An integrated process of chemical precipitation and sulfate reduction for treatment of flue gas desulphurization wastewater from coal-fired power plant

Abstract

Flue gas desulphurization process in coal-fired power plants, produces wastewater with concentrated sulfate, chloride, metals and refractory organic compounds, which leads to serious pollution and corrosion problem during recycling. In this study, an integrated process of chemical precipitation and sulfate reduction for treatment of coal-fired power plant flue gas desulphurization wastewater was developed. Without additional of heavy metal trapping and strong oxidizing agents, chemical precipitation was performed as pre-treatment for removal of suspended solid (97%) in raw flue gas desulphurization wastewater. Comparison study on treatment of pre-treated flue gas desulphurization wastewater were performed in three parallelly operated sequencing batch reactors, by cultured sulfate reducing bacteria strain BY7, SR10 and SR3, respectively. This study demonstrated that strain BY7 and SR10 sulfate reducing bacteria were able to adapted to high-salinity flue gas desulphurization wastewater, with high efficiencies of sulfate reduction (86–94%), metals (70–100%) and refractory organic compounds removal (85–95%). The highest sulfate loading rate of 0.5 kg SO42−/m3·d was achieved in sequencing batch reactors with strain BY7 and SR10. Besides, a sustainable removal of chloride and fluoride were achieved (about 35% and 55%, respectively), which probably relate to co-precipitation or biosorption processes. Up to 14 out of 25 refractory organic compounds in flue gas desulphurization wastewater could be completely removed after integrated treatment process. As response to flue gas desulphurization wastewater stress, abundance of monounsaturated fatty acids were increased, and upregulated expression of genes related to salt detoxification were observed in SBR_BY7 and SBR_SR10. Therefore, this study provided a potential low-cost flue gas desulphurization wastewater recycling technology with simultaneously removal of sulfate, refractory organic compounds, heavy metal and salts.