Nitrogen! A relatively inert, triple-bonded element that makes up 70% of the atmosphere. An integral part of our biological make up. It can be found in almost, if not, every living organism on this earth. If we look at the nitrogen cycle, we can see why:
From the atmosphere it falls to the ground where it is reduced and oxidised into more reactive forms and plants take them up. Then up the food chain they go…and back down, if you get what I mean. If we eat it, we release it and when we do, it’s in the form of organic nitrogenous compounds. Some of these compounds include urea, amines and amides. Along with human and animal waste, there are other nitrogen contributors like decaying plant matter, agricultural, industrial and pharmaceutical runoffs. When released they undergo different processes including ammonium oxidation and denitrification.
As discussed in my last post ammonium oxidation is carried out by ammonium oxidising bacteria (AOB) and results in the formation of nitrite. It is half of the nitrification process which is the complete oxidation of ammonium to nitrate. This process occurs in the soil naturally and in wastewater treatment (WWT) in the activated sludge tank.
Denitrification
After nitrification is denitrification and this is the reduction of nitrate to nitrogen gas which is re-released to the atmosphere. This is carried out by denitrifying bacteria. In my research project, I didn’t measure for this process because it was not in my original plan. However, there was a strong possibility that it was occurring. Remember in the last post, I stated that carbon dioxide was being produced within the reactor despite it being a fully closed system. The process responsible for this could have been heterotrophic denitrification which is carried out by ordinary heterotrophic organisms. One could argue that this step is the most important in a wastewater treatment process due to the fact that it completely removes the toxic nitrogenous compounds from the water, rendering it “clean”.
Nitrogen assimilation
Algae are efficient at consuming nitrogen in its different forms and the nitrogen is usually incorporated into the biomass. This is quite an advantageous reality which is why algae is widely researched for more than just bio-fuels. In my research, I didn’t expect for the algae to make much of an impact in assimilating the ammonium because of the stoichiometry of the photosynthesis reaction when compared to that of nitrification. However, it played a very important role by aerating the reactor.
My two cents…
Nitrogen is one of the most important nutrients in this world but it can be toxic in different forms. Carbon dioxide is also beneficial to photosynthetic organisms however it is a dangerous greenhouse gas. It is absolutely beneficial to combine the nitrogen removal properties of bacteria and carbon dioxide consumption properties of algae. This is biotechnology that can assist us in adapting to climate change. But, how do we make affordable for countries to use it? How do you convince governments to fund it? If I did it in a temperate country with fake sunlight, then how much better do you think it would be to kick-start in Barbados, the land of eternal summer?
Let me know what you think.
the Awkward Chemist 