| Condensant and powder activated carbon are widely used in surface water treatment because of the removal effect of organic matter in water.In this study mainly adopts two processes: coagulation and powdered activated carbon adsorption.Ferric chloride and polyaluminum chloride are selected as coagulants,and powdered activated carbon is selected to treat the raw water in the upstream of the Yellow River.Firstly,the coagulation effects and water treatment characteristics of the two coagulants at different dosages are compared and studied.Then,the adsorption effects and characteristics of organic matter by powdered activated carbon at different dosages and adsorption times are discussed.Finally,the combined use of powdered activated carbon and coagulants is analyzed and compared,and the removal characteristics of organic matter are compared before and after coagulation when adding powdered activated carbon.Based on the results of this study,the following conclusions were drawn:(1)The turbidity of the raw water in the upper reaches of the Yellow River varies greatly,with a maximum of 1019.8 NTU and a minimum of only 9.3 NTU.The organic matter content is relatively low,and the variation range is small.The CODMn value is between0.25-3.25 mg/L.The integral volume values of humic acid-like and fulvic acid-like organic matter are 23.82% and 49.58% of the total integral volume,respectively.It can be seen that the river is less polluted,and the dissolved organic matter is mainly from endogenous sources,which is more affected by endogenous release,and the degree of organic matter humification is relatively high.The a(260)value,which characterizes the hydrophobic components of dissolved organic matter in the raw water,is 5.21m-1,and the a(280)value,which characterizes the aromatic organic matter content,is 3.59m-1.The self-purification effect of the Yellow River water body has a certain adsorption and migration effect on some land-based organic matter.(2)Using ferric chloride and polyaluminum chloride as coagulants to treat the raw water from the upper reaches of the Yellow River,the removal efficiency of turbidity,CODMn,DCODMn,and UV254 will increase with the increase of the dosage.When the dosage of polyaluminum chloride is 60mg/L,turbidity slightly increases.The two coagulants have selectivity in the removal of organic matter: at lower dosages,they tend to remove humic substances with strong hydrophobicity and a higher content of aromatic rings,and polyaluminum chloride has a better removal effect on organic matter in various regions of three-dimensional fluorescence.With the increase of dosage,the proportion of organic matter with higher molecular weight,higher degree of condensation,and deeper humification decrea ses slowly.When the dosage is greater than 30mg/L,due to the higher dosage,its removal pro portion increases.When the dosage is greater than 40mg/L,ferric chloride has a better remova l effect on humic acid-like organic matter,and at a dosage of 60mg/L,ferric chloride has a ver y good removal effect on tyrosine-like,tryptophan-like,and fulvic acid-like organic matter.(3)Different dosages of powdered activated carbon were used to treat the upstream Yellow River raw water with varying adsorption times.The removal efficiency of DCODMn and UV254 by powdered activated carbon increased with increasing dosage and adsorption time.The removal effect of organic matter was selective with different dosages and adsorption times: at lower dosages and shorter adsorption times,organic matter with smaller molecular weight and lower degree of condensation tended to be adsorbed.At a dosage of5mg/L,the removal effect on protein-like and fulvic-like organic matter was better.With increasing dosage and prolonged adsorption time,the adsorption proportion gradually decreased,while the removal effect of organic matter with stronger hydrophobicity and more aromatic rings gradually increased.At dosages greater than 20mg/L,the removal effect was better for organic matter with deeper humification degree.At dosages greater than 40mg/L,the removal rate of humic acid-like organic matter was higher than that of fulvic acid-like organic matter.At dosages greater than 200mg/L,the removal rate of microbial metabolic products was higher than that of tryptophan-like organic matter.Powdered activated carbon was also combined with coagulants,which not only reduced the water treatment load of single coagulation or single adsorption,but also improved the removal effect of organic matter.At lower dosages of coagulants and powdered activated carbon,the removal effect was more significant when the powdered activated carbon was added later than when it was added first.At higher dosages,both combinations of water treatment process with powdered activated carbon,either added before or after coagulation,could fully exert their advantages and the difference in organic matter removal efficiency was not significant. |
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