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水体氮污染是引起富营养化的主要原因之一[1-2]。近些年来,国家对城镇污水处理厂出水的氮含量不断提出更高的要求。因此,采用更为高效的技术对城市污水处理厂尾水进行深度脱氮处理,以降低尾水中的氮含量,已是大势所趋。硫自养反硝化和异养反硝化是目前2种非常成熟的生物脱氮技术。针对含氮废水,硫自养反硝化菌可以利用单质硫或还原态硫化物作为电子供体进行反硝化脱氮,不需要外加碳源,且污泥产量低、活性高[3]。而以异养反硝化为主体的脱氮工艺因其具有处理时间短、处理水量大、易于维护管理的特点,目前还无法被取代。异养反硝化虽然脱氮速率快,但出水氮含量很难达到更低水平,故将硫自养反硝化作为其补充能够取得更加优异的脱氮效果。
因此,在异养反硝化系统中投加硫源,构建协同反硝化体系,成为本领域的研究方向之一。李祥等[4]在启动成功的异养反硝化反应器中添加硫磺作为硫源,培养硫自养反硝化菌,在没有额外添加无机碳源的情况下,运行116 d后,体系的总氮去除率达85%以上,并且减少了60%的污泥量。XU等[5]在污水处理厂二沉池出水中加入有机碳源后,再让其通入以硫磺为填料的自养反硝化反应器,使出水总氮由(12.9±1.8) mg∙L−1进一步降至2.5 mg∙L−1以下。已有研究者在活性污泥中添加硫源来实现以异养为主的协同反硝化,但目前膜生物反应器内以异养为主的协同反硝化研究还相对较少,而相比于活性污泥法,膜生物反应器法具有污泥少、不发生污泥膨胀、操作简便的优势。因此,若能在膜生物反应器中实现以异养为主的硫自养与异养协同反硝化,将具有十分重要的工程意义。
因为陶粒成本低、挂膜速度快、脱氮效率高,所以,采用膜生物反应器法的污水处理厂大多采用陶粒作为填料来进行挂膜。在硫自养反硝化中,从反应速率、投资成本、副产物生成等方面考虑,以单质硫作为硫源更具优势[6]。因此,将陶粒和硫磺混合作为反硝化生物填料更加符合实际应用,且硫磺既能作为硫源,也能和陶粒一起作为填料被反硝化生物附着,形成生物膜。基于上述原因,本研究将硫磺颗粒与陶粒填料混合填充至反应柱中,形成自养与异养耦合的反硝化体系,针对城市污水处理厂尾水,在不同的陶粒和硫磺比例下,通过对反应器进出水离子之间变化关系的探究及微生物学分析,揭示反应器中硫自养和异养协同反硝化的作用机制,并分析将其运用于城市污水处理厂尾水深度脱氮的可行性。
基于异养-硫自养反硝化耦合技术的陶粒-硫磺混合生物填料对城市污水处理厂尾水的深度脱氮
Deep nitrogen removal from urban wastewater by ceramsite-sulfur mixed biological fillers based on heterotrophy-sulfur autotrophic denitrification coupling technology
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摘要: 针对城市污水处理厂脱氮能力的不足,设计了2种不同体积比的陶粒-硫磺混合生物填料反应器(陶粒与硫磺的体积比分别为2∶1和5∶1),并用其对城市污水处理厂尾水进行了深度处理。结果表明,陶粒与硫磺体积比为2∶1的混合生物填料反应器(R2,高硫耦合组)在C/N为4,HRT为4 h的条件下处理模拟废水时脱氮效率最高,TN平均去除率和平均出水质量浓度分别为(92.62±1.36)%和(2.39±0.22) mg∙L-1。相比于R1(异养对照组),R2在保证脱氮效率的同时,碳源投加量更少;此外,R2在最佳条件下促进了体系内反硝化微生物群落Thauera(陶厄氏菌属)和Thiobacillus(硫杆菌属)的生长,二者的相对丰度之和为39.13%。Abstract: Aiming at the deficiency of nitrogen removal capacity of urban sewage plant, two biological packing reactors with different volume ratios of ceramsite and sulfur mixing fillers (ceramsite/sulfur ratios: 2:1 and 5:1) were designed to further treat urban wastewater. The results showed that the biological packing reactor with ceramsite/sulfur: 2∶1 mixing fillers (R2, high sulfur coupling group) had the highest nitrogen removal efficiency at a C/N ratio of 4 and HRT of 4 h, and the average TN removal rate and effluent concentration were (92.62±1.36) % and (2.39±0.22) mg∙L-1, respectively. Compared with R1 (heterotrophic denitrification group), R2 (high sulfur coupling group) could ensure the denitrification efficiency with less carbon source addition. In addition, R2 (high sulfur coupling group) promoted the growth of denitrifying microbial communities Thauera and Thiobacillus in the system under the optimal parameters, and their total abundance was 39.13%.
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表 1 反应器的运行条件
Table 1. Operating conditions of reactor
阶段 运行时间/ d HRT/ h 进水NO3−-N/(mg∙L−1) 进水COD/(mg∙L−1) C/N 进水SO42-/( mg∙L−1) 1 1~21 4 30.45±0.856 63.62±2.66 2 51.69±5.14 2 23~43 2 30.67±1.02 62.11±2.55 2 37.91±3.97 3 45~65 1 30.1±0.97 62.52±3.24 2 35.11±6.26 4 67~87 4 30.87±0.95 120.5±3.14 4 27.52±1.76 5 89~109 2 30.24±1.18 120.97±2.71 4 40.74±6.79 6 111~131 1 29.72±1.28 121.67±3.57 4 27.92±7.15 7 133~153 4 30.72±0.62 180.7±3.76 6 31.83±6.48 8 155~175 2 29.98±1.19 180.81±4.57 6 34.37±7.71 9 177~197 1 30.16±1.24 183.06±5.61 6 41.74±4.39 表 2 样品编号
Table 2. Sample numbers
样品
编号取样
阶段C/N 取样
反应器样品
编号取样
阶段C/N 取样
反应器S1 1 2 R1 S6 4 4 R3 S2 1 2 R2 S7 7 6 R1 S3 1 2 R3 S8 7 6 R2 S4 4 4 R1 S9 7 6 R3 S5 4 4 R2 -
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