The role of dissolved organic nitrogen in by-product formation during drinking water chloramination
by Yang Xin
Ph.D. Civil Engineering
xxiv, 187 leaves : ill. ; 30 cm
Membrane introduction mass spectrometry was developed and verified for direct quantification of cyanogen chloride (CNCl) and cyanogen bromide (CNBr) in environmental samples....[ Read more ]
Membrane introduction mass spectrometry was developed and verified for direct quantification of cyanogen chloride (CNCl) and cyanogen bromide (CNBr) in environmental samples.
Effects of contact time, monochloramine doses, monochloramine application modes, pH, temperature, and bromide ion concentrations on formation of DBPs were investigated. Longer reaction times led to continued formation over time for dichloroacetonitrile (DCAN), 1,1-dichloro-2-propanone (1,1-DCP) and chloroform. Linear relationships were observed between the formation of DCAN, 1,1-DCP, CNCl or chloroform and the monochloramine dosage. Chloramination modes exhibited the largest impact on chloroform formation. pH values between 5 and 6 resulted in the highest DBP concentrations.
Sixteen NOM isolates obtained from various water sources were chloraminated. Strong correlations were observed among the concentrations of dichloroacetic acid (DCAA), chloroform, and DCAN. Total organic halogen (TOX) and specific UV absorbance (SUVA) values were found to have linear relationships with these concentrations, but not those of chloropicrin (CP) and CNCl. The cumulative normalized excitation-emission matrix (EEM) volumes at specific regions obtained from fluorescence spectroscopy correlated linearly with yields of DCAA, chloroform, DCAN, TOX and CNCl.
DBP formation in waters treated with chlorine, ozone, coagulants, and monochloramine was evaluated. Prechlorination enhanced formation of THM, 1,1,1-trichloro-2-propanone (1,1,1-TCP) and total organic chloride (TOCl) and the concentrations of most DBPs increased with increasing chlorine doses. Preozonation reduced DCAN and TOCl formation and increasing ozone doses did not necessarily reduce the formation of THM and 1,1-DCP. Increasing coagulant doses reduced most DBP and TOCl formation but total organic bromide (TOBr) formation varied little.
Model organic-N compounds were chloraminated. Long reaction times and high monochloramine to organic-N molar ratios enhanced the formation of CP. CNCl was formed from chloramination of all organic-N compounds tested, with glycine generating the highest amount. The nitrogen in CNCl and DCAN was from both organic-N compounds and isotopped monochloramine.