Reusing effluent of flue gas desulfurization wastewater treatment process as an economical calcium source for phosphorus removal

Abstract

Flue gas desulfurization (FGD) wastewater treatment by conventional neutralization, chemical precipitation and coagulation process removes most suspended solids and heavy metals, and provides an effluent rich in calcium, alkalinity and chloride, which obstructs its reclamation and reuse but is in favor of phosphorus (P) precipitation. The goals of this study were to investigate feasibility of reusing FGD effluent as a calcium source for P removal from P-rich wastewater. Results revealed that increasing the volumetric ratio between FGD effluent and P-rich wastewater achieved higher pH value and Ca/P ratio, and thus enhanced P removal efficiency to 94.3% at the ratio of 40%. X-ray diffraction and scanning electron microscope analysis of harvested precipitates showed that increasing pH from 8 to 10 induced the conversion of hydroxyapatite to tri-calcium phosphate, and then to whitlockite. This study demonstrated that for reusing FGD effluent for P removal was highly feasible, both technically and economically. This process not only saves the cost of precipitants for P removal, but also provides an economical alternative for current zero liquid discharge technology for FGD wastewater, which requires high energy consumption and capital costs.

Pilot-scale study on seeded precipitation assisted nanofiltration for flue-gas desulfurization wastewater softening

“…The traditional treatment process of FGD wastewater includes neutralization, chemical precipitation and coagulation (NPC) units. Since the NPC process cannot remove main salt ions in FGD wastewater, the wastewater cannot be recycled and reused (Dou et al 2017). In general, the NPC effluent is used for ash field spraying or hydraulic slug flashing, which lead to further environment pollution (Han et al 2020).…”

Water Reclamation and Reuse

“…The molasses-processed wastewater addition contributed to a higher lactic acid concentration, a lower pH, and a lower NH3-N concentration than in the silage samples. Dou et al (2017) tested the technical and economic feasibility of reusing flue gas desulfurization (FGD) wastewater as a calcium source for enhancing phosphorus (P) removal from P-rich wastewater. The P removal efficiency reached 94.3% at a volumetric ratio of FGD effluent/P-rich wastewater of 40%.…”