MBR／RO组合工艺中定期冲洗缓解RO膜污染的研究

Effect of Periodical Cleaning on Reduction of RO Membrane Fouling in Combined MBR/RO Process

针对MBR/RO组合工艺,以RO的膜污染机理为理论基础,分别以清水和Na+、K+盐溶液为冲洗用水,研究了采用定期冲洗缓解RO膜污染的效果。结果表明,采用清水定期冲洗可以消减结构松散的污染层,缓解膜污染的发生。RO进水溶液中,Ca2+以架桥作用络合有机物分子,加速了有机物污染层的形成,然而高浓度的Na+或K+盐溶液不但可置换出架桥于有机物之间的Ca2+,而且其产生的渗透压可迫使污染层发生膨胀,减弱了有机物分子间的结合。因此,用高浓度的盐溶液冲洗不但具有清水冲洗的作用,而且可对密实的有机物污染层产生一定程度的破坏,更有效地延长了RO的运行周期。就4种盐溶液(NaC、lKC、lNaNO3、Na2SO4)而言,采用NaC l溶液冲洗对缓解膜污染的效果最好。

In combined MBR/RO process, the effect of periodical cleaning with clean water and salt solution on reduction of RO membrane fouling was studied. The results show that the cleaning with clean water can relieve membrane fouling by reducing unconsolidated fouling layer. In RO feed water, Ca^2＋ can bridge organic substances, which results in denser fouling layer. But the salt solution with high concentration of Na^＋ or K^＋ can replace the Ca^2＋ between organic substances, and the high osmotic pressure caused by high salt concentration can expand the fouling layer and weaken the combination between organic substances. Therefore, the cleaning with high concentration salt solution has the advantage of water cleaning and breaks the dense fouling layer to a certain extent, which can effectively prolong the operation cycle of RO. In comparison among 4 types of salt solutions （ NaCl, KCl, NaNO3 and Na2SO4） , NaCl is found to be the most effective one.