二氧化氯预氧化对藻类絮体形态的影响

针对高含藻高含盐杨埕水库原水藻类特征,采用聚合氯化铝(PAC)、硫酸铝(AS)、聚合硫酸铁(PFS)和氯化铁(FC)4种混凝剂进行混凝除藻试验,用图像法对藻类絮体的分形维数进行测定,分析混凝剂种类及投量、二氧化氯投加量等因素对混凝除藻效果及藻类絮体形态的影响。结果表明,杨埕水库夏季藻类种属相对较为单一,以小型色球藻、微小平裂藻、不整齐蓝纤维藻为优势藻类;4种混凝剂的除藻性能优劣依次为:AS>PAC>PFS>AC。在AS最佳投加量(以Al2SO4计)70 mg/L下,藻类的去除率为85.3%。此时,杨埕水库夏季藻类以藻类絮体分形维数值为1.54,形成的絮体密实且沉降性好。以AS为混凝剂,投加量为70 mg/L下,二氧化氯投加量为0.8 mg/L时助凝效果最好,藻类的去除率比单独投加AS时提高了6.3%,藻类絮体分形维数值为1.71,形成的藻类絮体更加密实。二氧化氯过量投加无益于藻类去除。

Effect of Chlorine Dioxide Preoxidation on the Morphological Characteristics of Algae Floc

Coagulation tests for removing algae in high algae-laden and saline raw water in Yangcheng Reservoir were performed using polyaluminium chloride(PAC),aluminum sulfate(AS),polymeric ferric sulfate(PFS)and ferric chloride(FC)respectively.Fractal dimension was measured by image analysis.Effects of coagulant types and dosages,chlorine dioxide preoxidation on coagulation efficiency and morphological characteristics of algae floc were studied.Results showed that the algae in the Reservoir in summer were single-species with predominant species as Chrococcus mino,M.minima and Dactylococcopsis irregularis.The performance of the coagulants for algae removal from high to low was AS,PAC,PFS,AC.Under the optimum dosage of AS coagulant as Al2SO4 70 mg/L,the removal efficiency of algae was 85.3%,and the fractal dimension of algae floc was 1.54 at the optimum dose and the flocs had density and good sedimentation velocity.Removal efficiency and the fractal dimension enhanced by 6.3% when chlorine dioxide was dosed 0.8 mg/L and fractal dimension was 1.71.Overdose of chlorine dioxide has little benefit on algae removal.