航道疏浚过程中底泥污染物化学钝化研究

发布时间：2018-02-28 03:00

  本文关键词： 底泥 疏浚 污染特征 化学钝化　出处：《重庆交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：疏浚不仅是维护航道水深和通航的一种重要措施，而且也属于一种能去除底泥污染物的方法，但是由于疏浚过程中挖泥船的机械扰动、溢流、洒漏，，使得底泥中的污染物重新释放，造成二次污染。所以疏浚能否从根本上解决环境的污染，一直存在很大争议。从而选择行之有效的疏浚方案，包括疏浚方式、疏浚深度、疏浚时节都是当今研究的热点问题。 化学钝化技术是指通过向水体投加化学钝化剂来去除或者转化为其他无毒无害，相对稳定的物质，从而达到净化底泥以及水体的作用。本文则是将化学钝化技术运用到航道疏浚中来从而达到以改变疏浚方式为目的，使底泥中的污染物造成的二次污染最低。本实验以三峡水库常年回水区忠县黄花城河段的底泥为研究对象，通过实验室的模拟，研究了化学钝化剂在抑制疏浚底泥中污染物的释放规律，主要研究结论如下： ①随着时间的增加，各类污染物释放量总体越来越大。在0-8h释放速率最快，8-24h释放量趋于稳定，达到底泥对污染物的吸附解吸平衡。解吸曲线拟合符合Langmuir公式。COD、TP、氨氮的最大释放量分别为104mg/L、0.94mg/L、1.96mg/L。由此说明，三峡典型淤积河段忠县黄花港地区疏浚底泥中存在大量污染物，如果不进行有效控制，在底泥扰动后，将会造成二次污染。 ②最佳钝化剂为PAC和硝酸钙。虽然5种钝化剂对于COD、TP都有一定的钝化效果，对于COD而言，效果最好的是PAC和硝酸钙，过氧化钙和双氧水次之，高锰酸钾再次之，但是从钝化速度来讲，双氧水的速度最快，在2天就能达到很好的抑制率，但是长期性较差。对于TP，5种钝化剂的效果都比较理想，控制速度快，且效果良好。其中以PAC和硝酸钙效果最佳，释放量均低于0.1mg/L。对于氨氮而言，5种钝化剂均无明显效果，双氧水与高锰酸钾反而有很强的促进氨氮释放能力，且随着投加量的增加，促进效果越强。 ③PAC的最佳投加量为4g/kg干泥、硝酸钙的最佳投加量为6g/kg干泥。 ④扰动情况下， PAC与硝酸钙能让泥沙迅速沉降，能在4小时达到50NTU以下，过氧化钙和高锰酸钾次之，双氧水反而促进了底泥向上覆水中扩散。 ⑤通过注入底泥内部的方式能更好的达到控制底泥污染物释放的目的，且注入方式对硝酸钙的影响较PAC更大。 ⑥温度的升高对于COD、总磷和氨氮有促进作用。 ⑦温度的升高对于PAC抑制底泥中COD、 TP和氨氮解吸影响不大；温度的升高对硝酸钙抑制底泥污染物的释放均起促进作用，且30℃效果远大于10℃18.2℃。夏季疏浚过程中，用硝酸钙效果更好。
[Abstract]:Dredging is not only an important measure to maintain waterway depth and navigation, but also a method to remove sediment pollutants. However, due to the mechanical disturbance, overflow and leakage of dredging vessels during dredging, So whether dredging can fundamentally solve the pollution of the environment has always been controversial. Therefore, it has been very controversial to select effective dredging schemes, including dredging methods and depth of dredging. Dredging season is a hot topic in current research. Chemical passivation technology refers to the removal or conversion into other non-toxic and relatively stable substances by adding chemical passivating agents to water bodies. In this paper, the chemical passivation technology is applied to the dredging of waterway to change the dredging mode. The secondary pollution caused by pollutants in sediment is the lowest. This experiment takes the sediment of Huanghuacheng reach, Zhongxian County, as the research object, through the laboratory simulation. The regulation of the release of pollutants from dredged sediment by chemical passivating agent was studied. The main conclusions are as follows:. (1) with the increase of time, the release of various pollutants became more and more large, and the release rate was the fastest in 0-8 h, and the release rate of 8-24 h tended to be stable. The desorption curve fitted with Langmuir formula. The maximum release of ammonia nitrogen was 104mg / L 0.94 mg / L 0.94 mg / L 1.96 mg / L respectively. This shows that there are a lot of pollutants in dredged sediment of Huanghua Port area, Zhongxian County, three Gorges typical silt. If no effective control is carried out, secondary pollution will be caused after sediment disturbance. 2 the best passivating agents were PAC and calcium nitrate. Although the five passivating agents had certain passivation effect for COD, the best ones were PAC and calcium nitrate, calcium peroxide and hydrogen peroxide, and potassium permanganate again. But in terms of passivation speed, hydrogen peroxide is the fastest, it can reach a good inhibition rate in 2 days, but the long-term is poor. The results showed that PAC and calcium nitrate had the best effect, and the release amount was less than 0.1 mg / L. there was no obvious effect on ammonia nitrogen, but hydrogen peroxide and potassium permanganate had a strong ability to promote the release of ammonia nitrogen, and with the increase of the amount of ammonia nitrogen, the effect of hydrogen peroxide and potassium permanganate on the release of ammonia nitrogen was higher than that of potassium permanganate. The stronger the promotion effect. 3The optimum dosage of PAC is 4 g / kg dry mud, and the best dosage of calcium nitrate is 6 g / kg dry mud. (4) under disturbance, PAC and calcium nitrate can precipitate the sediment rapidly, reaching less than 50NTU in 4 hours, followed by calcium peroxide and potassium permanganate, and hydrogen peroxide can promote the diffusion of sediment to the overlying water. (5) the method of injecting into sediment can better control the release of pollutants from sediment, and the effect of injection on calcium nitrate is greater than that of PAC. 6 the increase of temperature can promote COD, total phosphorus and ammonia nitrogen. (7) the increase of temperature has little effect on the inhibition of COD, TP and ammonia nitrogen desorption in sediment by PAC, and the increase of temperature can promote the inhibition of pollutant release from sediment by calcium nitrate, and the effect at 30 鈩

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