[Chlorination characteristic and disinfection by-product formation potential of dissolved organic nitrogen compounds in municipal wastewater].

In order to explore the chlorinated disinfection by-product formation potential and chemical structure of dissolved organic nitrogen compounds in municipal wastewater, the water quality parameters, such as DON, DOC, NH4(+) -N and UV254 etc, were determined in the secondary effluent and the molecular weight distribution of the DON was investigated before and after the reaction with chlorine. DBPs were determined by gas chromatography, and the changes of DON were characterized using Fourier transform infrared spectroscopy and three-dimensional fluorescence spectroscopy before and after the reaction with chlorine. The results showed that DON, DOC, NH4(+) -N and UV254 were 2.47 mg x L(-1), 14.45 mg x L(-1), 5.42 mg x L(-1) and 15.88 m(-1), and m(DOC)/m(DON) and SUVA were 5.85 mg x mg(-1) and 1.09 L x (m x mg)(-1) in the secondary effluent. After the reaction with chlorine, the proportion of small molecular weight (M(r) < 6 000) DON increased from 78% to 70% , and the proportion of large molecular weight (M(r) > 20 000) DON decreased from 21% to 14%. The medium molecular weight (M(r)6000-20000) DON accounted for a small proportion and was unchanged. Among the DBPs, the concentration of bromochloroacetonitrile was the highest, which was 6.887 microg x L(-1), and the concentration of trichloroacetonitrile was the lowest, which was only 0.217 microg x L(-1). In FTIR spectrum, the dominating bands were at 3 500-3 400, 2 260-2 200, 1 700-1 640, 1 500-1 450, 1 150-1 100 and 850-800 cm(-1) respectively before the reaction, and the 1 380-1 350 cm(-1) and 600-550 cm(-1) bands were the dominating bands in addition to the original absorbing regions after the reaction. 3DEEM revealed that the variation of DON depends intimately on tryptophan protein-like substances, aromatic protein-like substances and fulvic acid-like substances.