Wilén Britt-Marie, Keiding Kristian, Nielsen Per Halkjaer
Water Environment Transport, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
Water Res. 2004 Nov;38(18):3909-19. doi: 10.1016/j.watres.2004.06.027.
Activated sludge flocs are known to deflocculate under short-term anaerobic conditions, but little is known about possible reflocculation under subsequent aerobic conditions. When activated sludge flocs from two wastewater treatment plants deflocculated under anaerobic conditions with well-defined shear conditions, they could be almost, but not completely, reflocculated by aeration for 1-2 h under the same shear conditions. If the biological activity was reduced by adding azide, chloramphenicol or by decreasing the temperature, no or only very little reflocculation took place. This indicated that the reflocculation was under direct or indirect microbial control. Only a small part of the reflocculation was due to improved flocculation properties obtained by oxidation of Fe(II) to Fe(III), which is a better flocculant. Fe(II) was produced under the anaerobic conditions by microbial iron reduction, and it was oxidized to Fe(III) within less than one hour after the aeration was started. However, by comparing two different sludges with different capabilities for iron reduction, iron oxidation and responses to substrate addition, it was found that the aerobic biological activity most likely was of greatest significance for the observed reflocculation and floc formation under aerobic conditions. This was further supported by adding organic substrates (glucose or ethanol) during the aerobic reflocculation phase, which promoted reflocculation. However, some substrates had the opposite effect (acetate and lactate), where a deterioration of the reflocculation was observed, probably due to different responses from different groups of microorganisms in the sludges.
已知活性污泥絮凝体在短期厌氧条件下会发生解絮凝，但对于随后好氧条件下可能的再絮凝情况却知之甚少。当来自两个污水处理厂的活性污泥絮凝体在具有明确剪切条件的厌氧条件下解絮凝时，在相同剪切条件下曝气1 - 2小时，它们几乎但并非完全能够再絮凝。如果通过添加叠氮化物、氯霉素或降低温度来降低生物活性，则不会发生再絮凝或仅有极少的再絮凝发生。这表明再絮凝受到直接或间接的微生物控制。再絮凝中只有一小部分是由于将Fe(II)氧化为Fe(III)（一种更好的絮凝剂）而改善了絮凝性能所致。Fe(II)是在厌氧条件下通过微生物铁还原产生的，曝气开始后不到一小时内就被氧化为Fe(III)。然而，通过比较两种具有不同铁还原能力、铁氧化能力和对底物添加反应能力的不同污泥，发现好氧生物活性最有可能对好氧条件下观察到的再絮凝和絮凝形成具有最大意义。在好氧再絮凝阶段添加有机底物（葡萄糖或乙醇）促进了再絮凝，这进一步证明了这一点。然而，一些底物却有相反的效果（乙酸盐和乳酸盐），观察到再絮凝恶化，这可能是由于污泥中不同微生物群体的不同反应所致。
