Production And Flocculating Performance Of Sludge Bioflocculant

Now, the wastewater and the excess biological sludge have increased sharply, and the untreated sludge would produce a series of impacts on the ecosystem and threaten human health. At the same time, the underutilized beneficial ingredients in the sludge would cause the waste of resources. The combination of pollution controlling and recycling is the trend of the solid waste treatment. According to the analyses above, this paper puts forward a new way of sludge handling and recycling, which is the preparation of biological flocculent by excess biological sludge. This method can not only realize sludge recycling, but also add a new way to prepare bioflocculant.First of all, the methods of sludge flocculant extraction were studied. The neutral aqueous solution, sodium hydroxide solution4%(w/w) and hydrochloric acid solution18%(V/V) were used to extract the flocculating active ingredient in the sludge, and results showed that the flocculant which was extracted by hydrochloric acid had a better flocculating activity. This indicated that the high flocculating activity ingredient in the activated sludge could dissolve in the acid solution. The suitable condition of flocculant extraction was10.0g dewatered sludge mixed with5.0mL18%(V/V) hydrochloric acid and95.0mL water. When the pH of the flocculation system ranged from4.0to11.0, the flocculating rate was higher. When the rough flocculant dosage was5～15mL,98.0%of flocculating rate for4g/L kaolin clay was achieved. This kind of sludge flocculant mainly distributed outside the cell.The content of sugar and protein in the purified sludge flocculant was76.3%and4.21%(w/w), respectively. Sodium hydroxide solution and ethanol were used to divide the rough flocculant into four pure parts PSF-1-PSF-4. Flocculation experiment results proved that The PSF-2had a higher flocculating rate for Kaolin suspension than others. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared(FTIR) spectra showed that more amine groups existed in the bioflocculant PSF-2and theseamino groups were believed to play an important role in flocculation.The research of Zeta potential showed that the positive charged flocculant would neutralize the negative charge on the surface of the kaolin particles in the flocculation system. So the mechanism of electrical neutralization existed in the flocculation process. Scanning electron microscopy images showed that the effect of adsorption and bridging also existed.The sludge flocculant had a good flocculation efect on Kaolin particles which was a typical hydrophobic particle, and could also flocculav the starch granules which was a typical water swelling particle. Under the assistance of Kaolin particles, sludge flocculant had a good decolorization effect on anionic dye, but a weak decolorization effect on cationic dye. The sludge flocculant also had the ability to separate the oil-water mixture system. At the same time, the sludge flocculant had a good thermal stability and a high reuse rate.