Du Jie-Di, Wang Yi-Li, Li Jiong, Xu Xin-Zhao, Wei Ke-Ji
Key Laboratory for Silviculture and Conservation of Ministry of Education and Beijing, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
Huan Jing Ke Xue. 2009 Jul 15;30(7):2022-9.
The impact of hydraulic retention time (HRT) in an anaerobic baffled reactor (ABR) on its operation performance and granular sludge characteristics was investigated through both testing its operation and analyzing the particle size distribution (PSD) and fractal dimensions of these sludge granules when treating low-strength wastewater. As HRT was gradually reduced from 24 h to 5 h, ABR had good performance on the organics removal and could reach about 90% for the COD removal, the VFA contents in ABR effluent and their pH values showed opposite trends. Most COD in wastewater was removed in the first two compartments of ABR during the running period of HRT from 24 h to 12 h, after that, the middle three compartments in ABR performed the most removal work. The MISS in latter compartments of ABR increased and the tendency of MLVSS/MISS ratios in the former three compartments were higher than that in the latter two ones appeared more and more remarkable along with the decrease of HRT. At HRT 24 h and 18 h, the granules grew bigger than before start-up,whose one-dimensional fractal dimension (D) decreased and two-dimensional fractal dimension (D2) increased, implying the smoother surface and more compact structure. As the HRT changed to 12 h and 8 h, the increasing D1 and decreasing D2 of granular sludge indicated its rougher surface and looser structure, and the bigger granules were formed with holes in their center. At HRT 5 h, smoother and more compact granules formed with smaller number median diameters of 0.72-0.82 mm than that at HRT 8 h. The looser granules were broken-up and some granules were discharged from ABR under the hydraulic disturbance and screening effect, at the same time, the growth of microorganism and their EPS (extracellular polymer substance) secretion could smooth the surface of the fragmentized granules. The fractal dimensions of granular sludge in the one-dimensional and two-dimensional topological spaces behaved inversely in each compartment of ABR at the same HRT, that is to say, the granular sludge along the ABR sequences became smoother on the surface meanwhile more compact structurally.
通过对厌氧折流板反应器（ABR）处理低强度废水时的运行测试以及分析其污泥颗粒的粒径分布（PSD）和分形维数，研究了水力停留时间（HRT）对ABR运行性能和颗粒污泥特性的影响。随着HRT从24小时逐渐降至5小时，ABR对有机物的去除效果良好，COD去除率可达90%左右，ABR出水的VFA含量及其pH值呈现相反趋势。在HRT从24小时运行至12小时期间，废水中的大部分COD在ABR的前两个隔室中被去除，之后，ABR中间的三个隔室承担了大部分的去除工作。随着HRT的降低，ABR后几个隔室中的混合液悬浮固体（MISS）增加，前三个隔室中MLVSS/MISS比值高于后两个隔室的趋势越来越明显。在HRT为24小时和18小时时，颗粒比启动前长得更大，其一维分形维数（D）减小，二维分形维数（D2）增加，这意味着颗粒表面更光滑，结构更紧凑。当HRT变为12小时和8小时时，颗粒污泥的D1增加而D2减小，表明其表面更粗糙，结构更松散，并且形成了中心有孔的更大颗粒。在HRT为5小时时，形成了更光滑、更紧凑的颗粒，其数量中值直径为0.72 - 0.82毫米，比HRT为8小时时更小。在水力干扰和筛选作用下，较松散的颗粒破碎，一些颗粒从ABR中排出，同时，微生物的生长及其胞外聚合物（EPS）的分泌可使破碎颗粒的表面变得光滑。在相同HRT下，ABR各隔室中颗粒污泥在一维和二维拓扑空间中的分形维数表现相反，也就是说，沿ABR流程的颗粒污泥表面变得更光滑，同时结构上更紧凑。
