被污染土壤低温热解技术除汞废水Fenton氧化研究

发布时间：2018-07-16 16:42

【摘要】：随着《土壤污染防治行动计划》的正式实施,土壤污染修复已成为环境修复领域的研究热点之一。当前,处治污染土壤的方法包括物理修复、化学修复、生物修复等方法,针对土壤中污染物类别、浓度高低以及土壤区域用途目的的不同,选择不同的污染土壤修复技术。低温热解技术针对高浓度汞污染农耕土地,进行复垦修复的工程性处理方法,汞的去除效率达到了70%~90%左右。低温热解技术已实际运用于修复某有机化工厂污染的土壤、河道底泥的治理,并取得了良好的效果。但该区域污染物来源于化工厂排放的废水,污染土壤中除了汞之外,还有极其复杂的有机污染物积累于土壤中,由于土壤在破碎和干化后仍存在5%~20%的含水率,在利用低温热解技术处理过程中,污染土壤产生了部分成分尚不清楚的废水。本论文从完善低温热解技术体系,为该新型实用技术进一步推广应用的角度出发,围绕低温热解处理污染土壤过程产生的废水,开展了如下研究:(1)弄清废水中污染物成分、及其浓度,确定废水类型。对废水进行GC/MS扫描,发现废水中存在有苯系物、酚类物质以及多环芳烃类物质;对废水中COD、氨氮、挥发酚等污染物进行检测发现COD浓度高达15000~20000 mg/L,氨氮在2000 mg/L上下,挥发酚也严重超标,计算B/C大约在0.14~0.18之间,确定该废水属于高浓度难降解的有机废水。(2)由于废水中有机物浓度远超过《污水综合排放标准》(GB8978-1996)所规定排放标准,因此需要寻求有效方法对废水进行处理。参照常见难降解废水的性质和处理方法,采用Fenton氧化法对低温热解除汞废水进行处理。以COD去除率为指标得到Fenton氧化法废水处理的最佳试验条件,包括初始反应pH为3~4、FeSO4·7H2O投加量13.9 g/L、H2O2投加量为84 ml/L、反应时间40min、重复氧化三次;最终得到COD的去除率达到了83%。(3)评价Fenton氧化法对废水处理的综合效果。在最优实验条件下,对废水处理后COD浓度从17900 mg/L降低为3034 mg/L、氨氮浓度从1934 mg/L降低为1111 mg/L、挥发酚由16.8 mg/L将抵至3.32 mg/L,三种污染物浓度在处理后去除率分别为83%、42.55%、80%,废水的生化指标B/C从0.18提高到0.36,可生化性提高100%。(4)不同浓度的热解废水以及其他类型的废水Fenton氧化处理对比研究。由于土壤含水率的变化以及被污染的程度不同,产生的废水有机物浓度不同,在相同试验条件下,对不同处理对象进行研究,验证Fenton氧化法对不同浓度有机废水的有效性,从侧面反映了热解废水水质的复杂性和难降解性。综上,低温热解技术工程性修复某化工厂污染农耕土壤过程中产生的废水属于高浓度难降解有机废水,废水中COD浓度最高达到20000 mg/L,挥发酚也高达18.6 mg/L。若该废水直接排入环境会造成严重的二次污染,目前对废水行业的研究中,对此类废水的处理并无明确方法,本文采用Fenton氧化法对废水进行处理,COD、氨氮、挥发酚等污染物浓度在处理后去除率分别为83%、42.55%、80%,废水中污染物浓度大幅度降低,虽不能满足《污水综合排放标准》但废水生化指标从0.18提高到0.36,水质可生化性明显提高,为实现废水排放后续的生化处理或者其他处理技术提供了良好基础,对完善低温热解技术体系提供了技术途径。
[Abstract]:With the implementation of the action plan for the prevention and control of soil pollution, the remediation of soil pollution has become one of the hotspots in the field of environmental remediation. At present, the methods of treating contaminated soil include physical repair, chemical repair, bioremediation and so on. The selection of soil pollution types, concentration and purpose of soil regional use is different. Different remediation techniques for contaminated soil. Low temperature pyrolysis technology for high concentration of mercury polluted farmland and reclamation and restoration by engineering method, the removal efficiency of mercury has reached about 70%~90%. Low temperature pyrolysis technology has been applied to remediation of contaminated soil in an organic chemical plant and the treatment of sediment in the river, and good results have been achieved. However, the pollutants in this area are derived from the effluent from the chemical plant. Besides the mercury in the contaminated soil, the extremely complex organic pollutants are accumulated in the soil. The water content of the 5%~20% still exists after the soil is broken and dried. In the process of treating the soil with low temperature pyrolysis, the polluted soil produces some unknown waste water. In this paper, from the perspective of improving the low temperature pyrolysis technology system and further application of the new practical technology, the following studies have been carried out on the waste water produced by the process of low temperature pyrolysis to treat the contaminated soil process. (1) clarify the pollutants in the waste water and its concentration and determine the type of wastewater. The GC/MS scanning of the wastewater has been carried out to find the existence of waste water. There are benzene series, phenols and polycyclic aromatic hydrocarbons; the detection of COD, ammonia nitrogen and volatile phenol in the wastewater has found that the concentration of COD is up to 15000~20000 mg/L, the ammonia nitrogen is above 2000 mg/L, and the volatile phenol is seriously exceeding the standard, the calculation B/C is about 0.14~0.18, and the wastewater is a high concentration and difficult degradation organic wastewater. (2) due to waste. The concentration of organic matter in water is far beyond the emission standard stipulated in the integrated wastewater discharge standard (GB8978-1996), so it is necessary to seek effective methods to treat the wastewater. Referring to the properties and treatment methods of the common refractory wastewater, the Fenton oxidation method is used to treat the low temperature hot mercury waste water. The COD removal rate is used as the index to obtain the Fenton oxidation. The optimum test conditions for the treatment of the wastewater include the initial reaction pH 3~4, the dosage of FeSO4 / 7H2O 13.9 g/L, the H2O2 dosage of 84 ml/L, the reaction time 40min, and the repeated oxidation three times. Finally, the removal rate of COD is achieved by 83%. (3) evaluation of the combined effect of Fenton oxidation on wastewater treatment. Under the optimal experimental conditions, COD concentration after wastewater treatment is concentrated. From 17900 mg/L to 3034 mg/L, the concentration of ammonia nitrogen decreased from 1934 mg/L to 1111 mg/L, the volatile phenol was from 16.8 mg/L to 3.32 mg/L, and the removal rate of three kinds of pollutants was 83%, 42.55%, 80%, respectively, and the biochemical indexes of the wastewater were increased from 0.18 to 0.36, and the biodegradability of 100%. (4) different concentrations of pyrolysis wastewater and other classes could be improved. Comparative study on Fenton oxidation treatment of wastewater. Due to the change of soil moisture content and the different degree of pollution, the concentration of organic matter in the wastewater is different. Under the same test conditions, the different treatment objects are studied to verify the effectiveness of the Fenton oxidation method for different concentrations of organic waste water, and the water quality of the pyrolysis wastewater is reflected from the side. In summary, the waste water produced in the process of remediation of contaminated agricultural soil in a chemical plant with low temperature pyrolysis technology is high concentration and difficult to degrade organic wastewater. The highest COD concentration in the wastewater is up to 20000 mg/L, and the volatile phenol is also up to 18.6 mg/L.. If the wastewater is directly discharged into the environment, it will cause serious two pollution. In the research of wastewater industry, there is no clear method to treat such wastewater. In this paper, the Fenton oxidation method is used to treat wastewater. The removal rate of COD, ammonia nitrogen and volatile phenol is 83%, 42.55%, 80% respectively after treatment, and the concentration of pollutants in the wastewater is greatly reduced, although it can not meet the wastewater discharge standard, but the wastewater biochemical index can not be met. From 0.18 to 0.36, the biodegradability of water quality is improved obviously. It provides a good basis for the implementation of biochemical treatment or other treatment techniques for the follow-up of wastewater discharge, and provides a technical way for improving the low temperature pyrolysis technology system.
【学位授予单位】：贵州师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703;X53

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