用粉末活性炭作前助凝剂提高PAC除藻效果的研究

采用烧杯搅拌实验研究了用粉末活性炭作前助凝剂提高聚合氯化铝(PAC)去除铜绿微囊藻的有效性。结果表明,单独使用粉末活性炭作前助凝剂的除藻效果并不好,而先投加20 mg/L高岭土,再将15 mg/L PAC与粉末活性炭同时投加,除浊除藻效果明显提高。考虑首先充分发挥粉末活性炭对有机物的去除能力,在除浊除藻率仍然较高的情况下,采用粉末活性炭先于高岭土2 min投加的方式,粉末活性炭的最佳助凝剂量为10mg/L。采用粉末活性炭、高岭土和FeCl3依次投加的完整助凝技术路线,除浊除藻效率最高。碱性水体比酸性水体有利于联用三种助凝剂除藻。扫描电镜(SEM)观察结果表明,采用助凝技术,藻细胞主要与高岭土无机颗粒发生凝聚,投加粉末活性炭有助于絮凝体体积增长,而在絮凝阶段投加FeCl3可使絮凝体的分维数达到1.947的最高值。联用粉末活性炭、高岭土和FeCl3是非常有效的助凝除藻新技术。

Study on the Enhanced Removal of Algae by Adding Powdered Activated Carbon in PAC Flocculation Process

The effect of Kaolin and powdered activated carbon as coagulation aid on Microsystis aeruginosa removal through PAC flocculation was studied with jar test. The results showed that powdered activated carbon used as a sole coagulation aid didn＇t contribute to M. aeruginosa removal. However, the turbidity and M. aeruginosa removal efficiency improved markedly when 20 mg/L Kaolin was added first, followed 15 mg/L PAC and powdered activated carbon were added simultaneously. It indicates that powdered activated carbon was added 2 min before Kaolin in order to utilize the adsorption capacity of powdered activated carbon to organic contaminations. The best coagulation aid dosage of powdered activated carbon was 10 mg/L. The turbidity and M. aeruginosa removal efficiency reached peak with the integrated coagulation aid route of powdered activated carbon, Kaolin and FeC13. The treat efficiency of coagulation aids was higher in alkalinous water than in acid water. It was demonstrated by SEM that algal cells coagulated mainly with Kaolin inorganic particulates. The volume of flocs increased after adding powdered activated carbon. The fractal dimension of flocs attained 1. 947 with combining use powdered activated carbon, Kaolin and FeC13. Therefore, it was advised to add powdered activated carbon, Kaolin and FeC13 in sequence to remove algae from raw water.