Laboratory-based aerobic denitrification using methanotrophic biomass as substrate. (2020)
Type of ContentTheses / Dissertations
Thesis DisciplineBiological Sciences
Degree NameMaster of Science
PublisherUniversity of Canterbury
AuthorsPenn, Alison Alineshow all
Nitrate levels in our water resources have doubled since 20th century. This is largely due to anthropogenic activities such as overuse of nitrogen fertilizers, combustion of fossil fuels, and improper disposal of human and animal waste. Drinking water with high nitrate concentration can be highly toxic and is known to be associated with methemoglobinemia and cancer. Combined with the nature of nitrate ion (NO3-) to be readily soluble in water, it is important to develop infrastructure to control the release of nitrates in the ecosystem.
Various conventional methods currently used to remove nitrate from water include ion exchange, distillation and reverse osmosis. However, these methods show poor selectivity towards nitrate removal and are expensive to operate. One of the promising alternative strategies is to implement a bioremediation process that uses denitrifying bacteria. Denitrifying bacteria are able to convert nitrates in soil into atmospheric nitrogen. Harnessing the natural ability of these microorganisms would be a cost-sensitive and a low-maintenance approach to control the release of nitrates in water bodies.
Researchers at ESR and Chemical and Process Engineering (CAPE - University of Canterbury) are currently focused towards developing innovative approaches to reduce nitrate in the aquifer by promoting denitrifying bacterial growth in situ. This thesis focuses on this noble cause by exploring the denitrification capabilities of several denitrifying bacteria across different media compositions. The denitrifying bacteria studied in these experiments in the thesis were Bacillus subtilis, Paracoccus denitrificans, Acidovorax spp., Paenibacillus macerans and Pseudomonas stutzeri. Among different media tested, we also test the denitrification capacity of these bacteria when it uses methanotroph biomass as a carbon and energy source. We demonstrate that aerobic denitrification can be observed with all the media tested in this study - Lysogeny broth (LB), denitrification media, and also with modified media with yeast extract and methanotrophic biomass as carbon and energy sources. The highest amount of nitrate reduction was observed with LB medium and sub-optimal nitrate reduction was observed with yeast extract and methanotrophic biomass. Given that denitrification is a low energy yielding process, it makes sense for the denitrification to be suboptimal with complex media. This knowledge can be further explored to identify an economically viable optimal media that can be used for biological denitrification of waste-water treatment.