饮用水中可同化有机碳（AOC）容易引起细菌滋生，影响饮用水水质安全，因此通常用AOC反映饮用水水质的生物稳定性。传统的饮用水处理工艺对水中AOC类物质的去除效果有限，不能保障饮用水的生物稳定性。本文采用混凝/臭氧/锰基陶瓷膜-生物活性炭组合工艺，即混凝/臭氧/MnCMF-BAC，进一步深度处理去除AOC。采用傅里叶变换离子回旋共振质谱（FT-ICR MS），从分子结构层次解析AOC的去除机理，揭示水源水和管网系统中AOC的变化规律及其与溶解性有机物（DOM）相关特性。研究发现珠三角地区6个地表水源水中，AOC浓度存在季节性变化规律，即夏季水中AOC浓度>秋季>春季>冬季，夏季AOC平均浓度为562.2 ± 279.9 μg/L。主成分分析（PCA）结果表明，AOC浓度和蓝藻数量相关性较高。对比土壤源有机物和藻源有机物对AOC的贡献，发现藻细胞破裂后，胞内有机物释放是造成水源水AOC浓度较高的主要因素。实验室小试研究表明，采用混凝、臭氧、MnCMF和BAC等单元进行单独处理或者组合处理，出水AOC去除效果差别比较大，其中混凝/臭氧/MnCMF-BAC组合工艺对AOC去除率最高，达到92.5 ± 3.7%。采用FT-ICR MS仪器方法解析了各处理单元中DOM及AOC的变化规律，发现混凝剂和MnCMF能够催化臭氧产生羟基自由基，促进AOC的去除，BAC单元通过吸附和生物降解作用去除AOC。混凝/臭氧/MnCMF组合与BAC单元之间具有协同去除AOC的效果。采用混凝/臭氧/MnCMF-BAC组合工艺对水源水进行连续80天中试实验。结果表明，在臭氧投加量为3 mg/L，BAC单元水力停留时间为45 min时，组合工艺出水AOC浓度在30.2-45.4 μg/L之间，满足水质生物稳定性标准要求（<50 μg/L）。混凝/臭氧/MnCMF组合处理能够将含氮的、大分子的多环芳烃（PAH）转化成碳氢氧（CHO）类型的中等分子量的酚类有机物（HuPh），BAC单元能够选择性去除HuPh。PCA分析表明，PAH是AOC主要前体物，HuPh是主要AOC物质。混凝/臭氧/MnCMF组合工艺发生的主要反应类型是加氧反应，而BAC单元主要是脱羧反应。本论文组合工艺处理出水成本为0.44元/吨，具有良好的经济可行性。
Assimilable organic carbon (AOC) in drinking water can result in the regrowth of some pathogenic bacteria, which affects the safety of drinking water quality, thus the AOC is selected as an indicative parameter to evaluate the biological stability of drinking water. Currently, the traditional treatment process cannot remove the AOC from drinking water, thus it is not good enough to guarantee the biostability of drinking water. In this study, the integrated coagulation/ozonation/Mn2O3 doped ceramic membrane-biological activated carbon (coagulation/ozonation/MnCMF-BAC) process was applied to remove AOC from drinking water. The Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to reveal the mechanism of AOC removal at the molecular level. The occurrence of AOC in source water and pipeline systems was found to be correlated with dissolved organic matter (DOM).It is found that the AOC concentrations in six raw water samples collected from the pearl river delta area varied seasonally as: summer > autumn > spring > winter, and the average AOC concentration in summer is 562.2 ± 279.9 μg/L. The principal component analysis (PCA) results showed that the AOC has a good correlation with blue algae. The contribution of soil-derived organics and algae-derived organics to AOC showed that the release of intracellular organic matter (IOM) after cell disruption is the main source causing higher AOC concentration in the source water.The removal effect of coagulation, ozonation, MnCMF, BAC, and the combination processes on AOC was studied through laboratory experiments, and the integrated coagulation/ozonation/MnCMF-BAC process exhibited the highest removal rate of AOC (92.5 ± 3.7%). The FT-ICR MS was used to identify the variation of DOM and AOC at molecular levels, and it was found that both coagulant and MnCMF can catalyze the ozone to produce highly active radicals, and can reach higher removal of AOC due to the production of hydroxyl radical, furthermore, the BAC filter can remove AOC through adsorption and biodegradation to a lower level. The synergistic effect between the coagulation/ozonation/MnCMF unit and the BAC filter was proved.The experiment of the integrated coagulation/ozonation/MnCMF-BAC processes was conducted in a pilot-scale system with 96m3/day for 80 days. The results showed that, at an ozone dosage of 3 mg/L and the hydraulic retention time of the BAC filter of 45 min, biostable finished water was achieved with an AOC concentration of 30.2-45.4 μg/L (<50 μg/L). The FT-ICR MS results showed that the coagulation/ozonation/MnCMF unit efficiently transformed nitrogen-containing polyaromatic hydrocarbons (PAH) with large molecular weight (Mw) (500-1000 Da) into CHO-type highly unsaturated phenolic compounds (HuPh) with medium Mw (300-500 Da), which were effectively removed by subsequent BAC filtering. PCA revealed that PAH are potential AOC precursors, and the HuPh are key AOC components. The main reaction was oxygen addition of the coagulation/ozonation/MnCMF unit and decarboxylation of the BAC filter. The cost of drinking water production was estimated to be 0.44 yuan/ton, which is economically feasible. The occurrence of chlorine-resistant bacteria, pathogens, and antibiotic resistance genes in the distribution system increased with the delivery of drinking water. The O3-BAC advanced treatment process can limit the growth of bacteria by controlling the concentration of AOC in the distribution system.
