Wastewater post-treatment for simultaneous ammonium removal and elemental sulfur recovery using a novel horizontal...

A novel horizontal mixed anoxic-aerobic fixed-bed reactor configuration based on nitrification coupled with autotrophic denitrification using hydrogen sulfide as an electron donor was developed. The nitrification removal efficiency (RE) reached values greater than 99% but was slightly affected by the accumulation of dissolved sulfur species in the liquid phase. The denitrification RE reached 99% with a H₂S inlet load of 28.6 g S m^-3 h^-1, although the use of aluminum polychloride (PAC) as a sulfur coagulant in the anoxic zone affected the buffering capacity of the system and resulted in a decrease in the RE. The performance of the reactor was primarily affected by the buffering capacity of the system, and this effect could be controlled with an increase in the NaHCO₃ concentration. The recovery of biogenic elemental sulfur was possible using PAC as a coagulant, although the solid collected at the bottom of the settling tank contained only 1.5% S⁰.