Manganese sulfide-sulfur and limestone autotrophic denitrification system for deep and efficient nitrate removal: Feasibility, performance and mechanism

Despite the great potential of sulfur-based autotrophic denitrification, an improvement in nitrate removal rate is still needed. This study used the desulfurized products of Mn ore to develop the MnS-S0-limestone autotrophic denitrification system (MSLAD). The feasibility of MSLAD for denitrification was explored and the possible mechanism was proposed. The nitrate (100 mg/L) was almost removed within 24 h in batch experiment in MSLAD. Also, an average TN removal of 98 % (472.0 mg/L/d) at hydraulic retention time of 1.5 h in column experiment (30 mg/L) was achieved. MnS and S0 could act as coupled electron donors and show synergistic effects for nitrate removal. γ-MnS with smaller particle size and lower crystallinity was more readily utilized by the bacterium and had higher nitrate removal efficiency than that of α-MnS. Thiobacillus and Sulfurimonas were the core functional bacterium in denitrification. Therefore, MnS-S0-limestone bio-denitrification provides an efficient alternative method for nitrate removal in wastewater.