Li Baikun, Bishop Paul L
Department of Civil and Environmental Engineering, University of Cincinnati, 765G Baldwin Hall, Cincinnati, OH 45221-0071, USA.
Water Res. 2004 Mar;38(5):1248-58. doi: 10.1016/j.watres.2003.11.019.
The microbial activity within activated sludge floc is a key factor in the performance of the activated sludge process. In this study, the microenvironment of activated sludge flocs from two wastewater treatment plants (Mill Creek Wastewater Treatment Plant and Muddy Creek Wastewater Treatment Plant, with aeration tank influent CODs of 60-120 and 15-35 mg/L, respectively) were studied by using microelectrodes. Due to microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the surface layer (0.1-0.2mm) of the sludge aggregate at the Mill Creek plant. The presence of an anoxic zone inside the sludge floc under aerobic conditions was confirmed in this study. When the dissolved oxygen (DO) in the bulk liquid was higher than 4.0mg/L, the anoxic zone inside the activated sludge floc disappeared, which is helpful for biodegradation. At the Muddy Creek plant, with its lower wastewater pollutant concentrations, the redox potential and DO inside the sludge aggregates were higher than those at the Mill Creek plant. The contaminant concentration in the bulk wastewater correlates with the oxygen utilization rate, which directly influences the oxygen penetration inside the activated sludge floc, and results in redox potential changes within the floc. The measured microprofiles revealed the continuous decrease of nitrate concentration inside the activated sludge floc, even though significant nitrification was observed in the bulk wastewater. The oxygen consumption and nitrification rate analyses reveal that the increase of ammonia flux under aerobic conditions correlates with nitrification. Due to the metabolic mechanisms of the microorganisms in activated sludge floc, which varies from one treatment plant to another, the oxygen flux inside the sludge floc changes accordingly.
活性污泥絮体中的微生物活性是活性污泥法运行效果的关键因素。在本研究中，利用微电极对两座污水处理厂（米尔溪污水处理厂和泥泞溪污水处理厂，曝气池进水化学需氧量分别为60 - 120mg/L和15 - 35mg/L）活性污泥絮体的微环境进行了研究。由于微生物对氧气的利用，米尔溪污水处理厂活性污泥絮体中的好氧区域局限于污泥聚集体的表层（0.1 - 0.2mm）。本研究证实了在好氧条件下污泥絮体内部存在缺氧区。当主体液体中的溶解氧（DO）高于4.0mg/L时，活性污泥絮体内部的缺氧区消失，这有利于生物降解。在泥泞溪污水处理厂，由于其废水污染物浓度较低，污泥聚集体内部的氧化还原电位和溶解氧高于米尔溪污水处理厂。主体废水中的污染物浓度与氧气利用率相关，氧气利用率直接影响活性污泥絮体内部的氧气渗透，并导致絮体内部的氧化还原电位变化。实测的微剖面显示，尽管在主体废水中观察到显著的硝化作用，但活性污泥絮体内部的硝酸盐浓度持续下降。氧气消耗和硝化速率分析表明，好氧条件下氨通量的增加与硝化作用相关。由于不同污水处理厂活性污泥絮体中微生物的代谢机制不同，污泥絮体内部的氧气通量也相应变化。
