Ca^(2+)在饮用水铜绿微囊藻控制中的应用

Application of calcium ions for the control of Microcystis aeruginosa in drinking water treatment works

为改善饮用水藻类的混凝去除效果,以铜绿微囊藻为研究对象,考察了单独投加Ca^(2+)、Ca^(2+)与PAC联用、Ca^(2+)与CO_(3)~(2-)原位结晶三种方法的除藻效果,并对Ca^(2+)和结晶产物CaCO_(3)的除藻机制进行探讨.结果表明,单独采用Ca^(2+)时,Ca^(2+)在低浓度下对藻细胞具有吸附电中和作用,高浓度时同时还有架桥作用,但两者均无法实现对铜绿微囊藻的去除.Ca^(2+)与PAC联用,Ca^(2+)可以通过吸附电中和显著提高PAC的除藻效果,最大去除率可达98.0%,同时Ca^(2+)与溶解性藻源有机物(dAOM)的络合可将残余铝降低50%以上.含藻水中原位CaCO_(3)结晶对铜绿微囊藻的去除率最高可达83.5%,其产物为带正电荷、粒径2~4μm左右的球型球霰石.球霰石对藻细胞的去除机制包括球霰石与藻细胞的互絮凝,以及球霰石团聚物对藻细胞的卷扫絮凝,同时球霰石还可以作为加重剂促进藻晶产物沉降分离.自来水厂采用CaCO_(3)原位结晶与PAC联用除藻,可望降低PAC投加量和残余铝风险,并解决CaCO_(3)原位结晶导致的浊度和pH偏高问题.研究成果为饮用水除藻提供了新思路.

In order to improve the flocculation removal effect of algae in drinking water treatment works,taking Microcystis aeruginosa as the research object,the algae removal effects of three methods:Ca^(2+)alone,Ca^(2+)combined with poly-aluminum chloride(PAC),and Ca^(2+)and CO_(3)2-in-situ crystallization were investigated.The algae removal mechanism of Ca^(2+)and the crystalline product CaCO_(3) are discussed.The results show that when Ca^(2+)was used alone,Ca^(2+)had an adsorption and electric neutralization effect on algae cells at low concentrations,and a bridging effect at high concentrations,but both can not achieve the removal of Microcystis aeruginosa.Ca^(2+)combined with PAC,Ca^(2+)could significantly improve the algae removal effect of PAC through adsorption and electric neutralization,and the maximum removal rate could reach 98.0%.At the same time,Ca^(2+)could aid in the decrease of residual aluminum of PAC coagulation by complexation with dissolved algae organic matter(dAOM),which could reduce the residual aluminum by more than 50%.The removal rate of Microcystis aeruginosa by in-situ CaCO_(3) crystals in algae-containing water could reach up to 83.5%,and the product was positively charged vaterite with a particle size of about 2 to 4μm.The removal mechanism of vaterite to algae cells includes mutual flocculation of vaterite and algae cells,as well as the sweeping flocculation of vaterite aggregates to algae cells.At the same time,vaterite could also be used as a weighting agent to promote the sedimentation and separation of algae crystal products.The use of in-situ crystallization of CaCO_(3) and PAC to remove algae in water plants was expected to reduce the dosage of PAC and the risk of residual aluminum,and solve the problem of turbidity and high pH caused by in-situ crystallization of CaCO_(3).The research result provides new ideas for algae removal in drinking water.