城市污水处理厂污水磷的化学沉淀特性及影响因素研究

发布时间：2018-01-19 07:38

本文关键词： 城市污水化学除磷三氯化铁 PAC 影响因素　出处：《西安建筑科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着城市污水处理厂污染物排放标准日趋严格,大多数污水处理厂存在出水总磷难以达标的问题,因而通常需要在一些处理工段上辅以化学除磷。但是化学除磷效果往往受实际废水水质以及不同工段工况等多种因素影响。水质等对化学沉淀除磷影响的国内外研究报道不多。本研究对西安市某污水处理厂的几种工段水质(进厂原水、污泥浓缩上清液、污泥脱出水,厌氧池澄清液、二沉池出水)进行批次化学除磷实验。目的是探明不同化学除磷药剂、水中溶解性有机物(如VFA、腐殖酸等)对化学除磷的影响以及相互之间的作用机理与沉淀产物组成,揭示城市污水处理厂不同工段水质磷的化学沉淀特征,为指导污水处理厂化学除磷奠定基础。论文得到了以下主要成果:(1)通过六种沉淀剂硫酸亚铁,氯化钙,氧化钙,硫酸铝,三氯化铁,聚合氯化铝(PAC)对几个工段水样的批次实验,得出:采用钙盐为沉淀剂的磷去除率总体上较低,而铁盐和铝盐相对效果比较好。其中,二沉池出水采用PAC和三氯化铁可以使磷去除率达70%以上;进厂原水采用铝系盐磷去除率较高,采用铁盐的磷去除率较低;厌氧池澄清液以PAC为沉淀剂可以使磷去除率达75%以上;污泥脱出水采用三氯化铁和PAC可以去除72%以上的磷酸盐;污泥浓缩水用三价铁盐,PAC去除效果较好,磷的去除率约75%。(2)快速搅拌200r/min 1min慢速搅拌50 r/min 10min,沉淀时间为30min为批次实验最佳反应条件。(3)在pH=6.5,随着VFA浓度的增加,磷去除率逐渐下降,VFA在高于60mg/L时对磷去除率影响较大,在10mg/L~50mg/L范围内影响较小;腐殖酸的加入对磷去除率影响较小,在含量为40mg/L下,磷去除率基本没有变化;超过60mg/L之后,磷去除率缓慢降低。(4)以铁盐、铝盐为沉淀剂形成的化学沉淀物主要为铁盐、铝盐自身水解产物和与磷酸盐结合的沉淀产物。总体上PAC的沉淀物种类比较复杂,沉淀物主要有AlPO4、Al2 O3、Al6P6 O24·4H2O、Al(H2 PO4)3、Al8 H12(P2O7)9、Al2P6 O18,AlH6(PO4)3·2H2O等,铁盐沉淀磷的主要产物主要有Fe(OH)3、Fe2P、Fe4(PO4)3(OH)3、Fe3 PO7等。(5)在pH=4左右,模拟计算出:磷酸铁生成速率最大。铁盐化学除磷在pH=4.5下效果好,论文分析原因有:一是此p H下铁盐的水解作用比较强,水解产生的水解产物对磷有很强的吸附作用,二是有一部分的铁盐与磷酸根直接结合。污水pH为7左右,用铁盐进行化学除磷需提前调pH。铝盐在“沉淀模式”条件下溶液偏碱性,产生的Al(OH)3(am)和Al(OH)3(s)能吸附磷酸根离子,因此磷的去除率较高。
[Abstract]:With the increasingly stringent standards of pollutant discharge in municipal wastewater treatment plants, most wastewater treatment plants have the problem that the total phosphorus of effluent is difficult to reach the standard. Therefore, chemical phosphorus removal is usually needed in some treatment sections. However, the effect of chemical phosphorus removal is often affected by many factors, such as actual wastewater quality and different working conditions, etc. The effect of chemical phosphorus removal at home and abroad, such as water quality, is affected by chemical precipitation. There are few reports on the study. The water quality of several sections of a sewage treatment plant in Xi'an is studied (. Raw water into the factory. Batch chemical phosphorus removal experiments were carried out on sludge concentrate supernatant sludge stripping water anaerobic tank clarifier and secondary settling tank effluent. The purpose of this experiment was to find out different chemical phosphorus removal agents and dissolved organic matter (such as VFA) in water. The effect of humic acid on chemical phosphorus removal, the interaction mechanism and the composition of precipitate products, and the characteristics of chemical precipitation of phosphorus in different sections of municipal wastewater treatment plant were revealed. In order to guide chemical phosphorus removal in wastewater treatment plant, the following main achievements were obtained: 1) through six precipitators, ferrous sulfate, calcium chloride, calcium oxide, aluminum sulfate, ferric chloride. The experiments on several sections of water samples by polyaluminum chloride (PAC) showed that the phosphorus removal efficiency of calcium salt as precipitant was lower, but the relative effect of iron salt and aluminum salt was better. PAC and ferric chloride can make phosphorus removal rate more than 70%. The removal rate of phosphorus by aluminum salt is higher than that by iron salt. Using PAC as precipitating agent, the phosphorus removal rate of the clarifier in anaerobic tank can reach more than 75%. More than 72% phosphate can be removed from sludge effluent by ferric chloride and PAC. The removal rate of phosphorus is about 75r / min ~ (2)) stirring 200r / min / min 1 min and stirring 50 r / min / min for 10 minutes. The optimum reaction condition was 30 min. The phosphorus removal rate decreased with the increase of VFA concentration. When VFA is higher than 60 mg / L, the phosphorus removal rate is more significant, but less in the range of 10 mg / L ~ 50 mg / L; The addition of humic acid had little effect on the phosphorus removal rate, and the phosphorus removal rate had no change when the content was 40 mg / L; After more than 60 mg / L, the phosphorus removal rate decreased slowly. 4) Iron salt was the main chemical precipitate formed by aluminum salt and iron salt. On the whole, the types of precipitates in PAC are quite complex, and the main precipitates are AlPO4 and Al 2O 3. Al6P6 O _ 24 路4H _ 2O _ 2 H _ 2PO _ 4H _ 2H _ 2O _ 3H _ 2O _ 8 H _ 2O _ (12) P _ 2O _ 7H _ 2O _ (9) Al _ 2P _ (6) O _ (18) AlH _ (6) O _ (4) O _ (4). The main products of Fe ~ (2 +) precipitation are Fe ~ (2 +) O ~ (2 +) Fe ~ (2 +) P _ (4) Fe _ (4) O _ (4) O _ (4) O _ (3) Fe _ (3) PO7 and so on. The results show that the rate of iron phosphate formation is the largest. The effect of iron salt chemical phosphorus removal is good under pH=4.5. The main reasons are as follows: first, the hydrolysis of iron salt is stronger at this pH. The hydrolytic product produced by hydrolysis has a strong adsorption effect on phosphorus. Second, some iron salts are directly combined with phosphate, and the wastewater pH is about 7. It is necessary to adjust the pH in advance for chemical phosphorus removal with iron salt. The solution of aluminum salt is alkaline under the "precipitation mode", and the resulting Al _ 2O _ H _ 3a) and Al _ 2O _ H _ (3) can adsorb phosphate ion. Therefore, phosphorus removal rate is higher.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X703

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