“refuse heap.” The Hebrew is a general reference to a refuse or garbage heap. Although the word gets translated “dunghill” in some older translations, there is no specific reference to “dung” in the word. The poor are scavengers and live off of things that the rich people don’t want. The same thing is true today in many third-world countries.
“For the pillars of the earth are Yahweh’s.” Yahweh upholds the physical earth and implied is that in the same way He upholds the moral and ethical standards on earth such that justice is eventually done for all.