Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands.
Water Res. 2011 Jan;45(1):263-73. doi: 10.1016/j.watres.2010.07.055. Epub 2010 Jul 27.
The study aims to evaluate the role of a polymeric substrate (starch) on sludge settleability. Despite being an important COD component of the wastewater, the relationship between polymeric substrates and bulking sludge has been hardly studied. The polymers are hydrolysed at a rate smaller than the consumption rate of monomers. This means that the soluble substrate resulting from hydrolysis is likely to be present at growth rate limiting concentrations. According to the kinetic selection theory this leads to bulking sludge. However, a recently postulated theory suggests that, strong diffusion limited micro-gradients of substrate concentration inside flocs lead to bulking sludge, and not a low substrate concentration as such. If the polymeric COD is first incorporated in the sludge floc and afterwards hydrolysed in the sludge floc then there is essentially no substrate gradient inside the biological flocs. The experiments showed that conditions leading to bulking sludge with monomers (glucose) did not lead to bulking when starch was used. A bulking sludge event was even cured just by substituting the monomer with starch. These results are clearly in line with a diffusion gradient--based theory for bulking sludge. Nevertheless, flocs growing on starch are more open, fluffy and porous than flocs formed on maltose or glucose, most likely because the starch needs to be hydrolysed at the surface of the micro-colonies forming the flocculated sludge. Some additional observations on occurrence of filamentous bacteria in oxygen diffusion limited systems are also discussed in this manuscript.
本研究旨在评估聚合基质（淀粉）对污泥沉降性能的作用。尽管聚合物是废水中 COD 的重要组成部分，但聚合基质与膨胀污泥之间的关系几乎没有得到研究。聚合物的水解速度小于单体的消耗速度。这意味着水解产生的可溶性基质可能处于生长速率限制浓度。根据动力学选择理论，这会导致出现膨胀污泥。然而，最近提出的一种理论表明，在絮体内部存在强烈的扩散限制底物浓度微梯度会导致出现膨胀污泥，而不是底物浓度本身很低。如果聚合 COD 首先被纳入污泥絮体，然后在污泥絮体中水解，那么在生物絮体内部基本上就没有底物梯度。实验表明，在使用单体（葡萄糖）导致出现膨胀污泥的条件下，使用淀粉不会导致出现膨胀污泥。仅通过用淀粉代替单体甚至可以治愈膨胀污泥事件。这些结果显然与基于扩散梯度的膨胀污泥理论一致。然而，在淀粉上生长的絮体比在麦芽糖或葡萄糖上形成的絮体更开放、蓬松和多孔，这很可能是因为淀粉需要在形成絮状污泥的微菌落表面进行水解。本文还讨论了在氧气扩散限制系统中丝状菌出现的一些其他观察结果。
