Biodegradation of sulfite in flue gas absorbent by using a biotrickling filter at anaerobic condition

A biotrickling filter (BTF) packed with a ball-shaped fiber packaging material was tested in terms of its ability to remove sulfite (SO32−) in a flue gas absorbent. Trickling rates of 9.0 m3/(m2 h) to 18 m3/(m2 h) are recommended at Na2SO3 concentrations greater than 4.5 g/L. An increase in COD/SO32− ratio could accelerate desulfurization, and COD/SO32− ratios ≥1.8 were appropriate. A 100% reduction of SO32− could be achieved at strict anaerobic conditions while maintaining the oxidation-reduction potential (ORP) at about −430 mV in the work. NH4+-N was quickly consumed then converted to NO3−-N, which functioned as an electron acceptor at anaerobic condition and was reduced to N2. The value of pH dropped from 8.19 to the lowest, 7.73, when the SO32− removal efficiency was 99%. A positive relationship was observed between the SO32− reduction and alkalinity. SO32− was fully removed at 3 h when the alkalinity reached the maximum. Overall, the BTF could efficiently reduce SO32− in a simulated flue gas absorbent, and it could be used for the biodegradation of sulfite in a simulated flue gas absorbent to replace the regeneration step of dual-alkali FGD.