在这项研究中，随机选择了186家水厂，每年从每个水厂采集五次原水和成品水样本，并通过原子吸收技术分析铁和铝。水样按供水来源（地面、表面或两者的组合）、水的类型（原水、成品或未经处理的分布样品）和处理过程中使用的混凝类型（硫酸铝、氯化铁、阳离子聚合物等其他混凝剂或无混凝剂）进行分类。样本还根据美国环境保护局的10个地区和4个人口类别进行分类。结果表明，铝更可能存在于地表水中，而不是地下水中。只有9%的地下水含有可检测到的铝，而78%的地表水含有可检测到的铝。 数据还表明，当使用明矾进行混凝时，铝的浓度有40%到50%的可能性会增加到原水的初始浓度以上。在少数使用铁作为混凝剂的设施中，铁和铝的浓度降低。包括16个参考文献、表格和图表。

A random selection of 186 water utilities was used for this study in which raw and finished water samples were collected from each facility five times throughout a year and analyzed for iron and aluminum by atomic absorption techniques. The water samples were categorized by the supply source (ground, surface, or a combination of both), the type of water (raw, finished, or untreated distribution samples), and the type of coagulation used in the treatment process (aluminum sulfate, ferric chloride, other coagulants such as cationic polymers, or no coagulant). The samples were also categorized according to the 10 USEPA regions and 4 population categories. The results indicate that aluminum is more likely to exist in surface waters than in groundwaters. Only 9 percent of the groundwaters had detectable amounts of aluminum, whereas 78 percent of the surface waters had detectable aluminum. The data also indicate that when alum is used for coagulation, there is a 40 to 50 percent chance that the concentration of aluminum will increase above the original concentration in raw water. In the few facilities that used iron as a coagulant, the concentrations of iron and aluminum decreased. Includes 16 references, tables, figures.