Treatment of wastewater with high inorganic salt content

The study deals with the waste disposal of an aqueous solution with a high salt content (about 5% sodium sulfate) and an organic fraction consisting primarily of naphthalenesulfonic acids. First, a process based on crystallization for the removal of sodium sulfate from the wastewater was developed, leading to a recovery of about 70% of the sodium sulfate. The wastewater with the residual salts content was fed to a batch mesophilic anaerobic digestion process. The acclimatization of a methanogenic consortium to different mixtures of the desalted wastewater and a growth substrate was studied. Complete acclimatization of the biomass to the solution was observed over a broad range of wastewater amount in a growth medium (from 3.5 to 224 ml of wastewater per liter of feeding solution). After a suitable acclimatization period of time the biomass was able to digest the pure wastewater up to an amount of 57.1 ml per liter of the feeding solution, obtaining TOC removal rates of 0.04 kg TOC/kg VSS.d.