Seasonal Dynamics of Bacteria in Corrosive Biofilms Formed on the Surface of Wastewater Treatment Plants

Abstract

The corrosive biofilm is formed on metal surfaces of wastewater treatment plants. The numbers of sulfate reducing and ammonifying bacteria (up to 109 cell/cm3 and up to 108 cell/cm3, respectively) are dominant in this film, while the quantity of acidophobic tionic bacteria is the smallest (up to 102 cell/cm3). The relationship between the bacteria produced hydrogen sulfide and the measure of wastewater acidity has been established indicating that with the rise of hydrogen sulfide production the water pH decreases. The rate of steel corrosion under exposure to enrichment cultures of sulfate reducing bacteria separated from biofilms depends on the season, separation of bacteria and their metabolic activity. The correlation between the number of iron reducing bacteria, concentration of phosphate ions in wastewater and the rate of steel corrosion has been established.