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针对含有Ca2+、Mg2+及SiO32-的反渗透(RO)浓水,提出了化学除硬→絮凝沉淀→离子交换→超滤处理的新型预处理流程.研究了该预处理方法对RO浓水中易结垢离子的去除效果,及其对气隙式膜蒸馏(AGMD)性能的影响.实验结果表明,经过该预处理过程后Ca2+、Mg2+和SiO32-的含量均低于5mg/L.与常规的除硬处理不同,经过该预处理过程后,RO浓水中的难溶盐CaCO3、Mg(OH)2均未达到饱和,进行膜蒸馏浓缩时,不会立即在膜表面沉积.经预处理后,原RO浓水中的主要成分为NaCl,其可在膜蒸馏浓缩得到结晶固体.未经预处理的RO浓水浓缩7倍时,产水通量衰减了40.55%,电导率增大了22.71%,CODCr含量为40~60mg/L;对于预处理后的浓水,该衰减程度减小24.02%,且产水电导率保持相对稳定,COD含量低于10mg/L,产水可以用作工业循环冷却水和工业洗涤水,经活性炭吸附后可用作锅炉用水.预处理后的RO浓水进入AGMD装置浓缩168h,产水通量衰减缓慢,产水电导率一直维持在5μS/cm以下,整个过程中COD均小于10mg/L.
Aiming at the reverse osmosis (RO) concentrated water containing Ca2 +, Mg2 + and SiO32-, a new pretreatment process of chemical hard addition → flocculation → ion exchange → ultrafiltration was proposed. The results showed that the contents of Ca2 +, Mg2 + and SiO32- were all lower than 5mg / L after the pretreatment process.Compared with the conventional removal of the AGMD, Hard treatment is different, after the pretreatment process, RO concentrated water insoluble salt CaCO3, Mg (OH) 2 are not saturated, the membrane distillation concentration will not immediately deposited on the membrane surface after pretreatment, the original The main component of RO concentrated water is NaCl, which can be concentrated in the membrane distillation to obtain a crystalline solid.Unrefined RO concentrate concentrated seven times, the water flux decayed 40.55%, the conductivity increased by 22.71%, CODCr The content of 40 ~ 60mg / L; for the pretreatment of concentrated water, the attenuation decreased by 24.02%, and the water conductivity remained relatively stable, COD content of less than 10mg / L, water can be used as industrial circulating cooling water And industrial washing water, which can be used as boiler water after being adsorbed by activated carbon. RO pre-treated concentrated water enters AGMD unit Shrinking 168h, water flux decay slow, water conductivity has been maintained at 5μS / cm below the entire process of COD were less than 10mg / L.