The production processes of many industries such as those for petrochemicals, synthetic fuel processing, mining, and cassava starch use many cyanide compounds and generate high concentrations of cyanide. Cyanide can enter the human body by inhalation, ingestion, and adsorption. Moreover, cyanide is toxic to most species in freshwater or marine environments at a level of 0.1 mg/L at normal pH and temperature. The objectives of this study were to investigate cyanide degradation by a mixed bacterial culture containing SUTS 1, to identify other cyanide-degrading bacteria and to study the production of ammonia and nitrate from cyanide degradation. A mixed culture of bacteria capable of growth on cyanide was isolated from a wastewater stabilization pond of the cassava starch industry. The two species of bacteria found in this culture were identified as Agrobacterium tumefaciens SUTS 1 and Pseudomonas monteilii SUTS 2. The maximum growth rate of the mixed culture was 108 cells within 2 days. Cyanide degradation was studied using starting cyanide concentrations of 25, 50, and 150 mg/L. The residual cyanide, ammonia, nitrate, nitrite, pH, and cell counts were analyzed. At 25 and 50 mg/L cyanide, the mixed culture obtained a very high removal efficiency of more than 99.99%. Ammonia and nitrate were produced in the range of 0.14-0.28 mg/L and 1.71-2.69 mg/L, respectively. At 150 mg/L cyanide, the removal efficiency was lower whereas the concentrations of ammonia and nitrate increased to 1.40 mg/L and 5.21 mg/L, respectively. Nitrite was not detected in any experiment.
Siraporn Potivichayanon, Suranaree University of Technology, Thailand
Rujirat Kitleartpornpairoat, Suranaree University of Technology, Thailand
Stream: Environmental Sustainability & Human Consumption: Waste
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