Pilot-scale Study On Heterogeneous Fenton Technology In Drinking Water Treatment

Heterogeneous Fenton advanced oxidation technology has overcome the shortcomings of homogeneous Fenton process,such as sludge production,narrow response range of pH,unable to separate active components from the reaction solution and so on.The heterogeneous Fenton advanced oxidation technology used in this study does not require special equipment,such as ultrasonic generator,ozone generator,ultraviolet lamp and so on.The reaction conditions are mild and usually have no special requirements for temperature and pressure.This technology has a good application prospect.In the pilot scale,the Coagulation-sedimentation-filtration-heterogeneous Fenton-activated carbon combination process was used as the main process,the Coagulation-sedimentation-filtration-activated carbon process as the control process,and the method of comparative study was used to investigate the effect of the heterogeneous Fenton advanced oxidation process on the natural organic matter,disinfection by-products and microorganisms in the water.The research results of heterogeneous Fenton-activated carbon process can provide theoretical and technical support for the production and practice of this technology.Raw water is transported from Miyun Reservoir by pump,which is the end of the middle route of South-to-North Water transfer Project.By measuring the formation of disinfection by-products in raw water,conventional process effluent,conventional process-heterogeneous Fenton-activated carbon effluent and conventional process-direct activated carbon filtration effluent,the control effect of heterogeneous Fenton-activated carbon process on disinfection by-products of drinking water was studied.The changes of extracellular polymer and microbial activity of microorganisms in effluent were studied in order to investigate the control effect of heterogeneous Fenton-activated carbon process on microorganisms in drinking water treatment.The results are as follows:The main results are as follows:（1）the natural organic matter（NOM）,can be well removed by heterogeneous Fenton column when the residence time is 15 min,and the dosage of hydrogen peroxide is 0.15 mM.The organic matter adsorbed on the surface of the catalyst can be oxidized to organic matter with smaller apparent molecular weight by heterogeneous Fenton catalytic reaction,and its oxidation effect is positively correlated with the dosage of hydrogen peroxide in a certain range.（2）Heterogeneous Fenton treatment can improve the removal efficiency of dissolved organic matter by subsequent activated carbon treatment and reduce the processing load of subsequent activated carbon process.The DOC concentration of subsequent activated carbon effluent is lower.After the raw water was treated by activated carbon process,the concentration of DOC in the effluent is（1.04±0.11）mg·L^-1.When the raw water was treated by heterogeneous Fenton-activated carbon process,the DOC was reduced to（0.90±0.11）mg·L^-1.Three-dimensional fluorescence analysis showed that heterogeneous Fenton column and activated carbon column had a good effect on the removal of fulvic acid,humic acid and microbial metabolites from natural organic matter,which were represented by C1,C2 and C3,respectively.Exclusion chromatography analysis showed that there was a synergistic effect between heterogeneous Fenton oxidation and activated carbon filtration.Heterogeneous Fenton treatment can selectively remove substances with apparent molecular weight of 2.5-5.0 K Da from NOM,while activated carbon filtration has a strong removal effect on small molecules（<1K Da）.The heterogeneous Fenton-activated carbon process combines the advantages of the two processes.The average molecular weight in the effluent of the heterogeneous Fenton-activated carbon process is about 1K Da smaller than that of the activated carbon process.（3）The heterogeneous Fenton technology can reduce the formation of disinfection by-products.Compared with the conventional process-activated carbon process,the amount of disinfection by-products produced by heterogeneous Fenton-activated carbon process is less.Multivariate statistical analysis showed that organic matter with molecular weight less than 1K Da represented by F1was more likely to form HAAs disinfection by-products,while the organic matter with molecular weight of 1.5-2.5K Da represented by F2,humic-like substances and fulvic-like substances are more likely to react with disinfectant to form THMs.Tyrosine and tryptophan aromatic proteins may be precursors of HANs and HKs.There is a significant strong correlation between the removal rate of F2（1-1.5K Da）and the removal rate of total disinfection by-products（p<0.01,r=0.870）.The results show that the organic matter with apparent molecular weight of 1-1.5K Da may be the main component of disinfection by-product precursor.（4）Heterogeneous Fenton can enhance the removal ability of subsequent activated carbon filtration to remove organic matter.Under the condition of low organic matter concentration,the content of EPS protein secreted by microorganisms is low,the functional groups of-CO-NH and-CH₂were obviously reduced,the electronegativity was weak,and the flocculation activity is poor.（5）the heterogeneous Fenton-activated carbon filtration process can enhance the subsequent disinfection effect.It can control the growth of microorganisms in drinking water.At the same dosage of chlorine,the lower the concentration of organic matter,the more chlorine can be guaranteed to be used for disinfection.At the same time,the flocculation activity of EPS is poor and its protective effect on microorganisms is weakened,which leads to the disinfectant can inactivate microorganisms more easily,and the microbial activity in effluent is obviously decreased.