The impacts of recycling filter backwash water(FBWW)blended with corresponding raw water W1(simulated water)and W2('Longtan’ lake water)on specific bulk water parameters

i.e.DOC

UV254 and specific ultraviolet absorbance(SUVA)removal were evaluated in coagulation-sedimentation processes.Fluorescence characteristics of dissolved organic matter(DOM)in source waters

FBWWs and treated water were identified and compared.As compared with control trial without FBWW

three volumetric recycling ratios at 2%

5% and 8% were investigated.The results indicated that fluorescent components in raw water and corresponding untreated FBWWs DOM were mainly humic-like fluorophore(Peak A)and protein-like fluorophore(Peak T)

with Ex/Em wavelengths at 245.0-265.0 nm/400.0-435.0 nm

280.0-305.0 nm/305.0-345.0 nm

respectively.Additionally

a broad Peak C with relatively lower fluorescence intensity was observed in all fluorescence spectra.At observed recycling rates

organic matter removal rates in treated water were improved with FBWW1

while the enhanced removal efficiencies of DOM in treated samples with FBWW2 were unconspicuous.Fluorescence EEM spectra in the DOM of treated water samples were analogous to those of source water accordingly.The process of recycling FBWW could improve humic-like substances(Peak A)removal

but the protein-like matters were resistant to elimination or even enriched with unvaried structure.The DOM removal in the coagulation process of recycling filter backwash water could be well identified by the three-dimensional excitation emission matrix(3D-EEM)fluorescence technique

therefore it could be used in wide applications.