Balance nitrogen and phosphorus efficient removal under carbon limitation in pilot-scale demonstration of a novel anaerobic/aerobic/anoxic process.

Nutrient removal in carbon limited wastewater with high efficiency and energy saving remains a bottleneck for wastewater treatment plants (WWTPs). This study established a pilot-scale anaerobic/aerobic/anoxic (AOA) system with processing capacity of 100 m3/d for the first time. During almost 300 days of stable operation, enhanced nitrogen and phosphorus removal at a C/N of 5 was achieved, and the concentrations of total nitrogen (TN) and total phosphorus (TP) in effluent were 3.60 ± 1.55 and 0.24 ± 0.13 mg/L. Tetrasphaera and Candidatus Competibacter were the dominant phosphorus accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) in the AOA system. Moreover, the low phosphorus release ensured sufficient intracellular carbon storage by endogenous denitrification, which was the critical factor for nitrogen and phosphorus removal in carbon limited wastewater. The denitrification phosphorus removal (DPR) ability further removed phosphorus and prevented secondary phosphorus release to maintain a low phosphorus concentration in effluent. Finally, rapid start-up, high nutrient removal efficiency and low energy consumption make the proposed AOA process suitable for application in newly constructed and renovated WWTPs.

Enhanced simultaneous partial nitrification and denitrification performance of aerobic granular sludge via tapered aeration in sequencing batch reactor for treating low strength and low COD/TN ratio municipal wastewater.

The aerobic granular sludge simultaneous partial nitrification, denitrification and phosphorus removal (AGS-SPNDPR) process was carried out via tapered aeration in sequencing batch reactor (SBR) for treating low strength and low COD/TN ratio municipal wastewater. The results showed that aerobic granular sludge was successfully cultivated with good sedimentation performance when treating the municipal wastewater. Meanwhile, the median granule size increased to 270 (R1) and 257 (R2) µm on day 80. The excellent removal performance of COD (92%) and NH4+-N (95%) were achieved under different aeration modes, while the higher TN removal efficiency (76%) was achieved by tapered aeration. The accumulation of NO2--N in R2 indicated that the tapered aeration was beneficial to achieve simultaneously partial nitrification and denitrification. Meanwhile, the high-efficiency phosphorus (95%) removal was realized via additional carbon source, and SPNDPR process was formed under tapered aeration. The bacterial community analysis indicated denitrifying glycogen-accumulating organisms (DGAOs) Candidatus_Competibacter and ammonia-oxidizing bacteria (AOB) Nitrosomonas were more effectively enriched via tapered aeration, while phosphorus-accumulating organisms (PAOs) Candidatus_Accumulibacter were effectively enriched under additional organic carbon. AOB, denitrifying bacteria and PAOs were simultaneously enriched by tapered aeration and additional carbon source, which was beneficial to nutrients removal. This study might be conducive to the application of AGS-SPNDPR system for treating low strength and low COD/TN ratio municipal wastewater under tapered aeration.

Innovative technology of municipal wastewater treatment for rapid sludge sedimentation and enhancing pollutants removal with nano-material.

This study aims to develop a novel technology for actual municipal wastewater treatment to achieve rapid sludge sedimentation and high pollutants removal efficiency. The SBRs were modified and operated with periodic addition of 20 µL·L-1 nanofloc®. Results revealed that NH4+-N and chemical oxygen demand (COD) was efficiently removed in both laboratory- and pilot-scale SBRs, and the average removal efficiency of total nitrogen (TN) and total phosphorus (TP) was as high as 72.43 ± 2.66% and 98.63 ± 0.74%, respectively, with hydraulic retention time (HRT) of 8 h. Besides, the sludge volume index at 30 min (SVI30) was only 40.06 ± 1.99 mL·g-1, comparable with aerobic granular sludge (AGS). This novel technology could be proposed as a competitive method to upgrade, reconstruct and delay the expansion of municipal wastewater treatment plants (WWTPs) due to its rapid sludge sedimentation and efficient pollutants removal with low HRT.