Abstract: Wastewater containing soluble selenium is treated in a bioreactor. Microorganisms in the reactor reduce the selenium to elemental selenium, which is insoluble. The elemental selenium is discharged from the reactor in waste sludge. The sludge is treated to recover selenium. In one method, the sludge is washed with chemicals, for example surfactants, and agitated to disrupt the adhesion of the selenium particles to the cells. The selenium particles are then separated from the cells using a physical separation process such as a centrifuge or differential filtration. In another method, the sludge is de-watered or dried to a very high solids content. The selenium particles are dissolved using an oxidizer under high pH conditions. A solids fraction is removed from the resulting slurry. A resulting selenium brine is further refined to recover the selenium.