Assessment of the Environmental and Operational Factors Affecting the Bioremediation of H2S Gas as Air Pollutant

• Main Authors: Mohamed A. Zytoon, Magda M. Abd El-Aty, Faten Nofal, Ahmed I. Issa, Adel M. Zakaria
• Format: Article
• Language: English
• Published: Alexandria University 2007-09-01
• Series: Journal of High Institute of Public Health
• Subjects: environmental factors; operational factors; bioremediation; h2s; air pollutant

This study aims at optimizing environmental and operational factors affecting the bio-remediation of H2S as air pollutants. Sulfur gases are emitted from many industrial sources and have adverse effects on the public health and the environment. Bioremediation of waste gases represents a new treatment alternative that has been seen as a competitive to the physico-chemical treatment technologies. Sulfur gases, such as H2S were among the inorganic gases that have been proven to be suitable candidates to Bioremediation. The process of biological treatment depends on using sulfur eating bacteria which can use the target sulfur gas or compound as energy or supplementary source converting it to another sulfur form. Sulfur bacteria are dominant microorganisms in many natural media. The bioreactor used was an aerobic reactor for oxidizing H2S to elemental sulfur by Sulphur Oxidizing Bacteria (SOB). It consisted of aerobic bioreactor, a settler, and H2S-laden gas producing system. The microorganism used is SOB isolated from sewage sludge. Microbial activity is affected by environmental factors and operational factors. The results revealed that the optimum CO3-- concentration range for complete removal and conversion, i.e. 100% recovery of H2S is 61.5 to 615 g/m3. The SOB was highly preferment within a nitrogen concentration range of 30.8 to 123.1 g/m3, achieving 100% removal or conversion efficiency. The minimum P concentration that maintained maximum activity of the resident SOB was about 24.6 g/m3. The mesophilic range was the optimum for the SOB used in this study (38-43oC). The highest performance of the bioreactor was attained at pH range from 7.5 to 9 with optimum operation at pH 8. Results explained that the resident SOB at pH 8 tolerated total sulfide concentrations higher than at pH 7. 100% removal efficiency of the bioreactor reaching at O2/H2S range 0.5- 1.5. The maximum elemental sulfur yield obtained was 92.4%. The increase of H2S inlet concentration required increase of contact time. The measurements of SOB concentration in the suspension reported average about 3.56×108 cells/ml (range from 3.5 to 3.62×108cells/ml). This implies that the maximum cell capacity was about 1.23×10-12 g H2S/cell.h. The activity of the SOB was not affected at SO4-- concentrations below 20,000 g/m3. The removal efficiency was 100% below this concentration. The S2O3-- concentrations higher than 10,000 to 15,000 g/m3 may be inhibitive to the SOB. This study recommended encourages the using of air pollutant gases bioremediation in industries scale.