Abstract:

According to the requirements for urban reclaimed water to be used as make-up water for the circulating cooling water of thermal power plants, this study investigates the regulation mechanisms of supersaturation, coexisting ions, and ionic strength on the crystallization process by selecting efficient seed crystals and optimizing dosing parameters. Large-scale engineering trials are conducted based on the catalytic softening device to evaluate the softening performance under different effluent pH and long-term operating conditions. The results show that calcite seeds can significantly lower the nucleation energy barrier of calcium carbonate, achieving a 90% calcium hardness removal rate at a supersaturation value of 2.36, while effectively mitigating the inhibitory effect of magnesium ions on the crystallization induction period. Engineering trial results further demonstrate that when the effluent pH is controlled between 9.8 and 10.0, the system maintain a stable effluent Ca²⁺ hardness of 50-60 mg/L and a removal rate of 80%-85% over a 15 days continuous operation period. The crystallized particles are mainly composed of calcite, with smooth surfaces and uniform particle size distribution, and can be recycled. No by-products are generated in the process,indicating that this process provides an efficient, economic and environmentally friendly treatment pathway for the hardness removal and recycling of urban reclaimed water.

Key words: reclaimed water, circulating water replenishment, water softening, catalytic softening crystallization

摘要：

根据城市污水再生中水用于热电厂循环冷却水补给水软化要求，通过筛选高效晶种与优化投加参数，考察过饱和度值、共存离子和离子强度对结晶过程的调控机制，并基于催化软化装置开展规模化工程试验，探究不同出水pH及长期运行工况下的软化效能。结果表明：方解石晶种可显著降低碳酸钙成核能垒，在过饱和度值为2.36时，实现90%的钙硬度去除率，同时能有效减弱镁离子对结晶诱导期的抑制作用。工程试验结果表明，当出水pH调控至9.8~10.0时，系统在15 d的长期稳定测试过程中出水钙硬度稳定在50~60 mg/L，Ca²⁺去除率稳定在80%~85%。结晶颗粒主要成分为方解石，表面光滑且粒径分布均匀，可以回收利用。该工艺过程无副产物产生，为城市污水再生中水的硬度脱除及再生利用提供了一种高效、经济且环境友好的处理路径。

关键词: 再生水, 循环水补水, 水质软化, 催化软化结晶法

CLC Number: 

• TQ085