Bio-Flocculation - Microbial Assisted Flocculation for the Treatment of Industrial Wastewater


Flocculants are the organic or inorganic compounds that promote suspended particles in liquids to agglomerate and to forming a floc. Varieties of flocculants are used in wastewater treatment processes to improve filterability of small particles and sedimentation as well. The term bio-flocculants means the flocculants which derived from biological source. Bio-flocculants have been most widely studied on bacteria (Zakaria, 2012) and fungi (Deng and Ting, 2005). These can be used for flocculation instead of chemical flocculants (that generates harmful by-products). Bio-flocculants are eco-friendly and not producing any harmful byproducts during treatment. Microbial derived bio-flocculants have potential to be used for the treatment of various industrial effluents.


In 2005, Deng and Ting reported Aspergillus parasiticus to produce a bio-flocculants for Kaolin suspension and water-soluble dyes. They were observed 98.1% (after 72 h incubation) of flocculation efficiency of bio-flocculants for Kaolin suspension. After characterization of the bio-flocculants, they found that it was mainly composed of sugar (76.3%) and protein (21.6%). Fourier transform infrared (FTIR) spectra showed that amino, amide and hydroxyl groups were present in the bio-flocculants molecules. This bio-flocculants was also found effective for soluble anionic dyes in aqueous solution. The de-colorization efficiency of bio-flocculants was 92.4 and 92.9% for Reactive Blue (RB) 4 and Acid Yellow (AY) 25 respectively. The amino and amide groups in the bio-flocculent molecule are supposed to play an important role in flocculation from the viewpoint of electrostatic interaction.


In 2008, Zheng et al. were isolated bio-flocculants producing bacteria from soil and identified as Bacillus sp.. They reported that the bio-flocculants produced by isolated Bacillus sp. consisted of sugars (3.6%, w/w), uronic acid (37.0%, w/w), amino sugars (0.5%, w/w) and proteins (16.4%, w/w). FTIR analysis of that bio-flocculants revealed the presence of carboxyl, hydroxyl and methoxyl groups.


In 2012, Zakaria was accounted for the production of bio-flocculants by Pseudomonas aeruginosa ATCC-10145. He studied the effects of carbon-nitrogen sources, pH and temperature for on bio-flocculants production. The effects of cationic compounds on flocculating activity was tested and he observed that the flocculating activity was stimulated by Ca²⁺, K⁺, Na⁺, Zn²⁺, Mg²⁺ and Cu ²⁺ whereas inhibited by Fe³⁺ and Al³⁺. He was reported 80.50% flocculating activity for kaolin suspension with 1% of bio-flocculants suspension. He also observed the heat stability of bio-flocculants and noted 60.16% reduction in the after heating at 100⁰C for 60 min. Chemical analyses of the purified bio-flocculants revealed that it was a sugar-protein derivative. It consists of protein (27%, w/w) and carbohydrate (89%, w/w) including neutral sugar, uronic acid and amino sugar as the principal constituents in the relative weight proportions of 30.6%, 2.35% and 0.78% respectively. Additionally, elemental analysis of the bio-flocculants revealed the mass proportion of C, H and N was 19.06%, 3.88% and 4.32 % correspondingly. FTIR analysis showed that it consisted of carboxyl, hydroxyl, amino and sugar derivative groups.


Thus bio-flocculants are eco-friendly and appealing candidate in the biological wastewater treatment technology (BWWTT). However, the pilot scale studies of bio-flocculants regarding their sustainability and cost consideration are also required for their implementation in BWWTT at commercial scale.

References:

-Deng S1, Yu G, Ting YP (2005) Production of a bioflocculant by Aspergillus parasiticus and its application in dye removal, Colloids Surf B Biointerfaces; 44(4):179-86.
- Zakaria E. (2012) Production and characteristics of a heavy metals removing bioflocculant produced by Pseudomonas aeruginosa. Pol J Microbiol; 61(4):281-9.
- Zheng Y, Ye ZL, Fang XL, Li YH, Cai WM. (2008) Production and characteristics of a bioflocculant produced by Bacillus sp. F19, Bioresour Technol.;99(16):7686-91.


About Author / Additional Info:
Research Scholar-
Research Interest: Biofuels and biological wastewater treatment