Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Microalgae: A Green Purification of Reject Water for Biogas Production
Linköping University, Department of Physics, Chemistry and Biology.
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
Abstract [en]

Microalgae are a diverse group of unicellular microorganisms found in various environments, ranging from small garden ponds to lakes with extreme salinity. Common for all microalgae is their ability to convert solar energy and carbon dioxide into chemical energy via photosynthesis. Additionally, they are capable of assimilating large amounts of nitrogen and phosphorus to produce proteins and lipids. These abilities have made microalgae an interesting candidate for next generation wastewater treatment coupled with production of biogas, a renewable energy source in advancement. At the Nykvarn wastewater treatment plant in Linköping, Sweden, 15,400,000 m3 of wastewater are treated annually to remove nitrogen and phosphorus that otherwise would risk to cause eutrophication in surrounding lakes and rivers. Moreover, the treatment plant manages large amounts of sewage sludge that is anaerobically digested to produce biogas and simultaneously reduce the sludge volumes. At the Nykvarn wastewater treatment plant, dewatering of the digested sludge results in a sludge fraction of about 30 % dry content and reject water, which is very nutrient-rich and therefore requires treatment in a SHARON process before it is reintroduced to the main stream of the wastewater treatment plant.

In this thesis, the potential of microalgae for nutrient assimilation was studied by monitoring the nutrient removal efficiency of a mixed culture of microalgae when fed with 1) 100 % incoming wastewater, 2) 80 % incoming wastewater + 20 % reject water and 3) 60 % incoming wastewater + 40 % reject water. Furthermore, the effect of a process additive on the nutrient removal efficiency was evaluated. The results showed that microalgae are capable of removing 100 % of ingoing ammonium nitrogen and phosphate phosphorus when fed with incoming wastewater. At transition to 20 % and 40 % reject water, the culture was light-limited with a resulting ammonium reduction of 60 % and a phosphate reduction of around 30 %. The process additive slightly improved the ammonium reduction, however, mainly by formation of nitrite and nitrate by nitrifying bacteria. Moreover, a bio-methane potential test compared the methane potential of the microalgal biomass and the biomass from the SHARON process. The test resulted in an accumulated methane production around 70 mL g-1 VS-1 for the microalgal biomass and 35 mL g-1 VS-1 for the biomass from the SHARON process. That is, the mixed microalgal culture used in this experiment has a methane potential twice that of the biomass from the SHARON process. Finally, an economic analysis of a microalgae based process for purification of reject water showed that the operating costs exceed those of the SHARON process due to high energy consumption. It is thus necessary to choose a cultivation system that effectively utilize the solar energy, as well as maximize the biogas yield from anaerobic digestion of microalgal biomass.

Place, publisher, year, edition, pages
2016. , p. 68
Keywords [en]
Microalgae, wastewater treatment, reject water, nutrient removal, SHARON, biofuel, biogas
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:liu:diva-135549ISRN: LITH-IFM-A-EX--16/3168--SEOAI: oai:DiVA.org:liu-135549DiVA, id: diva2:1083123
External cooperation
Tekniska verken i Linköping AB (publ.)
Subject / course
Chemical Biology
Supervisors
Examiners
Available from: 2017-03-29 Created: 2017-03-20 Last updated: 2017-03-29Bibliographically approved

Open Access in DiVA

fulltext(1653 kB)107 downloads
File information
File name FULLTEXT01.pdfFile size 1653 kBChecksum SHA-512
0150a84e9f51ba05152666d76cef8b95b342e6b4e4e51f96acb736e5c3cbfda16572e1bc670b0385f8bf71663c6cc847aefb2203796b7a2b03f4a19e55bafe3b
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Waern, Sandra
By organisation
Department of Physics, Chemistry and Biology
Biological Sciences

Search outside of DiVA

GoogleGoogle Scholar
Total: 107 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 347 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf