Feasibility of dechlorination using ultra-high lime with aluminum process (UHLA) has been demonstrated by previous studies. However, the negative influences of UHLA on water qualities (pH, conductivity, and residual calcium concentration) after dechlorination and the products generated in dechlorination process have not been thoroughly analyzed. In this study, changes of water qualities at various dechlorination conditions were investigated, and favorable conditions for Friedel’s salt formation were explored by X-ray diffraction analysis. The pH and conductivity after dechlorination increased with the improvement of chloride removal effect. The calcium ion concentration in effluent also fluctuated with different dosages of CaO. At the maximum chloride removal efficiency of 71.4%, the pH, conductivity, and calcium ion concentration in effluent were 12.8, 10.9 ms/cm, and 22.7 mg/L, respectively. X-ray diffraction analysis for precipitants indicated that Friedel’s salt with the highest purity was also generated at the optimal dechlorination efficiency. The high dechlorination efficiency of 80.5% was achieved with the development of a stepwise addition strategy. Chemical costs for treating one ton of wastewater containing 500 mg/L chloride were $3.96.

Graphical abstract

中文翻译：

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铝法超高石灰在脱氯过程中产生的水质和产物

先前的研究证明了使用超高石灰铝法（UHLA）进行脱氯的可行性。但是，UHLA对脱氯后的水质（pH，电导率和残留钙浓度）以及在脱氯过程中生成的产品的不利影响尚未得到彻底分析。在这项研究中，研究了在各种脱氯条件下水质的变化，并通过X射线衍射分析探索了弗里德尔盐形成的有利条件。脱氯后的pH值和电导率随着除氯效果的提高而增加。废水中的钙离子浓度也随CaO剂量的不同而波动。在71.4％的最大氯去除率下，pH，电导率，废水中的钙离子浓度分别为12.8、10.9 ms / cm和22.7 mg / L。沉淀剂的X射线衍射分析表明，在最佳脱氯效率下，也产生了纯度最高的弗里德尔盐。随着逐步添加策略的发展，达到了80.5％的高脱氯效率。处理一吨含500 mg / L氯化物的废水的化学费用为3.96美元。

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