滦河水体溶解性有机物的综合分级表征及其混凝去除过程

Study on the comprehensive fractional characteristics of DOM in Luan River and its removal by coagulation

天然水体溶解性有机物(DOM)是微污染物的潜在载体,是消毒副产物的主要前驱物,自身又可能成为微污染物,因此研究其内在特性和去除机理有着重要的基础性科学意义。本研究综合利用化学、物理分级方法(即树脂和超滤分级法),对中国北方典型饮用水源——滦河水体的DOM进行全面分级表征。此水体DOM基本化学分级特征是憎水酸(HoA)、亲水性物质(HiM)含量较高,且具有季节稳定性;其物理分级特征是分子量<1 kDa及3 kDa^10 kDa的组分含量较高,也表现出一定的时间稳定性。选用工业聚合铝(PAC)研究此DOM的基本混凝特征和内在混凝机理,结果表明,强憎水部分HoA及3 kDa^10 kDa间的有机物较易被去除,而较大分子量范围10 kDa^30 kDa间的有机物去除率较低,说明混凝过程中此DOM的物理性质不起主要作用,而化学性质更为重要。特别对DOM各组分作进一步(结合)分级研究,发现HoA主要在>10 kDa范围。<1 kDa的有机物中主要为HiM,但其中还含有HoA和弱憎水酸(WHoA),这使特定条件下部分<1 kDa有机物被混凝去除成为可能。另外,HoA中按分子量大小仍可分为易去除和难去除部分,但分布不连续,易去除部分在3 kDa^10 kDa和>30 kDa区间,而其10 kDa^30 kDa部分较难去除,说明可能存在其他结构性影响因素,值得深入研究。

Dissolved organic matter （ DOM）, the potential carrier of micro-pollutant and primary precursors of disinfection by-products, may also become micro-pollutant itself. Therefore, it is important to characterize the DOM for minimizing it in drinking water. The DOM from Luan River, a typical source water in north of China, was fractionated and characterized by resin adsorption （RA） and uhrafihration （UF） techniques. The chemical fractions distribution of the DOM is that the hydrophobic acids （HoA） and the hydrophilic matter （HiM） are richer than others across all the sampling seasons. The physical （size）distribution of the DOM is that the fractions with molecular weight in 〈 1 kDa and of which the 3 kDa - 10 kDa range are dominated fractions during most of the sampling period. PAC produced by plant was choosed as coagulant to research the DOM removal mechanism by coagulation process. The results showed that HoA and 3 kDa - 10 kDa fractions are easy to be removed. Contrarily, the DOM of which the molecular weight is between 10 and 30 kDa has a lower removal efficiency. It could be concluded that the chemical property of DOM is more important than physical property in coagulation. Especially, we found that the molecular weight of most HoA was above 10 kDa when each component of DOM was fractionated by UF. Organics with molecular weight 〈 1 kDa are mostly HiM, and then HoA and WHOA. This makes it possible that part of 〈 1 kDa organics are removed by coagulation under specific conditions. Moreover, HoA can be divided into two parts according to its molecular weight and removal efficiency, of which one part in 3 kDa - 10 kDa could be easily removed and the other in 10 kDa - 30 kDa is contrary. It indicates that there are some other factors possibly interfering the coagulation of DOM.