Low temperature, autotrophic microbial denitrification using thiosulfate or thiocyanate as electron donor

Area of Science:

• Environmental Microbiology
• Bioremediation
• Wastewater Treatment

Background:

• Mining wastewaters are acidic and contain pollutants like nitrate, nitrite, ammonium, inorganic sulfur compounds (thiosulfate, tetrathionate), and thiocyanate.
• Environmental release of these compounds causes acidification, eutrophication, and toxicity.
• Stricter regulations and increased mining demand low-cost, ambient-temperature remediation techniques.

Purpose of the Study:

• To develop and assess a method for removing nitrogenous and inorganic sulfur compounds from mining wastewater.
• To investigate the efficacy of coupled autotrophic thiocyanate oxidation and nitrate reduction under low-temperature, acidic conditions.
• To identify the microbial communities involved in the remediation process.

Main Methods:

• Utilized aerobic and anaerobic continuous cultures to treat simulated mining wastewater.
• Employed DNA sequencing to monitor and identify microbial community development over time.
• Operated cultures at low temperatures (approx. 8°C) and varying pH (neutral to acidic).

Main Results:

• Successfully coupled inorganic sulfur compound oxidation (thiosulfate, thiocyanate) with nitrogenous compound removal.
• Achieved remediation under low temperatures (approx. 8°C) and neutral to acidic pH.
• Identified a microbial consortium including Flavobacterium, Thiobacillus, and Comamonadaceae lineages.

Conclusions:

• This study presents the first successful remediation of mining wastewater by coupling autotrophic thiocyanate oxidation to nitrate reduction at low temperatures and acidic pH.
• The identified microbial community demonstrates potential for effective bioremediation of complex mining effluents.
• The findings offer a promising, low-cost solution for treating challenging mining-related wastewaters.