Study On Flocculation Removal Of Cyanobacteria In Water And Utilization Of Algal Sludge

Cyanobacteria is a worldwide water environment problem,its large-scale outbreak can seriously affect the water ecosystem.In recent years,the in situ flocculation separation of cyanobacteria in water near its explosive site has been gradually popularized and applied in eutrophic lakes.The effluent is stable and reaches the standard,but a large amount of cyanobacterial sludge containing flocculants is produced,which is easy to cause secondary pollution to the environment.Therefore,while studying the efficient removal of cyanobacteria in water,it is of great practical significance and broad application prospect to seek an effective,harmless and resource utilization method to turn cyanobacteria sludge into treasure.Based on a large number of experimental studies and ecological research,this paper focuses on the following aspects.First,using polyaluminum chloride（PAC）,polyferric sulfate（PFS）and polyacrylamide（CPAM）are used as flocculants to separate cyanobacteria from water.The optimal conditions for flocculating cyanobacteria in water with certain cyanobacteria concentration are studied.Secondly,cyanobacteria sludge is used as the raw material of biochar,and its rich organic matter is used to prepare stable carbon fixing material-cyanobacteria sludge biochar（CB）,which reduces the release of a large amount of CO₂ greenhouse gases due to the degradation of cyanobacteria by microorganisms.Meanwhile,because the surface of cyanobacteria sludge biochar contains rich functional groups,it can be used as an excellent adsorbent for pollutants such as lead,chromium,malachite green and sulfamethoxazole.Based on the static batch adsorption experiments,using organic elemental analyzer（EA）,scanning electron microscope（SEM）,Fourier transform infrared absorption spectroscopy（FTIR）,X-ray diffraction（XRD）and nitrogen isothermal adsorption curve of stripping of cyanobacteria mud biochar analysis of the physical and chemical properties were characterized.To study the adsorption capacity of cyanobacterium sludge biochar for pollutants and explore its adsorption mechanism Finally,the equivalent concentration of flocculant and biochar extract of cyanobacteria sludge were used as culture medium respectively to explore the effects of their application on corn seed growth and root tip cells in the environment,and explore the potential ecological risks of the above flocculants and biochar application in cyanobacteria sludge.The conclusions drawn from the above research are as follows:（1）It was found that a single flocculant had a good removal effect under specific process conditions,and PAC reached 91.96%removal effect under the best process conditions.The removal effect of PFS reached 90.22%under the optimal process conditions.Under the best process conditions,the removal effect of CPAM reached89.65%.After the combination of PAC and CPAM,the effect of removing algae increased to 92.80%.Under the combined condition of PFS and CPAM,the algae removal effect was increased to 93.35%.Under the combined condition of PAC and PFS,the dealgal effect could be increased to 96.70%,and the dealgal effect was obviously improved after the combination.（2）Characterization analysis:specific surface area analysis（BET）confirmed that oxygen restriction at high temperature could increase the specific surface area and pore size of the material.Scanning electron microscopy（SEM）showed that porous materials could be formed by limiting oxygen at high temperature,which was convenient for adsorption.Infrared spectrum analysis（FTIR）showed that functional groups such as-OH,-CH₂ and C=O were formed on the surface of cyanobacteria sludge after oxygen restriction at high temperature.X-ray energy spectrum（XRD）shows that the treated cyanobacteria sludge is favorable to the adsorption reaction.In summary,the preparation of biomass materials from cyanobacteria sludge is an effective way to transform resources.（3）Study on the adsorption performance of biomass materials（CB）prepared from cyanobacteria sludge to typical pollutants in water.The experimental results show that the quasi-second-order kinetic equation and Langmuir isothermal adsorption model are more appropriate to describe the adsorption process of CB to lead,and the adsorption capacity of Pb is higher（62.36 mg/g）when p H=5.The quasi second-order kinetic equation and Langmuir isothermal adsorption model are in good agreement with the Cr（Ⅵ）adsorption process,and Cr（Ⅵ）has a higher adsorption capacity（19.29 mg/g）when p H=2.The quasi second-order kinetic equation and Langmuir isothermal adsorption model can better describe the adsorption of CB to malachite green,and the adsorption capacity of MG is higher（747.9 mg/g）when p H>6.The quasi-second-order kinetic equation and Frundlich isothermal adsorption model were consistent with the adsorption process of sulfathoxazole by CB,and the adsorption capacity of SMX was higher（10.66 mg/g）when p H=7.Cyanobacterial sludge biochar has good adsorption performance in pollutant adsorption.（4）Different flocculant solutions had no significant toxic effect on the root shoot growth of maize seeds in the short term,but the root tip cells were damaged to different degrees.Biochar extracts prepared at different carbonization temperatures had no obvious toxicity on the root shoot growth of maize seeds in the short term,but the root tip cells were slightly damaged.The short-term use of algal flocculant and cyanobacterial sludge biochar has no significant impact on the environment,but its long-term ecological risks cannot be ignored.Meanwhile,the high temperature carbonization of cyanobacterial sludge is an effective way to reduce environmental risks before resource utilization.