| With the improvement of environmental standards, shortcomings of traditional sludge treatment methods gradually appeared. Therefore, the reclamation of sludge has become an effective way to solve the problem of sludge disposal. Sludge is mainly composed of intracellular and extracellular proteins, polysaccharides and other organic matters. The proteins and polysaccharides excreted outside the cell were the active substances of bioflocculants repaired by traditional fermentation method. Based on consideration of resource reclamation, this study applied sludge as a raw material for preparing bioflocculant and provided a new way for the bioflocculant preparation.Sludge bioflocculant preparation method was determined by comparing the flocculating activity of hydrolysates under different conditions. The activities and applied range of the sludge bioflocculant were characterized. And the flocculating mechanism was investigated. The following findings were made:(1) Respectively using ultrasonic technology, combined technology (dilute hydrochloric acid+ultrasonic), only using dilute hydrochloric acid technology extract the ingredients with flocculating activity in the sludge. And these three methods had carried on the comparative study. The results showed that using the sludge bioflocculant which were prepared by three extraction methods, to flocculate kaolin suspension, flocculation efficiency was 30.0%,95.0% and 30.0% at pH 3.0 to 9.0 respectively. The amount of dilute hydrochloric acid as extraction agent had no significant effect on preparation of flocculant.(2) Sodium hydroxide solution and ethanol were used to divide and dry the SBF into three pure parts SBF-1-SBF-3. Studied the pure SBF (SBF -1, SBF -2, SBF -3) on the flocculation effect of starch wastewater and Congo red dye wastewater. Results showed that when pH=6.0-10.0, SBF-1 and SBF-2 had good flocculation effect to the starch wastewater, the SBF-2 could be effectively to treat the starch wastewater and the flocculating rate could reach more than 98.5% especially. Sludge bioflocculant could also flocculate the starch granules which is a typical water swelling particles particle. When pH of flocculating system is 9.0, the treatment of Congo red wastewater was put forward by using SBF-1,SBF-2 and SBF-3 as flocculant, the flocculating rate was respectively 97.4%,90.5%,82.7%, COD removal rate could reach 100%. Sludge bioflocculant which have a positive charge had good flocculation effect to treat acid dyes wastewater. As could been seen from de flocculation test of SBF on methylene blue wastewater, when the range of pH is 2.0-12.0, SBF had no flocculation effect for the methylene blue wastewater treatment. These showed that sludge bioflocculant could not treat the cationic dye. (3) Studied the SBF on the flocculation effect of organic wastewater. When the pH of flocculation system is 4.0-8.0,12.0mL SBF for simulative oily wastewater achieved good flocculation effect, both flocculating rate and COD removal rate were up to 93.0%. When the pH value is 4.0, SBF dosage was 4.0 mL/120.0mL, for the p-nitro phenol wastewater flocculating rate was up to 41.6%. As a result, sludge bioflocculant had a good effect in oil-water mixture system, but for water-soluble organic wastewater, purify the effect is not obvious.(4) Studied the SBF on the flocculation effect of heavy metal wastewater. When the pH of flocculation system is 5.0, the maximum flocculating rate 30.6% was observed when the SBF dosage was 6.0mL/100.0mL, coagulant aid CaCl2 dosage was 1.5 mL/100mL at the same time. SBF for heavy metal wastewater such as potassium dichromate had no flocculation effect. |
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