It is not possible to give a dosage in general. It depends on the contamination, temperature and treatment time of the water.

One of the methods is breakpoint chlorination that should be done in the lab.

In general chlorination should meet the hygienic standards and maintain the residual concentration of free chlorine in the water supply network.

You can easily find lots of information in the literature and study materials, for example this one, to start with:

https://ocw.tudelft.nl/course-lectures/disinfection/?course_id=14657

If asked in a field context, 2-4 mg/L dosage (chlorine bleach at ~5%) with ~30 minutes exposure.