School of Environmental Science and Engineering, Shandong University, Jinan, 250100, China.
School of Environmental Science and Engineering, Shandong University, Jinan, 250100, China; Shandong Provincial Engineering Center on Environmental Science and Technology, Jinan, 250061, China.
Water Res. 2018 Oct 1;142:405-414. doi: 10.1016/j.watres.2018.06.020. Epub 2018 Jun 9.
Benthic Oscillatoria sp. may form dense surface blooms especially under eutrophic and calm conditions, which poses a threat to drinking water safety because it can produce toxic and odorous metabolites. This is the first study to investigate the effect of the conventional coagulant polyaluminium ferric chloride (PAFC) on removal of Oscillatoria sp., and the behavior of Oscillatoria sp. cells in sludges formed from different dosages of PAFC (control, optimum, and overdose system) during storage was also studied. Oscillatoria sp. cells can be removed efficiently by coagulation of PAFC. The adverse environmental stresses of sludge, such as lack of light and anoxic environment, decrease cell viability and induce the increase of superoxide dismutase activity (SOD) and malondialdehyde content (MDA) in Oscillatoria sp. cells during the first 4 days. Because Oscillatoria sp. can adapt to the low-light and hypoxic circumstances in sludge gradually, the cells regrow with prolonged storage time. Compared to planktonic Microcystis aeruginosa and Cylindrospermopsis raciborskii, regrowth of Oscillatoria sp. during storage may present a bigger threat, even though Microcystis aeruginosa and Cylindrospermopsis raciborskii cells will be damaged and release toxic compounds. Growth rates of algae in coagulated systems were lower than that in control system because of the restriction of flocs. It is worth noting that the chlorophyll a level was increased by a factor of 3.5 in the optimal-dose system, and worse, the overdose system increased by a factor of 6 in chlorophyll a after 8 d storage due to the benefit of higher Fe levels. Concentrations of extracellular geosmin and cylindrospermopsin also increased during storage, especially after 4 d, and varied in the following sequence for a given storage duration: control system > overdose system > optimum system. Overall, due to decrease of SOD and MDA in Oscillatoria sp. cells after 4 d storage, algae cells regrew rapidly, especially in overdose system. Hence, sludge should be treated within 4 d and excess PAFC dosing should be avoided.
底栖颤藻属可能在富营养化和平静的条件下形成密集的表层水华，这对饮用水安全构成了威胁，因为它会产生有毒和有气味的代谢物。这是第一项研究，旨在探讨传统混凝剂聚合氯化铝铁（PAFC）对去除颤藻属的效果，以及颤藻属细胞在不同剂量 PAFC（对照、最佳和过量系统）形成的污泥中的行为。PAFC 可以有效地去除颤藻属细胞。污泥中缺乏光照和缺氧等不利环境压力会降低细胞活力，并在最初的 4 天内诱导颤藻属细胞中超氧化物歧化酶活性（SOD）和丙二醛含量（MDA）的增加。由于颤藻属可以逐渐适应污泥中的低光和缺氧环境，随着储存时间的延长，细胞会重新生长。与浮游微囊藻和柱孢鱼腥藻相比，颤藻属在储存过程中的再生长可能构成更大的威胁，尽管微囊藻和柱孢鱼腥藻细胞会受到损伤并释放有毒化合物。由于絮体的限制，混凝系统中藻类的生长速度低于对照系统。值得注意的是，在最佳剂量系统中，叶绿素 a 的水平增加了 3.5 倍，而在过量剂量系统中，由于 Fe 水平较高，在 8d 储存后，叶绿素 a 的水平增加了 6 倍。在储存过程中，胞外土臭素和柱孢鱼腥藻素的浓度也增加了，尤其是在 4d 后，在给定的储存时间内，浓度的顺序为：对照系统>过量剂量系统>最佳剂量系统。总体而言，由于在 4d 储存后颤藻属细胞中的 SOD 和 MDA 减少，藻类细胞迅速重新生长，特别是在过量剂量系统中。因此，污泥应在 4d 内处理，并应避免过量添加 PAFC。
