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
Phosphorus (P) is an essential element for all living organisms
The amounts of total dissolved phosphorus (TDP) and molybdate reactive phosphorus in the liquid were monitored following the standard method of ammonium molybdate spectrophotometry (GB11893-89, China), and organophosphorus (OP) was calculated from the difference between TDP and PO43À-P (Juston & DeBusk ).The metal ions (Al3þ, Fe3þ, Mg2þ and Ca2þ) in the sample were extracted with concentrated HNO3, and the metal ion contents were determined by inductively coupled plasma emission spectroscopy (Prodidy, Liman Instrument Manufacturing Co., Ltd, USA)
In order to verify that the combined electrochemical-ethylenediaminetetraacetic acid (EDTA) treatment can promote the release of P from sludge, the sludge was treated with electrochemical treatment and combined electrochemical-EDTA treatment, the indicators of the raw sludge and treated sludges were compared
Summary
Phosphorus (P) is an essential element for all living organisms. There are about 70 billion tons of phosphate rock available for mining worldwide. Phosphate rock is a non-renewable resource; phosphate rock in the world is only enough for humans to continue mining for 50–100 years, currently (Cordell et al ; Rittmann et al ). Many scholars are devoted to researching efficient and sustainable phosphorus recovery technologies. China produces more than 40 million tons of WAS per year (Tou et al ), with the development of industrialization and urbanization, its output continues to increase. The loss of a large amount of organic substances, nitrogen, phosphorus and other pollutants of WAS will cause water environment pollution (Wang et al ; Zhao et al ). The recycle of P from WAS cannot only reduce the pollution of the receiving waters, and realize the reuse of P
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