给水厂排泥水中镉污染控制技术的实验研究

发布时间：2018-07-26 20:25

【摘要】：我国部分地区水源受列重金属镉污染,经过给水厂水处理工艺净化,原水中大部分镉聚集到排泥水中,对受镉污染严重的排泥水进行回用,会升高给水厂出水中镉浓度超标的风险,为降低排泥水上清液中镉的浓度,保证排泥水安全回用,本文使用六联搅拌器,对人工配制的镉污染排泥水进行“破碎-再絮凝”实验。通过研究排泥水“破碎-再絮凝”过程中各条件变化对镉迁移的影响,深入研究了“破碎-再絮凝”过程中镉在排泥水固液两相间的迁移转化规律,在此基础上提出排泥水中镉的强化去除方法,保障自来水厂排泥水的安全回用,结果表明:(1)排泥水的“破碎-再絮凝”过程有利于上清液中镉的去除,絮体的破碎和再絮凝过程都能吸附部分镉。镉的去除效果与破碎强度有关,破碎强度越大镉的去除效果越好,试验中的最佳破碎强度为600rpm,此时对上清液中镉的去除率为37.9%,再絮凝过程中镉的去除量在1.3-1.9μg/L之间,去除率约为7.9%-11.5%。(2)pH变化对镉去除的影响较大,主要是由于pH对镉的溶解度影响较大,pH升高有益于降低上清液镉的深度,pH降低不利于镉的去除,甚至污呢中的镉有解吸的风险。(3)排泥水“破碎-再絮凝”过程中,投加适量的阳离子絮凝剂,能进一步降低上清液中镉的浓度。絮凝剂存在最佳的投加量范围,破酸铁和氯化铝的最佳投加量范围分别在4mg/L和5mg/L左右,对镉的强化去除量分别为2μg/L和1.5μg/L,去除率分别增加12.1%和9.1%;聚合破酸铁和聚合氯化铝的最佳投加量分别为22mg/L和5mg/L,对镉的强化去除量分别为1.6μg/L和0.9μg/L,去除率分别增加9.7%和5.5%,过量的絮凝剂会导致已吸附的镉释放,阴离子和阳离子的PAM对镉的影响不同,“破碎-再絮凝”过程中投加阴离子PAM对镉的去除没有影响,投加阳离子PAM不利于镉的强化去除。(4)排泥水污泥中镉主要以铁锰氧化物结合态存在,“破碎-再絮凝”过程中上清液中镉的深度降低,主要是由于污泥中铁锰氧化物结合态镉的量增加,投加絮凝剂后排泥水中的镉也主要是在溶解态和铁锰氧化物结合态之间适移;使用PAM调节污泥后,污泥中不稳定的离子交换态镉和部分铁锰氧化物结合态镉转变为有机结合态镉。(5)排泥水污泥对镉的吸附过程主要是以分子扩散模型为主的多种动力学机理共同作用的结果;吸附饱和后,继续搅拌产生的镉释放过程是以准一级速率方程为主的多种动力学机理共同作用的结果。温度升高不利于污泥对镉的吸附。最后结合实验的结果与分析,针对部分地区水源地受到镉污染的情况,对水厂排泥水现有回用工艺提出改进建议。
[Abstract]:Some water sources in China are polluted by cadmium, which is a heavy metal. After the water treatment process of the water supply plant, most of the cadmium in the raw water accumulates into the mud discharge water, and the waste mud water which is seriously polluted by cadmium is reused. In order to reduce the concentration of cadmium in the supernatant of waste mud water and ensure the safe reuse of the sludge water, the six mixers are used in this paper. The experiment of "crushing-reflocculation" was carried out on the artificially made mud water contaminated with cadmium. By studying the effect of various conditions on cadmium migration in the process of "crushing and reflocculation" of mud discharge water, the migration and transformation of cadmium between solid and liquid phases in the process of "crushing and reflocculation" were studied in depth. On this basis, the enhanced removal method of cadmium in mud water is put forward to ensure the safe reuse of mud water from water plant. The results show that: (1) the process of "crushing and flocculation" of mud water is beneficial to the removal of cadmium in supernatant. Some cadmium can be adsorbed in the process of floc crushing and reflocculation. The removal efficiency of cadmium is related to the crushing strength. The higher the crushing intensity is, the better the removal effect is. The optimum crushing strength is 600 rpm, and the removal rate of cadmium in supernatant is 37.9 渭 g / L, and the removal rate of cadmium in flocculation process is between 1.3-1.9 渭 g / L. The removal rate was about 7.9- 11.5. (2) the change of pH had a great effect on the removal of cadmium, mainly because pH had a great effect on the solubility of cadmium. The increase of pH was beneficial to the reduction of the depth of cadmium in supernatant and the decrease of pH was not conducive to the removal of cadmium. Even cadmium in the waste water has the risk of desorption. (3) in the process of "crushing and reflocculation", adding a proper amount of cationic flocculant can further reduce the concentration of cadmium in the supernatant. The optimum dosage range of flocculant is about 4mg/L and 5mg/L respectively. The enhanced removal of cadmium was 2 渭 g / L and 1.5 渭 g / L, respectively, and the removal rates were increased by 12.1% and 9.1%, respectively. The optimum dosages of polyacid-breaking iron and polyaluminium chloride were 22mg/L and 5 mg / L, respectively. The enhanced removal of cadmium was 1.6 渭 g / L and 0.9 渭 g / L, respectively, and the removal rate was increased by 9.7% and 0.9 渭 g / L, respectively. 5.5. excessive flocculant will lead to the release of adsorbed cadmium, The effects of anionic and cationic PAM on cadmium were different, and the addition of anionic PAM in the process of "crushing and reflocculation" had no effect on the removal of cadmium. The addition of cationic PAM was not conducive to the enhanced removal of cadmium. (4) the cadmium in sludge was mainly iron-manganese oxide bound, and the depth of cadmium in supernatant decreased during the process of "crushing and reflocculation". It is mainly due to the increase in the amount of iron-manganese oxide bound cadmium in sludge, and the suitable shift of cadmium in mud water after adding flocculant between dissolved state and iron-manganese oxide bound state. After PAM is used to regulate sludge, The unstable ion-exchange cadmium and some iron-manganese oxide bound cadmium in sludge are transformed into organic bound cadmium. (5) the adsorption process of cadmium in sludge is mainly the result of various kinetic mechanisms based on molecular diffusion model. After adsorption and saturation, the release process of cadmium produced by continuous stirring is the result of a combination of several kinetic mechanisms based on the quasi first order rate equation. The increase of temperature is not conducive to the adsorption of cadmium by sludge. Finally, based on the results and analysis of the experiment, some suggestions are put forward to improve the existing reuse process of the waste mud water from the cement plant in view of the cadmium pollution in the water sources in some areas.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X703

【参考文献】