Abstract:

The wastewater produced during the production of cosmetic raw materials has complex water quality components, high organic content, and is difficult to degrade. The use of coagulation technology to treat this wastewater can slow down the burden of biochemical treatment units and improve the efficiency of wastewater treatment. To reveal the mechanisms of pollutants removal and the change of sludge properties in the coagulation process using inorganic polymer coagulant, the effects of the dosage of poly aluminum chloride (PAC), poly ferric sulfate (PFS) and poly aluminum ferric chloride (PAFC) as coagulants and polyacrylamide (PAM) as coagulant aid on the removal efficiencies of pollutants and the sludge properties were investigated. The functional groups, surface morphology, elemental composition and thermal stability of sludge flocs were analyzed by using Fourier transform infrared spectroscopy (FTIR), X-ray energy spectroscopy (EDX), scanning electron microscopy (SEM) and thermogravimetric analyzer (TGA), respectively. The molecular weight distribution of organic compounds and the changes of organic composition in the wastewater were analyzed by three-dimensional fluorescence spectroscopy (3D-EEM) and ultrafiltration, respectively. The operation conditions of the coagulation process were then optimized based on the above results. It showed that natural organic matter (NOM) in the influent had high fluorescence intensity. The molecular weight distributions of organic compounds were higher than 100×10³ and lower than 3×10³, which accounted for 22.89% and 50.57%, respectively. When influent COD was 6700—7500 mg/L and PAM concentration was 0.03 g/L, the removal efficiencies of COD were 87.20%, 79.89% and 83.74% and the effluent turbidity were 2.54 NTU, 9.3 NTU and 5.51 NTU under 2.8 g/L of PAC, 2.8 g/L of PFS and 3.0 g/L of PAFC, respectively. The fluorescence intensity of NOM decreased obviously. The removal of organic compounds was the highest when PAC and PAM were used simultaneously and the molecular weight of organic compounds in the effluent mainly distributed in the range of (10—30)×10³ and <3×10³ with a proportion of 31.84% and 25.92%, respectively. The formed flocculation sludge had a good thermal stability, fluffy surface and porous network structure. The coagulation process can adsorb lipid macromolecules and improve the biodegradability of the high-strength wastewater generated in the cosmetics raw materials production.

Key words: wastewater, polymer, pyrolysis, coagulation performance, coagulation mechanism, molecular weight

摘要：

化妆品原料生产过程中产生的废水水质成分复杂、有机物含量高、难降解，利用混凝工艺处理该废水能够减缓生化处理单元的负担，提高污水处理效率。为揭示无机高分子混凝剂混凝过程中污染物的去除机制和污泥性质的变化，考察了不同的絮凝剂聚合氯化铝（PAC）、聚合硫酸铁（PFS）、聚合氯化铝铁（PAFC）和助凝剂聚丙烯酰胺（PAM）投加浓度对污染物去除率和污泥性质的影响。采用傅里叶变换红外光谱（FTIR）、X射线能谱（EDX）、扫描电镜（SEM）、热重分析仪（TGA）分析污泥絮体官能团、表面形貌、元素组成和热稳定性的变化，采用三维荧光光谱（3D-EEM）和超滤技术分析出水中有机物分子量的分布规律和有机物成分的变化，优化最佳混凝工艺运行条件。结果表明：进水中的天然有机物（NOM）荧光强度高，有机物分子量主要分布在>100×10³和<3×10³区间，其所占比例分别为22.89%和50.57%。当进水COD为6700~7500 mg/L时，在助凝剂PAM投加浓度为0.03 g/L，PAC、PFS和PAFC投加浓度分别为2.8 g/L、2.8 g/L和3.0 g/L的条件下，COD去除率分别为87.20%、79.89%和83.74%，出水浊度分别为2.54 NTU、9.3 NTU和5.51 NTU，NOM荧光强度大大减弱。其中，PAC+PAM对废水中有机物去除效果最好，出水有机物分子量主要分布在(10~30)×10³和<3×10³范围内，其所占比例分别为31.84%和25.92%，形成的混凝污泥具有较好的热稳定性，污泥表面蓬松,呈多孔网状结构。混凝工艺可吸附脂类大分子物质，提高了高浓度化妆品原料生产废水的可生化性。

关键词: 废水, 聚合物, 热解, 混凝性能, 混凝机理, 分子量