Preparation Of Bioflocculant And Its Performance Research

Flocculant-producing bacteria were isolated mainly from the air and activated sludge. After secondary screening, three strains that had higher and stable flocculating activity were obtained and they were named as M-2, M-3, G-3, respectively. M-2 strain was identified as Bacillus and M-3 strain was identified as Micrococcus Cohn. With M-3 strain as an example, Experimental results indicate that corn meal and soybean powder were the optimum carbon and nitrogen sources, respectively. Optimal cultivating conditions of M-3 strain were shown as follows: cultivating temperature 30℃, initial pH of culture medium 8.5, cultivating time 36 or 60 hours and shaking speed 160 rpm. Flocculating activity was tested for the flocculant made from M-3. The results show that the flocculant made from M-3 has higher flocculating activity and preferable thermal stability and acid-alkali stability and belongs to extracellular biopolymeric flocculants. The optimal pH value of kaolin suspension is 9.0, and there was wider range of concertration with higher flocculating activity. The optimal flocculant's concentration is 1mL/100mL. Effects of metallic ions on flocculating activity were studied. The results show that Ca2+ is the best aiding coagulant and its optimal concentration is 4mL/100mL for 1% CaCl2 solution.Composition of the crude flocculant was studied by color reaction of polysaccharideand protein, UV-spectrophotometry and infrared absorption spectroscopy. The proportion of the polysaccharide is 75.38% and no protein is present. The flocculant was anionic polymer flocculant of polysaccharide. Flocculating mechanism was mainly adsorption bridging and charge neutralization from above studying.The crude flocculant performance was studied in the papermaking wastewater, carton wastewater and power plant wastewater. The effects of hydraulic mixing time, flocculant volume, the volume of CaCl2 solution and pH values factors on coagulation were studied. The best treatment conditions were determined by orthogonal test and some water quality index were monitored to evaluate the flocculant effect in these wastewater treatment processes. Single bacterium bioflocculant was studied in papermaking wastewater treatment. In the condition of pH value of 12, the flocculants volume of 7mL, the CaCl2 solution (1%) volume of 5mL, the flocculation rate was 98%, the removal rate of COD was 59.95%, and the removal ammonia-nitrogen was more than 96%. For application of compound bioflocculant in papermaking wastewater, the results show that the flocculation rate was 85.4% and its comprehensive effect was less than single bacterium bioflocculant. Combination of bioflocculant and traditional flocculants was also studied in papermaking wastewater treatment. It has good results with polyaluminium chloride(PAC)as traditional flocculants. The result showed that the flocculation rate was 97%, the COD removing rate was 67.1% , and the removal ammonia-nitrogen was 95.81% , in the condition of the PAC volume of 0.3mL, the flocculants volume of 4mL, the CaCl2 solution volume of 6mL and the pH value of 11. For application of single bacterium bioflocculant in carton wastewater treatment, the flocculation rate was 92.6%, removal rate of COD was 60.74% ,and the removal ammonia-nitrogen was more than 89%, in the condition of the pH value of 9, the flocculants volume of 9mL,the CaCl2 solution volume of 8mL. For application of compound bioflocculant in carton wastewater, the research showed the flocculation rate was 98%.The removal rate of COD was 59.30% ,and the removal ammonia-nitrogen rate was more than 96% , in the condition of the pH value of 12, the flocculants volume of 7mL, the CaCl2 solution volume of 5mL. Dosage of single bacterium bioflocculant was less than that of compound bioflocculant,but it had higher flocculating activity.For combination of bioflocculant and PAC in carton wastewater, the result showed that the flocculation rate was 95.7%,the COD removing rate was 60.7% ,and the removal ammonia-nitrogen was more than 90% , in the condition of the PAC volume of 0.4mL, the flocculants volume of 5.5mL ,the CaCl2 solution volume of 4mL and the pH value of 9.For single bacterium bioflocculant used in power plant wastewater treatment, in the condition of pH value of 12, the flocculants volume of 6mL, the CaCl2 solution (1%) volume of 4mL, the study showed the flocculation rate was 96.3%, the removal rate of COD was 65.5%,but it had the low removal ammonia-nitrogen rate.