It wasn't that bad but the leaves not crisp. This step what I tried and seem to work. I was glad with the result fresh and crisp lettuce ( even crispier than the one just come from the store :)
Soak them into the water for about 10-15 minutes. Beside make it fresh and crisp. Soaking it in the water for that long I believe make all the dirt came out and who knows might the chemical too.
Take the lettuce out of the water and drain it with strainer or salad dryer if you have one.
Here is the final result of the old lettuce become fresh and ready to enjoy !
What simple way and easy to do it.