Treatment of post-digestion liquors with the application of struvite precipitation and reverse osmosis

Abstract

Abstract Since the post-digestion liquors exhibited a high content of biogenic substances and organic matter, an attempt was made to develop an effective treatment of their treatment, allowing the treated liquors to be directly released into a natural reservoir. The liquors were treated with the application of reverse osmosis (RO) and chemical precipitation (struvite) as a pre-treatment step. The application of a unit RO process did not ensure an adequate removal of contaminants, mainly due to the excessive concentration of in the permeate. The treatment of post-digestion liquors with a struvite precipitation and a subsequent RO process turned out to be effective and allowed to decrease contaminants’ concentration below discharge limits, allowing direct release of permeate to a natural receiver. However, it was necessary to apply an increased ratio of magnesium and phosphates during struvite precipitation (Mg2+: : = 1.5:1:1.5), preceding reverse osmosis treatment. As compared to the MgCl2·6H2O, the appli...