The integrated fixed‐film activated sludge (IFAS) process is considered one of the cutting‐edge solutions to the traditional wastewater treatment challenges, allowing suspended sludge and attached biofilm to grow in the same system. In addition, the coupling of IFAS with anaerobic ammonium oxidation (Anammox) can further improve the efficiency of biological denitrification. This paper summarises the research progress of IFAS coupled with the anammox process, including partial nitrification anammox, simultaneous partial nitrification anammox and denitrification, and partial denitrification anammox technologies, and describes the factors that limit the development of related processes. The effects of dissolved oxygen, influent carbon source, sludge retention time, temperature, microbial community, and nitrite‐oxidising bacteria inhibition methods on the anammox of IFAS are presented. At the same time, this paper gives an outlook on future research focus and engineering practice direction of the process.

Microbial desalination cells (MDCs), as an emerging desalination technology, have attracted increasing attention in recent years due to their ability to simultaneously achieve salt removal and wastewater treatment without the need for external energy input. In this study, the performance of two MDC systems with different cathode types—a biocathode (MDC1^#) and a permanganate cathode (MDC2^#)—was comparatively evaluated for the treatment of saline wastewater, with a particular focus on voltage output, desalination efficiency, and chemical oxygen demand (COD) removal. Experimental results showed that the average output voltage of MDC2^# reached 742.02 mV, which was significantly higher than that of MDC1^# (695.6 mV). Its maximum power density was as high as 6.22 W/m3, approximately six times that of MDC1^#. Moreover, MDC2^# exhibited a higher average chloride removal rate in the desalination chamber (32.34 mg/h), compared to 17.13 mg/h for MDC1^#, indicating superior desalination performance. However, in terms of electron recovery, MDC1^# achieved a much higher average Coulombic efficiency (28.8 ± 18.7%), nearly three times that of MDC2^#, suggesting more efficient electron utilization with the biocathode. Regarding ammonium removal, MDC1^# demonstrated a higher initial removal efficiency within the first 96 h (74.3%, with an average rate of 4.17 mg/h), but this declined sharply over time, with the later-stage rate dropping to only 0.32 mg/h (less than 10% of the initial rate). In contrast, MDC2^# maintained a relatively stable ammonium removal rate throughout the operation (ranging from 0.58 to 3.27 mg/h, with an average of 1.92 mg/h). In addition, both systems achieved stable COD removal at the anode, with efficiencies consistently above 85%. Overall, the permanganate cathode is more suitable for applications that require high voltage output and efficient desalination, whereas the biocathode shows significant advantages in organic pollutant removal and energy recovery. This study provides a theoretical foundation for the rational selection of cathode types based on the characteristics of saline wastewater, offering valuable guidance for optimizing MDC system performance.

High-quality biofilm carriers are crucial for the formation of biofilm, but problems such as slow biofilm growth on the carrier surface have been troubling a large number of researchers. The addition of a carrier changes the flow state in the reactor, which in turn affects the microbial attachment and the quantity of microorganisms. Also, aerobic microorganisms need to use dissolved oxygen in the water to remove water pollutants. In this paper, a novel recirculating flow carrier with a hollow cylinder structure is proposed, with a certain number of hollow inverted circular plates placed at equal distances inside. In this paper, the hydraulic residence time, aeration volume, and the spacing of the inflow plates of the recirculating flow biofilm carrier, which are three important factors affecting the hydraulic characteristics of the reactor, are first investigated. At the same time, it was compared with the common combined carrier to find the optimal operating conditions for the hydraulic characteristics. Secondly, a reactor start-up study was carried out to confirm that the new recirculating flow biofilm carrier could accelerate the biofilm growth by changing the hydraulic characteristics. The results showed that under the same conditions, the hydraulic properties of the reactor were better with the addition of the recirculating flow carrier, with an effective volume ratio of 98% and a significant reduction in short flows and dead zones. The stabilized removal of COD, NH₃-N, and TN in the reactor with the addition of the recirculating flow carrier reached about 94%, 99%, and 91% respectively, at the beginning of the 15th day, which effectively proved the feasibility of the recirculating flow carrier.

Treating high-ammonia wastewater remains a significant challenge, primarily due to high energy consumption, risks of secondary pollution, and insufficient operational stability. Microbial Desalination Cells (MDCs), a bioelectrochemical technology, offer potential for simultaneous pollutant removal and energy recovery. However, a systematic understanding of their performance under high ammonia loads (e.g., > 1000 mg/L NH₄-N) and the coupled effects of key operational parameters is lacking. This study constructed a three-chamber MDC to evaluate the effects of inter-electrode spacing, initial desalination-chamber NH₄-N concentration, and anodic substrate type on electrochemical output and apparent NH₄-N migration-related performance under controlled batch conditions. In addition, desalination-chamber NH₄-N concentration profiles were descriptively compared under different anodic COD levels. Results showed that decreases in NH₄-N concentration in the desalination chamber were consistent with transmembrane ion transport under the tested batch conditions, as evaluated using the membrane-area-normalized apparent migration flux ([Formula: see text]). Shortening the inter-electrode spacing from 5.5 to 3.5 cm increased the NH₄-N migration removal rate ([Formula: see text]) from 2.12 to 3.17 mg L^- 1 h^- 1 and [Formula: see text] from 42.4 to 63.4 mg m^- 2 h^- 1. Compared with glucose, acetate increased [Formula: see text] from 55.8 to 77.8 mg m^- 2 h^- 1. These results identify operating-condition-dependent changes in apparent NH₄-N migration-related performance and reveal their trade-off with power output and COD-removal-based coulombic efficiency (CE). The findings provide a laboratory-scale basis for subsequent contribution-partitioning studies and enrichment-side recovery coupling.