The Interstellar Medium (ISM) can give us information of the chemical evolution of the universe, since is the place where the life stars cycle is developed. Over more than 30 years is known that there’s a remarkable difference in the computation of the ionic abundances of the elements of the ISM using collisional excited lines and recombination lines, being higher for the last ones, which is known as the abundance discrepancy problem. Different scenarios have been proposed to try to explain these problem, such as: temperature inhomogeneities, high density incrustations in a regular density medium, regions H-poor embedded in a standard metallicity gas, and, electrons that don’t follow a Maxwellian velocity distribution. Particularly, in this work, metallicity inhomogeneities will be explored, using the photoionization code CLOUDY. We'll show the result of bi-abundance models that try to reproduce the observational behaviour of the planetary nebula NGC 6153.