Process for recovering elemental selenium from wastewater

Patent metadata

Field	Value
Publication number	US-2017158535-A1
Application number	US-201515325642-A
Country	US
Kind code	A1
Filing date	Jul 6, 2015
Priority date	Jul 14, 2014
Publication date	Jun 8, 2017
Grant date	—

Abstract

A first aspect of the present invention relates to a process for recovering crystalline elemental selenium (Se) from an aqueous composition, such as waste water or groundwater. A second aspect of the present invention further relates to a microbial sludge comprising crystalline elemental selenium, which sludge may be used in the further recovery of elemental selenium.

First claim

1 - 14 . (canceled)

15 . A process for recovering elemental selenium (Se) from an aqueous composition, comprising:
(a) providing an aqueous composition comprising selenite; (b) reacting at least a part of the selenite with sulfide into selenium sulfide; (c) reducing with a microbial sludge at least a part of the selenium sulfide formed into hydrogen sulfide and crystalline elemental selenium; and (d) separating least a part of the microbial sludge comprising the crystalline elemental selenium formed from the aqueous composition.

16 . The process according to claim 15 , wherein the aqueous composition is wastewater or an effluent from a wastewater treatment installation.

17 . The process according to claim 15 , wherein the aqueous composition comprises between 0.1 and 4000 mg per liter selenite.

18 . The process according to claim 15 , wherein prior to step (a) at least a part of any selenate present in the aqueous composition is converted into selenite.

19 . The process according to claim 18 , wherein selenate is converted into selenite by means of a microbial reduction.

20 . The process according to claim 19 , wherein the microbial reduction is by means of complete oxidizing sulphate reducing micro-organisms.

21 . The process according to claim 20 , wherein in step (b) the sulfide is a sulfide salt or hydrate thereof.

22 . The process according to claim 21 , wherein the sulfide salt is sodium sulfide (Na 2 S) or a hydrate thereof.

23 . The process according to claim 22 , wherein in step (c) an anaerobic microbial sludge comprising sulfate reducing micro-organisms is used as a starter-culture.

24 . The process according to claim 23 , wherein the sulfate reducing micro-organisms comprise complete oxidizing sulfate reducing micro-organisms.

25 . The process according to claim 24 , wherein the complete oxidizing sulphate reducing micro-organisms are selected from the genus Desulfobacte.

26 . The process according to claim 25 , wherein the Desulfobacte comprise Desulfobacter postgatei, Desulfotomaculum acetoxidans Desulfobacterium, Desulfotomaculum, Desulfococcus, Desulfobacca acetoxidans or combinations thereof.

27 . The process according to claim 15 , wherein step (c) is carried out at a pH between 4 to 10 and at a temperature between 10° C. to 75° C.

28 . The process according to claim 15 , wherein in step (d) the microbial sludge is separated from the aqueous solution by allowing the sludge to settle in a clarifier, such that the crystalline elemental selenium comprising sludge is separated from the aqueous solution.

29 . The process according to claim 15 , further comprising recovering the crystalline elemental selenium from the microbial sludge.

30 . The process according to claim 15 , wherein at least a part of the hydrogen sulfide produced in step (c) is reused in step (b).

31 . A microbial sludge comprising crystalline elemental selenium obtainable by the process according to claim 15 .

32 . The microbial sludge according to claim 31 , wherein the sludge comprises crystalline particles of elemental selenium having a volume/surface average particle diameter (d32) in the range of 0.1 to 100 μm.

33 . The microbial sludge according to claim 32 , wherein the sludge comprises crystalline particles of elemental selenium having a volume/surface average particle diameter (d32) in the range of 1-50 μm.

34 . The microbial sludge according to claim 33 , wherein the sludge comprises crystalline particles of elemental selenium having a volume/surface average particle diameter (d32) in the range of 1-10 μm.

Assignees

• Univ Wageningen

Inventors

• Hageman Simon Petrus Wilhelmus
• Van Der Weijden Renata Dorothea
• Buisman Cees Jan Nico

Classifications

• C02F3/345 Primary

  for biological oxidation or reduction of sulfur compounds · CPC title

• C02F2101/106

  Selenium compounds · CPC title

• C01B19/02

  Elemental selenium or tellurium · CPC title

• C02F1/70

  by reduction {(C02F1/4676 takes precedence)} · CPC title

• C12P3/00

  Preparation of elements or inorganic compounds except carbon dioxide {(recovery of carbon dioxides as by-products C12F3/02)} · CPC title