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Effect of lake water on algal biomass and microbial community structure in municipal wastewater based lab-scale photobioreactors
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. (ACWA)ORCID iD: 0000-0002-4435-4367
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.ORCID iD: 0000-0001-5480-0167
University of Tartu, Estonia.
University of Tartu, Estonia.ORCID iD: 0000-0003-1818-6678
Show others and affiliations
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.

Place, publisher, year, edition, pages
2015. Vol. 99, no 21, 6537-6549 p.
Keyword [en]
biomass production; metagenome analysis; photobioreactor; wastewater treatment
National Category
Microbiology
Research subject
Biotechnology/Chemical Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-27706DOI: 10.1007/s00253-015-6580-7ISI: 000357649200031Scopus ID: 2-s2.0-84937630449OAI: oai:DiVA.org:mdh-27706DiVA: diva2:795556
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: 2016-03-10Bibliographically approved
In thesis
1. Communities of microalgae and bacteria in photobioreactors treating municipal wastewater
Open this publication in new window or tab >>Communities of microalgae and bacteria in photobioreactors treating municipal wastewater
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:nbn:se:mdh:diva-27696 (URN)978-91-7485-192-2 (ISBN)
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
2. Microbiological analysis of municipal wastewater treating photobioreactors
Open this publication in new window or tab >>Microbiological analysis of municipal wastewater treating photobioreactors
2016 (English)Doctoral 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.

Abstract [sv]

I takt med att världens befolkning ökar, så produceras dagligen allt mer avfall. Detta kan orsaka stora problem för miljön. När det byggs nya system för vattenrening behöver vi även ta hänsyn till kravet att minska energiåtgången. Dagens vattenreningssystem har vissa tillkortakommanden när det gäller reningsnivåer och energianvändning. Ett alternativ till dagens system, kan vara fotobioreaktorer, dvs. vattenrening med hjälp av mikroalger. Dessa system använder mikroalger och bakterier för att rena vattnet från föroreningar, kväve och fosfor.

Vattenrening med fotobioreaktorer är en relativt ny teknik. Flera aspekter gällande biologin i dessa system har ännu inte studerats i detalj. Den här avhandlingen presenterar en översikt av de alger och bakterier som är aktiva i fotobioreaktorer. Andra viktiga aspekter som tillväxt, arter samt vattenreningsförmåga har också studerats.

Ett antal försök genomfördes där alger från Mälaren tillsattes i vatten från Västerås kommunala vattenreningsanläggning. Storleken på försöken varierade mellan 250 ml och 20 liter. Det visade sig att algerna hade en bra tillväxt samt att mängden ammonium och fosfor minskade i vattnet under försöksperioden.

De alger som tillväxte mest i studien tillhörde Scenedesmus, Desmodesmus och Chlorella. Förutom alger tillväxte även ett stort antal bakterier från grupperna Proteobacteria and Bacteroidetes. Dessa bakterier visade sig syntetisera viktiga vitaminer, t.ex. vitamin B12, som algerna normalt inte kan syntetisera själva.

Sammanfattningsvis, så presenterar denna avhandling viktig information gällande alger och bakterier i en fotobioreaktor. Informationen kan vara ett viktigt bidrag till framtida utveckling av storskaliga fotobioreaktorer för vattenrening.

Place, publisher, year, edition, pages
Västerås: Mälardalen University, 2016
Series
Mälardalen University Press Dissertations, ISSN 1651-4238 ; 196
Keyword
photobioreactors, wastewater treatment, microalgae, microbiology
National Category
Water Treatment
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-30045 (URN)978-91-7485-251-6 (ISBN)
Public defence
2016-01-29, Paros, Mälardalens högskola, Västerås, 09:15 (English)
Opponent
Supervisors
Funder
Knowledge Foundation, 2011006VINNOVA, 2012-01243
Available from: 2015-12-21 Created: 2015-12-21 Last updated: 2016-01-13Bibliographically approved

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