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近年来,随着工业和经济的快速发展,大量废水未进行有效处理而直接排放,使众多湖泊、水库等饮用水水源中的氨氮、有机物等含量超标,成为微污染水源水[1-4],传统的“混凝→沉淀→过滤→消毒”净水工艺难以对这些污染物质进行有效控制。随着我国人民生活水平的提高和健康安全意识的加强,人们对生活饮用水品质的重视程度也日渐提升,出水水质标准要求也变得更加严格[5-8]。因此,为保障供水水质安全,应对现代水源水污染,需要在充分利用现有工艺设施的基础上,研发和应用新技术和新工艺,改良常规水处理工艺。
强化混凝工艺可以利用水厂中原有的絮凝池进行工艺升级改造,无须新建水处理构筑物,资金投入较小,是微污染水源水处理的一个重要发展方向[9-10]。但单纯的强化混凝只能提高浊度及不溶性有机物的去除,对可溶性有机物及氨氮的处理能力甚微。
活性污泥法是城市污水处理中较广泛使用的方法,它能从污水中去除溶解性和胶体状态的可生化有机物以及一些被活性污泥吸附的悬浮固体和其他物质[11]。如果能将污水处理中常用的生物脱氮技术引用到强化混凝中来,与强化混凝工艺进行耦合[12],在满足对不溶性有机物去除的同时,提高对水中可溶性有机物的处理效果,不失为一种经济有效的方法。
本研究通过对传统絮凝池中机械搅拌桨桨板结构进行研究并加以改造,使其在搅动过程中形成一定的速度梯度,从而使其沿着搅拌桨直径方向,携入不同含量的空气,在水体中形成一个良好的溶解氧浓度梯度,进而在强化混凝的同时,实现同步硝化反硝化脱氮的功能。
微污染水源水脱氮的强化混凝工艺
Enhanced coagulation process for denitrification from micro-polluted water source
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摘要: 通过对机械搅拌桨桨板结构优化改造,实现在絮凝池内同步进行强化混凝及生物脱氮反应,分析桨板长度梯度、板间间距及其与固定挡板间夹角对絮凝池内溶解氧浓度梯度产生影响,设计出了一种搅拌时池内可以形成厌氧-缺氧-好氧环境的新型机械搅拌桨,Fluent流场分析进一步验证了池内横向、纵向都会产生溶解氧浓度梯度。新型搅拌桨与传统搅拌桨生物脱氮对比实验表明,当采用新型搅拌桨时,絮凝池对
${\rm{NH}}_4^ + $ -N、TN去除效果远优于传统搅拌桨。进一步进行模拟微污染水源水的强化混凝生物脱氮应用实验,出水浊度为0.47 NTU,COD、${\rm{NH}}_4^ + $ -N和TN的浓度分别为10.54、5.01和5.84 mg·L−1,表现出良好的处理效果。对污泥粒径的研究表明,PAC投加可有效改善污泥絮体结构,为微污染水源水的处理提供了新思路。-
关键词:
- 桨板结构优化 /
- Fluent流场分析 /
- 强化混凝 /
- 生物脱氮
Abstract: In this study, the synchronous enhanced coagulation and biological denitrification reactions in the flocculation tank were realized by modifying the structure of the stirring paddle. The effects of the paddle length gradient, the spacing between the paddles, and the angle between the paddles and the transverse brackets on the dissolved oxygen concentration gradient in the tank were determined, finally a new mechanical stirring paddle was designed, an anaerobic-anoxic-aerobic reaction environment occurred in the tank when the stirring paddle rotates. Through Fluent analysis of flow field in flocculation tank, the dissolved oxygen concentration gradient along the longitudinal and transverse directions in the flocculation tank was further verified. Biological denitrification experiments were carried out using new mixing paddles and conventional paddles, respectively. When the new mixing paddle was used, the${\rm{NH}}_4^ + $ -N and TN removal effects were far superior to the traditional mixing paddle in the flocculation tank. The synchronous enhanced coagulation and biological denitrification experiments were further conducted to treat the simulated micro-polluted water sources, the turbidity of the effluent was 0.47 NTU, and the concentrations of COD,${\rm{NH}}_4^ + $ -N and TN were 10.54, 5.01 and 5.84 mg·L−1, respectively, which showed good performance on micro-polluted water sources treatment. The results of sludge particle size measurement proved that PAC dosing could effectively improve sludge floc structure, which provides a new development direction for the treatment of micro-polluted source water. -
表 1 原水水质
Table 1. Raw water characteristics
水样 浊度/NTU COD/(mg·L−1) TN/(mg·L−1) ${\rm{NH}}_4^ + $ -N/(mg·L−1)人工配水(范围) 43~52 49~54 8~10.3 6~9.3 人工配水(均值) 50.00 51.67 8.42 7.60 实际微污染水 54.35 63.26 11.54 13.01 表 2 2种机械搅拌桨出水水质对比
Table 2. Comparison of effluent water quality with two kinds of mechanical stirring paddles
水质类型 浊度/NTU COD/(mg·L−1) ${\rm{NH}}_4^ + $ -N/(mg·L−1)TN/(mg·L−1) 进水 54.35 63.26 11.54 13.01 新型搅拌桨出水 0.49 11.12 6.43 6.82 传统搅拌桨出水 0.42 9.75 8.44 9.37 表 3 2种机械搅拌桨污染物去除率对比
Table 3. Comparison of pullutants removal rate with two kinds of mechanical stirring paddles
% 搅拌桨类型 浊度去除率 COD去除率 ${\rm{NH}}_4^ + $ -N去除率TN去除率 新型搅拌桨 99.1 82.42 44.28 47.58 传统搅拌桨 99.22 84.58 26.86 27.98 -
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