Novel micro-granular sludge process for highly efficient treatment of low-strength and low C/N ratio municipal wastewater

• Published in: Chemosphere (Oxford) 2022-01, Vol.287, p.132322-132322, Article 132322
• Main Authors: Wu, Boran, Wang, Xiuzhong, Wang, Chengxian, Lu, Bin, Yi, Jing, Dai, Xiaohu, Chai, Xiaoli
• Format: Article
• Language: English
• Subjects: activated sludge; anaerobic ammonium oxidation; Anammox; carbon; chemical oxygen demand; Denitrification; Granular sludge; liquids; Municipal wastewater; nitrogen; particle size; Powder carrier; total nitrogen
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.132322

A novel high-concentration powder bio-carrier (HPB) process was developed for the high-load treatment of low-strength municipal wastewater with low carbon/nitrogen (C/N) ratio (∼3). The powder carrier facilitated the rapid micro-granulation of sludge within 20 days and the average particle size increased rapidly from 47 μm to 210 μm. Accordingly, the concentration of mixed liquid volatile suspended solids (MLVSS) increased from 1.8 g/L to 4.3 g/L, which enabled the HPB process to maintain a short hydraulic retention time (HRT) of 3.6 h. Correspondingly, the high volumetric load of 0.4–1.3 kg chemical oxygen demand (COD)/(m3∙d) and 0.12–0.24 kg total nitrogen (TN)/(m3∙d) could be achieved and twice higher than those of conventional activated sludge process, e.g., anaerobic/anoxic/oxic process. The carrier-induced sludge granulation also significantly optimized the microbial structure, and the high-throughput sequencing revealed the increasing abundances of denitrifying bacteria and anammox bacteria, which was consistent with the nitrogen removal efficiency rising from 44.6% to 77.4%. Accordingly, the enhanced nitrogen removal could be achieved with TN of effluent steadily below 5 mg/L. Especially, the mass balance analysis on carbon and nitrogen further indicated the advantage of newly developed HPB process in carbon source saving for nitrogen removal. All the results are believed to suggest a promising strategy for the highly efficient treatment of low-strength municipal wastewater. [Display omitted] •A novel micro-granular process was first developed with diatomite as moving carrier.•Micro-granular sludge system was rapidly started up with powder carrier in 20 days.•HPB volumetric nitrogen loading was twice as high as that of conventional process.•Coupling endogenous/short-cut denitrification with anammox enhanced N-removal.•Carbon source consumption of nitrogen removal can be saved by up to 36%.