A rapid method to quantify the biomass of viable Acidithiobacillus ferrooxidans in iron-based bioleaching matrix of sewage sludge

Overlay plate counting is the traditional way to determine the biomass of viable Acidithiobacillus ferrooxidans in iron-based bioleaching matrix of sewage sludge. However, the time required is 12 days at a minimum. Here, a rapid method based on a quantitative relationship between the extant rate of iron bio-oxidation by Acidithiobacillus ferrooxidans and the CFU counts was developed. The method reduces the time to similar to 3 h. In the new method, the biomass is calculated by dividing the extant iron bio-oxidation rate by the specific rate of iron oxidation by Acidithiobacillus ferrooxidans. The extant rate of iron bio-oxidation was determined in a 2-h iron oxidation test. The effects of environmental factors such as pH on iron oxidation in all tests were the same. The basal specific rate of iron oxidation by Acidithiobacillus ferrooxidans was 10(-9) mg/h/CFU. During bioleaching, the specific rate increased by 10(-10) mg/h/CFU when the net contact time between Acidithiobacillus ferrooxidans and available ferrous iron increased by one hour. Therefore, according to the law, the biomass can be rapidly determined by the extant rate and the net contact time.