Industrial Acidic Wastewater Treatment by Sulfate Reducing Microorganisms

The effluents of polymerization plants are acidic due to the use of sulfuric acid as flocculation agent and their wastewater contains high amounts of sulfate ions. In wastewater industry, several physical, chemical and biological treatment methods are used. The main purpose of this study is to examine the feasibility of anaerobic biological treatment of sulfate in industrial effluents by using sulfate-reducing bacteria. The research method is quantitative, and experiments and data collection from 2017-2020. The main variables of this research are temperature, effluent pH and the population of microorganisms. Experiments at two temperature levels of 25 and 60 oC and two different pHs, 7.5 and 8.5, were performed and four series of experiments were done. The results showed that by increasing the temperature of the solution from 25° to 60 °C at a concentration of 50 mg/L sulfate ion and a pH of 7.5, microorganisms showed 17.6% better performance. Also, the performance of microorganisms in anaerobic biological treatment at concentration of 50 mg/L of sulfate ion was 45.3% minimum and 49.9% at maximum. Comparison of experimental results at two different pHs of 7.5 and 8.5, indicates that at the same temperatures of 25 and 65°C, with increasing pH, the performance of microorganisms has improved by 16.4%. The efficiency of wastewater treatment increases 19.6% by changing pH from 7.5 to 8.5. Results showed that the correlation between temperature and sulfate ion concentration follows the 1st degree equation. Also, the weak pH environment provides suitable conditions for the removal of ions in the effluents, and the correlation between increasing the pH of the solution and decreasing the concentration of sulfate ions is a 2nd degree equation. Study showed that temperature and pH are the two effective factors in the process of biological treatment of effluents.