The Effect Of SS And P In Wastewater On The Coagulant Consumption And The Study On The Optimization Of Coagulant Dosing Methods

Currently,most advanced treatment units of sewage treatment plants adopt methods for the removal of suspended substance and phosphates from water by the technology of coagulation sedimentation.However,substantial numbers of sewage treatment plants have the situation that dose coagulant unreasonably.The phenomenon that effluent water quality is not up to standard and a great deal waste of coagulant are frequently caused by the overdose or a shortage of coagulant.Facing the problem that dosing coagulant unreasonably in advanced treatment units,this research confirm the competition or promotion relationship between the suspended substance and phosphate by analyzing the law of the two in the wastewater coagulation process and confirm optimal dosing way of coagulant by studying on the effect of wet distribution concentration of coagulant on effluent water in wastewater coagulation process and studying on the distribution of Al(III)at different dilution condition.This research mainly includes as follows:(A)The artificial wastewater and actual wastewater are investigated and this research analyse the law of consumption of suspended substance and phosphate on the coagulant.(B)This research make a thorough inquiry on the effect of wet distribution concentration of coagulant on effluent water by adding coagulant at different wet distribution concentration to the artificial wastewater and actual wastewater.(C)This research confirm the optimal way of confecting coagulant by changing dilution condition of Al(?)in polymeric aluminum chloride solution,includes of wet distribution concentration,dilution time,pH and dilution temperature.The test results show that:(?)The influence on the consumption of suspended substance and phosphate on the coagulant in wastewater coagulation processWhen the coagulant dosage is 6mg/L,the consumption of coagulant in artificial wastewater contained only P(fitting equation figures out)-the consumption of coagulant in artificial wastewater contained P and SS = 20.28-10=10.28mg/L.The consumption of coagulant in artificial wastewater contained only SS(fitting equation figures out)-the consumption of coagulant in artificial wastewater contained P and SS = 31.14-21=10.14 mg/L?The difference between above number is small,shows that the process for removal of SS and the process for removal of phosphate are completed independently,but they are to promote mutual relations.(?)The effect of wet distribution concentration of coagulant on effluent waterWithin 2%~20% wet distribution concentration,when the PAC dosage is the same,phosphate removal rate showed a decreasing trend with the increase of wet distribution concentration of coagulant.When the coagulant dosage is 1 mg/L,2% wet distribution concentration of PAC has a removal rate of P at 27%,but 20% wet distribution concentration of PAC only has 19%.When the coagulant dosage is 2 mg/L,2% wet distribution concentration of PAC makes SS decreased to 9.53 NTU,but 20% wet distribution concentration of PAC makes SS decreased to 37.36 NTU.Within 2%~30% wet distribution concentration,when the FeCl3 dosage is 4 mg/L,2% wet distribution concentration of FeCl3 makes P declines to 1.5 mg/L,but 30% wet distribution concentration of FeCl3 only makes P declines to 2.67 mg/L.When the coagulant dosage is 2 mg/L,2% wet distribution concentration of FeCl3 makes SS decreased to 23 NTU,but 30% wet distribution concentration of FeCl3 makes SS decreased to 70 NTU.(?)The form distribution of Al(?)in polyaluminium chloride solution under different dilution conditions:(1)With the increase of wet distribution concentration,the percentages content of Ala is basically unchanged(0.04-0.07)under wet distribution concentration of 2%-15%.However,when increasing the wet distribution concentration to 20%,the percentage content of Ala drops sharply from 0.07 to 0.02.The percentage content of Alb basically presents a descending trend from 0.2 to 0.1.The percentage content of Alc basically maintains the level of 0.75 to 0.9,being the dominant form of the total aluminum.(2)Within 8h dilution time,the percentages contents of Ala,Alb and Alc maintain at relatively stable conditions.During 8h to 24 h,the percentage content of Ala increases from 0.06 to 0.14,the percentage content of Alb decreases from 0.2 to 0.06 and Alc is the dominant form of the polyaluminium chloride solution without being significantly affected by dilution time,maintains at 0.75~0.76.(3)Under the pH of 4.5-8.5,the percentages contents of Ala,Alb and Alc are basically unchanged,maintain as 0.25,0.21 and 0.54 respectively.When pH value is larger than 8.5,the percentages contents of Ala and Alb drop gradually from 0.21 to 0.06 and from 0.21 to 0.15 respectively,while the percentage content of Alc increases drastically from 0.55 to 0.78.(4)With the rising of temperature(4~25?),the percentage content of Ala grows gradually from 0.06 to 0.18,showing an ascending range of 200%;the percentage content of Alc decreases from 0.73 to 0.51 with a drop of 30%;while the percentage content of Alb increases slightly with temperature from 0.20 to 0.3.