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Marie Peralta: Open-pond Cultivation of Microalgal Polycultures on Landfill Leachate

October 3, 2019


I’m Marie Peralta. I am a biology major and my project is the open-pond cultivation of microalgal polycultures on landfill leachate. So these past presentations have kind of gone over already of the benefits of
microalgae but here I want to focus on is microalgae, is it really a
feasible source of renewable fuel? While some advantages that I’ve outlined
here is that yes, microalgae grow very
quickly and they yield very high biomass. And potentially it eliminates the food versus fuel debate, because growing microalgae, we
don’t need to grow it on land that food crops could grow in, and here, cultivation on non-arable land, and also you can use waste effluent to grow the microalgae, but some disadvantages of that is that you need a lot of water to grow the
algae and also they are very high energy in terms of processes that are
involved like harvesting, like centrifugation, for example. And so Erica kind of already went
over what landfill leachate is, but it is the liquid waste generated by the landfill site. The thing is, it has to be managed to prevent contamination to the environment
also for public health needs and contamination in, like with Erika’s presentation you saw those lakes and if a bloom would happen it
would just destroy the natural diversity and whatever is in the pond already. And also, landfill leachate is widespread, it’s everywhere, there are landfills everywhere. [Dr. Wilkie:] Unfortunately. [Marie:] Yeah, unfortunately they’re everywhere and I want to point out that leachate from
different landfills demonstrate different properties, so I’m going to get into that
later and nutrients present in landfilll leachate allow for algae growth. And here is a picture of the Alachua County Southwest landfill that was closed back in 1999. As you can see, this is like, basically a nice green field and I want
to go back to the whole arable land because nothing, there really isn’t
anything happening here. You could potentially put those raceway ponds here as well. And here’s Dr. Wilkie. So, um, I think growing microalgae in
landfill leachate could be a single solution for many problems. For instance, I pointed out growing microalgae for biofuel production and also potentially the landfill leachate bioremediation, as you will see later in my results, this alludes to that, and also a reduction of greenhouse gas emissions. Josh and Jill,
their projects show that you can harness the CO2 coming from the flue gas and that CO2 could be used for the cultivation of the algae in the raceway ponds. So my research objective really was growth of microalgae outdoors in 100 liter raceway ponds, cultivated in 100% landfill
leachate. So my methods were, the 100 liter, I had,
yeah, I had the 100 liter open raceway pond. I used microscopy to evaluate
the biodiversity of the microalgal cultures over time and also controlling
the pH of the culture, with the CO2. I also inoculated ponds with indigenous algae, specifically the pond one out there.
I used exclusively that algae and I also monitored the characteristics of my
samples daily. I took pH readings every day. I also measured growth and I used spectroscopy to do that, and I also looked at the total ammonium nitrogen, TAN, and
I measured that over time, and I also characterized the leachate. So here is a table of my findings for the leachate. I want to point out that this is the leachate that we
harvested last year. Erica’s leachate was from 2016. [Dr. Wilkie:] Hers was an older vintage. [Marie:] Yeah. Mine was older. So, I took mine from the 2015 leachate. And so here you can see that the pH, a little bit higher than usual. The alkalinity is quite high as well, and
here I want to focus mostly here on the TAN. I remember Erica’s numbers
were around 700, mine, since mine was older, mine is about 880 or 890. Here is a result from on one trial. Over time I saw that the optical density,
which is indicative of the growth of the algae, it, um, had a two day lag period but its reading increased over time. And also I want to, these are the TAN readings that corresponded with these samples as well. So over time I noticed
that the nitrogen levels decreased over 11 days. And this is about, this was around 800 and this is about 4, 4 milligrams per liter. And this is just a visual of my samples
each day so this is just water for reference and this is just pure landfill leachate. This is my T0, the day I started innoculating my pond with the algae and also with the 100% landfull leachate. And over time you can see that as each day passed the pond got greener. Here’s, um, I Iooked at the inoculum that I had in the beginning and I also saw the microalgae that I had at day 8 and as you can see there is a lot more diversity in the original inoculum. Here I think, um, we might have Scenedesmus here. And there’s just a lot of different types of microalgae there. So this is just a polyculture at 100 magnification, but here at day 8, I notice it could, I don’t want to be too optimistic but it might be a biculture,
but right now looks pretty much like a single culture. And I think, this might be Choedaria. [Dr. Wilkie:] Who? [Marie:] Choedaria. I think it’s the, yeah, it’s the algae that Jill saw. So, um, [Laughter] this is, um, Sally Palmi came here, I think on Wednesday, and she got to see the ponds and I think [Dr. Wilkie:] And she’s not here today. [Marie:] Yeah, not here today, so [Laughter] [Dr. Wilkie:] I don’t think she had any tolerance. I’m here. [Laugher] So, um, the conclusion here is that you can definitely utilize carbon dioxide gas to control the pH levels
in the landfill leachate and algae ponds and also outdoor microalgae cultivation with 100% landfill leachate is totally possible and I would like to further look at the leachate remediation in terms of the TAN going down over time.

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