摘要
碳氮比(C/N)是制约污水净化过程脱氮效率的重要因素之一。以周期循环式活性污泥法(CASS)工艺为基础,分别考察了排水比、曝气时间以及进水模式对C/N=1.8的低碳源生活污水脱氮效果的影响。研究结果表明,在低C/N值进水下,排水比是影响CASS脱氮效果的最主要因素。当排水比分别为30%、40%和50%时,CASS工艺出水的TN平均质量浓度分别为17.8 mg·
关键词
目前我国城镇生活污水普遍存在碳氮比(C/N)较低的问题,由此使得污水处理难以实现高效脱氮除
周期循环式活性污泥法(cyclic activated sludge system, CASS)是一种以传统SBR工艺为基础的变形工艺,此工艺集好氧曝气、厌氧反应、沉淀和排水于一体,在控制时序上具有灵活多变、易于调控的优点。因此通过方法③对该工艺的控制参数进行优化,以充分利用原污水碳源、提高反硝化脱氮效果。针对间歇式反应器的优化参数主要有排水比、曝气时间和分段进水方式。适当增大CASS工艺排水比,可减缓反应器前一周期对后一周期进水的稀释作用,从而相对增加反应器内碳源浓度;缩短曝气时间则可增加反硝化反应时长;分时段进水方式与
实验进水取自广东省某城镇污水厂进水井,具体指标及平均值如
注: 样本量=93
如

图1 不同排水比的CASS控制时序
Fig.1 CASS control sequence of different drainage ratios
由

图2 不同排水比CASS去除效果
Fig.2 CASS removal effect in different drainage ratio
好氧与厌氧反应时间比是影响脱氮效果的关键参数。分别将曝气时长调整为60min、90min和120min以控制好氧和厌氧时间比来提升脱氮效果,具体控制时序如

图3 不同曝气时长的CASS控制时序
Fig.3 CASS control sequence for different aeration durations
如

图4 曝气时间变化对污染物去除效果影响
Fig.4 The aeration time on the removal effect of pollutants
采用分时段进水的方式,CASS工艺可灵活分配原水中的碳源,实现更好的脱氮效果。本实验分别采用两种不同进水和曝气组合方式(“三段进水A”和“三段进水B”),研究CASS工艺脱氮效果,工艺控制时序如

图5 不同进水模式的CASS控制时序
Fig.5 CASS control sequence for different water inlet modes
如

图6 分时段进水对污染物去除效果影响
Fig.6 The effect of segmented water intake on pollutant removal effect
污水处理过程中碳源分配及去向主要包括:同化作用、异化作用、脱氮除磷以及出水,其中有机物和氮相关的化学计量系数采用国际水协(IWA)的推荐值;根据进水和出水TN的差值计算反硝化TN量,反硝化COD利用系数采用2.86(gCOD/gTN),计算结果见
由
以CASS工艺为基础,探讨了排水比、曝气时间以及进水模式对低C/N污水脱氮效果的影响,实验主要结论如下:
(1)实验进水平均COD为79.4 mg·
(2)通过碳源分配计算可知,即使原水中所含碳源无法满足反硝化需求,但当工艺控制参数及时序得到优化时,CASS工艺可在不外加碳源的前提下发挥脱氮潜力。当排水比为50%时,出水TN平均质量浓度可以达到6.6 mg·
作者贡献声明
庞维海:实验设计和论文修改;
李惠平:实验操作和论文撰写;
张琨:技术和材料支持。
王曦:技术和材料支持。
谢丽:实验设计和论文修改。
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