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Communities of microalgae and bacteria in photobioreactors treating municipal wastewater
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. (ACWA)ORCID iD: 0000-0002-4435-4367
2015 (English)Licentiate 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.

Place, publisher, year, edition, pages
Västerås: Mälardalens högskola , 2015.
Series
Mälardalen University Press Licentiate Theses, ISSN 1651-9256 ; 193
National Category
Water Treatment
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-27696ISBN: 978-91-7485-192-2 (print)OAI: oai:DiVA.org:mdh-27696DiVA: diva2:795313
Presentation
2015-04-17, Lambda, Mälardalens högskola, Västerås, 10:00 (English)
Opponent
Supervisors
Funder
Knowledge Foundation, 2011006VINNOVA, 2012-01243
Note

Additional funding was from SVU (12-123), Puracand Mälarenergi, and by grant IUT2-16 of the Ministry of Educationand Research of the Republic of Estonia (J. Truu, M. Truu, T. Ligi).

Available from: 2015-03-17 Created: 2015-03-16 Last updated: 2015-06-11Bibliographically approved
List of papers
1. Cultivation of microalgae for potential heavy metal reduction in a wastewater treatmet plant
Open this publication in new window or tab >>Cultivation of microalgae for potential heavy metal reduction in a wastewater treatmet plant
2012 (English)In: / [ed] Jinyue Yan, 2012Conference paper, Oral presentation with published abstract (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.

National Category
Engineering and Technology
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-18283 (URN)
Conference
ICAE, International conference on applied energy, 5-8 July, Suzhou, China
Projects
ACWA
Available from: 2013-02-27 Created: 2013-02-26 Last updated: 2015-03-17Bibliographically approved
2. Characterization of algal and microbial community growth in a wastewater treating batch photo-bioreactor inoculated with lake water
Open this publication in new window or tab >>Characterization of algal and microbial community growth in a wastewater treating batch photo-bioreactor inoculated with lake water
Show others...
2015 (English)In: Algal Research, ISSN 2211-9264, Vol. 11, no Sept, 421-427 p.Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2015
Keyword
Algal cultivation; Biomass production; Community analysis; Photo-bioreactors; Wastewater treatment
National Category
Water Treatment
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-27699 (URN)10.1016/j.algal.2015.02.005 (DOI)000363046900051 ()2-s2.0-84943663075 (Scopus ID)
Funder
Knowledge Foundation, 2011006VINNOVA, 2012-01243
Note

Additional funding from SVU (12-123), Purac and Mälarenergi, and by grant IUT2-16 of the Ministry of Education and Research of the Republic of Estonia (J. Truu, M. Truu, T. Ligi).

Available from: 2015-03-16 Created: 2015-03-16 Last updated: 2017-01-03Bibliographically approved
3. Effect of lake water on algal biomass and microbial community structure in municipal wastewater based lab-scale photobioreactors
Open this publication in new window or tab >>Effect of lake water on algal biomass and microbial community structure in municipal wastewater based lab-scale photobioreactors
Show others...
2015 (English)In: Applied Microbiology and Biotechnology, ISSN 0175-7598, E-ISSN 1432-0614, Vol. 99, no 21, 6537-6549 p.Article in journal (Refereed) Published
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.

Keyword
biomass production; metagenome analysis; photobioreactor; wastewater treatment
National Category
Microbiology
Research subject
Biotechnology/Chemical Engineering
Identifiers
urn:nbn:se:mdh:diva-27706 (URN)10.1007/s00253-015-6580-7 (DOI)000357649200031 ()2-s2.0-84937630449 (Scopus ID)
Funder
Knowledge Foundation, 2011006VINNOVA, 2012-01243
Note

Additional funding by SVU (12-123), Puracand Mälarenergi, and the Ministry of Education and Research of the Republic of Estonia (grants IUT2-16 and 3.2.0801.11-0026).

Available from: 2015-03-16 Created: 2015-03-16 Last updated: 2017-12-04Bibliographically approved

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