Purpose of Review

Different selenium species released into the environment by anthropogenic activities pollute surface and ground water resources and can cause severe damage to the environment and ecosystems due to bio-accumulation. Though several physico-chemical methods are available to treat selenium oxyanion-containing wastewater, biological methods have gained significant importance due to their capability to convert selenium oxyanions to elemental selenium nanoparticles. The purpose of this review is to summarize the literature available on biological removal of selenium oxyanions and their recovery as elemental selenium nanoparticles.

Recent Findings

In recent times, the capability of several bacterial and fungal strains to reduce selenate and selenite to form elemental selenium nanoparticles has been reported. The shape, size and location of these selenium nanoparticles along with the selenium oxyanion removal efficiency depend on the operating parameters. Moreover, bioreactor configurations and operation strategies greatly influence the selenium removal and recovery efficiency.

Summary

Several conventional bioreactor systems can be used to remove selenate and selenite from wastewater and form selenium nanoparticles. However, the selenium nanoparticles are mostly entrapped in the biomass and require a secondary treatment to recover them. On the other hand, some novel bioreactors, viz. inverse fluidized bed bioreactor, rotating biological contractor, horizontal rotating packed bed bioreactor, moving bed biofilm reactor, and hybrid bioreactor, can possibly recover selenium nanoparticles following bioreduction of selenium oxyanions in a single stage system. Thus, this review will help in finding research gaps in this area and providing solutions for resource recovery from selenium oxyanion-containing wastewater.

中文翻译：

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废水中硒酸盐和亚硒酸盐的生物去除：硒作为纳米颗粒的回收选择

审查目的

人为活动释放到环境中的不同硒物种会污染地表和地下水资源，并由于生物蓄积而严重破坏环境和生态系统。尽管有几种物理化学方法可用于处理含硒氧阴离子的废水，但由于生物方法具有将硒氧阴离子转化为元素硒纳米粒子的能力，因此生物方法已变得非常重要。这篇综述的目的是总结有关生物上去除硒酸氧阴离子及其作为元素硒纳米颗粒的回收的文献。

最近的发现

近年来，已经报道了几种细菌和真菌菌株还原硒酸盐和亚硒酸盐以形成元素硒纳米颗粒的能力。这些硒纳米粒子的形状，大小和位置以及硒氧阴离子的去除效率取决于操作参数。此外，生物反应器的配置和操作策略极大地影响了硒的去除和回收效率。

概要

几种常规的生物反应器系统可用于从废水中去除硒酸盐和亚硒酸盐，并形成硒纳米颗粒。然而，硒纳米颗粒大部分被困在生物质中，需要进行二次处理才能回收。另一方面，一些新颖的生物反应器。逆流化床生物反应器，旋转生物收缩器，卧式旋转填充床生物反应器，移动床生物膜反应器和混合生物反应器可以在单级系统中生物还原硒氧阴离子后回收硒纳米粒子。因此，本综述将有助于发现该领域的研究空白，并为从含硒氧阴离子的废水中回收资源提供解决方案。