以聚合氯化铝(PAC)为絮凝剂,高岭土和铁盐(FeCl3)为助凝剂,研究去除水中铜绿微囊藻的适宜条件。结果表明,高岭土作前助凝剂、氯化铁作后助凝剂时,可显著提高PAC去除铜绿微囊藻的效果。PAC投加前将高岭土混匀在原水中,在絮凝阶段投加氯化铁后絮凝体体积增大,沉降速度明显加快。实验室条件下,氯化铁宜在絮凝开始后第3min投加,适宜投加量为1mg/L。研究表明,氯化铁作后助凝可使叶绿素a的去除率达94.07%,而且去除效果受水体pH值的影响变小。
This paper takes its aim at finding the optimal way of removing Microcystis aeruginosa, a kind of frequently accounted alga in eutrophic waters, through PAC flocculation with FeCl3 and kaolin as sub-flocculant. As a kind of alga in eutrophic waters, Microcystis aeruginosa tends to release toxic extracellular polymers during its telophase growth. Therefore, we have chosen it as the model algae to evaluate algae removal efficiency through enhanced flocculation. As a matter of fact, our experiments have been done, which enabled us to find polyaluminum chloride (PAC) used as a superior flocculant to FeCl3 and PFS in alga removal at the same dosage. However, the removal efficiency of M. aeruginosa through PAC can be remarkably improved with the help of kaolin as pre-coagulant aid. When 20 mg/L kaolin and 15 mg/L PAC were added in the sequence when mixed uniformly into the sample, it was found that the removal efficiency of Chla turned to be speeded up to 82.34%, whereas the residue turbidity was found to drop to 2.0 NTU. In addition, if PAC was used as a main flocculant with kaolin and FeCl3 as pre- and postflocculant aids, it was possible to neutralize the charge with FeCl3 added. Moreover, increase of the volume of FeCl3 also resulted in speeding up the floc-sedimentation. It is thus suggested that FeCl3 could be added in 3 min after flocculation with 1 mg/L as an optimum dosage. And, finally, the effects of pH value could be evaluated in the range of 5 -9 on M. aeruginosa removal through PAC flocculation. Therefore, the results of our experiments have shown that the effects could be expected to get minimized while satisfied results could be obtained with FeCl3 used as post-flocculant aid. Furthermore, since kaolin is one kind of clay, which can be found almost everywhere, the method we propose here is highly promising for its low cost and high efficiency.