| Drinking water safety has cause a great of concern in the world. The disinfection by-products (DBPs) which were formed during the chlorination of drinking water received widely public attention. Most of the researchers were focused on the natural organic matters (NOM) as the DBPs precursors, but ignored other precursors. In this research, normal precursors (NOM in soils) and special precursors (nitrogen compounds and cellular materials), were chosen to be chlorinated according to the Uniform Formation Conditions (UFC) ,to evaluate three main species of disinfection by-products (DBPs) during drinking water treatment, i.e. trihalomethanes (THMs), haloacetonitriles (HANs), and chloral hydrate (CHD). The effect of bromide on the DBPs formation by three kinds of nitrogen compounds and one species of bacterium were also evaluated. Ultraviolet absorbance at 254nm and Three-Dimensional Excitation Emission Matrix Fluorescence Spectrum (3DEEM) were also tested, to assess them as surrogates of DOC concentration and reactivity. The results could provide theoretic support to the drinking water treatment and could be valuable references for the wastewater engineers and microbiological experts. The NOM were extracted from soil samples, the nitrogen compounds contained tyrosine, uracil, tryptophan, threonine, asparagines, adenine, cytosine, thymine and glycine. Acinetobacter junii and Staphylococcus sciuri were the two species of bacteria.The results of the chlorination confirmed that nitrogen compounds and bacteria were the DBPs precursors during the chlorination. THMs, HANs and CHD formation were detected after chlorination. TCM was the only THMs formed by every material, TCAN were formed with small concentration by the materials without thymine and bacteria. Tyrosine, tryptophan and asparagines produced DCAN after chlorination. There was only glycine which didn't form CHD. There was no obvious linear relationship between the content of formed DBPs and DOC. Tyrosine and tryptophan had the higher DBPs formation potential (FP) with 175.79μgDBPs/mgC, 187.53μgDBPs/mgC, respectively. Adenine (2.94μgDBPs/mgC) and glycine (3.74μgDBPs/mgC) had the lower DBPsFP. DBPsFP of B1 (47.65μgDBPs/mgC) was greater than the DBPsFP of B2 (33.0547.65μgDBPs/mgC).DBPs formed by nitrogen compounds and cellular materials of bacteria had similar tend in the presence of bromide.The results of the chlorination of nitrogen compounds and bacteria with different concentrations of bromide ion showed that, in addition to TCM, TCAN, DCAN and CHD, brominated THMs and HANs were formed, including TBM, DBCM, BDCM and DBAN, BCAN. The sum of the three species of DBPs was increased in the existence of ?bromide. For THMs, the amount of BDCM,DBCM and TBM increased linearly with the increase of Br-, while the TCM continuously decreased with the increase of Br-, Take tyrosine for example, the TCM decreased from 633.00μg/L to 328.77μg/L, while the content of TBM increased from 1.29μg/L to 91.12μg/L. For HANs, the total HANs formation increased with the increase of Br- concentration. The formation of DBAN and BCAN were increased while the Br- increased from 0.2 to 2 mg/L, that of TCAN,DCAN showed opposite tendency. The CHD concentrations were continuously decreased from 121.13μg/L to 62.96μg/L (tyrosine) with the concentration of Br- from 0.2 to 2 mg/L. In General, THMs were the main DBPs species when there was high concentration of bromide. The results confirmed that the presence of bromide in water can contribute to the increase of DBPs formation during the chlorination, especially the more toxic brominated DBPs. Thus, it was with great value to remove the high concentration of bromide for the drinking water safety.
|
PDF Full Text Request