The present invention relates to a method of immobilizing aqueous waste, including low level nuclear waste, by converting the waste to a solid. Solidification is accomplished with the addition of a compound having the formula Me(II)O or Me(II)(OH).sub.2 in combination with compounds of the general formula Me(II)O.R.sub.2O.sub.3, R.sub.2O.sub.3, R(OH).sub.3 or ROOH, where Me is a cation selected from the group consisting of Ca, Ba, Sr, Mn, and Zn, and R is selected from the group consisting of Al, Fe and Cr. Exemplary compounds of the above formula include commercially available calcium aluminate cements, which when added to the waste in combination with a hydroxide of a divalent metal, bind the nitrate ions or nitrite ions in the waste and convert it to a solid.