制革业是我国重要的工业门类,年废水排放量2亿t以上.制革废水中油脂、皮屑、胶原蛋白等大分子有机物含量较高,同时兼具高盐、高碱、高负荷的特点,已被相关部门列为重点监控的工业污染源.在制革废水的处理方面,不仅要关注进出水的水质参数,同时也要监测废水处理过程污染物的转化规律,以便为废水处理工艺的优化和废水处理设备的研发提供基本数据.溶解性有机物(DOM)广泛存在于各类水体中,是表征废水理化性质和净化程度的重要参数.目前,对于制革废水处理过程DOM性质的研究尚很欠缺.以此为切入点,采用元素分析、热重分析、红外光谱和核磁共振表征制革废水不同处理工段的DOM样品.研究发现:制革废水处理时间的延长导致DOM中C元素含量升高,H/C原子比先增加后降低,说明大分子有机物首先被分解为小分子链状结构,最终存在于水体的是极难降解的终极结构组分.DOM脂肪族化合物和蛋白组分的热解发生在第二阶段(110～530 ℃),第三阶段(530～800 ℃)主要完成芳环的降解或C—C键的断裂.废水原水DOM主要含有—OH,—NH2,CO等官能团,FTIR图谱证明了废水处理中后期高聚合度芳香族物质的存在,这是微生物新陈代谢作用的结果.DOM中烷基C含量先增加后减少,含量最大值(25.25%)出现在二级生化池;芳香C含量的最小值(28.28%)出现在二级生化池,而后迅速上升,暗示了废水处理过程含C官能团种类和数量的交替变化规律.对制革废水DOM性质的跟踪识别有助于从总体上推断污染物的净化机制。

Nowadays,the wastewater quantity discharged yearly from tannery industry is around 0.2 billion t in China.The contaminants of tannery wastewater include macromolecular organic matters,such as grease,fur scraps and collagen,and the alkaline wastewater appears to be of high content of salt and COD.The quality of tannery wastewater is monitored strictly among all kinds of industry wastewater.In the treatment process of tannery wastewater,the quality of inlet and outlet water is generally analyzed.In fact,the transformation behavior of contaminants should be additionally checked to optimize the treatment conditions.Dissolved organic matter(DOM) is commonly existed in water-bodies and helpful to understand the physicochemical characteristics,while the related work should be further studied on tannery wastewater.The approaches of elemental analysis,thermal gravimetric analysis(TG),Fourier infrared spectroscopy(FTIR) and 13C nuclear magnetic resonance(13C NMR) were used to reveal the characteristics of DOM in the treatment process of tannery wastewater.The results showed:the carbon content of DOM samples increased gradually,atomic ratios of H/C increased firstly and then decreased,indicating the organic matters were decomposed into chain structures firstly,finally forming the component hard to degraded.The pyrolysis process of DOM mainly proceeded in the regions of 110～530 ℃(aliphatic compound,protein,etc.) and 530～800 ℃(aromatic ring,single bond of C—C,etc.).The functional groups of DOM included —OH,—NH2,CO and so on,and the aromatic substances were detected,shown from FTIR figures,in the later period of the reaction,caused by the metabolism effect of micro-organism.The content of alkoxy-C increased to the maximum in the second biochemical pond,and the minimum content of aromatic-C appeared in the second biochemical pond,suggesting the transformation behavior of carbon functional groups.The investigation on DOM in tannery wastewater is significant to understand the purification mechanism of contaminants in tannery wastewater.