I am about to start experiments on nitrogen removal by MBBR. I started some trial tests in batch mode to see if biofilms form before the main ones, and I have some questions regarding the operation.
1) First and foremost, water keeps evaporating from the reactor, and I do not know how to prevent this.
2) What is the best inoculum (seed sludge) to substrate ratio to start the experiments?
3) What is the best way to measure the filling ratio?
4) What is the optimum range for DO? I have seen several ranges, and I do not know which is the best.
Any other suggestions and references are welcomed.
Hi
It is different for each system according to the operating parameters and input feed conditions, but the most important issue is to optimize each of the parameters according to the environmental and operational conditions.
1- A closed bioreactor can be used to prevent water evaporation
2- According to the calculations of hydraulic retention time and reactor volume and inlet flow and system conditions are different, but usually about 3000 to 8000 mg / l is the optimal amount of membrane bioreactor.
3- The hydraulic retention time is equal to the volume of the reactor at the input flow rate
4. Lower DO and higher SRT usually have better results in nitrogen removal, but the optimal DO range is 2 to 6 mg / L.
Hi Kasra,
This might be helpful:
Article Biodegradation of organophosphorus pesticides in Moving Bed ...
Best,
Navid
Thanks Kasra Pourrostami Niavol for the clarification and slight editing of the question. The reply above by Soroush Azizi is completely correct for MBR.
Kasra Pourrostami Niavol , Your first question about the evaporation from the reactor. I am very familiar with this problem. A long time ago I learned to use a air humidifier on the airflow that is used for the reactor.
It is essentially a bottle of water which the airflow is passed through. I have the air entering the bottle from a pipe that goes through the lid and end in the bottom of the bottle. The air make bubbles which take up water vapor and this air i take from the headspace in the top of the bottle with a tube into the reactor I work with. I'll look for a picture of a setup.
I hope that the following information is helpful to you:
The optimum inoculum/substrate ratio (defined by F/M) should be obtained carefully considering Michaelis-Menten Kinetics. In brief, it depends on the substrate concentration and substrate utilisation rate. Please read my article "Selectors in advanced biological wastewater treatment systems" for a brief overview.
You can find more detailed calculations regarding MBR design in "Application of membrane bioreactor for textile wastewater treatment". More specific to your question is Section-5.1: Determination of F/M and BOD volumetric loading. Regarding your fourth question, please refer to "Section-7: Calculate the O2 demand" and "Section-8: Fine bubble aeration design – determining airflow rate at average design flow rate" in this article.
I have attached both files for your reference. Would you mind letting me know if you need further help in your research?
Kasra Pourrostami Niavol , Your second question about the best inoculum. Just find activated sludge from a WWTP with similar loading as you intend the experimental reactor to handle. In your case a sludge with good nitrification capacity.
We add 1-10 g/L sludge in the reactor and recirculate the water over the reactor with addition of substrate for some day before we let the sludge wash out with the substrate flow.
Henrik Rasmus Andersen , Thank you for your practical solutions.
Kasra Pourrostami Niavol , About the 3rd question on the filling ratio: It is supposed to be based on the bulk volume of the carriers compared to the tanks volume. We suspect this doesn't work very well in small laboratory reactors so we take the manufacturers recommendation of the number of carriers per unit volume that correspond to the preferred filling ratio and recalculate how many carriers we have to count out to make a specific filling ratio. E.g. a supplier recommend 300 carriers per liter correspond or 50 % filling ratio, so if my experiment should be with 10 % filling I add 60 carriers per liter of water in the reactor.
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