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Microbiological analysis of municipal wastewater treating photobioreactors
Mälardalen University, School of Business, Society and Engineering, Future Energy Center. (ACWA)ORCID iD: 0000-0002-4435-4367
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 [en]
photobioreactors, wastewater treatment, microalgae, microbiology
National Category
Water Treatment
Research subject
Energy- and Environmental Engineering
Identifiers
URN: urn:nbn:se:mdh:diva-30045ISBN: 978-91-7485-251-6 (print)OAI: oai:DiVA.org:mdh-30045DiVA: diva2:885741
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
List of papers
1. 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
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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
2. Inhibition of nitrification in municipal wastewater treating photobioreactors: effect on algal growth and nutrient uptake
Open this publication in new window or tab >>Inhibition of nitrification in municipal wastewater treating photobioreactors: effect on algal growth and nutrient uptake
2016 (English)In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 202, 238-243 p.Article in journal (Refereed) Published
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.

Keyword
photobioreactors, microalgae, wastewater treatment, nitrification, algal-bacterial interactions
National Category
Water Treatment
Research subject
Energy- and Environmental Engineering
Identifiers
urn:nbn:se:mdh:diva-30043 (URN)10.1016/j.biortech.2015.12.020 (DOI)000367673500032 ()2-s2.0-84951304290 (Scopus ID)
Funder
Knowledge Foundation, 2011006VINNOVA, 2012-01243
Available from: 2015-12-21 Created: 2015-12-21 Last updated: 2017-12-01Bibliographically 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
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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
4. Comparative analysis of the metagenomes extracted from wastewater treating photobioreactors
Open this publication in new window or tab >>Comparative analysis of the metagenomes extracted from wastewater treating photobioreactors
Show others...
(English)Manuscript (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.

Keyword
photobioreactors, metagenomics, microalgae, wastewater treatment, pathogens, antibiotic resistance, functional analysis
National Category
Water Treatment
Research subject
Biotechnology/Chemical Engineering
Identifiers
urn:nbn:se:mdh:diva-30044 (URN)
Funder
Knowledge Foundation, 2011006VINNOVA, 2012-01243
Available from: 2015-12-21 Created: 2015-12-21 Last updated: 2016-02-25Bibliographically approved

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