Improvement of phosphorus release from sludge by combined electrochemical-EDTA treatment

Abstract

In this paper, combined with the addition of ethylenediaminetetraacetic acid (EDTA), the electrochemical treatment of waste activated sludge (WAS) was investigated to explore its effect on the release of phosphorus (P) from WAS. The results showed that during the electrochemical treatment, the addition of EDTA could significantly promote the release of P from the WAS to the supernatant, the optimal amount of EDTA was 0.4 g/g total suspended solids (TSS), when the release of total dissolved phosphorus (TDP), organic phosphorus (OP) and molybdate reactive phosphorus (PO43−-P) were 187.30, 173.84 and 13.46 mg/L, respectively. OP was the most likely form of P to be released during this process. Moreover, combined electrochemical-EDTA treatment could promote the release of P and metal ions from extracellular polymeric substances (EPSs) to the supernatant, and increase the solubility and disintegration of sludge. EDTA chelated the metal ions of sludge flocs and phosphate precipitates to cause sludge floc decomposition, thereby promoting the release of P from WAS. HIGHLIGHTS Successfully developed combined electrochemical-EDTA treatment technology to promote the release of P in WAS.; OP was the most likely phosphorus form to be released.; Changes of P and metal elements content in EPSs had been investigated.; EDTA destroys sludge flocs and promotes P release by chelating heavy metals.;

Keywords

• electrochemical-edta treatment
• extracellular polymeric substances
• metal ions
• organophosphorus
• phosphorus release
• waste activated sludge