Development And Application Of New Ca²⁺-Containing Composite Coagulant

Water is the basis for human survival and development.With the development of society and the impact of human activities,water pollution is becoming more and more serious,and water quality safety is gradually being valued by humans.As the most common and extensive process in drinking water treatment,coagulation process has an important impact on filtration and precipitation in subsequent water treatment.In this paper,the coagulation experiment of different water samples is carried out to understand the influence of raw water quality on the coagulation process,and develop a new coagulant.In addition,according to the investigation results,the water quality characteristics,different aluminum coagulants,turbidity,floc formation,organic matter removal rate and the effect of residual aluminum after treatment were studied for the problems frequently encountered in the process of coagulation treatment of drinking water in China.In view of the disadvantages existing in the existing coagulant,the traditional coagulant AlCl₃ and polyaluminium chloride?PACl?were subjected to Ca²⁺modification treatment,and the pure kaolin system,the pure humic acid system and the humic acid protein mixed system were respectively carried out.Coagulation experiment.The turbidity,organic matter removal,residual aluminum and floc formation properties?particle size,strength factor,recovery factor and fractal dimension?were investigated.The experimental results show that PACl?polyaluminum chloride?and AlCl₃ are added in the pure particle system.Ca²⁺has no obvious effect on the turbidity removal rate.Under low dosage,it can effectively reduce the residual aluminum concentration in the post-sinking water.AlCl₃ is used as a coagulant.When the dosage is 0.10 mmol·L^-1,the residual aluminum concentration after sedimentation Reduced from 0.15 mg·L^-1 to 0.10mg·L^-1.In the humic acid system,the calcium ion in the coagulant can significantly reduce the negative charge of the humic acid molecule,reduce the residual aluminum concentration after the sinking and increase the floc size.For the humic acid and protein system,when the dosage of 0.16 mmol·L^-1 is used,when the PACl containing Ca²⁺is used as the coagulant,the presence of calcium ions increases the particle size of the flocs at equilibrium by about 50?m.Improve the sedimentation of flocs.Under alkaline conditions?pH=8.5?,the concentration of DOC in the water after the modified coagulant was reduced by 0.2⁰.6 mg·L-1,and the residual aluminum was decreased by 0.4⁰.7mg·L^-1.Under acidic conditions?pH=5.5?,the concentration of DOC and residual aluminum in the modified coagulant did not change significantly.After the coagulant modification,this article took the Baiyangdian pit pond sewage?containing algae,high ammonia nitrogen,high phosphorus water?for coagulation experiments.The turbidity,residual aluminum,ammonia nitrogen,total phosphorus,COD and DOC,floc size and organic matter removal after coagulation of coagulant before and after modification were analyzed.COD and DOC,floc size,organic matter removal,etc.,coagulant dosage is improved after 0.08-0.12 mmol·L^-1 modification,and the residual aluminum removal can be increased by 0.3 mg·L^-1,ammonia nitrogen removal can be increased by 0.4 mg·L^-1,and total phosphorus removal is increased by0.2 mg·L^-1.The DOC and COD of the coagulated effluent of the modified coagulant decreased to different extents.The particle size of the coagulated floc was affected by algae in the water,and the floc size could reach 800-1000?m.During the flocculation and flocculation process of the coagulation experiment,it was found that the strength factor and recovery factor of the flocs produced by the AlCl₃ coagulant became larger,the floc structure was more stable,the sedimentation performance became better,and the PACl coagulant floc was coagulated due to coagulation.The nature of the agent itself,the intensity factor becomes larger,and the shear resistance of the floc becomes stronger,but the recovery factor becomes smaller and the regeneration ability becomes weaker.In terms of organic matter removal,the main residual organic matter in the water is humic acid due to the specific removal of the protein in the water by the coagulant during the coagulation process,and the protein content is not high.The fluorescence response of the modified coagulant decreased from 3,500 to 3,000,and the organic matter removal rate became significantly higher.