Experimental Study On The Removal Of Organic Matter By Pre-oxidation After The Return Flow Of Sludge Water From Water Supply Plants

Nowadays,the use of water resources has attracted widespread attention.As a water resource available to water supply plants,most of the current treatment methods are direct discharge,and large-scale water plants will design special sewage treatment devices;The direct discharge of sludge water will not only lead to waste of water resources,but also silt up rivers and affect the environment.There is no efficient and safe way to use sludge water.Therefore,the safe reuse of sludge water has become the focus of current research.The sludge discharge water contains a large amount of sediment,organic matter,and incomplete coagulant,and rash reflux will also cause water quality risks,so consider the application of advanced oxidation technology in the return of sludge water.Advanced oxidation method is a new type of water treatment technology developed in recent years,because of its high efficiency,wide range of application,thorough reaction and other advantages,has become a widely concerned international water treatment technology,but the removal of organic matter in sewage also has high cost,large amount of oxidant and other problems,seriously restricting the large-scale application of the technology.Although advanced oxidation technology is currently mostly used in sewage treatment,researchers have turned their attention to organic matter that is difficult to remove with conventional treatment in feed water.Therefore,it is necessary to carry out research on optimizing the synergy of sludge water reflux based on advanced oxidation technology to reduce the safety problems caused by sludge water reflux.Taking a water plant in Nanchang section of the Ganjiang River as the test object,the dosage of coagulant in the water plant,the effluent efficiency of the sludge water under different reflux ratios and different dosages was obtained,and the risks brought by the reflux of sludge water were evaluated.Taking a water plant in Nanchang section of the Ganjiang River as the test object,the dosage of coagulant in the water plant,the effluent efficiency of the sludge water under different reflux ratios and different dosages was obtained,and the risks brought by the reflux of sludge water were evaluated.In the experiment,in order to find a suitable oxidant and activate the oxidant,two activation methods were adopted:Fe²⁺solution and ultraviolet light;The oxidants selected were hydrogen peroxide（H₂O₂）,potassium peroxymonosulfate（PMS）,potassium persulfate（PDS）,and different molar ratios Fe²⁺/H₂O₂,Fe²⁺/PMS,Fe²⁺/PDS,UV/H₂O₂,UV/PMS,UV/PDS oxidation reflux after mixing water samples and combined with the effluent efficiency after coagulation process,from the number of particles in the effluent,ammonia nitrogen,nitrate nitrogen,total nitrogen and UV₂₅₄and other indicators to study and evaluate the pollutant removal effect,through the comparison of the effect of separate reflux coagulation treatment,the main substances of oxidation and the content change trend are studied,and the optimal molar ratio of various oxidation methods in the test concentration range is determined according to the test results.According to the optimal molar ratio obtained by the test,the response surface test was designed,and the three-factor three-level response surface optimization test was designed with UV₂₅₄,ammonia nitrogen and total nitrogen removal rate as the factors of coagulant dosage,oxidant and activation mode,and the removal effect of UV₂₅₄,ammonia nitrogen and total nitrogen was analyzed when the water was produced after coagulation of oxidized mixed water samples,and the test parameters were optimized.Through three-dimensional fluorescence characterization verification and Fourier transform ion cyclotron resonance mass spectrometry（ESI-FT-ICR MS）,the composition structure of DOM in water was analyzed,and the main oxidation mechanism was explored.The main findings and conclusions are as follows:1.The three-dimensional fluorescence intensity of fulvic acid and humic acid substances in the sludge discharge water of the Ganjiang River water body and the water supply plant is the largest,and the Ganjiang River water body is a natural water body dominated by self-source DOM,and the reflux of sludge water will lead to the enrichment of tryptophan substances and dissolved microbial metabolites in the raw water;For the coagulation and precipitation test of Ganjiang raw water,the optimal dosage of its coagulant can be obtained is 20mg/L,and the reflux coagulation test of sludge water with different dosage and different reflux ratios can obtain the optimal return flow of sludge water at 4%,which can play a role in strengthening coagulation,and the turbidity of the effluent is reduced but will cause the enrichment of organic matter in the water.2.According to the combination of two activation methods and three oxidants to obtain six oxidation methods to treat the effluent efficiency of mixed water samples,the dosage of oxidants obtained was Fe²⁺/H₂O₂:5/10μmol/L,Fe²⁺/PMS:5/10μmol/L,Fe²⁺/PDS:10/10μmol/L,UV/H₂O₂:5μmol/L,UV/PMS:5μmol/L,UV/PDS:5μmol/L.Through the designed response surface test data,it can be seen that for the removal of organic matter in water,various factors affect from strong to weak as oxidant,activation mode and coagulant,and the interaction level from large to small is the interaction between oxidant and activation mode,interaction between dosage and oxidant,interaction between activation mode and dosage.According to the prediction results of the response surface model and the subsequent repeated test results,the best test conditions were obtained:the removal rate of UV254 was 70.23%,the removal rate of ammonia nitrogen was 71.68%,and the removal rate of total nitrogen was 61.23%under the optimal working conditions of 22.5mg/L of coagulant,UV activation and 7.5μmol/L of oxidant PDS.3.According to the three-dimensional fluorescence spectrum and regional integration analysis of the effluent,it can be found that the response intensity of tryptophan,fulvic acid and microbial metabolites in the effluent after Fe²⁺/H₂O₂oxidation is large;After Fe²⁺/PDS oxidation treatment,the effluent not only contains fulvic acid substances,but also tyrosine components,tryptophan components,soluble microbial metabolic products and humic acid components,among which the removal effect of soluble microbial metabolic products is more significant.After the oxidation treatment of Fe²⁺/PMS,fulvic acid and humic acids,as well as tryptophan components,tyrosine components and their dissolved microbial metabolites.The fluorescence intensity of each region of UV/H₂O₂is significantly weakened,but it will cause the fluorescence response intensity of tyrosine substances to increase,and UV/PMS oxidation will also bring the same problem,and UV/PDS can generally solve the situation of organic matter enrichment in water.Similar conclusions were obtained from the quantitative analysis of FIR in the water.ESI-FT-ICR MS characterization of coagulation precipitation water after sludge water reflux and mixed water sample after UV/PDS oxidation sludge water reflux The results of coagulation precipitation treatment effluent can be seen as follows:the enrichment of organic matter brought by sludge water reflux cannot be removed by coagulation treatment,which will lead to the enrichment of lignin/CRAM,polycyclic compounds,and unsaturated hydrocarbons in the water,and the molecules in the DOM in the UV/PDS oxidation treatment water do increase the oxygen content through oxidation reaction,and lead to lignin/The carboxylic acid alibuciring molecules oxidize and cleave to form high oxygen compounds,and some of them are mineralized.