Hi all,
Has anyone encountered that there is insignificant nitrogen removal in microalgal wastewater treatment batch test? There is also a trend whereby at the 12th hour of sampling, there is a sudden surge in nitrogen concentration. What are the limiting factors for nitrogen removal using microalgae and what causes nitrogen content to increase after 12h into the batch test?
Thank you
Dear Tsuey,
It is hard to say. You should have a look into the pH level and make sure that the carbon supply is regulated to both feed the algae and keep the pH stable. It could be that the algae is missing some micro-nutrient, but I have never experienced that with wastewater. The increase in nitrogen indicate that the algae are decaying, probably releasing more nitrogen to the media.
Do you have more data on the wastewater composition and operational parameters on the batch test (e.g., pH, light intensity, biomass density, etc.)?
Dear Borja,
Thank you for your response.
For the wastewater composition:
COD: 500 ppm,
NH3-N: 30 ppm,
NO3-N: 0.5 ppm
Antibiotic concentration: 10 ppm
Operational parameters:
pH: 7.6
Light intensity: 3000 lux
Biomass density: 4.5x10^6 cells/L
Mixing: By stirring with magnetic bar
Is there anything that I missed out?
Hi Shan Yeap,
Would you write me what kind of algae you are using for N removal? Species of algae is important when we talk about nitrogen.
Vegetable are not very able to treat wastewater but only reduce a little N and P . Carbonium is breng from CO2 and nutrients from water. Bacteria have a better methabolism for Nitrogen removal
Hi Olcayto,
Thank you for bringing your attention to my query. I am currently using Chlorella sp. which was isolated from brackish water (mentioned by supplier).
Hi Paolo,
Correct me if I'm wrong but algae has high capability in removing nutrients hence, it is widely implemented in HRAP specifically targeting nutrients removal. Bacteria may have good metabolism for N removal but it has to be in anoxic condition
Dear Tsuey, following up on Borja's points, it did not escape my attention that you report on " Antibiotic concentration: 10 ppm "; this antibiotic concentration is very high, and can cause very significant inhibitory effects on your culture that can also lead to cell death; this could explain your confusing results.
Have you tried to carry out the experiments in the absence of antibiotics?; It may well be necessary whatever your set of hypothesis is you set out to answer; you could use such data as reference, and you could also move up with the antibiotic concentrations through your experimental design to learn more about the effects of antibiotics on your algae culture.
All the best, Benedek
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Dear Benedek,
I have yet to study the nutrient removal in the absence of antibiotics. I did not attempt as the algal cells seemed to be growing well (in terms of cell density) for an extended period. I shall look into this matter. Thanks for the suggestion!
As to the feedstock, is a pharmaceutical wastewater sourced from an idustrial effluent? In case you are NOT controlling the antibiotic concentration, a possible, short-term surge in the antibiotic concentration in your feedstock influent - beyond inhibitory levels - could also have caused the inhibition of nitrogen uptake and the observations you made.
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