Byproducts Originated From Tyrosine During Chlorine Disinfection Process

Drinking water is one of the basic resources of human.The safety of drinking water attracted more and more concerns of scholars and governments.During drinking water production,disinfection is an important process for sterilization.Based on economic and efficiency consideration,chlorine disinfection is still the most widely used disinfection technology in domestic and foreign waterworks.The biggest negative issue with chlorine disinfection is the production of varieties of toxic by-products,called as disinfection byproducts(DBPs),which seriously affect the safty of drinking water supply.The generation,control and influence of disinfection by-products represented by trihalomethanes(THMs)and haloacetic acids(HAAs)have been thoroughly elaborated in many reports.In recent years,nitrogenous disinfection byproducts(N-DBPs)have been put much attention on due to their stronger toxicity.The main precursors are nitrogenous organic compounds including amino acids,peptides and proteins,which are ubiquitous in water environment.Amino acids are the simplest and most basic forms of such precursors.In this paper,tyrosine was chosen as a model precursor,through laboratory simulate experiments,N-(C-)DBPs identification,generation and influencing factors were analyzed.The results can provide the appropriate theoretical data for the disinfection by-product research and treatment.In this paper,liquid-liquid extraction-gas chromatography(LLE-GC-ECD)was used to detect THMs,liquid-liquid microextraction(LLME)and methanol-esterification-GC/MS were used to detect HAAs.Liquid-liquid extraction-gas chromatography-mass spectrometry(GC-MS)was optimized and emplied for identification and detection of disinfection by-products.The results showed that:a series of reactions occurred during tyrosine(Tyr)chlorinated as precursors,such as substitution,decarboxylation,hydrolysis.4-Chlorophenol,2,4-dichlorophenol,chloro-1,4-benzoquinone,phenylacetonitrile,p-hydroxybenzene acetonitrile and other intermediates were indentified as intermediates.And these intermediates can be further decomposed to form haloacetic acid,chloroform and other by-products with simple chemical structures.The yields of the regulated THMs and HAAs,gradually increased with extended chlorination time while the yields of other unregulated by-products decreased;chlorine dosage,temperature and pH increase can significantly increase the formation of THMs and HAAs,while the other DBPs show different variation with the addition of chlorination,temperature and pH;production of DBPs can be significantly reduced under dark conditions.