Study On Parametric Variation Of ORP In Coagulation And Fe~0 Pretreatment

Coagulation process is currently an economical,effective water treatment technology,which commonly used for water supply and wastewater treatment.As a measurement in water treatment,oxidation reduction potential?ORP?is used to characterize the oxidation capacity of solution.It has many advantages such as low cost,simple operation method,rapide test and on-line measurement.The aims of this research were to establish a quantitative relationship between ORP and charge density,removal efficiency as well as poly aluminum chloride?PAC?dosage,and discussing the dominant effect of adsorption charge neutralization and sweep flocculation on the coagulation treatment of high-turbidity and high-color wastewater by experiment studying the variation law of ORP and other relevant parameters in coagulation and zero-valent iron?Fe⁰?pretreatment.High-turbidity,high-color and organic wastewater were simulated respectively,with PAC as a coagulant,kaolin,direct black dye and humic acid as materials.By coagulation and agitation experiments,the influences of PAC dosage,charge density and basicity in kaolin and dye solutions on solution removal efficiency and ORP under the same PAC basicity and different PAC dosage,as well as under the same PAC dosage and different PAC basicity were researched;then by experiment studied the relationship of PAC and Fe⁰on humic acid solution removal and ORP.The main conclusions are shown as follows:In kaolin and dye solutions,PAC dosage is correlated with solution removal efficiency and absolute ORP slope,both of which increase with PAC dosage increasing.In the kaolin solution,absolute ORP slope and turbidity removal efficiency conform to an exponential relationship?y=a-b·c^x,the coefficient of correlation,R,is between 0.9756and 0.9934?under the same PAC basicity and different dosage;turbidity removal efficiency increases with basicity increasing under the same PAC dosage and different basicity.In the dye solution,absolute ORP slope and color removal efficiency conform to a linear relationship?y=a+bx,the coefficient of correlation,R,is between 0.9070 and 0.9854?;charge density and absolute ORP slope conform to a logistic model relationship?the coefficient of correlation,R,is between 0.9026 and 0.9929?under the same PAC dosage and different basicity,while charge density and color removal efficiency conform to a power function relationship[y=a?1+x?^b,the coefficient of correlation,R,is between0.8949 and 0.9805].Absolute ORP slope changed slightly when humic acid was treated by PAC only.The removal rate of A206 and UV254 was 89.4%and 91.2%respectively,while that of COD was28.72%.When humic acid was treated by Fe⁰ alone,the removal rate of COD reached71.18%,enhancing the biodegradability of humic acid,the removal rate of A206 and UV254was 12.45%and 12.53%respectively,and absolute ORP slope and Fe⁰ quality conform to an exponential relationship[y=1.377-1.865e^?-x/0.145?,the coefficient of correlation,R=0.9997].When PAC/Fe⁰ were adopted for humic acid treatment,ORP changed to an extent basically the same as that when only Fe⁰ was used.The removal rate of A₂₀₆ and UV₂₅₄ reached 92.33%and 92.01%respectively,and that of COD reached 90.53%,further enhancing the biodegradability of humic acid.Based on the above experimental studys,this paper holds that both charge neutralization and sweep flocculation have effects on the coagulation of kaolin and dye solutions,but the latter has greater effects on kaolin solution,while the former has greater effects on dye solution.The effect of Fe⁰ on the ORP of humic acid solution increased exponentially,and COD removal rate could be increased significantly.