Optimized start-up strategies for elemental sulfur packing bioreactor achieving effective autotrophic denitrification

The start-up efficiency of the elemental sulfur packing bioreactor ((SPB)-P-0) is constrained by the slow growth kinetics of autotrophic microorganisms, which is essentially optimized. This study aims to optimize start-up procedures and offer scientific guidance for the practical applications of (SPB)-P-0. Through comparing the startup efficiencies under various conditions related to inoculation, backwashing, and EBCT, it was found that these conditions did not significantly influence start-up time, but they did impact denitrification performance in detail. Using activated sludge as the inoculum was not recommended as the 2.5 +/- 0.2 mg-N/L higher nitrite accumulation and 26.0 +/- 5.1 % lower TN removal rate, compared to self-enrichment. Starting with a long-toshort EBCT (1 -> 0.33 h) achieved higher nitrate removal of 11.5 +/- 0.6 mg-N/L and eliminated nitrite accumulation compared to constantly short EBCT (0.33 h) conditions. Daily and postponed backwashing were suggested for long-to-short EBCT and constantly short EBCT start-up, respectively. Enrichment of Sulfurimonas was beneficial for the effective nitrite reduction process.

Automated summary

The start-up efficiency of the elemental sulfur packing bioreactor is affected by various factors including inoculation, backwashing, and EBCT. It was found that these factors did not significantly impact start-up time, but they did influence denitrification performance. It is not recommended to use activated sludge as the inoculum, and starting with a long-to-short EBCT achieved better nitrate removal compared to constantly short EBCT conditions. Enrichment of Sulfurimonas was beneficial for the nitrite reduction process.