Nitrogen and sulfur metabolism in anaerobic hydrogen-producing microbiome as a challenge for 2,4-DCP dechlorination

Abstract

This research aimed to assess the effectiveness of anaerobic hydrogen-producing microbiomes (HMb) in treating different concentrations of 2,4-dichlorophenol (2,4-DCP) under controlled conditions. The dechlorination experiments were conducted at 41°C in 120-mL vials using a rotary culture device to ensure thorough mixing. The study focused on dechlorination kinetics and efficiency, dynamic changes in the nitrogen-sulfur cycle, and the impact of organic carbon availability. Results indicated that at concentrations below 50 mg/L, HMb achieved a maximum dechlorination rate (Rm) of about 0.7 mg/L-day, which declined to 0.3 mg/L-day at 100 mg/L, suggesting inhibition at higher concentrations. Over 180 days, NH4+-N concentrations decreased, while NO3--N fluctuated, highlighting complex nitrogen transformations influenced by carbon supply and microbial activity. Sulfate concentrations significantly declined in the first 60 days due to sulfur-oxidizing bacteria, including nitrogen-reducing sulfur-oxidizing bacteria (NR-SOB), which promoted anaerobic hydrogen production. Firmicutes increased from 19.5 % to 69.2 %, while Actinobacteria decreased from 73.0 % to 26.8 %, showing response to environmental conditions. The study highlights HMb's potential in bioremediation, enhancing dechlorination processes for environmental and renewable energy benefits.