Correlation Between Multivariate Analysis Of 3D Fluorescence Spectra And Disinfection By-product Generation Potential

The key aspect of drinking water treatment is disinfection,which is used to inactivate water-borne pathogenic microorganisms to maintain the safety of drinking water for residents.However,disinfectants can react with organic matter present in the water to produce a variety of disinfection by-products（DBPs）that are hazardous to human health,and some DBPs have a potential"tri-causal"effect on humans（i.e.carcinogenic,teratogenic,mutagenic）,therefore,the World Health Organisation and many national water quality standards have set guideline values for their maximum production.However,DBPs are diverse and low yielding,and their levels in water are generally measured inμg/L or even ng/L,making it difficult to monitor their production in real time.The organic matter present in water is a precursor to DBPs and its content can be quantified using indicators such as DOC and UV₂₅₄,so it has been proposed and demonstrated that the use of indicators such as DOC,UV₂₅₄and SUVA can indicate the production of DBPs.However,these indicators only correlate well with some DBPs under specific conditions and do not have universal applicability.The three-dimensional fluorescence spectroscopy technique is used to characterise the composition and dosing of organic matter in water by means of a fluorescence matrix composed of different excitation and emission wavelengths,and therefore more detailed information on organic matter can be obtained.In this study,a multivariate analysis method was used to quantify the 3D fluorescence spectra and to construct a relationship between the attenuation of the 3D fluorescence spectra and the generation potential of DBPs,in order to select water quality parameters that are more accurate and easy to detect for predicting the generator potential of DBPs.In this study,raw water at the influent of a water plant in Xi’an was selected for study,and the conventional treatment process of coagulation-precipitation-filtration-disinfection in a water plant was simulated by using FeCl₃or Al₂（SO₄）₃as coagulant and two disinfection means,chlorine or chloramination,respectively.This paper Systematically compares the conventional indicators of water quality and the relationship between three-dimensional fluorescence spectra（area integration,parallel factor analysis）and the generation potential of DBPs（trihalomethanes（THMs）,haloacetic acids（HAAs）,haloacetonitrile（HANs）,1,1,1-trichloro-2-propanone（1,1,1-TCP）and trichloronitromethane（TCNM））.The main results were obtained as follows:（1）With chlorine as the disinfectant,component 1（C1,terrestrial/anthropogenic humic substances）of the parallel factor analysis correlated better with the production potential of most DBPs.UV₂₅₄correlated best with the four categories of THMs,HAAs,HANs and 1,1,1-TCP in the water quality routine when FeCl₃was coagulated,with an R² of0.869±0.069;the area integral The correlation was higher in the FA region than in the other regions,with an R² of 0.909±0.024;C1（Ex 256 nm,Em 419 nm）had the best correlation in the parallel factor analysis,with an R² of 0.918±0.065.The correlation of UV₂₅₄was marginally higher in the water quality routine when Al₂（SO₄）₃was coconated,with an R² of0.903±0.158 In addition,comparing the correlation between TCNM and the indicators,it was found that the correlation between the conventional indicators and the regional integration was poorer than 0.5,with R²below 0.5 and no significant linearity;while the correlation coefficient between C1 The correlation coefficient of C1 was 0.631,which was significantly higher than other indicators.The correlation coefficient of C1 was 0.631,which was significantly higher than the other indicators.Therefore,C1 was finally determined to be the indicator of DBPs generation potential during Na Cl O disinfection.（2）When chloramine was used as a disinfectant,component 2（C2,humic-like substances）of the parallel factor assessment correlated well with the production potential of most DBPs.When FeCl₃was coagulated,UV₂₅₄showed the best correlation with THMs,HAAs,HANs and 1,1,1-TCP among the conventional water quality indicators,with an R² of0.88±0.06;the HA region showed the best correlation among the regional integrals,with an R² of 0.912±0.059;C2（Ex 268 nm,Em 468 nm）in the parallel factor analysis The highest correlation was found in the HA region,with an R² of 0.912±0.059.In addition,the correlation between TCNM in NH₂Cl disinfected FeCl₃coagulation and the indicators was poor,with R²below 0.4,indicating that these indicators For Al₂（SO₄）₃coagulation,UV₂₅₄correlated best with THMs and HAAs among the conventional water quality indicators,with an R² of 0.823±0.016;the HA zone correlated better than the other zones in the area integral,with an R² of 0.885±0.068;and C2 correlated highest in the parallel factor analysis,with an R² of 0.891±0.031.In addition,the correlation between HANs,1,1,1-TCP and TCNM was poor when NH₂Cl disinfected Al₂（SO₄）₃coagulation,（R²<0.6）demonstrating that none of these indicators were indicative of the production potential of HANs,1,1,1-TCP and TCNM.The above data suggest that C2 can indicate the generation potential of DBPs under NH₂Cl disinfection conditions.