碱洗（清洗时间2小时）

1、确认所有阀门位置正确，不会产生背压等不良状况。

2、配置化学清洗液NaOH水溶液，调节PH值在10-11.5之间，控制溶液温度约30℃。

步骤3-5参考酸洗5-7步骤

6、开启浓缩液侧回流阀和渗透液侧回流阀，调节清洗液泵出口阀门和回流阀，进行循环30min，整个过程 中监测清洗液温度，在容许的范围内，温度越高清洗效果越好。

7、循环清洗结束后停掉清洗液泵，对纳滤膜过滤系统进行1小时浸泡。

8、浸泡结束后，重复步骤（6）。

9、碱洗结束，排放掉清洗液罐中碱清洗液；将清洗液罐洗干净后，灌满纯水，并用纯水冲洗纳滤过滤膜直至PH值接近中性。

10、开启清洗液泵，调节浓缩液出口阀，观测并记录测试膜系统纯水通量和操作压力与（酸洗3）的操作条件相同，同时记录出此时膜系统纯水通量和操作压力。

Alkali washing (cleaning time 2 hours)

1. Confirm that all valve positions are correct and there will be no adverse conditions such as back pressure.

2. Prepare a NaOH aqueous solution for chemical cleaning, adjust the pH value between 10 and 11.5, and control the solution temperature to about 30 ℃.

Steps 3-5 refer to pickling steps 5-7

6. Open the concentrate side reflux valve and permeate side reflux valve, adjust the outlet valve and reflux valve of the cleaning solution pump, and circulate for 30 minutes. Monitor the temperature of the cleaning solution throughout the process, and within the allowable range, the higher the temperature, the better the cleaning effect.

7. After the cycle cleaning is completed, stop the cleaning solution pump and soak the nanofiltration membrane filtration system for 1 hour.

8. After soaking, repeat step (6).

9. After the alkaline cleaning is completed, discharge the alkaline cleaning solution from the cleaning solution tank; After cleaning the cleaning solution tank, fill it with pure water and rinse the nanofiltration membrane with pure water until the pH value is close to neutral.

10. Turn on the cleaning solution pump, adjust the concentrated solution outlet valve, observe and record the pure water flux and operating pressure of the testing membrane system under the same operating conditions as (acid washing 3), and record the pure water flux and operating pressure of the membrane system at this time.