混凝对二级出水中有机物分布特性的影响

Effect of coagulation on distribution properties of dissolved organic matters in secondary effluent

以城市污水处理厂二级出水为研究对象,通过烧杯实验,确定了以三氯化铁(FeCl3)和聚合氯化铝(PAC)为混凝剂时两种混凝剂的最佳投加量,在此基础上采用XAD树脂分离技术和超滤膜法对水中溶解性有机物(DOM)进行分级表征,研究了混凝前后水中DOM的亲疏水特性、分子量分布规律以及比紫外吸收值(SUVA)和E4/E6(A465 nm/A665 nm)的变化。结果表明,当FeCl3和PAC投加量分别达到30 mg/L和60 mg/L时,可以使出水水质满足《城镇污水处理厂污染物排放标准》(GB18918-2002)中的一级A标准;FeCl3对含碳碳不饱和双键及芳香环的有机物的去除效果优于PAC;FeCl3对小分子有机物的去除效率更高,而PAC对分子量>100 000的大分子有机物的去除效果优于FeCl3;混凝处理对疏水性有机物的去除效果优于对亲水性有机物的去除效果,同时其对酸性物质的去除效率高于对非酸性物质的去除效率。

Aiming at the advanced treatment of the secondary effluent,the optimal dosage of coagulant with ferric chloride（FeCl3） and polyaluminium chloride（PAC） as coagulant was determined in this study.On this basis,dissolved organic matter（DOM） was characterized by XAD resin separation technology and ultrafiltration membrane method,and the effect of coagulation on hydrophilic and hydrophobic characteristics,molecular weight distribution,specific ultraviolet absorbance（SUVA） and E4/E6 of DOM before and after coagulation was investigated.The results show that the effluent quality can meet the first class level A standard of Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant（GB18918-2002） when the dosages of FeCl3 and PAC are 30 mg/L and 60 mg/L,respectively.Removal efficiency of unsaturated C—C double bonds and aromatic organics by FeCl3 is better than that by PAC.Comparatively,FeCl3 is more efficient on small molecular organics removal,while the removal rate of the big molecular organics of 100 000 by PAC is higher.Effect of coagulation process on hydrophobic matter removal is better than that on the hydrophilic ones.Besides,removal rate of acid organic matter by coagulation is higher than that of non-acid organic matter.