海水淡化水的后处理研究

STUDY ON THE POSTTREATMENT OF DESALTED SEAWATER

针对反渗透海水淡化淡化水低碱度和低盐度的特点,以以色列的后处理水质标准为目标,采用石灰石溶解法对淡化水进行矿化,同时对双极膜电渗析盐室出水进行回用。考察不同填料粒径(2、3、4 mm)及体积流量(50、75、100 L/h)下矿化过程的变化情况。结果表明,随着粒径的减少,CaCO3的溶解速度越快,其出水的Ca2+含量和pH越高;流量越大,相对应的取样口矿化水Ca2+含量越低,即相应的CaCO3溶解量越少。在矿化水与淡化水以体积比1:6混合后,为满足出水碱度,需加入NaHCO3的量为100mg/L,且最终得到的出水水质达到GB5749-2006要求。

The water produced by reverse osmosis seawater desalination, is usually, characterized by very low salinity and alkalinity, and the corresponding posttreatment is needed. This research aims at proposing a demineralisation method based on the limestone dissolution according to water quality criteria published in Isreal. Simultaneously, the water produced by the salt compartment of bipolar membrane electrodialysis can be recycled effectively by the demineralisation process. The research investigated different demineralisation processes when particle size of calcium carbonate varied from 2--4 mm and water flow rate varied from 50-100 L/h. The results showed that the smaller particle size lead to higher dissolution rate of calcium carbonate, and higher flow rate lead to less dissolution of calcium carbonate. After the demineralized water was recombined with desalted water bypassing the dissolution reactor, 100 mg/L sodium bicarbonate was added to meet the final water alkalinity.