Develop a Sulfur-driven Autotrophic Denitrification Process for The Treatment of Industrial Wastewater Containing High Levels of Salinity in an Alkaline Environment

Abstract

This research aimed to develop a rapid start-up procedure for Sulfur-driven Autotrophic Denitrification (SdAD) tailored for the remediation of wastewater with varying salinity levels, mainly targeting saline industrial wastewater with specific alkalinity. The study focused on evaluating the efficiency of two systems, Sulfide-based Autotrophic Denitrification (SbAD) and Thiosulfate-based Autotrophic Denitrification (TbAD), under different salinities (0.1%, 3.5%, and 6%). The SbAD process was initially assessed, revealing that after 186 extensive enrichments, consistent nitrogen removal was achieved. The results indicated that while the system performed well at 0.1% and 3.5% salinities, its efficiency decreased significantly at a 6% salinity level. Subsequently, the TbAD system was evaluated, demonstrating a more rapid achievement of consistent nitrogen removal within 57 days of enrichments. Further enhancement was achieved through subculture purification, which increased the nitrate removal efficiencies to 161.689 mg NL-1day-1 at 0.1% salinity, 94.039 mg NL-1day-1 at 3.5% salinity and 40.663 mg NL-1day-1 at 6% salinity. Metagenomics and proteomics analyses were conducted to understand microbial community dynamics and their roles in the SdAD system. These analyses revealed that Proteobacteria and Bacteroidota dominated at the phylum level. The critical species from Halomonas, Thiobacillus, and Rhodanobacter show a strong positive correlation with the system's salinity, denitrification rate, and sulfur conversion rate, respectively. The innovations of this study are significant. Firstly, it demonstrated the effectiveness of the SbAD system in treating saline wastewater in an alkaline environment. Secondly, it developed a rapid initiation method for the TbAD system, which shows practical applicability in industrial settings for high-salinity wastewater treatment. Thirdly, a method for improving treatment efficiency using TbAD subculture purification with thiosulfate was established. In conclusion, the SdAD system developed in this research represents a promising biological method for treating nitrate contamination in saline wastewater. The findings advanced our understanding of how salinity affected the microbial community structure and functional dynamics within the SdAD system, thereby promoting the application of this sustainable bioprocess in industrial wastewater treatment contexts.