化学沉淀—混凝气浮法处理酸洗、磷化污水的研究

发布时间：2018-03-13 02:32

  本文选题：化学沉淀　切入点：气浮　出处：《辽宁科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：钢绳在现代工业中应用非常广泛,但钢绳在生产过程中会产生大量污水。钢绳生产污水是钢绳在生产过程中经酸洗、磷化、冲洗、电镀等过程形成的,其中含有氨氮、油类、锌离子、铁离子、铅离子、磷酸盐、硫酸盐等多种污染物,污水成分复杂,污染物浓度高、毒性大,对环境污染严重。本文采用化学沉淀-混凝气浮工艺对某钢绳厂的生产污水进行了实验研究及实际工程应用研究,并对气浮过程进行了理论探讨。本文首先采用化学沉淀法初步去除钢绳生产污水中的磷酸盐离子和重金属离子,然后采用混凝气浮法进一步去除污水中残余的重金属离子和其他污染物。选择多种无机混凝剂进行混凝实验,结果表明不同混凝剂单独使用时对污水的处理效果不同,PAFC单独使用时处理效果优于其他无机混凝剂。通过比较PAFC单独使用及与有机混凝剂联合使用的处理效果可知,无机与有机混凝剂联合使用的处理效果优于单一混凝剂,适当的配比有利于提高处理效率和降低药耗。实验确定化学沉淀法去除钢绳生产污水的主要污染物的最佳pH为9,磷与钙的投加摩尔比为1.0:1.3,反应时间为30min,反应后沉淀静置时间为30min,在最佳沉淀条件下在对污水中磷酸盐的去除率为99.6%,Pb2+的去除率为95.3%,Zn2+的去除率为99.0%。利用样机进行混凝气浮实验确定,最佳混凝气浮条件为:PAFC用量为20mg/L、PAM用量为3mg/L、pH值为7.5、气浮压力为0.6Mpa,在最佳条件下混凝气浮系统对污水中磷酸盐、Pb2+、Zn2+、COD的去除率分别达到了85.2%、85.1%、83.3%、77.0%。将本研究的工艺流程和最佳运行参数应用于某钢绳生产污水的实际处理工程上,连续运行的结果表明本工艺流程处理钢绳生产污水效果良好。其设计流量为40m3/d,进水磷酸盐浓度为228mg/L,Pb2+浓度为40mg/L,Zn2+浓度为285mg/L,COD为230mg/L,HRT为8h。经过连续稳定的运行,经本工艺处理后出水中各污染物的平均浓度如下:磷酸盐浓度为0.4mg/L,Pb2+浓度为0.6mg/L,Zn2+浓度为0.5mg/L,COD为25mg/L。其中磷酸盐浓度、COD浓度均能达到《辽宁省污水综合排放标准》(DB 21/1627-2008)中的直接排放要求;《辽宁省污水综合排放标准》中未要求的Pb2+、Zn2+也能达到《污水综合排放标准》(GB 8978-1996)中一级排放的要求,每吨污水的处理成本约为2.49元。理论探讨认为,气浮压力与回流比对气浮池的溶气效率有较大影响。在回流比为30%,气浮压力为0.6MPa时,气浮池内空气浓度为22.20L/m3,单位体积的污水中微气泡数量为9.89×1014个/m3。在工程允许的情况下应尽量提高回流比,增加气浮池的溶气效率。在温度为20℃时,最佳气浮条件下气泡的上升速度为0.68mm/s。
[Abstract]:Steel rope is widely used in modern industry, but it will produce a lot of sewage in the process of production. The sewage of steel rope production is formed by acid pickling, phosphating, washing, electroplating and so on, which contains ammonia nitrogen, oil, etc. Zinc ion, iron ion, lead ion, phosphate, sulfate and so on many kinds of pollutants, the sewage composition is complex, the pollutant concentration is high, the toxicity is big, The environmental pollution is serious. In this paper, the chemical precipitation-coagulation air flotation process is used to study the production sewage of a steel rope plant and its practical engineering application. In this paper, the chemical precipitation method is used to remove phosphate ions and heavy metal ions from steel rope wastewater. Then the residual heavy metal ions and other pollutants were removed by coagulation flotation method. A variety of inorganic coagulants were selected for coagulation experiments. The results show that the treatment effect of different coagulants on wastewater is different. The treatment effect of PAFC alone is better than that of other inorganic coagulants. By comparing the treatment effect of PAFC alone with organic coagulant, it can be seen that the effect of PAFC is better than that of other inorganic coagulants. The treatment effect of inorganic and organic coagulant is better than that of single coagulant. The optimum pH value, molar ratio of phosphorus to calcium is 1.0: 1.3, the reaction time is 30 min and the sedimentation time is 30 min. The optimum pH of chemical precipitation method for removing the main pollutants from steel rope production sewage is 9, the molar ratio of phosphorus to calcium is 1.0: 1.3, and the reaction time is 30 min. The precipitation time is 30 min, the removal rate of phosphate in wastewater is 99.6% under the optimum precipitation conditions, the removal rate of 95.3% Zn2 is 99.0%. The optimum coagulation air flotation conditions are as follows: the dosage of 20 mg / L PAFC is 20 mg / L PAM, pH value is 7.5 mg / L ~ (-1), and the air flotation pressure is 0.6 Mpa. under the optimum conditions, the removal rate of COD of phosphate Pb2 ~ (2 +) ~ (2 +) Zn ~ (2 +) ~ (2 +) in sewage by coagulation air flotation system reaches 85.21,83.33.37.00.The technological process of this study and the most important one are obtained. The best operation parameters are applied to the practical treatment project of the sewage produced by a steel rope. The results of continuous operation show that the process has a good effect on the treatment of steel rope wastewater, the design flow rate is 40 m3 / d, the influent phosphate concentration is 228 mg / L Pb2, 40 mg / L Pb2 concentration is 285 mg / L ~ (2) COD is 230 mg / L ~ (-1) H ~ (-1) HRT, and the HRT is 8 h. The average concentrations of pollutants in the effluent treated by this process are as follows: phosphate concentration 0.4 mg / L Pb2 0.6 mg / L Zn _ 2 0.5 mg / L ~ (2) COD 25 mg 路L ~ (-1). The phosphate concentration and COD concentration can reach the level of DB21 / 1627-2008. The discharge requirements of Pb2 Zn-2, which are not required in Liaoning Comprehensive sewage discharge Standard, can also meet the requirements of the first class discharge in the Integrated sewage discharge Standard (GB8978-1996). The treatment cost per ton of sewage is about 2.49 yuan. The theoretical discussion shows that the ratio of air flotation pressure to reflux ratio has a great effect on the gas dissolution efficiency of the air floatation tank. When the reflux ratio is 30 and the floating pressure is 0.6 MPA, The air concentration in the air floatation tank is 22.20L / m ~ (3), and the number of microbubbles in the wastewater per unit volume is 9.89 脳 1014 / m ~ (3). The reflux ratio should be increased as much as possible, and the gas dissolution efficiency of the air flotation tank should be increased when the temperature is 20 鈩，

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