A novel dynamic membrane-equipped element sulfur-based denitrification reactor for efficient and easily maintainable treatment of high-nitrate wastewater

Using powdered sulfur (S0) with high specific surface area enables high efficiency in an elemental sulfur-based denitrification (ESDeN) reactor but faces challenges with S0 retention. While integrating the ESDeN process with microfiltration membranes (MM) has been shown to effectively reject S0 powder, severe membrane fouling and high membrane costs restrict its practical application. This study, for the first time, reports a dynamic membraneequipped ESDeN (ESDeN-DM) reactor. The DM was formed by in-situ pre-coating a solid mixture (particle size: 0.4 mu m to 110 mu m) of S0 powder and denitrifying sludge onto inexpensive nylon fabrics. Initially, we optimized the DM formation conditions, determining that a nylon fabric pore size of 25 mu m and a pre-coating flux of 300 L m-2 h-1 resulted in permeate turbidity lower than 5 NTU within 60 mins. Subsequently, we identified the duration (12.5 days) of a transmembrane pressure (TMP)-dependent run (<= 30 KPa) for the reactor and found that the TMP increase was related to the thickening and densification of the cake layer. Finally, we conducted a comparative examination of the ESDeN-DM reactor and the conventional ESDeN-MM reactor during long-term operation. The results demonstrated that the ESDeN-DM reactor achieved a comparable denitrification rate to the ESDeN-MM reactor (both with the maximum value more than 3 kg N m-3 d-1) but exhibited significantly better membrane fouling tolerance (56 % longer TMP-dependent run time), easier regeneration of specific flux (online backwash versus offline chemical cleaning), and exceptional cost-effectiveness (over 90 % total cost reduction). This study presents a highly efficient and easily maintained membrane-equipped ESDeN process with great potential for treating high-nitrate industrial wastewater.