Application of Submerged Ultrafiltration in Pretreatment of Flue Gas Desulfurization Wastewater

Abstract

Nowadays, the zero liquid discharge of flue gas desulfurization (FGD) wastewater from coal-fired units has attracted the attention of all countries in the world. The pretreatment methods generally have the problems of high operation cost, small treatment capacity, and poor flexibility. However, the membrane method can avoid the above problems.In the current research, it has not been found that someone directly uses submerged ultrafiltration to pretreat FGD wastewater. Therefore, this paper innovatively proposed to directly use ceramic ultrafiltration membrane to treat FGD wastewater, which can ensure effluent quality and improve the flexibility of the pretreatment system. In this paper, the performance of submerged ultrafiltration membrane for the filtration of FGD wastewater from a power plant was studied to optimize the filtration performance and improve the effluent quality. The effects of operating parameters such as membrane permeate flux, aeration rate and filtration/backwashing time combination on the membrane performance were studied. The results showed that when the filtration/backwashing time combination was 15 min/30 s, with the increased in permeate flux from 55 L/(m 2 •h) to 100 L/(m 2 •h), the steady transmembrane pressure (TMP) increased from 39 kPa to 70 kPa, and the fouling rate increased significantly from 4.5 kPa/h to 7.3 kPa/h; When the aeration rate increased from 10 m 3 /(m 2 •h) to 30 m 3 /(m 2 •h), the membrane pollution was much reduced. Excessive aeration rate cannot further alleviate the membrane pollution, but also brought greater energy consumption; Increasing backwashing time can effectively inhibit the formation of gel layer on the surface of the membrane and prolong the initial stage of low-pressure operation; The rejection of suspended solids (SS) and turbidity of the equipment studied in this paper can reach more than 99% under various working conditions, which can satisfy the water quality requirements of the subsequent steps. The submerged ultrafiltration membrane was suitable for the pretreatment of FGD wastewater because it can ensure the quality of permeate under the premise of long-term operation.