Search Results (5)

Sulfur-mediated autotrophic denitrification (SAD) is an innovative and sustainable water treatment technology, which operates without an external carbon source and achieves lower sludge production. Firstly, this review provides a detailed examination of sulfur-based fillers, encompassing their respective types, preparation methods, advantages and drawbacks. Subsequently, it reviews the mainstream functional microbial communities across various process stages, such as Thiobacillus, Sulfurimonas, and Ignavibacterium. Moreover, the process characteristics of mainstream SAD reactor types, such as fluidized bed, fixed bed, and moving bed biofilm reactors, are reviewed, and the effects of key process parameters like pH, temperature, and dissolved oxygen on treatment efficiencies are further analyzed. Additionally, the applications cases of SAD in advanced wastewater treatment, river remediation, wetland restoration, and groundwater purification are summarized, demonstrating its broad and diverse application potential in environmental engineering. Finally, key challenges of SAD are identified, including the complexity of microbial metabolic interactions, the accumulation of intermediate products, and the need for improved fillers and reactor configurations. Future research priorities are discussed in three areas: microbial community regulation, control and utilization of intermediate products, and development of advanced fillers and reactor configurations. Overall, this review integrates key technical parameters and operational experience of SAD, providing a consolidated reference for researchers and practitioners interested in the development and application of this technology. Full article

Sulfur-based autotrophic denitrification (SAD) is limited by low efficiency and poor stability in carbon-deficient photovoltaic (PV) wastewater treatment. This study developed four sulfur-based composite fillers (S⁰-CFs) comprising 75% elemental sulfur and mineral additives (boron mud, magnesite, and/or siderite) fabricated via melt mixing–jet granulation. Lab-scale operation showed that at a hydraulic retention time (HRT) of 1 h, all S⁰-CFs achieved high TN removal (89.1–93.8%) with effluent NO₃⁻-N below 1.5 mg/L (>93% nitrate removal efficiency) and stable pH. Although effluent COD increased with a short HRT (1 h) due to biofilm detachment, no leaching of organic or inorganic pollutants from the fillers was observed, and TP was consistently removed. 16S rRNA sequencing confirmed enrichment of autotrophic denitrifiers Thiobacillus and Sulfurimonas, verifying SAD as the dominant pathway. In a 270-day pilot-scale operation, nitrate removal varied with temperature (7.3–27.2 °C) and HRT, reaching 88.2% on average (range: 86.6–90.0%) at 1 h HRT during warm periods (25.8–27.2 °C), dropping to 13.5–38.1% under cold conditions (7.3–16.0 °C) at 0.5 h HRT, and then stabilizing at 64.1% by adjusting HRT to 1 h. Fluoride was removed at 0.51–1.49 mg/L. Additionally, operational cost was 34.5% lower than heterotrophic denitrification. These results demonstrated that S⁰-CF enabled efficient, stable, and cost-effective nitrogen removal, making SAD more suitable for low-carbon industrial wastewater treatment. Full article

With the continuous improvement of wastewater treatment standards, advanced nitrogen removal from municipal wastewater treatment plant effluents faces severe challenges. This paper systematically analyzes the application potential of sulfur-based autotrophic denitrification (SAD) technology in advanced wastewater treatment, focusing on its denitrification efficiency, operational costs, and carbon reduction benefits. Compared to conventional heterotrophic denitrification (HD), SAD technology demonstrates significant advantages, including high denitrification efficiency, low operational costs, low sludge production, and low CO₂ emission, through the reduction of external organic carbon source addition and energy consumption. Among the autotrophic denitrification processes, SAD has the highest denitrification rate with low cost and low safety risk. Through sulfur source selection and process optimization, the denitrification rate could reach 1.2 kg N/m³·d, and the accumulation of byproducts can be effectively controlled. As calculated, SAD can reduce over 55% sludge production, reduce 50–80% operational costs, and reduce over 80% greenhouse gas (GHG) emissions. Despite challenges such as long start-up periods, SAD technology shows promising application prospects for advanced treatment of low C/N ratio wastewater. Future research should focus on process optimization and scale-up engineering applications to promote the large-scale implementation of this technology. Full article

The aim of this study was to evaluate the effect of a solid slow-release carbon source (3-hydroxybutyrate-co-3-hydroxyvalerate, PHBV) on heterotrophic and sulfur autotrophic cooperative denitrification (HAD) of aquaculture wastewater. Batch tests were carried out to analyze the effect of different PHBV/S volume ratios in the range of 30–70% on the denitrification of synthetic aquaculture wastewater under a short hydraulic retention time (HRT). The performance of the HAD process showed that the NO₃⁻-N removal was increased with an increase in the PHBV/S volume ratio. When the PHBV/S ratio reached 70%, the average NO₃⁻-N concentration of effluent was 0.38 mg/L in the stable phase. The variation in pH and alkalinity showed that the average pH value and residual alkalinity were above 7.03 and 57.63 mg/L at the PHBV/S ratio of 50%. Based on the relationship between sulfate generation and nitrate removal under different ratios of PHBV/S, analysis of the proportion of autotrophic and heterotrophic denitrification (HD) showed that sulfur autotraophic denitrification (SAD) was enhanced at a PHBV/S ratio of 50%, and competition for nitrate substrates occurred between autotrophic and heterotrophic at a PHBV/S ratio of 70%. Full article

In this study, anammox, sulfur-based autotrophic denitrification, and heterotrophic denitrification (A/SAD/HD) were coupled in an expanded granular sludge bed (EGSB) reactor to explore the feasibility of enhancing denitrification performance by adjusting the S₂O₃^2−/NO₃⁻ (S/N) ratio to accommodate dynamic influents. The results indicated that the optimal influent conditions occurred when the conversion efficiency of ammonium (CEA) was 55%, the S/N ratio was 1.24, and the chemical oxygen demand (COD) was 50 mg/L, which resulted in a total nitrogen removal efficiency (NRE) of 95.0% ± 0.5%. The S/N ratio regulation strategy was feasible when the influent COD concentration was less than 100 mg/L and the CEA was between 57% and 63%. Characterization by 16S rRNA sequencing showed that Candidatus Jettenia might have contributed the most to anammox, while Thiobacillus and Denitratisoma were the dominant taxa related to denitrification. The findings of this study provide insights into the effects of CEA and COD on the performance of the A/SAD/HD system and the feasibility of the S/N ratio regulation strategy. Full article