Abstract：
Algal blooms worldwide pose many challenges to drinking water production. Pre-oxidation with NaClO, KMnO4, or ozone is commonly used to enhance algal removal in conventional drinking water treatment processes. However, these currently utilized oxidation methods often result in significant algal cell lysis or impede the operation of the subsequent units. Higher algal removal with pre-chlorination in algal solutions prepared with natural water, compared to those prepared with ultrapure water, has been observed. In the present studies, preliminary findings indicate that ammonium in natural water alters chlorine species to NH2Cl, leading to improved treatment efficiency. NH2Cl with 1.5-3.0 mg∙L-1 as Cl2 with an oxidation time of 3-7 h significantly enhancing algal removal by coagulation. The selective oxidation of surface-absorbed organic matter (S-AOM) by NH2Cl, followed by the subsequent peeling off of this material from the algal surface, leading to an increase in zeta potential from -20.2 mV to -3.8 mV, constitutes the primary mechanism of enhanced algal removal through coagulation. These peeled S-AOM retained their large molecular weight and acted as polymer aids. Compared with NaClO and KMnO4, NH2Cl displays the best performance in improving algal removal, avoiding cell lysis, and decreasing the potential for nitrogenous disinfection byproducts formation under the reaction conditions used in this study. Notably, in major Chinese cities, water purification plants commonly rely on suburban lakes or reservoirs as water sources, necessitating the transportation of raw water over long distances for times up to several hours. These conditions favor the implementation of NH2Cl pre-oxidation. The collective results indicate the potential of NH2Cl oxidation as a viable pretreatment strategy for algal contamination during water treatment processes.
摘要：
全球范围内的藻华给饮用水生产带来了许多挑战。用NaClO预氧化，KMnO4或臭氧通常用于增强常规饮用水处理过程中的藻类去除。然而,这些目前使用的氧化方法通常导致显著的藻类细胞裂解或阻碍后续单元的操作。在用天然水制备的藻类溶液中进行预氯化，可以去除更高的藻类，与用超纯水制备的相比，已被观察到。在目前的研究中,初步发现表明，天然水中的铵将氯物种改变为NH2Cl，提高治疗效率。以1.5-3.0mgL-1为Cl2的NH2Cl，氧化时间为3-7h，可显着提高通过混凝去除藻类的能力。NH2Cl对表面吸收的有机物（S-AOM）的选择性氧化，随后从藻类表面剥离这种材料，导致zeta电位从-20.2mV增加到-3.8mV，构成了通过混凝增强藻类去除的主要机制。这些剥离的S-AOM保持其大分子量并充当聚合物助剂。与NaClO和KMnO4相比，NH2Cl在提高藻类去除方面表现出最佳性能，避免细胞裂解，并降低了在本研究中使用的反应条件下形成含氮消毒副产物的可能性。值得注意的是,在中国主要城市，净水厂通常依靠郊区湖泊或水库作为水源，需要长距离运输原水，时间长达几个小时。这些条件有利于NH2Cl预氧化的实施。集体结果表明，NH2Cl氧化作为水处理过程中藻类污染的可行预处理策略的潜力。
