Construction of heterotrophic-sulfur autotrophic integrated fluidized bed reactor for simultaneous and efficient removal of compound pollution of perchlorate and nitrate in water

A heterotrophic sulfur autotrophic integrated fluidized bed reactor was established for simultaneous and efficient removal of ClO4− and NO3− from water. The optimum operating conditions forecasted through the response surface method (RSM) were the hydraulic retention time (HRT) of 0.50 h, the influent acetate (CH3COO−) concentration of 55 mg/L and the reflux ratio of 14, contributing to ClO4− and NO3− removal of 98.99% and 99.96%, respectively, without secondary pollution caused by residual carbon (NPOC <3.89 mg/L). Meanwhile, the effluent pH fluctuated in a range of 6.70–8.02 and sulfur-containing by-products (i.e., SO42− and S2−) could be controlled by adjusting operation conditions throughout the experimental stage. The increase of the influent CH3COO− concentration reduced the load borne by autotrophic reduction process and further reduced SO42− production. Shortening HRT, increasing the influent CH3COO− concentration and decreasing the reflux ratio could all reduce alkalinity consumption. Shortening HRT and decreasing the reflux ratio could shorten contact time between sulfur and water and thus inhibit S0 disproportionation. High-throughput sequencing result showed that Proteobacteria and Chlorobi were the dominant bacteria. Sulfurovum, Sulfuricurvum and Ignavibacterium were the major heterotrophic denitrifying bacteria (DB)/perchlorate reducing bacteria (PRB), Ferritrophicum and Geothrix were DB, and Chlorobaculum was S0 disproportionation bacteria.