First application of the novel anaerobic/aerobic/anoxic (AOA) process for advanced nutrient removal in a wastewater treatment plant.

The stringent effluent quality standards in wastewater treatment plants (WWTPs) can effectively mitigate environmental issues such as eutrophication by reducing the discharge of nutrients into water environments. However, the current wastewater treatment process often struggles to achieve advanced nutrient removal while also saving energy and reducing carbon consumption. The first full-scale anaerobic/aerobic/anoxic (AOA) system was established with a wastewater treatment scale of 40,000 m3/d. Over one year of operation, the average TN and TP concentration in the effluent of 7.53 ± 0.81 and 0.37 ± 0.05 mg/L was achieved in low TN/COD (C/N) ratio (average 5) wastewater treatment. The post-anoxic zones fully utilized the internal carbon source stored in pre-anaerobic zones, removing 41.29 % of TN and 36.25 % of TP. Intracellular glycogen (Gly) and proteins in extracellular polymeric substances (EPS) served as potential drivers for post-anoxic denitrification and phosphorus uptake. The sludge fermentation process was enhanced by the long anoxic hydraulic retention time (HRT) of the AOA system. The relative abundance of fermentative bacteria was 31.66 - 55.83 %, and their fermentation metabolites can provide additional substrates and energy for nutrient removal. The development and utilization of internal carbon sources in the AOA system benefited from reducing excess sludge production, energy conservation, and advanced nutrient removal under carbon-limited. The successful full-scale validation of the AOA process provided a potentially transformative technology with wide applicability to WWTPs.

Towards advanced simultaneous nitrogen removal and phosphorus recovery from digestion effluent based on anammox-hydroxyapatite (HAP) process: Focusing on a solution perspective.

In this paper, the state-of-the-art information on the anammox-HAP process is summarized. The mechanism of this process is systematically expounded, the enhancement of anammox retention by HAP precipitation and the upgrade of phosphorus recovery by anammox process are clarified. However, this process still faces several challenges, especially how to deal with the âˆ¼ 11% nitrogen residues and to purify the recovered HAP. For the first time, an anaerobic fermentation (AF) combined with partial denitrification (PD) and anammox-HAP (AF-PD-Anammox-HAP) process is proposed to overcome the challenges. By AF of the organic impurities of the anammox-HAP granular sludge, organic acid is produced to be used as carbon source for PD to remove the nitrogen residues. Simultaneously, pH of the solution drops, which promotes the dissolution of some inorganic purities such as CaCO3. In this way, not only the inorganic impurities are removed, but the inorganic carbon is supplied for anammox bacteria.

Achieving advanced nitrogen removal from low-carbon municipal wastewater using partial-nitrification/anammox and endogenous partial-denitrification/anammox.

To achieve advanced nitrogen removal from low-carbon wastewater, a partial-nitrification/anammox and endogenous partial-denitrification/ anammox (PN/A-EPD/A) process was developed in a sequential batch biofilm reactor (SBBR). Advanced nitrogen was achieved with the effluent total nitrogen (TN) of 3.29 mg/L when the influent COD/TN and the TN were 2.86 and 59.59 mg/L, respectively. This was attributed to a stable PN/A-EPD/A, which was achieved through the integration of four strategies, including treating the inoculated sludge with free nitrous acid, inoculating anammox biofilm, discharging excess activated sludge and residual ammonium at the end of oxic stage. The 16S rRNA high-throughput sequencing results demonstrated that anammox bacteria coexisted with ammonia oxidizing bacteria, nitrite oxidizing bacteria, denitrifying glycogen accumulating organisms (DGAOs) and denitrifying phosphorus accumulating organisms (DPAOs) in biofilms. The abundance of anammox bacteria in the inner layer of the biofilm is higher, while that of DGAOs and DPAOs is higher in the outer layer.

Engineering-scale application of sulfur-driven autotrophic denitrification wetland for advanced treatment of municipal tailwater.

An engineering-scale sulfur driven autotrophic denitrification vertical-flow constructed wetland (SADN-VFCW) was established to treat low C/N ratio tailwater from municipal wastewater treatment plants (MWTPs). One-year stable operation results indicated that the addition of sulfur prominently enhanced TN, NO3--N and TP removal with efficiencies higher than 68.9%, 69.2% and 45.5%, respectively. Higher nitrogen and phosphorus removal rates were achieved in summer than that in other seasons. Furthermore, the microbial analysis revealed the structure of the microbial community changed significantly after sulfur addition, which proved that sulfur promoted the enrichment of autotrophic (Thiobacillus, Sulfurimonas, Ferritrophicum) and heterotrophic (Denitratisoma, Anaerolineaae, Simplicispira) functional bacteria, thus facilitating pollutants removal. Function prediction analysis results also indicated the abundance of nitrate removal/sulfur metabolism functions was significantly strengthened. This study achieved reliable engineering-scale application of SADN-VFCW and offered great potential for simultaneous in-depth treatment of N and P in municipal tailwater by SADN system.