To achieve high-efficiency nutrient removal in constructed wetlands (CWs), a novel simultaneous nitrogen and phosphorus removal (SNPR) process was developed by combining nitrification, endogenous denitrification, and denitrifying phosphorus removal. In SNPR process, denitrifying glycogen-accumulating organisms (DGAOs) and denitrifying polyphosphate-accumulating organisms (DPAOs) utilized NOx--N(NO3--N or NO2--N) as electron acceptor and poly-beta-hydroxy-alkanoates (PHAs) as carbon sources for endogenous denitrification and denitrifying phosphorus removal processes. Results from 217 days of operation showed that a high-level of nitrogen removal efficiency of 83.73% was achieved with influent COD/N of 4. The success was attributed to the fact that most of influent carbon sources could be transformed into PHAs before nitrification via enriching DGAOs and DPAOs in CW, which simultaneously improved nitrification and denitrification due to reducing oxygen and carbon sources consumption by aerobic heterotrophs. Phosphorus was mainly removed via denitrifying phosphorus removal, and PO43--P removal efficiency reached up to 87.84% with even common gravel used as substrate. Stoichiometry analysis revealed that DGAOs were the main organisms providing nitrite to DPAOs, suggesting that the effective PO43--P removal under high DGAO abundance condition might be attributed to the coordination of DGAOs and DPAOs in SNRP processes.

The effects of phenol on aerobic granular sludge including extracellular polymeric substances (EPS) and microbial community were investigated for low strength and salinity wastewater treatment. Elevated phenol over 20 mg/L stimulated biological phosphorus removal mainly via co-metabolism with nearly complete phenol degradation, whereas resulted in significant accumulation of nitrate around 4 mg/L. Aerobic granules kept structural stability via enhancing production of extracellular polymeric substances (EPS), especially folds of polysaccharides (PS) and varying functional groups identified through EEM, FTIR and XPS spectral characterizations at increasing phenol loads. Illumina MiSeq sequencing results indicated that elevated phenol decreased the bacterial diversity and richness, and caused remarkable variations in structural and compositions of microbial population. Multiple halophilic bacteria including Stappia, Luteococcus, and Formosa laid the biological basis for stability of aerobic granules and efficient biological nutrients and phenol removal. Redundancy analysis (RDA) suggested the key role of phenol in shaping the relative abundances and predominant genera. This study proved that aerobic granular sludge was feasible for low-saline and phenol-laden low-strength wastewater treatment.

This study used salinity (0.5 wt%, 0.75 wt%) to accelerate the formation of ammonia oxidizing bacteria (AOB)-enriched aerobic granular sludge in a lab-scale anaerobic/micro-aerobic simultaneous partial nitrification, denitrification and phosphorus removal (SPNDPR) reactor. Results confirmed that the average granule diameter increased from 298.7 to 425.4 µm after 45 days of salinity stress even with low dissolved oxygen. Extracellular polymeric substances increased from 149.5 to 387.7 mg/g VSS after salinity (0.75 wt%) treatment, in turn accelerating granulation. Partial nitrification was maintained under the salinity condition due to the relative high activity and abundance of AOB, and the observed nitrite accumulation ratio averaged 98.9%. Salinity favored glycogen-accumulating organisms over polyphosphate-accumulating organisms (PAOs)/denitrifying-PAOs, with the abundance of Candidatus_Competibacter increasing from 4.86% to 15.34% and the simultaneous partial nitrification-denitrification efficiency increasing from 74.4% to 91.1%, promoting N-removal potential. The P-removal performance was good under 0.5 wt% salinity but was inhibited under 0.75 wt% salinity.

In this study, the granular sludge was operated under low aeration condition in sequencing batch reactor (SBR) and advanced continuous flow reactor (ACFR), respectively. Through increasing the sludge retention time (SRT) from 22 days to 33 days, the ACFR was successful startup in 30 days and achieved long term stable operation. Under SBR operation condition, the aerobic granular sludge (AGS) showed good nitrogen (60%), phosphorus (96%) and COD removal performance. During stable operation of continuous-flow, the nitrogen removal efficiency was increasing to 70%, however, the phosphorus removal efficiency could only be restored to 65%. Meanwhile, the sludge discharge volume from ACFR was about half of that in SBR. Results of high-throughput pyrosequencing illustrated that methanogenic archaea (MA), ammonia oxidizing archaea (AOA), denitrifying bacteria (DNB), denitrifying polyphosphate-accumulating organisms (DPAOs) played an important role in the removal of nutrients in ACFR. This study could have positive effect on the practical application of AGS continuous flow process for simultaneous biological nutrient removal (SBNR).

Low temperature is a great challenge for the biological treatment of wastewater. In this study, the rapid start-up of aerobic granular biofilm (AGF) reactor was realized by adding micro-sized polyurethane (PU) sponges as matrices at 10 °C. The results showed that the granulation process of AGF was different from that of traditional aerobic granular sludge and biofilms, which was formed by using the sludge intercepted in PU matrix instead of sponge skeletons as granulation carriers. During the 5-month operation period, stable pollutants removal performance was achieved within 70 days, besides, the corresponding ammonium, total nitrogen, and total phosphorus removal efficiencies were 98%, 70%, and 95%, respectively. The addition of PU matrices inhibited the growth of filamentous bacteria and provided support for high structural stability of AGF. With the operation of the reactor, the relative abundance of traditional denitrifying bacteria (genera Thauera and Acidovorax, etc.) decreased gradually, and the putative denitrifying phosphorus accumulating genus, Dechloromonas, occupied a dominant position in the system. This experiment showed that AGF system could be successfully started-up and operated with efficient pollutants removal performance under low temperature when using micro-sized PU sponges as matrices.

A novel strain NP5 with efficient heterotrophic nitrification, aerobic denitrification and phosphorus accumulation ability was isolated and identified as Pseudomonas putida strain NP5. The removed ammonium and phosphate were mainly converted into intracellular components by assimilation, and negligible nitrification intermediates and N2O were accumulated during heterotrophic nitrification. In addition, the optimal conditions for nutrient removal were: succinate as carbon source, C/N 10, P/N 0.2, temperature 30 °C, salinity 0% and shaking speed 160 rpm. Besides, strain NP5 possessed an exceptional heavy metal and nanoparticles resistance. Cr6+ was found to be the most toxic among the tested metals, and it could be removed simultaneously. Moreover, an obvious phosphorus release was observed under anaerobic condition, and repeated exposure to the anaerobic/aerobic conditions could significantly improve the nutrient removal. Furthermore, the successful expression of key enzymes for nitrogen and phosphorous removal provided additional evidence for possibility of simultaneous nitrification, denitrification and phosphorus removal.

A novel medium containing iron oxide-based porous ceramsite (IPC) and commercial ceramsite (CC) was used in two laboratory-scale upflow biological aerated filters (BAFs) to treat city wastewater to compare their efficacy in wastewater treatment. The IPC BAF and CC BAF were operated in water at 20-26°C, an air/water (A/W) ratio of: 3:1 and hydraulic retention times (HRTs) of 7, 3.5, 1.75, and 0.5 h and the removal of ammonia nitrogen (NH3-N), total nitrogen (TN), total organic carbon (TOC), and phosphorus (P) were studied. Our results indicated that IPC BAF was superior to CC BAF in terms of TOC, TN, NH3-N, and P removal. IPC had higher total porosity and larger total surface area than CC. The interconnected porous structure of IPC was suitable to microbial growth, protozoan, and metazoan organisms were primarily found in the accumulated biofilm layer. Biomass, in the biofilm layer, was detected at three distinct distances (300, 900, and 1500 mm) from the bottom of the inlet filter, again indicating that the IPC was more suitable for biomass growth. The presence of biomass improves the simultaneous removal efficiency of nitrogen and phosphorus in the IPC BAF. Thus, our findings support IPC as a material for use in filter media in wastewater treatment BAFs.