消毒副產物與天然有機物之關係

由於消毒副產物來自於天然有機物與消毒劑反應而生，因此天然有機物被認 為是眾多消毒副產物的前驅物質，然而不同性質的天然有機物應會形成不同的消 毒副產物。故前人開始研究如何將天然有機物分類，並探討各類天然有機物與消 毒副產物之間的相互關係，其中藉由樹脂分離，將天然有機物依親疏水性不同分 成結構性質相異的有機物類群之方法最為廣泛利用且研究。表 2-2 呈現三鹵甲烷、

鹵乙酸與氮系消毒副產物與不同性質之天然有機物的關係，並可歸納出以下兩點 結論：（1）三鹵甲烷與鹵乙酸的前驅物質大致上來自於疏水性之天然有機物。（2）

氮系消毒副產物之前驅物質則大致上來自於親水性天然有機物。

在 2.2 節中提到過，臭氧可將疏水性天然有機物轉化為親水性天然有機物，

且亦有研究發現，在加氯消毒前，先以臭氧氧化處理原水，可大幅減少三鹵甲烷 與鹵乙酸生成(Chiang et al., 2010; Ko et al., 2000)，可見三鹵甲烷與鹵乙酸的生成 確實與疏水性天然有機物有關。然而氮系消毒副產物與天然有機物性質（尤其是 親水性）在整體淨水程序之間之變化尚未釐清，且傳統淨水程序對於親水性天然 有機物處理效果本來就低於疏水性有機物(Hu et al., 2010; Marhaba et al., 2003)，

Buchanan 等人 (2005) 研究亦顯示，始終有部份親水性物質無法被 UV 和 VUV 氧化或是被生物處理方式去除，故理論上對於氮系消毒副產物之控制較無良好對 策。因此，若能得知天然有機物組成於整體淨水程序時之變化，對於消毒副產物

（尤其是氮系消毒副產物）之控制應有絕佳之幫助。

表 2-2 不同天然有機物組成類群與消毒副產物之關係

DBPs Description Reference

THMs, HAAs

The more hydrophobic and more acidic fractions provide the most active precursor sites; i.e., they have the largest formation potentials for THMs and HAAs.

(Croué et al., 2000)

THMs, HAAs

1. Hydrophobic acid, hydrophilic acid, hydrophilic base and hydrophobic neutral are the dominant DBPs precursors.

2. Chloroform and dichloroacetic acid are major DBPs species for each of the DOM fractions.

(Lu et al., 2009)

THMs, HAAs

1. LMW (larger molecular weight) and hydrophobic NOM are the main precursors to the formation of THMs.

2. SMW (smaller molecular weight) and hydrophobic NOM are the main precursors of HAAs.

3. For both source waters, ozonation appeared to have the greatest effect on the more hydrophilic fractions, generally increasing the DBP formation potential of the smaller more hydrophilic NOM, while generally decreasing that of the larger more hydrophilic NOM.

(Chowdhury et al., 2008)

THMs, HAAs

Bromine and iodine have been noted to be more reactive with hydrophilic and LMW (low molecular weight) fractions of NOM in the formation of THMs and HAAs.

1. The hydrophobic fraction of organic matter, or aromatic organic matter, produced more THM and HAA than other organic fractions.

2. The hydrophilic bases were associated with haloacetonitrile (HAN) formation.

3. The nitrogen-enriched transphilic fractions of natural organic matter (NOM) were associated with the highest NDMA formation yield (up to 27 ng-NDMA/mg-DOC)

(Chen and Westerhoff, 2010)

HNMs HNM precursors consist of some hydrophilic organic matter with low-molecular weight

(Hu et al., 2010)

HAN, NDMA

1. Haloacetonitriles can be produced from the chlorination of free amino acids, heterocyclic nitrogen in nucleic acids, proteinaceous materials, and combined amino acids bound to humic structures.

2. The formation mechanisms of N-nitrosodimethylamine (NDMA) and related nitrosamines are nitrosation of organic nitrogen precursors (e.g.,dimethylamine) by nitrous acid and/or nitrite.

(Lee et al., 2007b)