I welcome to everybody to transfer their experiences to use of 'Microbial flocculants (EPS, extracellular polymeric substances)' as a substitution for chemical flocculants.
We researched on the extraction EPS from activated sludge by Klebsiella for use of them as a bioflocculant for sludge dewatering. but efficiency was not satisfactory, of course when we used the Klebsiella together with Cacl2 the efficiency obtained very higher than before. Is reasonable to apply Cacl2 for a bioflocculant?
The cost of the EPS production?
What is the important criteria for selection of bacteria for EPS?
Do you think this biotechnology can be use in a full scale in view of economical aspects?
It seems interesting, but I have seen others EPS uses (bioplastic for example) rather than extract them for sludge dewatering purposes.
My group researches the production and application of bioflocculants, but we use agricultural byproduct proteins rather than microbially-produced substances. At the moment, it appears that hemoglobin from poultry blood could produced profitably as a flocculant (techno-economic analysis of this currently in progress). The performance of the flocculant depends a lot on the application. We are researching covalent modifications of the flocculant that could modify the performance characteristics. A major obstacle for us at the moment is the identification of an application area that would be receptive to an alternative flocculant.
We don't interact with any other researchers working in bioflocculants, but we're certainly open to it.
This might be deviate from the question you have asked but some researches has explored the use of chitosan as (bio)flocculants/coagulants, it can be extracted/produced via biological routes and the scaling up seems promising too. Please refer some of the works I have came across.
http://www.hindawi.com/journals/ijps/2014/162173/
http://www.sciencedirect.com/science/article/pii/S0008621507003229
http://link.springer.com/article/10.1007%2Fs00253-012-4668-x
http://www.sciencedirect.com/science/article/pii/S0014305708007222
I am just studying the possibility for the practical production of a microbial chitosan-like bioflocculant. This depends on the production costs. Please refer to the sentences shown below (this is a part of the introduction section of my next manuscript). Anyway, for the practical production, we need cheap substrates such as organic wastewaters, cheap fermentation and recovery processes, and cheap man power. My friend in Australia is studying the use of chitosan for dewatering of sludge and obtained good results. However, chitosan from crab is expensive for treatment of wastewaters. In my case, I am trying to use organic wastewaters and membrane technologies as cheap and low energy downstream processes (removal of bacterial cells with a MF membrane and recovery of the bioflocculant with a UF membrane without centrifugation and ethanol precipitation) to reduce the cost. I thank that as bioflocculants are eco-friendly agents, we need to replace chemical flocculants with bioflocculants in future even if the costs are a bit higher than those of chemical ones, at first from purification of environmental wasters.
A Japanese market report says that the recent selling prices for PAC and aluminum sulfate are approximately 20 yen kg-1 (0.2 US$ kg-1) and those for polyacrylamide-based polymer flocculants are 500-1300 yen kg-1 (5-13 US$ kg-1) (Market of water treatment, purification & business 2012, CMC publishing Co., Ltd., Tokyo, in Japanese). In contrast, the most successful microbial polysaccharide production at the industrial scale is the production of xanthan by Xanthomonas campestris, which has so far achieved >50 g l-1 in the cultures (Morris & Harding, 2009; Freitas et al., 2011; Kreyenschulte et al., 2014). The selling price of xanthan is 3-5 US$ kg-1 (Donot et al., 2012, Kreyenschulte et al., 2014) or 14 US$ kg-1 (Morris & Harding, 2009), which may be comparable with those of synthetic polymer flocculants. As for some other polysaccharides such as levan, pullulan, and curdlan, high microbial production (>50 g l-1) has been achieved (Donot et al., 2012). Therefore, if efficient BF-producing strains are available and the fermentation conditions and processes are optimized, it may be possible to raise the present BF production to the commercial production level.
(1) Morris, G. & Harding, S. E. (2009). Polysaccharides, Microbial. In Encyclopedia of Microbiology (Third Edition), pp. 482-494. Edited by Schaechter M et al . Waltham, MA: Academic Press.
(2) Freitas, F., Alves, V. D., & Reis, M. A. M. (2011). Advance in bacterial exopolysaccharides: from production to biotechnological applications. Trend in Biotechnol 29, 388-398.
(3) Kreyenshulte, D., Krull, R., & Margaritis, A. (2014), Recent advances in microbial biopolymer production and purification. Crit Rev Biotechnol 34, 1-15.
(4) Donot, F., Fontana, A., Baccou, J. C., & Schorr-Galindo, S. (2012). Microbial polysaccharides: main examples of synthesis, excretion, genetics and extraction. Carbhydr Polym 87, 951-962.
polyacrylamide based flocculants are the work horse for wastewater sludge treatment.
For different applications and sludge variants there are tailor made products or at least a broad range of products to choose from. To have different variants is important for a broader application.
As mentioned previously, flocculants efficiency and effectivity very much depend on treatment process, e.g. gravity settling, filtration, centrifugation ... For the first process I would think EPS natural flocculants may find a market and yes it is reasonable to use additives to optimize their action.
THANKS A LOT WITH MY BEST REGARDS TO ALL ANSWERS WRITERS THAT PARTICIPITATE IN THIS SUBJECT.
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