract [en]

    Sorption capacity of microalgae in 10 different mixtures of wastewater and lake water was evaluated for their ability to reduce heavy metal concentrations in wastewater. Cu, Zn and Ba concentrations were mostly reduced whereas Al and As concentrations actually increased in some samples. Co and Ni concentrations were more reduced in samples with pure wastewater compared to samples with wastewater/lake water mixtures. Hence, a mixture of wastewater and lake water seemed to decrease the metal reduction process in the water. Finally, for Fe and Mn concentrations, there was no significant difference between samples with pure wastewater and wastewater/lake water mixture. In positive cases reduction of heavy metal concentrations in the samples with 50-70% of wastewater worked best.

  • 6.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering.
    Nehrenheim, Emma
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering.
    Odlare, Monica
    Mälardalen University, School of Sustainable Development of Society and Technology. Mälardalen University, School of Business, Society and Engineering.
    Liu, Xiaoling
    Tsinghua University, China.
    Li, S
    Tsinghua University, China.
    CULTIVATION OF INDIGENOUS ALGAE FOR INCREASED BIOGAS PRODUCTION2013Conference paper (Refereed)
    Abstract [en]

    There is an increased demand for biogas in the society and one way to meet this is to use cultivated microalgae as fermentation substrate. In the present study, a co-digestion experiment was established where municipal food waste was fermented with harvested microalgae cultivated in lake water. The experiment was carried out as a laboratory batch experiment with fermentation bottles, where 0, 12, 25 and 37% of the food waste was replaced with harvested microalgae, respectively. The results showed that the biogas production was generally improved after addition of microalgae. During the first 25 days of fermentation, replacement of 12% food waste with microalgae gave the highest biogas production rate. However, higher proportions of microalgae (25% and 37%) slightly decreased the gas production rate compared to 12% and compared to using food waste alone. 

  • 7.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    M.A., Shabiimam
    Indian Institute of Technology, Bombay, India..
    Truu, Jaak
    University of Tartu, Estonia.
    Ligi, Teele
    University of Tartu, Estonia.
    Truu, Marika
    University of Tartu, Estonia.
    Characterization of algal and microbial community dynamics in a wastewater photo-bioreactor using indigenous algae from lake mälaren2014Conference paper (Other academic)
    Abstract [en]

    Microalgae grown in photo-bioreactors can be a valuable source for biomass especially when combined with the treatment of wastewater. While most published research has been studying pure cultures, consortia of algae and bacteria from the wastewater have more complex dynamics affecting both the biomass production and pollutant removal. In this paper we investigate dynamics of algal and bacterial communities in mixed culture photo-bioreactors using chlorophyll and real-time PCR analysis. Wastewater photo-bioreactors were inoculated with water from a nearby lake to add native algae species. The results indicated a decline in bacterial 16S rDNA copy numbers before algae started to multiply. The photo-bioreactors inoculated with lake algae produced more biomass and grew faster than the algae originating only from wastewater. The reactors were effective in removing ammonia from the wastewater which seemed work to mostly through nitrification thus causing an increase in nitrate concentration. There was also an increase in Cr, Co and Ni ion concentrations during the experiment suggesting they may have moved from organic complexes to the water phase as free ions.

  • 8.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    M.A., Shabiimam
    Indian Institute of Technology, Bombay, India..
    Truu, Jaak
    University of Tartu, Estonia.
    Truu, Marika
    University of Tartu, Estonia.
    Ligi, Teele
    University of Tartu, Estonia.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Characterization of algal and microbial community growth in a wastewater treating batch photo-bioreactor inoculated with lake water2015In: Algal Research, ISSN 2211-9264, Vol. 11, no Sept, p. 421-427Article in journal (Refereed)
    Abstract [en]

    Microalgae grown in photo-bioreactors can be a valuable source of biomass, especially when combined with wastewater treatment. While most published research has studied pure cultures, the consortia of algae and bacteria from wastewater have more complex community dynamics which affect both the biomass production and pollutant removal. In this paper we investigate the dynamics of algal and bacterial growth in wastewater treating batch photo-bioreactors. The photo-bioreactors were inoculated with water from a nearby lake. Lake water was obtained in August, November and December in order to add native algal species and study the effects of the season. The photo-bioreactors inoculated with lake water obtained in August and November produced more biomass and grew faster than those that only contained the algae from wastewater. The results indicated a rapid decline in bacterial abundance before algae began to multiply in reactors supplemented with lake water in November and December. The reactors were also successful in removing nitrogen and phosphorous from wastewater.

  • 9.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Truu, Jaak
    University of Tartu, Estonia.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Inhibition of nitrification in municipal wastewater treating photobioreactors: effect on algal growth and nutrient uptake2016In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 202, p. 238-243Article in journal (Refereed)
    Abstract [en]

    The effect of inhibiting nitrification on algal growth and nutrient uptake was studied in photobioreactors treating municipal wastewater. As previous studies have indicated that algae prefer certain nitrogen species to others, and because nitrifying bacteria are inhibited by microalgae, it is important to shed more light on these interactions. In this study allylthiourea (ATU) was used to inhibit nitrification in wastewater-treating photobioreactors. The nitrification-inhibited reactors were compared to control reactors with no ATU added.

    Microalgae had higher growth in the inhibited reactors, resulting in a higher chlorophyll a concentration. The species mix also differed, with Chlorella and Scenedesmus being the dominant genera in the control reactors and Cryptomonas and Chlorella dominating in the inhibited reactors. The nitrogen speciation in the reactors after 8 days incubation was also different in the two setups, with N existing mostly as NH4-N in the inhibited reactors and as NO3-N in the control reactors.

  • 10.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Truu, Marika
    University of Tartu, Estonia.
    Truu, Jaak
    University of Tartu, Estonia.
    Ligi, Teele
    University of Tartu, Estonia.
    Tiirik, Kertu
    University of Tartu, Estonia.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Effect of lake water on algal biomass and microbial community structure in municipal wastewater based lab-scale photobioreactors2015In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 99, no 21, p. 6537-6549Article in journal (Refereed)
    Abstract [en]

    Photobioreactors are a novel environmental technology that can produce biofuels with the simultaneous removal of nutrients and pollutants from wastewaters. The aim of this study was to evaluate the effect of the lake water addition to the production of algal biomass, and phylogenetic and functional structure of the algal and bacterial communities in the lab-scale bioreactors treating municipal wastewater.

    The lake water addition has significant benefit to the overall algal biomass growth and nutrient reduction in the reactors with wastewater and lake water (ratio 70/30 v/v). The metagenome based survey showed that the most abundant algal phylum in these reactors was Chlorophyta with Scenedesmus being the most prominent genus. The most abundant bacterial phyla were Proteobacteria and Bacteroidetes with most dominant families being Sphingobacteriaceae, Cytophagaceae, Flavobacteriaceae, Comamonadaceae, Planctomycetaceae, Nocardiaceae and Nostocaceae. These photobioreactors were also effective in reducing the overall amount of pathogens in wastewater compared to reactors with wastewater/tap water mixture. Functional analysis of the photobioreactor metagenomes revealed an increase in relative abundance genes related to photosynthesis, synthesis of vitamins important for auxotrophic algae, and decrease in virulence and nitrogen metabolism subsystems in lake water reactors.

  • 11.
    Krustok, Ivo
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Oopkaup, Kristjan
    University of Tartu, Estonia.
    Truu, Jaak
    University of Tartu, Estonia.
    Odlare, Monica
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Comparative analysis of the metagenomes extracted from wastewater treating photobioreactorsManuscript (preprint) (Other academic)
    Abstract [en]

    The metagenomes of lab-scale municipal wastewater treating batch photobioreactors were studied with a focus on nitrogen metabolism, pathogen abundance and antibiotic resistance genes. Previous studies based on the dataset showed that in general, as algae growth in the reactors increased, nitrogen metabolism and virulence genes decreased. With this study, a more detailed view of these gene groups is presented.

  • 12.
    Schwede, Sebastian
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Anbalagan, Anbarasan
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Krustok, Ivo
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Lindberg, Carl-Fredrik
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center. ABB AB Corporate Research, Västerås, Sweden.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Evaluation of the microalgae-based activated sludge (MAAS) process for municipal wastewater treatment on pilot scale2016Conference paper (Refereed)
    Abstract [en]

    The microalgae-based activated sludge (MAAS) process was evaluated regarding the removal efficiency of organic matter and nitrogen from physiochemically pretreated municipal wastewater at different hydraulic retention time (HRT) on pilot scale. Additionally, the interplay between the algal and bacterial consortium was evaluated regarding the ability of the algal consortium to provide oxygen for bacterial oxidation processes. The results showed in general high organic matter (COD removal 75-90%) and total nitrogen (40-50%) removal at all HRTs (6, 4 and 2 days). The dissolved oxygen (DO) concentration was maintained stable at 6 days (6.04±0.47 mg L-1) and 4 days (4.24±0.62 mg L-1) HRT. However, the DO significantly declined at 2 days HRT due to loss of biomass at the high influent flow in the sedimentation unit. Nevertheless, the MAAS process functioned as a symbiotic algal-bacterial system with bacterial organic matter oxidation and nitrification and algal nutrient removal.

  • 13.
    Zambrano, Jesús
    et al.
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Krustok, Ivo
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Nehrenheim, Emma
    Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
    Carlsson, Bengt
    Department of Information Technology, Uppsala University, Uppsala, Sweden.
    A simple model for algae-bacteria interaction in photo-bioreactors2016In: Algal Research, ISSN 2211-9264, Vol. 19, no nov, p. 155-161Article in journal (Refereed)
    Abstract [en]

    This work presents a simple model to describe the consortia of algae-bacteria in a photo-bioreactor. The model is inspired by the Activated Sludge Model (ASM) structure, which includes different process rates and stoichiometric parameters. The model comprises two main biomass populations (algae and bacteria), two dissolved substrates (ammonium and nitrate) and two dissolved gases (oxygen and carbon dioxide) in the reactor. The model was calibrated with data from batch experiments performed in two lab-scale photo-bioreactors. A sensitivity analysis was done to identify the parameters to be considered for the model calibration. Results indicate that the maximum algae and bacteria growth rate, bacteria growth yield and half-saturation constant for carbon were the most sensitive parameters. Moreover, the comparison between the experiments and the model shows good agreement in terms of predicting the ammonium, nitrate and oxygen concentrations in the photo-bioreactor.

1 - 13 of 13
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