Galois actions, purity and formality with torsion coefficients

I will explain how to use the theory of weights on étale cohomology to study formality with torsion coefficients, for certain  schemes defined over a finite field. As an application, I will give some partial results of formality with torsion coefficients for configuration spaces on the complex space and for the operad of little disks. This is joint work with Geoffroy Horel.