Investigation on the use of nitrified wastewater for the steady-state operation of a biotrickling filter for the removal of hydrogen sulphide in biogas

A biological process for the removal of hydrogen sulphide (H₂S) in digester biogas was investigated using nitrified municipal wastewater as a nutrient solution under anoxic conditions. Biogas was continuously fed into a 0.012 m³ biotrickling filter at an H₂S loading rate of approximately 1.50 g/d, counter-current to the nutrient solution. A zero-order macro-kinetic process was established on the basis of the degradation and formation rates for N and S species. The process performance was dependent on the presence of nitrate at low concentrations (in the order of 20 mg N-NO₃^–/L) found to be sufficient to maintain maximum H₂S removal efficiency (>99%) under steady-state conditions where nitrate degradation rate was constant. The developed process has the potential to be adopted as an attractive alternative for biogas cleaning and, in some cases, with simultaneous wastewater denitrification. The information contained within this paper may be used as a basis for further research and (or) in the design of a scaled-up process.