Bioreduction can facilitate oxyanions removal from wastewater. However, simultaneously removing selenate, nitrate and sulfate and recovering high-purity elemental selenium (Se⁰) from wastewater by a single system is difficult and may lead to carcinogenic selenium monosulfide (SeS) formation. To solve this issue, a two-stage biological fluidized bed (FBR) process with ethanol dosing based on oxidation-reduction potential (ORP) feedback control was developed in this study. FBR1 performance was first evaluated at various ORP setpoints (between −520 and −360 mV vs. Ag/AgCl) and elevated sulfate concentration. Subsequently, ethanol-fed FBR2 was used to reduce sulfate from FBR1 effluent, followed by an aerated sulfide oxidation reactor (SOR). At − 520 mV ≤ ORPs ≤ − 480 mV, FBR1 removed 100 ± 0.1% nitrate and 99.7 ± 0.3% selenate without sulfate reduction. At ORPs ≥ − 440 mV, selenate reduction was incomplete, whereas nitrate removal remained stable. Se⁰ recovery efficiency from FBR1 effluent was 37.5% with 71% Se purity. FBR2 converted 86% of the remaining sulfate in FBR1 effluent to hydrogen sulfide, but the over-oxidation of dissolved sulfide in SOR decreased the overall sulfate removal efficiency to ~46.3%. Overall, the two-stage FBR process with ORP feedback dosing of ethanol was effective for sequentially removing selenate, nitrate and sulfate and recovering Se⁰ from wastewater.

生物还原可以促进从废水中去除含氧阴离子。然而，通过单一系统同时去除硒酸盐、硝酸盐和硫酸盐以及从废水中回收高纯度元素硒（Se ⁰）是困难的，并且可能导致致癌的一硫化硒（SeS）的形成。为了解决这个问题，本研究开发了一种基于氧化还原电位（ORP）反馈控制的乙醇投加两阶段生物流化床（FBR）工艺。FBR1 性能首先在各种 ORP 设定点（-520 和 -360 mV 与 Ag/AgCl 之间）和升高的硫酸盐浓度下进行评估。随后，乙醇进料的 FBR2 用于减少 FBR1 流出物中的硫酸盐，然后是充气硫化物氧化反应器 (SOR)。在 − 520 mV  ≤ ORPs  ≤ − 480 mV，FBR1 去除了 100 ± 0.1% 的硝酸盐和 99.7 ± 0.3% 的硒酸盐，没有硫酸盐还原。在 ORP ≥ -  440 mV 时，硒酸盐还原不完全，而硝酸盐去除保持稳定。FBR1 流出物中的Se ^{0回收率为 37.5%，Se 纯度为 71%。}FBR2 将 FBR1 流出物中 86% 的剩余硫酸盐转化为硫化氢，但 SOR 中溶解的硫化物的过度氧化将整体硫酸盐去除效率降低至 ~46.3%。总体而言，具有ORP反馈加料乙醇的两级FBR工艺对于顺序去除硒酸盐、硝酸盐和硫酸盐以及从废水中回收Se ^{0是有效的。}