Investigation of different solid carbonate additives in elemental-sulfur-based autotrophic denitrification process coupled with anammox process

Abstract

Abstract This study aims at investigating the nitrate reduction using different packing materials for sulfur-based autotrophic denitrification (SAD) process coupled with anaerobic ammonium oxidation (ANAMMOX) process. Three identical lab-scale upflow anaerobic bed filter (UBF) column reactors packed with different sulfur/carbonate materials were used to evaluate the performance of autotrophic denitrification at varying loading conditions. Three packing materials were prepared as follows: elemental sulfur powder fused with shell powder (USS) or calcium carbonate powder (USC) was composited into uniform granules, and mixture of dispersed sulfur granules and limestone granules (DSL). The uniform filters exhibited a better adaptability for a faster flow rate and were more favorable for biomass attachment than the dispersed filters. The optimum denitrification performance was achieved by the USS reactor, with a maximum denitrification rate of 0.33 kg NO3-N ⋅ m−3 ⋅ d−1. Moreover, the denitrification performance also revealed SAD process to be an efficient way of removing the residual nitrate when coupled with the ANAMMOX process. In addition, the observation of microbial communities indicated that the relative abundance of Thiobacillus increased to 68.9% in USS reactor, which was 1.06 and 1.33 times than USC and DSL reactors, respectively. Overall, the USS achieved a better nitrogen removal performance and might be a better choice for SAD process.