Preparation Of Embedded Flocculant And Its Application In The Treatment Of Harmful Algal Water

With the rapid development of cities around Chaohu Lake,the eutrophication degree of Chaohu Lake is also increasing.Especially in summer,with the emergence of water blooms in Chaohu Lake,a common phenomenon is that a large number of phytoplankton grow rapidly,often forming algae and multiplying rapidly.A large number of algae cells and their toxic metabolites lead to water quality degradation and a series of serious water environmental problems,which have seriously threatened the safety of regional ecosystems and drinking water.Flocculation precipitation is the most common and widely used algae-removal process in algae-water separation station,which can effectively remove blue-green algae cells in algae-water.On the basis of investigating the removal effect of six different single flocculants on blue-green algae in Chaohu Lake,this paper selected the flocculants with better effect for the preparation of embedded flocculants,and characterized the prepared embedded flocculants and flocs by XRD,SEM and EEM to evaluate the damage of blue-green algae cells.The laboratory simulation study on the removal effect of embedded flocculants on the high algal water in Chaohu Lake was carried out,and the effects of the ratio of three kinds of embedded flocculants,algal density,settling time,p H and other factors on the removal effect of algal cells were investigated.The best process parameters for the removal efficiency of embedded flocculants on algal cells were obtained by analyzing the removal rate of algal cells,Zeta potential and the removal effect on the size of algal cells,It is also applied to the removal of blue algae in the algal water separation station of Changlin River.In addition,the mechanism of the action of the embedded flocculant on cyanobacteria cells was also discussed.The main findings are as follows:(1)Under the condition of rapid stirring speed of 300 r/min and time of 1 min,the optimization results of coagulation conditions for a single flocculant are as follows:the dosage of polyaluminum chloride(PAC)is 0.12 g/L,and the static precipitation time is 80 min;The dosage of ferric sulfate is 0.12g/L,and the static precipitation time is 120 minutes;The removal efficiency of iron chloride was 94.12%,92.05%,and 92.38%,respectively,when the dosage of iron chloride was 0.10 g/L and the settling time was 80 minutes.(2)Using three kinds of embedded flocculants to treat Chaohu Lake blue-green algae high algae water,the optimal flocculation optimization results are as follows:when the ratio of PAC-PAM embedded flocculant is 5:1,and the static sedimentation time is 100 minutes,the blue-green algae removal rate reaches 99.87%;The algae density has a significant impact on the removal of algae cell density.In a tenfold diluted algae solution,the removal effect of blue algae cells is only 38.16%,while the removal effect of blue algae original solution is the best.(3)The three groups of embedded flocculants can achieve good removal effects for suspended particles with large particle sizes in the original liquid,but the particle size distribution in the supernatant added with PAC-PAM embedded flocculant is the smallest,with a particle size distribution between 0.5 and 1.1 nm;According to Zeta potential analysis,the Zeta potential values of the three embedded flocculants under weak acidic conditions are lower than those under alkaline conditions.Among them,using PAC-PAM embedded flocculants has the lowest Zeta potential and the best flocculation effect.(4)Through scanning electron microscope analysis,after adding PAC-PAM embedded flocculant flocculant,the blue algae cells were completely removed from the algae water,while the other two groups of blue algae cells also maintained a plump shape,but with fewer wrinkles and cracks;According to the fluorescence spectrum analysis,the three groups of flocculants have good removal effects on extracellular organic matter,but the addition of PAC-PAM embedded flocculants produces the least soluble metabolic substances and humic substances.(5)The practical application of PAC-PAM embedded flocculant in algae water separation stations has shown significant effects,with a removal rate of over 99% of algae cells.The water quality at the outlet has been further purified,ensuring water safety and reducing operation and maintenance costs by 23.6%.It can play a good role during the blue-green algae bloom period.