Hi Chitrang Kapadia, Indeed, flocculation works through opposite charge neutralization. In the case of algal cells and also the majority of other microorganisms (e.g. bacteria), negative surface charges hold them in suspension but these can be neutralized with positively charged flocculants. In the case of inerts, they can be settled by natural sedimentation or even through physisorption (Van der Waal forces). We couldn't find much information about the inert particles but according to this reference (www.911metallurgist.com/selective-flocculation/), there might be a change of them adhering to flocculants due to "active sites" being physically entrapped. But be aware that in principle, this should only work with patch or bridging flocculations. You can learn more about different flocculation types here: www.mdpi.com/2311-5637/4/4/93 All the best, GreenCoLab team

​@@greencolab thank you for the response. I was looking at waste water treatment with Chitosan but it was not working for me. I tried using 50 ml 0.1% Chitosan in 500 ml but there were no flocks found after agitating it for 30 mins at 250 rpm and then letting it set for another 30 minutes. Could you please suggest where I could be going wrong? Thank you for your time.

​Hi@@chitrangkapadia9293 , Thank you for your question. There are a few important variables for chitosan to work properly. a. Chitosan preparation: it is important to dissolve it first in HCl and dilute it afterward - please follow the exact procedure we mention in this video concerning the stock preparation. b. Your wastewater profile: depending on the type of wastewater it can be more difficult to remove suspended solids. Check in the literature if there are flocculation studies regarding your wastewater. c. Wastewater pH and temperature: pH is very important for flocculation to work properly. The best would be to first optimize it, by adjusting pH prior to the addition of chitosan. Bear in mind that the higher the concentration of chitosan you add, the more acidic the wastewater will be (due to HCl in the stock solution). You can test for instance pH 5, 7 and 9. As for temperature, normal room temperature is ok. d. Chitosan concentration: chitosan is a very strong cationic flocculant so it is likely to follow the rule of “less is more”. Test different concentrations of chitosan, I would start with 5 mg/L and go up to 75 or 100 mg/L (this last one you already tested). e. Running speed: by the time you add chitosan you should mix it fast (I would use 150 rpm instead of 250 rpm) but at lower times (1 minute is enough). Then, use a low speed (10-20 rpm) for 5 to 10 minutes to allow floc formation. This could be the reason for your unsuccessful trial since you used very high speed during a long period and did not include a low-speed step. We hope this was helpful and wish you success in your lab experiments! Take care, GreenCoLab team

nice @@greencolab

Hi Edward, Thank you for your question. NaOH is used for adjusting the culture pH. It may not be necessary if you only need to lower pH. Nevertheless, we decided to include it in the material’s list as it is a commonly required reagent. All the best, GreenCoLab team

Hello @ambro4523, Thank you for your question. The simple answer to your question is yes, chitosan is an efficient polymer to remove organic matter from various wastewater. However, it is best to check the literature and know if chitosan or other flocculant type has been used to clean your wastewater type. Here you can find 3 articles regarding this topic, that will provide you additional information: - onlinelibrary.wiley.com/doi/full/10.1002/pi.5464 - dx.doi.org/10.5772/65289 - link.springer.com/article/10.1007/s10924-005-5533-0 We wish you success in your experiments! Best regards, GreenCoLab team

Hello @immanuelnathanaellumbangao495 , Thank you for your question! Unfortunately, we do not share internal protocols with external persons or entities. However, we share in detail the protocol in this video and can also assist you if you have any questions. Nevertheless, if you are interested in us assisting in the development of a different method, please feel free to reach us by email at: services@greencolab.com. All the best, GreenCoLab Team

Hi Trawas meme, Thank you for your question. Yes, you can use chitosan to harvest Chlorella by flocculation. Here is an article regarding this topic that will certainly help you: doi.org/10.1016/j.cej.2013.04.062. All the best, The GreenCoLab team

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Chitosan is soluble in acidic ph only

Hi Rohan, Thank you for your question. Chitosan is a weak base and is insoluble in water and organic solvents. However, it becomes soluble in dilute aqueous acidic solutions (pH

Hi Vemuri, Thank you for your input! All the best, GreenCoLab team

why you don't used acetic acid? @@greencolab

Hi@@TheLahevi, Thank you for your question. We decided to use HCl since it is a strong acid and can completely dissociate in water to release hydrogen ions, as opposed to acetic acid, which is a weak acid. Nevertheless, there are reports of chitosan being easily dissolved at 1% of acetic acid (v/v) so it can be used for creating chitosan stock solutions Please note: we also decided to use HCl because we didn't mind having altered salinities. While this is not relevant for acetic acid, the formation of acetate could change your bacterial community load and diversity, since acetate can be used as a carbon source. All the best, GreenCoLab team