电絮凝法深度脱氮除磷的研究

【作者】 吴剑坤；

【导师】 普红平；

【作者基本信息】 昆明理工大学 ， 环境科学， 2009， 硕士

【摘要】 生活污水虽属于浓度相对较低有机废水,但其中有机高分子物质和氮、磷等其他养分的含量都还很高。随着人类对环境资源开发利用活动的日益增加,使大量含氮、磷营养物质的生活污水、工业废水排入江河湖泊中,增加了水体氮、磷负荷,导致水体富营养化。因此开发城市二级污水处理厂的脱氮除磷工艺迫在眉睫。电絮凝技术是近年发展起来的颇具竞争力的水处理技术,与传统方法相比,具有高效、稳定和无需投加化学药剂等显著特点。但由于能耗的问题,并未引起足够的重视。本文通过电絮凝法对二级处理出水进行深度处理,探讨其脱氮除磷的效果。试验采用双铝极板,以NH3-N、TP和COD的去除率等为指标,分别通过改变电解时间、极板间距、电流密度、原水pH值等参数,研究各参数对处理效果的影响；采用正交试验法获得处理的最佳运行工况。电解时间太短,絮凝效果较差,电解的时间过长,电流效率会降低,也会使电耗、铝耗及处理成本增大。电解时间应该控制在30 min之内为宜；中性及弱碱性条件下,电絮凝法的处理效果最好；随着电流密度的增大,对COD,NH3-N,TP的去除率都增大,但考虑能耗的关系,电流密度可控制在7.82-15.6A/m2；极板间距的增加,COD去除率下降,试验中的极板间距对磷的去除率影响不是很大,氨氮的去除率随着电极间距的增大而减小,实际应用中考虑到电耗及其他因素,电极间距可控制在1.0-2.0cm范围内。对单因素分析的电解时间,原水pH值、极板间距、电流密度这4个影响因素进行正交试验,最终经过综合平衡,得出实验的最佳方案为原水pH值8.0,极板间距为1.5 cm,电流密度为15.6 A/m2,电解时间为25 min。实验通过称量电解前后电极材料的净重差来计算处理1 m3水所消耗的电极材料量,结果铝电极消耗量为2.5 g/m3；根据电絮凝过程的电流、电压和电解时间来计算电絮凝处理二级处理出水的电能消耗,结果电絮凝法处理二级处理出水电耗为4度/吨。本文利用电絮凝法对城市污水处理厂二级处理出水进行处理,试验结果为COD去除率可达70%以上,TP去除率达到70%以上,NH3-N去除率达30%以上。电絮凝法深度处理后COD和TP含浓度都达到了GB18918-2002一级A类标准。更多还原

【Abstract】 Although Domestic wastewater belongs to organic wastewater of relatively low concentration, the content of organic polymer material and nitrogen, phosphorus and other nutrients are also in high levels. As the increasing of activicies of environmental resource development by human, a large number of domestic wastewater, industrial wastewater contained nitrogen and phosphorus nutrients are discharged into the rivers and lakes, increasing the load of water nitrogen and phosphorus, which the direct consequence is eutrophication. Therefore the development of urban secondary wastewater treatment plant’s nitrogen and phosphorus removal process is imminent.Electrolytic flocculation technology is a water treatment technology developed in recent years and possesses the distinctive feature of efficiency, stability and no auto-adding chemical agents compared with traditional methods. However we don’t pay sufficient attention to it due to the issue of energy consumption. In this paper, we use electric flocculation to deeply treat the outlet of secondary treatment and explore its effect of nitrogen and phosphorus removal.The test uses dual aluminum plate and study the effect of treatment by respectively changing the electrolysis time, plate distance, current density, pH value of raw water and other parameter, according to the indicators of the removal rate of NH3-N, TP and COD; orthogonal test method is used to obtain the best operating conditions of treatment.The effect of flocculation is poor because of the short electrolysis time; current efficiency will be reduced, and power consumption, aluminum consumption and processing costs are increasing due to the long electrolysis time. Electrolysis time should be controlled within 30 min; the effect of electrocoagulation is best within the neutral and alkaline conditions; with the increase of current density, the removal rates of COD, NH3-N, TP are also increased, the current density can be controlled in 7.82-15.6A/m2 considered the energy consumption; COD removal rate is decreased with the increase in plate spacing, plate spacing on the impact of phosphorus removal rate is not great, ammonia nitrogen removal rate is increased as the electrode spacing decreased, the electrode spacing can be controlled within the limits of 1.0-2.0cm as the other factors are taken into account in actual applications. These four influencing factors of the electrolysis time, pH value of the raw water, plate spacing, current density in single factor analysis are carried out by orthogonal test, and in final comprehensive balance, we obtain the best test solution of pH value of raw water 8.0, plate spacing 1.5 cm, current density 15.6A/m2, electrolysis time 25min.The test calculates the consumption volume of the electrode material by handling 1m3 of water through weighing before and after experiment electrode material’s net weight, and finally the aluminum electrode’s consumption is 2.5g/m3; we use the electric current, voltage and electrolysis time in flocculation process to calculate the power consumption of the outlet of secondary treatment by electrocoagulation, which is 5 degrees/ton finally. The test use electrocoagulation to deal with the outlet of secondary treatment in urban wastewater treatment plant, the final of test are COD removal rate reached more than 70%, TP reached over 70%, NH3-N above 30%. COD and TP concentration after deeply treated have reached the GB18918-2002 first-class A level standard by electrocoagulation.更多还原