Effect Of PAC On Content And Speciation Of Aluminum By Coagulation And Sedimentation Process In Drinking Water

The content of suspended aluminum is removed easily,and the dissolved aluminum is not in water treatment.High content of aluminum is harmful to human,and the presence of aluminum is dissolved aluminum mainly in drinking water.The toxicity of the dissolved aluminum in each component is different,and the toxicity of the dissolved organic monomer aluminum is the heaviest.Therefore,taking the influent of a water plant as the experimental sample,the jar test was used to explore the effect of coagulant dosage,pH value,process conditions of coagulation and sedimentation on the removal rate of turbidity,the speciation and content of residual aluminum in the sinking water.In particular,process conditions have an effect on content of the total dissolved aluminum,dissolved monomeric aluminum,dissolved organic aluminum and organically monomeric aluminum.The main conclusions were summarized as follows:The dosage of the PAC was 2.5mg/L,the removal rate of turbidity reached on 98% in the coagulated effluent.The use of PAC increased the amount of residual aluminum content,and the increased was dominated by suspended aluminum content.The dosage of the PAC was 0.5mg/L,the content of total dissolved aluminum,dissolved monomeric aluminum,dissolved organic aluminum and organically monomeric aluminum was lower than those in the raw water.The initial pH value was 7,the removal rate of turbidity was up to 98.32%,and the aluminum content of each speciation was lower.The removal rate of turbidity was the highest,around at 97%?98% when the rapid mixing speed was 300r/min,rapid mixing time was 2min,slow mixing speed was 50r/min,slow mixing time was 25 min.The aluminum content of each speciation was lower relatively,especially aluminum content of each dissolved aluminum when the rapid mixing speed was 300r/min,rapid mixing time was 1.5min,slow mixing speed was 40r/min,slow mixing time was 25 min.With the prolongation of settlement time,the removal rate of turbidity increased and the suspended aluminum decreased gradually.The settlement time was chosen to be 30 min depending on the costs.At the same time,the removal rate of turbidity was 97.5%,and the content of dissolved monomeric aluminum,dissolved organic aluminum,organically monomeric aluminum were the lowest.Considering the effect of aluminum content and turbidity removal,it was recommended that the rapid mixing time was 300r/min,the rapid mixing time was 1.5min,the slow mixing speed was 40r/min,the slow mixing time was 25 min,and the settlement time was 30 min.In orthogonal experiment,initial pH,slow mixing speed,settlement time,dosage of the PAC were studied.Four factors had different effects on turbidity and content of residual aluminum in sinking water.The order of influence was settlement time > pH > PAC dosage > slow mixing speed when the content of dissolved aluminum was the focus of study.The total dissolved aluminum content was the lowest as long with the dosage of PAC was 1.5 mg/L,the pH was 7,the slow mixing speed was 40 r/min,and the settlement time was 40 min.The main factor affecting the removal of turbidity was the pH value.The highest turbidity removal rate were PAC dosage was 2.5 mg/L,pH was 7,slow mixing speed was 50 r/min,and settlement time was 40 min.The results of the turbidity removal rate and the total dissolved aluminum content in the orthogonal experiment were the same as those in the third chapter and the fourth chapter.However,considering the effect of aluminum content and turbidity removal,the best value of factors: initial pH was 7,slow mixing speed was 40 r/min,settlement time was 30 min,dosage of the PAC was 2.5mg/L.