The cyanobacteria-bloom in raw waters frequently causes an unpredictable chemical dosing of preoxidation and coagulation for an effective removal of algal cells in water treatment plants. This study investigated the e...The cyanobacteria-bloom in raw waters frequently causes an unpredictable chemical dosing of preoxidation and coagulation for an effective removal of algal cells in water treatment plants. This study investigated the effects of preoxidation with NaOCl and ClO_2 on the coagulation-flotation effectiveness in the removal of two commonly blooming cyanobacteria species, Microcystis aeruginosa（MA） and Cylindrospermopsis raciborskii（CR）, and their corresponding trihalomethane（THM） formation potential. The results showed that dual dosing with NaOCl plus ClO_2 was more effective in enhancing the deformation of cyanobacterial cells compared to single dosing with Na OCl, especially for CR-rich water.Both preoxidation approaches for CR-rich water effectively reduced the CR cell count with less remained dissolved organic carbon（DOC）, which benefited subsequent coagulation–flotation. However, preoxidation led to an adverse release of algogenic organic matter（AOM） in the case of MA-rich water. The release of AOM resulted in a poor removal in MA cells and a large amount of THM formation after oxidation-assisted coagulation-flotation process. The reduction in THM formation potential of CR-rich waters is responsible for effective algae and DOC removal by alum coagulation. It is concluded that the species-specific characteristic of cyanobacteria and their AOM released during chlorination significantly influences the performance of coagulation–flotation for AOM removal and corresponding THM formation.展开更多
Sufficient treatment of industrial organic wastewater with high salt and large amounts of suspended particulate matter remains a challenge worldwide.In this work,a novel coagulation-flotation combined process was deve...Sufficient treatment of industrial organic wastewater with high salt and large amounts of suspended particulate matter remains a challenge worldwide.In this work,a novel coagulation-flotation combined process was developed to treat the suspended particles as well as significantly reduce organic pollutants content in the actual high-salt organic wastewater.Four typical inorganic and organic flocculants(poly aluminum chloride(PAC),poly ferric sulfate(PFS),polyacrylamide(PAM),and modified cationic starch(CS))were selected for compounding to obtain an optimized flocculation system for high-salt wastewater.The results showed that the PAC-PAM with a 10:1 ratio in mass exhibited the best coagulation behaviors with the removal efficiency of turbidity and chemical oxygen demand(COD)being 95.33%and 9.21%,respectively,under the optimal operation conditions,and the sedimentation process of coagulant conformed to the quasi-second-order kinetics.The PAC-PAM flocs exhibited stronger netting,sweeping,and adsorption bridging capabilities,which were conducive to removing suspended particles.When the flotation was conducted after coagulation,the COD decreased significantly by 20.82%.In addition,this combined process could reduce the treatment time by 50%compared to the process with only coagulation treatment.During the flotation process,floc particles companies with hydrophobic polycyclic aromatic hydrocarbons could collide and adhere to microbubbles and be floated to the surface,resulting in an effective reduction of COD.This work could provide a novel strategy and step forward to design and optimize the pretreatment process engineering for organic high-salt wastewater.展开更多
基金the National Science Council of Taiwan (No. NSC102-2119-M-002-008) for the financial support
文摘The cyanobacteria-bloom in raw waters frequently causes an unpredictable chemical dosing of preoxidation and coagulation for an effective removal of algal cells in water treatment plants. This study investigated the effects of preoxidation with NaOCl and ClO_2 on the coagulation-flotation effectiveness in the removal of two commonly blooming cyanobacteria species, Microcystis aeruginosa（MA） and Cylindrospermopsis raciborskii（CR）, and their corresponding trihalomethane（THM） formation potential. The results showed that dual dosing with NaOCl plus ClO_2 was more effective in enhancing the deformation of cyanobacterial cells compared to single dosing with Na OCl, especially for CR-rich water.Both preoxidation approaches for CR-rich water effectively reduced the CR cell count with less remained dissolved organic carbon（DOC）, which benefited subsequent coagulation–flotation. However, preoxidation led to an adverse release of algogenic organic matter（AOM） in the case of MA-rich water. The release of AOM resulted in a poor removal in MA cells and a large amount of THM formation after oxidation-assisted coagulation-flotation process. The reduction in THM formation potential of CR-rich waters is responsible for effective algae and DOC removal by alum coagulation. It is concluded that the species-specific characteristic of cyanobacteria and their AOM released during chlorination significantly influences the performance of coagulation–flotation for AOM removal and corresponding THM formation.
基金financially supported by the National Nature Science Foundation of China(No.22278251)the National Key Research and Development Program of China(No.2022YFC3901304)the Key Research and Development Plan in Shanxi(No.202102090301028).
文摘Sufficient treatment of industrial organic wastewater with high salt and large amounts of suspended particulate matter remains a challenge worldwide.In this work,a novel coagulation-flotation combined process was developed to treat the suspended particles as well as significantly reduce organic pollutants content in the actual high-salt organic wastewater.Four typical inorganic and organic flocculants(poly aluminum chloride(PAC),poly ferric sulfate(PFS),polyacrylamide(PAM),and modified cationic starch(CS))were selected for compounding to obtain an optimized flocculation system for high-salt wastewater.The results showed that the PAC-PAM with a 10:1 ratio in mass exhibited the best coagulation behaviors with the removal efficiency of turbidity and chemical oxygen demand(COD)being 95.33%and 9.21%,respectively,under the optimal operation conditions,and the sedimentation process of coagulant conformed to the quasi-second-order kinetics.The PAC-PAM flocs exhibited stronger netting,sweeping,and adsorption bridging capabilities,which were conducive to removing suspended particles.When the flotation was conducted after coagulation,the COD decreased significantly by 20.82%.In addition,this combined process could reduce the treatment time by 50%compared to the process with only coagulation treatment.During the flotation process,floc particles companies with hydrophobic polycyclic aromatic hydrocarbons could collide and adhere to microbubbles and be floated to the surface,resulting in an effective reduction of COD.This work could provide a novel strategy and step forward to design and optimize the pretreatment process engineering for organic high-salt wastewater.
