You are testing two different household solutions with your cabbage indicator, one solution turns blue. a possible hydrogen ion concentration for this solution is:

pH 8  

Step-by-step explanation:

Red cabbage contains a compound called anthocyanin.

It produces different colours depending on the pH of the solution.

In the image below, you can see that the cabbage indicator is blue between pH 7 and pH 9, so a possible pH for your solution is pH 8.

a saline water is fed to a reverse osmosis unit at flow rate o rotameter connected to reject (retentate) line reads 8 installed in reject and permeate line reads 15.2 milli siemens/cm and 300 micro siemens/com respectively.