Abstract
Phosphorus is a nonrenewable and irreplaceable limited resource, and over 90% of phosphorus in influenttransfers into sludge in wastewater treatment plants. In this study, thermally activated peroxydisulfate (TAP) treatment was combined with struvite precipitation to enhance waste activated sludge (WAS) dewaterability and phosphorus recovery. TAP simultaneously enhanced dewaterability and solubilization of WAS. The optimal conditions of TAP treatment were PDS dosage 2.0 mmol/g TSS, 80 °C, pH 4.0~7.0 and 40 min, which enhanced dewaterability (capillary suction time (CST) from 94.2 s to 28.5 s) and solubilization (PO43−-P 177.71 mg/L, NH4+-N 287.22 mg/L and SCOD 10754 mg/L). Radical oxidation disintegrated tightly bound extracellular polymeric substances (TB-EPS) and further released bound water. The acidification effect neutralized the negative surface charge of colloid particles. Compared with thermal hydrolysis, TAP effectively promoted the release of PO43−, NH4+ and SCOD. Cation exchange removed most Ca and Al of the TAP treated supernatant. The optimal conditions of struvite precipitation were Mg/P 1.4 and pH 10.0, which achieved phosphorus recovery of 95.06% and struvite purity of 94.94%. The income obtained by struvite adequately covers the cost of struvite precipitation and the cost of WAS treatment is acceptable.
Highlights
IntroductionPublisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
The waste activated sludge (WAS) used in our experiments was drawn from the secondary settling tank of a wastewater treatment plant (113.36◦ E, 23.12◦ N) located in Guangzhou, China
In the absence of PDS, elevated temperature deteriorated WAS dewaterability with capillary suction time (CST) increased from 94.2 s to 3717.9 s in 60 min, which coincided with previous research [35]
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The activated sludge process, which produces waste activated sludge (WAS), is employed worldwide in wastewater treatment plants (WWTP). WAS management accounts for up to 60% of total operating expenses in WWTP [1]. With the increasing demand for WAS management, the rising growth of WAS has become a challenge worldwide. The dewatering of WAS is necessary for subsequent transportation, treatment and, disposal
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