The biological reduction of selenate and sulfate in agricultural drainage water

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5120667

Owens, L P

In many areas of the western US, subsurface drainage is produced when restrictive soils are irrigated and drained. The agricultural drainage water is saline and in many areas the concentration of selenium exceeds 100 {mu}g/L. Sulfate is present at concentrations ranging from 1,000 mg/L to 10,000 mg/L. Two upflow anaerobic sludge blanket reactors were constructed to evaluate the fate of selenate in a biological reactor treating a synthetic agricultural drainage water under sulfate-reducing conditions. Both lactate and molasses were evaluated as carbon sources for the microbiological process. Sulfate reducing conditions were established in both reactors with a 95+% reduction in sulfate from initial levels of 3,600 mg/L SO{sub 4}{sup {minus}2} Sulfate was reduced to sulfide via the dissimilatory sulfate reduction pathway. Selenate was reduced to elemental selenium through a sulfate-independent dissimilatory reduction pathway. The elemental selenium formed seleno-polysulfides in the sulfidic environment of the reactor. Conversion to seleno-polysulfides increased the solubility of the elemental selenium. The seleno-polysulfides were precipitated with iron salts. A residual total selenium level of about 20% of the initial 350 {mu}g/L Se remained in the effluent after precipitation of the seleno-polysulfides due to the presence of soluble organic selenium compounds. Denitrification of the influent nitrate at a concentration of 214 mg/L as NO{sub 3}{sup {minus}} was complete. A treatment scheme was proposed for the simultaneous removal of selenium, nitrate, and sulfate from agricultural drainage waters.

• Research Organization: Texas Univ., Austin, TX (United States)
• OSTI ID: 5120667
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540220* -- Environment
Terrestrial-- Chemicals Monitoring & Transport-- (1990-)
540320 -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
560300 -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AGRICULTURE
BIODEGRADATION
BIOREACTORS
CHEMICAL REACTIONS
CONTAMINATION
DECOMPOSITION
ECOLOGICAL CONCENTRATION
ELEMENTS
MICROORGANISMS
MONITORING
OXYGEN COMPOUNDS
REDOX REACTIONS
SELENIUM
SEMIMETALS
SOILS
SUBSURFACE ENVIRONMENTS
SULFATES
SULFUR COMPOUNDS