城市污水处理厂二级处理出水中磷的组分及去除特性研究

发布时间：2018-01-11 12:35

本文关键词：城市污水处理厂二级处理出水中磷的组分及去除特性研究　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】：我国城市污水处理厂广泛采用生物脱氮除磷工艺去除污水中的营养物,在夏季和水质变化较大的场合,部分污水处理厂出水总磷不能稳定达到国家《城镇污水处理厂污染物排放标准》(GB18918-2002中)中的一级A标准,为此,需要采用化学除磷进行强化和补充。而化学沉淀法对磷的去除效果与水中磷的形态密切相关。本研究以西安市第三、四和五污水处理厂的生物脱氮除磷系统为对象,对二级处理出水中磷的存在形态进行理论分析和现场测定,在此基础上,以第三、第四和第五污水处理厂的二级处理出水采用PAC和Al2(SO4))3进行化学沉淀和混凝试验,探讨相应的除磷效果。主要得到以下结论:(1)城市污水处理厂二级处理出水中的磷以多种形式存在,而水质控制工程中磷的分类方法不能更好的表达磷的组分,本试验根据化学法物质的分类,将城市污水处理厂二级处理出水中的总磷,分为悬浮态磷(粒径0.45um)、胶体态磷(粒径0.45um~1nm)以及溶解态磷(粒径1nm),可更加全面准确地反映二级出水中磷的存在形态。(2)通过对西安市第三、四、五污水处理厂二级处理出水各种磷形态的测定得出西安市第四和第五污水处理厂二级处理出水中的磷形态主要以溶解态磷存在,悬浮态磷、胶体态磷和溶解态磷所占总磷的比例分别为5%~15%、15%~25%、60%~70%和12.5%~20%、12.5%~20%、50%~75%;西安市第三污水处理厂二级处理出水中的悬浮态磷含量和胶体态磷浓度接近,其占总磷的比例分别为20%~27%、15%~30%。针对不同形态的磷,采用的去除对策也将不同。(3)依据磷化学,磷酸盐在不同的p H条件下的形态不同,主要包括H3PO4、H2PO4-、HPO42-及PO43-四种存在形态。由于城市污水处理厂二级处理出水的p H在6~9之间,通过理论计算,废水中的磷酸盐主要以H2PO4-、HPO42-形态存在,所以,在化学沉淀除磷的过程中,主要是H2PO4-、HPO42-与Al3+反应生成Al PO4沉淀,从而达到降低磷含量的目的,而非常规认识的PO43与Al3+反应形成沉淀。(4)通过烧杯试验,比较了聚合氯化铝和硫酸铝两种除磷剂的除磷效果。当总磷为0.9 mg/L(均值)时,PAC和Al2(SO4)3的投加量分别为4mg/L和6mg/L(以Al计),处理后的总磷浓度小于0.5mg/L,可以稳定达到国家城镇污水处理厂污染物排放标准GB18918-2002中的一级A标准。PAC比Al2(SO4)3的处理效果好、稳定。
[Abstract]:Biological denitrification and phosphorus removal process is widely used to remove nutrients from municipal wastewater treatment plants in China, and it is widely used in summer and in situations where water quality changes greatly. The total phosphorus of the effluent from some sewage treatment plants can not reach the first class A standard of the National Standard for pollutants discharge in the Municipal sewage treatment Plant (GB 18918-2002). Chemical phosphorus removal needs to be strengthened and supplemented. The removal effect of phosphorus by chemical precipitation method is closely related to the form of phosphorus in water. The biological denitrification and phosphorus removal system of the fourth and fifth sewage treatment plants was used as the object. The existing forms of phosphorus in the secondary treatment effluent were theoretically analyzed and measured on the spot. On this basis, the third was taken as the third. The secondary effluent of 4th and 5th sewage treatment plants was treated with PAC and Al2(SO4))3 to carry out chemical precipitation and coagulation tests. The main conclusions are as follows: 1) phosphorus in secondary treatment water of municipal wastewater treatment plant exists in many forms. However, the classification method of phosphorus in water quality control engineering can not express the components of phosphorus better. According to the classification of chemical substances, the total phosphorus of secondary treatment water of municipal wastewater treatment plant is treated. It can be divided into suspended phosphorus (particle size 0.45 nm), colloidal phosphorus (particle size 0.45 um) and dissolved phosphorus (particle size 1 nm). Can more comprehensively and accurately reflect the existence form of phosphorus in secondary effluent. 2) pass through the third and fourth parts of Xi'an city. The determination of various phosphorus forms in the secondary treatment effluent of the fifth sewage treatment plant shows that the phosphorus forms in the secondary treatment effluent of Xi'an 4th and 5th sewage treatment plants are mainly dissolved phosphorus and suspended phosphorus. The proportions of colloidal phosphorus and dissolved phosphorus to total phosphorus were 50.15% and 15.55%, respectively, and about 70% and 12.5% respectively. The suspended phosphorus content and colloidal phosphorus concentration in the secondary treatment water of the third sewage treatment Plant of Xi'an are close to each other, and the proportion of the suspended phosphorus to the total phosphorus is 20%, 2727% and 15% respectively. According to phosphorus chemistry, the species of phosphate in different pH conditions are different, including H3PO4H2PO4-. Four forms of HPO42- and PO43- exist. Due to the pH of secondary effluent from municipal wastewater treatment plant is between 6 and 9, through theoretical calculation, the phosphate in wastewater is mainly H2PO4-. Therefore, in the process of phosphorus removal by chemical precipitation, the reaction of H2PO4-HPO42- with Al3 resulted in Al PO4 precipitation. In order to reduce phosphorus content, unconventional PO43 reacted with Al3 to form precipitate. 4) beaker test was carried out. The phosphorus removal effects of two kinds of phosphorus removal agents, polyaluminium chloride and aluminum sulfate, were compared when the total phosphorus was 0.9 mg / L (mean value). The dosages of PAC and Al2(SO4)3 were 4 mg / L and 6 mg / L, respectively. It can stably reach the first class A standard of GB18918-2002 of the national municipal wastewater treatment plant's pollutant discharge standard. The treatment effect of Al2(SO4)3 is better and more stable than that of Al2(SO4)3.
【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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