The Performance And Control Strategy For Autotrophic And Heterotrophic Denitrifying Sulfide Removal

Based on the current complicated, high-cost and low efficiency bio-technology for high strength sulfur and nitrogen containing wasterwater treatment, the autotrophic and heterotrophic denitrifying sulfide removal process (A&H-DSR) was developed. The sulfide, nitrate and organic carbons are simultaneously converted to sulfur, N2 and CO2 by DSR process in which the symbiosis of autotrophs and heterotrophs exists. So, the DSR process is a high effective, low cost , high stable and advanced biotechnology for wasterwater treatment.This study mainly focuses on the operation and control strategy of DSR process. The performance and key parameters were determined in this study, and the high-effective sulfide-degrading strains Pseudomonas sp. C27 was isolated , indicating that the traditional metabolic pathway of sulfide removal by autotrophic bacterias are reversed. The high-effective abnormal behavior of sulfide removal for C27 provided a new way to study the cooperation of autotrophs and heterotrophs. On the other hand, the contribution of autotrophic and heterotrophic denitrification to the performance of DSR process was analyzed aiming to select reasnonable control strategies to enhance the performance and mitigate the inhibition by high levels of sulfide.The expanded granular sludge bed reactor was choosed as optimal operational mode for DSR process. The optimal molar ratios of S/N and C/N was determined as 5:6 and 1.26:1. Furthermore, the maximum sustainable loading rates of DSR process was 6.09 kgS/m³.d^-1,3.11 kgN/m³.d^-1,8.04kgAc-/m³.d^-1。The technology of micro-aerobic enhancement successfully mitigated the sulfide inhibition to the performance of DSR process. The maximum sustainable sulfide concentration was increased from 200mg/L to 300mg/L; Also, based on the analysis for the activity of functional enzymes, the sulfide oxidase was stimulated to secrete by functional strains, hence enhancing the performance of DSR process.The high-effective sulfide-degrading strains C27 can oxidize sulfide under the denitrifying condition, and the sulfide-oxidizing rate was two times more than that of autotrophic sulfide-oxidizers. The suggested metabolic pathway for C27 was provided based on the electrion balance and mass balance. Futhermore, the micro-aerobic conditions also can enhance its performance of denitrifying sulfide removal and its sustainable sulfide level of 300mg/L.In continuous flow test for C27, at the sulfide concentration of 561.4mg/L corresponding to the loadings of 0.215 kgS/m³.d^-1,0.146 kgN/m³.d^-1,0.092 kgC/m³d^-1, the removal of sufide, acetate and nitrate was 84.7%, 74.1% and >99% .The performance of DSR process was estimated under autotrophic, heterotrophic and mixotrophic conditions, and the results showed that the maximum sustainable loadings for autotrophic conditions was 1.6 kgS/m³.d^-1, or the system will breakdown. The performance under the operations of mixotrophic meidum were much better than that under autotrophic conditions, and the operations of mixotrophic condition can restore the system breakdown under the running of autotrophic medium. Additionally, the reseaons for the systematic breakdown of DSR process were that the heterotrophic denitrifiers were inhibited by high levels of sulfide leading to the numerous nitrite accumulation and the worse capacity of acetate removal. To restore the systematic breakdown and enhance the performance, the technology of micro-aerobic enhancement can be used.