微藻絮凝条件优化及絮体结构特征研究

Study on optimization of microalgae flocculation conditions and floc structure characteristics

以小球藻为原料,通过正交实验考察了藻液浓度、凝聚剂和絮凝剂用量、pH、搅拌强度对微藻絮凝效果和絮体结构的影响。结果表明,在实验范围内,浊度去除率可达96.43%;各因素中,随着藻液浓度增加,微藻絮凝效果和絮体强度、恢复率、分形维数也随之增加;适当增加凝聚剂用量,有利于提高絮凝效果和絮体强度、恢复率、分形维数;适当增加絮凝剂用量,可提高絮凝效果,但对絮体强度、恢复率、分形维数影响不明显;在酸性条件下,絮凝效果较高,在碱性条件下絮体强度、恢复率、分形维数较高;在保证药剂充分混合条件下,减小快速搅拌时间有利于提高微藻絮凝效果,但对絮体强度、恢复率、分形维数影响不明显。综合考虑絮凝效果和絮体结构两个指标,确认藻液浓度为192 mg/L、FeCl3为40 mg/L、PAM为20 mg/L、pH为5,快速搅拌为150 r/min,1 min和慢速搅拌为50 r/min,15 min时为最优组合。

Chlorella was taken as experimental material and orthogonal experiment was used to test the effects of algae concentration, count of coagulant, count of flocculant, pH, stirring strength on microalgae flocculation effects and floc structures. The results show that the turbidity removal rate can reach 96.43% in the experimental range; among all the factors, the turbidity removal rate, floe strength, recovery rate, fractal dimension increase with the algae concentration rising. Appro- priate increase of coagulant can improve the turbidity removal rate, floc strength, recovery rate, fractal dimension. Appropriate increase of flocculant can promote the turbidity removal rate but ef- fects on floe strength, recovery rate and fractal dimension are not obvious. The turbidity removal rate is much better in acidic condition and the floc strength, recovery rate, fractal dimension are much better in alkaline condition. Reduce the fast stirring time in the reagent thoroughly mixed is better for the microalgae flocculation effect, but has slight effect on floc strength , recovery rate and fractal dimension. Taking flocculation effects and floe structures into consideration, the best combination is set as algae concentration 192 rag/L, FeCI3 40 rag/L, PAM 20 my/L, pH5, fast stirring time（150 r/min） lmin and the low stirring time（50 r/rain） 15 rain.