深水循环混凝沉淀处理含铜绿微囊藻原水的效果和机理研究

The performance and mechanisms of Microcystis aeruginosa-laden water treatment by deep water circulation following coagulation and sedimentation

为了探明深水循环混凝沉淀工艺处理含藻水的效果和机理,采用U形管模拟深水循环装置对含有铜绿微囊藻的原水进行预加压,再进行混凝沉淀处理,测定了40~80 m深水循环混凝沉淀的处理效果,探究了深水循环除藻机理,并评价了水质安全性.结果表明：随着循环深度的加大,深水循环混凝沉淀效果越好;在投药量30 mg·L-1时,60~80 m深水循环混凝沉淀对藻类去除率达到95%以上,浑浊度小于1.6 NTU,处理效果比原水直接混凝沉淀、预氧化混凝沉淀显著提高.深水循环利于藻类去除的机理是,藻细胞内气囊受深水水压作用而坍塌破裂,气囊内气体透过细胞壁扩散进入水中,藻体失去气囊浮力,由上浮转而下沉.深水循环及混凝沉淀阶段水中的藻毒素、DOC均未增加,说明深水循环混凝沉淀工艺处理含藻水是安全的.

In order to investigate the performance and mechanisms of deep water circulation,coagulation and sedimentation for Microcystis aeruginosaladen water pretreatment,the U shaped tube was first used to simulate the deep water circulation device with water depth of 40 ~ 80 m,and the safety of the water quality was evaluated.Results show that with the increase of circulation depth,the performance of the overall treatment is improved.When the coagulant dose is 30 mg·L-1and the circulation depth is up to 60 ~ 80 m,the deep water circulation could increase the removal efficiency of Microcystis aeruginosa to more than 95%,and the turbidity of the effluent is lower than 1.6 NTU.This treatment efficiency is better than those of the direct coagulation and sedimentation process and the pre-oxidation coagulation and sedimentation process.The mechanism of Microcystis aeruginosa treatment by deep water circulation is that：with the pressure of deep water,the gas vesicles of Microcystis aeruginosa are collapsed or broken and the gas diffuse out of the cells,which leading to the Microcystis aeruginosa lose buoyancy and turn sinking but not floating.However,the cells of Microcystis aeruginosa are not broken after deep water circulation,and the microcystins and DOC do not increase any more,which indicates the process of deep water circulation following coagulation and sedimentation is safe for the treatment of Microcystis aeruginosa-laden water.