Simultaneous Nitrification-denitrification Research Articles

Unveiling organic loading shock-resistant mechanism in a pilot-scale moving bed biofilm reactor-assisted dual-anaerobic-anoxic/oxic system for effective municipal wastewater treatment

Microbial biomass and activity are frequently subjected to organic loading shock (OLS) from decentralized municipal wastewater. A hybrid moving bed biofilm reactor-assisted dual-anaerobic-anoxic/oxic system (D-A2MBBR) was established by integrating dual-anaerobic-anoxic/oxic with moving bed biofilm reactor to resist OLS for stable nutrients removal. The D-A2MBBR achieved 91.57% of chemical oxygen demand, 93.33% of ammonia-nitrogen, 80.20% of total nitrogen and 92.68% of total phosphorus removal, respectively, under the fluctuation of organic loading rate from 417.9 to 812.0 g COD m−3 d−1. The 16S rRNA gene sequencing revealed that Gemmobacter (7.28%) was identified as dominating anoxic denitrifying genus in oxic chamber, confirming the coexistence of aerobic and anaerobic/anoxic micro-environments. This circumstance boosted simultaneous nitrification-denitrification and phosphorus removal and the microbial community evolution inside the multilayer biocarrier-attached biofilms. In general, the D-A2MBBR was able to provide unique, cooperative and robust bacterial consortia to form a buffer against OLS, and ensuring effluent stability.

Role of carrier characteristics affecting microbial density and population in enhanced nitrogen and phosphorus removal from wastewater

This research aims to improve simultaneous nitrification-denitrification and phosphorus removal (SNDPR) using novel carriers and to demonstrate the effect of carrier characteristics on nutrient removal in a biofilm reactor. For this purpose, biofilms enriched with both polyphosphate-accumulating organisms (PAOs) and nitrifiers were cultivated in two parallel sequencing batch reactors containing conventional moving bed bioreactor carriers (MBBR) and a novel type of carriers (carbon-based moving carriers (CBMC)). The new carriers were produced based on recycled waste materials via a chemical-thermal process and their specific surface area were 10.4 times higher than typical MBBR carriers of similar dimensions. The results showed that the use of CBMC carriers increased bacterial adhesion by about 18.5% and also affected the microbial population inside the biofilms, leading to an increase in PAOs abundancy and thus an increase in biological phosphorus removal up to 12.5%. Additionally, it was corroborated that the volume of the anoxic zones with dynamic behavior is strictly influenced by the carrier structure and biofilm thickness due to a limitation in oxygen penetration. Accordingly, the formation of broader anoxic zones and shrinkage of these zones to a lesser extent resulted in the continuation of anoxic reactions for longer periods using the novel carriers. Thereby, an increase in nitrogen removal by about 15% was obtained mainly by denitrifying PAOs. The results also exhibited that a higher simultaneous nitrification-denitrification (SND) efficiency can be achieved by selecting an appropriate aeration program influencing the dynamic changes of anoxic zones. Overall, a biofilm system using the new carriers, with phosphorus and nitrogen removal efficiencies of 97.5% and 92.3%, was presented as an efficient, compact, and simple operation SNDPR process.

Low flux sponge membrane bioreactor treating tannery wastewater

Sponge membrane bioreactor (Sponge-MBR) has been proposed as an effective process to eliminate organic matters, nitrogen compounds and control fouling for domestic and hospital wastewater treatment. However, tannery wastewater with extremely organics and salt concentrations poses a great threat to the stability of biological treatment processes, rapidly increasing fouling and cost of physio-chemical treatment. This study examined the performance of Sponge-MBR to treat real tannery wastewater under organic loading rates of 1.38 ± 0.59 and 2.05 ± 0.61 kg COD m−3 d−1. The results showed that tannery wastewater vastly inhibited the growth of suspended biomass (MLVSS/MLSS ratio of 0.3). However, such ratio has been increased up to 24% in the attached biomass of sponge carriers. Up to 87 ± 14% of organic matters and 43 ± 10% of total nitrogen (TN) were eliminated even though the system suffered a high total dissolved solids (TDS) of 12,510 mg L−1. Using nitrogen balance analysis, the simultaneous nitrification-denitrification process occurred inside the sponges resulting in 21% TN removal via denitrification. Thanks to the dynamic movement of sponge carriers, the cake layer (i.e., solids and colloids) contributed only 28% of total resistance. This outcome resulted in decreasing 1.2-fold fouling rate as using sponge media in the MBR. Overall findings suggest that a low flux operation combined with sponge media (20%) in the MBR appears to be a viable option for real tannery wastewater treatment.

Selection and synthesization of multi–carbon source composites to enhance simultaneous nitrification–denitrification in treating low C/N wastewater

Low carbon/nitrogen ratio (C/N) wastewater is widespread and difficult to treat. To find a resolution to this issue, this study systematically evaluated the constituents of composite solid carbon (i.e., skeletons, carbon sources and crosslinking agents), and proposed a new multi-carbon source composite S1 (MCSC.S1). The effects on nitrogen removal were further determined through a sequencing batch moving bed biofilm reactor (SBMBBR). The results showed that MCSC.S1, which was composed of polyvinyl alcohol-sodium alginate (PVA-SA), corncob + poly (R-β-hydroxybutyrate) (CC + PHB), and H3BO3-4% CaCl2+Na2SO4 had high stability and absorption. With MCSC.S1, total nitrification removal was enhanced by more than 48.56% through releasing carbon and absorbing the attached denitrifying bacteria. In addition, it was found that MCSC.S1 can simulate the simultaneous nitrification and denitrification (SND) process and contribute to 29.85% of the total nitrogen removal. 16S gene-based analysis attributed this supplementary nitrogen removal to the enrichment of nitrification (i.e., Proteobacteria, Actinobacteria and Chloroflexi), denitrification of associated bacteria (i.e., Nitrospirota) in MCSC.S1 added reactor, and the increase in nitrogen recycling associated genes. These findings collectively demonstrate that the new MCSC.S1 could effectively enhance nitrogen removal efficiency in low C/N ratio wastewater.

Advances in Studies on Microbiota Involved in Nitrogen Removal Processes and Their Applications in Wastewater Treatment.

The discharge of excess nitrogenous pollutants in rivers or other water bodies often leads to serious ecological problems and results in the collapse of aquatic ecosystems. Nitrogenous pollutants are often derived from the inefficient treatment of industrial wastewater. The biological treatment of industrial wastewater for the removal of nitrogen pollution is a green and efficient strategy. In the initial stage of the nitrogen removal process, the nitrogenous pollutants are converted to ammonia. Traditionally, nitrification and denitrification processes have been used for nitrogen removal in industrial wastewater; while currently, more efficient processes, such as simultaneous nitrification-denitrification, partial nitrification-anammox, and partial denitrification-anammox processes, are used. The microorganisms participating in nitrogen pollutant removal processes are diverse, but information about them is limited. In this review, we summarize the microbiota participating in nitrogen removal processes, their pathways, and associated functional genes. We have also discussed the design of efficient industrial wastewater treatment processes for the removal of nitrogenous pollutants and the application of microbiome engineering technology and synthetic biology strategies in the modulation of the nitrogen removal process. This review thus provides insights that would help in improving the efficiency of nitrogen pollutant removal from industrial wastewater.

Rapidly achieving and optimizing simultaneous partial nitrification denitrification and anammox integrated process by hydroxylamine addition for advanced nitrogen removal from domestic wastewater

The achievement and stable maintenance of partial nitrification and partial anammox process for municipal sewage is a challenging research topic at present. In this study, a novel strategy of hydroxylamine (NH2OH) addition under low DO condition was adopted for rapidly achieving simultaneous partial nitrification denitrification and anammox process (SPNDA) to deal with domestic wastewater, the nitrite accumulation ratio (NAR) increased from 1% to 82% in the first 4 days. After the addition of NH2OH was stopped, the PN effect of SPNDA process remained relatively stable within 100 days. During the stable operation period with aerobic HRT of 5 h, the nitrogen removal efficiency was 87.9 ± 4.2%. Moreover, the abundance of denitrifying bacteria and Candidatus Brocadia increased from 1.79% and 0.062% to 22.49% and 0.38% respectively, which promoted nitrogen removal effect. Overall, this study provided a quickly way for achieving the cost-effective SPNDA process to enhance nitrogen removal with NH2OH addition.

Compartmentation of microbial communities in structure and function for methane oxidation coupled to nitrification–denitrification

A hollow-fiber membrane biofilm reactor was designed and constructed to achieve simultaneous nitrification–denitrification coupled to methane oxidation in low O2/CH4 ratio and high nitrogen removal rate. Three O2/CH4 ratio stages were operated. Ammonia removal rates reached 77.5 and 95 mg/(L·d) at the O2/CH4 ratio of 1.47 and 2.1, respectively. Microbial community analysis revealed that aeration through physical partition and O2/CH4 ratio stages achieved compartmentation of microbial community in structure and function. Combined functional genes analysis using qPCR, the aeration through gas distributer was proved to promote the enrichment of autotrophic ammonia oxidizers in the suspended liquid/mixed filler samples, and the aeration through hollow-fiber membrane favored the growth of methanotrophs and heterotrophic nitrification-aerobic denitrification bacteria. This study helps to develop effective regulatory strategies for high nitrogen removal based on the understanding of the community assembly process and the key driving factors.

Continuous aerobic granular sludge plants: Better settling versus diffusion limitation

The application of aerobic granular sludge in continuous wastewater treatment plants is receiving increased attention. The introduction of better settling sludge in existing installations is expected to increase the plant’s treatment capacity by allowing a higher biomass concentration in the reactor. A lot of recent research has therefore focused on how to get stable granules in a continuous flow plant, which make up the majority of current infrastructure. Still, the effect of aerobic granular sludge on the treatment capacity and energy requirements has not thoroughly been studied so far and is not that straightforward. While it is clear that the introduction of aerobic granular sludge will result in better settling, it will also bring about a higher diffusion limitation – which is often overlooked. This study scrutinized the effect of better settling versus diffusion limitation in a typical continuous activated sludge plant (predenitrification type) through a simulation study. When only considering the improved settling velocity, the treatment capacity increased by 40% compared to conventional activated sludge. However, diffusion limitation could almost totally counteract the positive effect of better settling for a non-improved continuous system. The continuous system could be improved for aerobic granular sludge by increasing the aerobic reactor volume fraction, while lowering the oxygen set-point to benefit from simultaneous nitrification–denitrification. The optimization led to a 20% improvement in treatment capacity and a 10% reduced energy consumption compared to a conventional activated sludge system. Overall, the performance of continuous wastewater treatment plants could indeed benefit from the excellent settling properties of aerobic granular sludge, as long as process operation was improved in order to take into account diffusion limitation.

Insights into the simultaneous nitrification, denitrification and phosphorus removal process for in situ sludge reduction and potential phosphorus recovery

A simultaneous nitrification-denitrification and phosphorus removal (SNDPR) system operated in an alternating anaerobic/aerobic/anoxic (A/O/A) mode was revisited from new perspectives of sludge reduction and potential phosphorus recovery. Reliable and robust removal performance was obtained even under winter temperatures, with average removal efficiency of COD, TP, NH4+-N and TIN being 89.68%, 93.60%, 92.15% and 79.01% at steady state, respectively. Inoculated sludge got enhanced in biomass density, settleability, and bioactivity. And relatively stable amounts of extracellular polymeric substances (EPS) with a stable protein/ polysaccharide (PN/PS) ratio were observed over operation. Meanwhile, a low observed sludge yield (Yobs) of 0.083 g MLSS/g COD (0.082 g MLVSS/g COD) was obtained. A maximum anaerobic phosphorus release up to 43.54 mg/L was found, thus providing phosphorus-rich and low-turbidity stream for further phosphorus recovery. Overall, the SNDPR system deserved attention for in situ sludge reduction and potential phosphorus recovery, beyond reliable and stable wastewater treatment.

Integrated simultaneous nitrification/denitrification and comammox consortia as efficient biocatalysts enhance treatment of domestic wastewater in different up-flow bioelectrochemical reactors

Simultaneous nitrification/denitrification (SND) can efficiently deplete NH4+ by using air-exposed biocathode (AEB) in bioelectrochemical reactors. However, the fluctuation of wastewater adversely affects the functional biofilms and therefore the performance. In this work, four up-flow bioelectrochemical reactors (UBERs) with some novel inocula were investigated to improve domestic wastewater treatment. The UBERs exhibited favorable removal of chemical oxygen demand (COD, 95%), NH4+-N (99%), and total nitrogen (TN, 99%). The maximum of current (2.7 A/m3), power density (136 mW/m3) and coulombic efficiency (20.5%) were obtained. Cyclic voltammetry analysis showed all the electrodes were of diversified catalytic reactions. Illumina pyrosequencing showed the predominant Ignavibacterium, Thauera, Nitrosomonas, Geminicoccus and Nitrospira were in all electrodes, contributing functional biofilms performing SND, comammox, and bioelectrochemical reactions. FAPROTAX analysis confirmed twenty-one functional groups with obvious changes related to chemoheterotrophy, respiration/oxidation/denitrification of nitrite and nitrate. Comfortingly, such novel diversified consortia in UBERs enhance the microbial metabolisms to treat domestic wastewater.

Simultaneous nitrification and aerobic denitrification by a novel isolated Ochrobactrum anthropi HND19

The study aimed to isolate a novel strain with heterotrophic nitrification and aerobic denitrification ability and evaluate the nitrogen removal characteristics. Results showed that Ochrobactrum anthropi HND19 could remove approximately 98.6% of NH4+-N (104.3 mg·L-1) and 97.6% of NO3−-N (98.6 mg·L-1), and the removal rates achieved 4.28 and 4.01 mg-N/(L·h) by heterotrophic nitrification and aerobic denitrification. The optimal incubate conditions of strain HND19 were 120 rpm (shaking speed), 5 ‰ (salinity), 30 °C (temperature), 7.5 (C/N ratio) with sodium acetate as carbon resource. And the removal efficiency of the total nitrogen (TN) realized 73.4% under the optimal conditions. Functional genes (hao, napA, nirK, norB, and nosZ) involved in the nitrogen removal processes were successfully amplified from strain HND19. These findings indicate that the strain HND19 possesses great application feasibility in treating wastewater with high-intensity nitrogen.

Response of simultaneous nitrification-denitrification to DO increments in continuously aerated biofilm reactors for aquaculture wastewater treatment

Abstract Intensive aquaculture usually produces large volumes of nutrient-rich wastewater, which is essential to treat to avoid eutrophication. This study aimed to evaluate the performance of five continuously aerated biofilm reactors treating simulated high-strength aquaculture wastewater under different dissolved oxygen (DO) levels, and the effects of DO increments on simultaneous nitrification-denitrification (SND). Continuous aeration was beneficial to complete nitrification. Total inorganic nitrogen (TIN), principally ammonium, was mainly removed by SND. The SND rate response to different DO levels was fitted well by the power function of y = 54.81 + 371.58/(1 − 0.16*x)^(−1/0.24) (R2 = 0.897, P = 0.000). When the TIN was removed completely, the optimal SND rate was defined and corresponded to a value of 121.8%. Accordingly, the optimal DO concentration was calculated as 2.10 mg/L, close to the actual level of 1.83 mg/L, at which the highest proportional removals of total nitrogen (58.0%) and TIN (57.3%) were obtained. Phosphorus was also removed by denitrifying polyphosphate-accumulating organisms.

Simultaneous nitrification-denitrification (SND) using a thermoplastic gel as support: pollutants removal and microbial community in a pilot-scale biofilm membrane bioreactor

ABSTRACT In this study, experiments were carried out to treat sanitary wastewater in a biofilm membrane bioreactor using a thermoplastic gel as a support to assist the nitrification-denitrification process. For this purpose, the system was operated in two different dissolved oxygen concentrations (2.3 ± 0.2 and 0.9 ± 0.3 mg O2/L for Phases I and II, respectively) and the removal of organic compounds and nitrogen, as well as the microbial community in suspended biomass and biofilm were evaluated. The MB-MBR system was able to withstand raw wastewater variations and maintaining a low permeate COD concentration (18 mg/L) even at low DO concentrations. On the other hand, it was found that oxygen concentration significantly influenced the process of nitrogen conversion. In Phase I the average removal of total nitrogen was 18 ± 8%, while in Phase II it increased to 66 ± 11%. The denitrification rate was two times higher (7.8 mg NO3 --N/h) at low dissolved oxygen, with a significant contribution of the biofilm (41%). Additionally, the high-throughput 16S rDNA sequencing showed that the oxygen concentration was determinant for arrangement patterns of the samples and not the sampling site (suspended biomass and support material). Thiothrix, Comamonas, Rhodobacter, Mycobacterium, Thermomonas, Sphingobium, Sphigopyxis, Pseudoxanthomonas, Nitrospira and, Novosphingobium were the main genera regarding the nitrogen cycle.

Aerobic granular sludge treating low-strength municipal wastewater: Efficient carbon, nitrogen and phosphorus removal with hydrolysis-acidification pretreatment

Low organic load while high fraction of particulates still challenging the application of aerobic granular sludge process in low-strength municipal wastewater treatment. The feasibility of adopting short cycle length to increase organic load and hydrolysis-acidification pretreatment to enhance anaerobic COD uptake was evaluated. As the cycle length decreased from 4 h to 2 h, the organic loading rate increased from 0.98 to 1.3 g L−1 d−1 and granulation appeared after two weeks. Moreover, with the hydrolysis-acidification pretreatment, the average effluent TN and TP concentrations decreased respectively from 17.8 to 13.7 mg L−1 and 0.76 to 0.41 mg L−1, meeting the Grade IA of the effluent standards in China. Furthermore, cycle tests were conducted to reveal the underlying mechanism of the pretreatment effects. The results showed that the hydrolysis-acidification pretreatment enhanced the COD storage and phosphorus release in anaerobic phase, and improved the simultaneous nitrification-denitrification process, as well as the phosphorus uptake in aeration phase.

Adaptation of anammox granules in swine wastewater treatment to low temperatures at a full-scale simultaneous partial nitrification, anammox, and denitrification plant

In the anammox process, maintaining a high anammox activity at low water temperatures for stable nitrogen removal is a challenge. In this study, to verify the adaptability of anammox to low water temperatures, we investigated effects of annual temperature fluctuations on nitrogen removal in a full-scale swine wastewater treatment plant, where anammox bacteria accumulated. Annual quarters were defined as L-1 (November–January), L-2 (February–April), H-1 (April–July), and H-2 (July–October). The total nitrogen removal rate was stable at 0.08–0.11 kg-N/m3/d, even during temperature fluctuations. Removal efficiencies of biochemical oxygen demand and total nitrogen were consistently high at 95–99% and 69–81%, respectively. The anammox activity and abundance of anammox bacteria were highest in granule L-1 and lowest in granule H-2. The optimal temperature for anammox activity shifted from 35 °C in granules H-1 and H-2 to 30 °C in granules L-1 and L-2, while the latter maintained a moderate activity compared to the former at low temperature. Candidatus Jettenia asiatica was predominant, especially in granule L-2, accounting for up to 54% of the microbial community composition at the genus level. The high specific anammox activity in granule L-2 was considered to be due to the abundance of anammox bacteria and the adaptation of Ca. Jettenia asiatica to low temperature. The anammox granules adapted well to low temperatures and demonstrated high efficiency in the simultaneous partial nitrification anammox and denitrification process without heating. Thus, constructing an energy-saving and cost-effective nitrogen removal system can be considered.

Improvement of the performance of simultaneous nitrification denitrification and phosphorus removal (SNDPR) system by nitrite stress

This study investigated a new way to improve the performance of simultaneous nitrification denitrification and phosphorus removal (SNDPR) system by regularly changing the anaerobic/micro-aerobic/anoxic mode to the anaerobic/anoxic mode with 30 mg/L of nitrite dosing. The results indicated that the removal efficiency of total inorganic nitrogen and PO43−-P was improved from 75.44% and 85.14% to 98.89% and 98.17%, respectively. And the good performance of the SNDPR showed a long-time sustainability when the C/N ratio was 5. The results of microbial community illustrated that the abundance of the main nitrite-oxidizing bacteria (NOB), Nitrospira sp., dropped from 5.71% to 0.85% and the abundance of denitrifying polyphosphate-accumulating organisms (DPAOs), Pseudomonas sp. and Acinetobacter sp., increased by 5 times after nitrite stress. The high level of nitric oxide (NO) and free nitrite acid produced by addition of nitrite strongly suppressed the undesired organisms NOB and ordinary heterotrophic denitrifying organisms, and promoted the enrichment of DPAOs. The NO accumulated in the nitrite denitrification process could inhibit NOB and promote AOB. This study revealed that NO plays an important role in regulating the microbial community in the SNDPR system.

Pollutant dynamics between The Black Sea and The Marmara Sea: Basis for wastewater management strategy

The study evaluated pollutant dynamics between The Black Sea and The Marmara Sea using data collected during a marine survey of the region around The Bosphorus strait, in the last five years. A hydraulic model was utilized to define two-layered water exchange in The Bosphorus. Analysis of pollutant exchange indicated The Black Sea as major polluter for the marine environment in The Marmara Sea. Four wastewater outfalls are located along The Bosphorus; Mass balances between the two ends of The Bosphorus indicated losses of 44 t/d total N and 138 t/d COD in the lower layer before reaching The Black Sea. This was explained with a simultaneous nitrification-denitrification process sustained in the low oxygen or anoxic zones around the outfalls, implying that a sustainable wastewater strategy should preclude additional treatment for The Bosphorus discharges, since they do not have an appreciable impact on the water quality of the lower flow.

Microbial nitrogen removal in synthetic aquaculture wastewater by fixed-bed baffled reactors packed with different biofilm carrier materials

Fixed-bed baffled reactors packed with carbon fiber (CFBR), polyurethane, or non-woven fabrics were developed to support microbial nitrification–denitrification reactions for nitrogen removal from synthetic aquaculture wastewater. The CFBR showed the best performance, with a short hydraulic retention time and low C/N ratio. Microbial communities in the reactor’s biofilms and deposited sludge were analyzed using high-throughput sequencing and quantitative polymerase chain reactions. The biofilms efficiently enriched the nitrifying and denitrifying bacteria in the CFBR. Moreover, bacteria capable of denitrification under aerobic conditions were detected in the aerobic chamber biofilm, showing positive correlations with the main nitrifiers and denitrifiers, which provides potential synergistic interactions for simultaneous nitrification–denitrification in the aerobic chamber. A network analysis revealed that the CFBR had more complex cooperative interactions than others. This study provides insights into the influence of different carrier materials on biofilm formation, proving that the CFBR has potential applications in aquaculture wastewater treatment.

Pilot-Scale Investigation of Floating Treatment Wetlands as Retrofits to Waste-Stabilization Ponds for Efficient Domestic Wastewater Treatment

This study investigates the efficacy of floating treatment wetlands (FTWs) for retrofitting waste-stabilization ponds (WSPs) operating in cold continental climates, such that in Alberta, Canada. The objective was to determine whether WSPs augmented with FTWs could achieve equal or superior treatment efficiency at shorter hydraulic retention times (HRTs of 25–45 days) than those required in the conventional WSPs (60–365 days). A field study was carried out on treatment of domestic wastewater in a two-stage pilot-scale FTW mesocosm (i.e., FTW treatment train composed of Stage 1 and Stage 2 FTW cells (S1-FTW→S2-FTW), with an overall volume of 84 m3 and 41.85 m3 per cell). An identical system without FTW served as a control (i.e., control treatment train of S1-C→S2-C). Overall, the FTW-augmented WSP system achieved greater treatment of 5-day biochemical oxygen demand (BOD5), total suspended solids (TSS), total nitrogen (TN), ammonium nitrogen (NH4+-N), dissolved reactive phosphorus (DRP), and total phosphorus (TP) than the control. The corresponding removal efficiencies were 91.5% versus 85.0%, 91.3% versus 87.7%, 85.0% versus 75.6%, 93.9% versus 86.1%, 77.6% versus 57.7%, and 75.8% versus 58.7%, with a statistically significant difference (p<0.05) for all except TSS. This difference in performance resulted from the better performance of the Stage 1 FTW cell for BOD5, TN, and NH4+-N removal, and the Stage 2 FTW cell for DRP and TP removal. Simultaneous nitrification-denitrification (SND) occurred in the FTW treatment train, whereas only nitrification occurred in the control treatment train, which resulted in statistically higher TN removal efficiency in the former. Contribution of plant uptake to phosphorus removal was marginal (6.76%) and adsorption-desorption on solid particles was assumed to be the major removal pathway. The FTWs generally decreased the physicochemical parameters, with stronger effects on diurnal variations than seasonal fluctuations. The effect of FTW on daily physicochemical conditions played a key role in superior performance of FTW treatment.

Utilization of Elemental Sulfur in Constructed Wetlands Amended with Granular Activated Carbon for High-Rate Nitrogen Removal

To investigate the role of granular activated carbon (GAC) on nitrogen removal performance of elemental sulfur-based constructed wetlands (S0-based CWs), three systems were constructed according to the different configurations in the functional layer, namely S-CW (S0 added in the functional layer), CSC-CW (GAC, S0 and GAC placed in layers in the functional layer) and SC-CW (S0 and GAC mixed evenly in the functional layer). In CSC-CW and SC-CW, the volumetric ratio of S0:GAC was 9:1. Three CWs were operated under four different hydraulic retention times (HRTs) ranged from 48 h to 6 h. Over the experiment, total inorganic nitrogen (TIN) removal rates of the three CWs were 3.1 – 23.6 g m−2 d−1, 3.5 – 24.1 g m−2 d−1 and 3.4 – 11.5 g m−2 d−1, respectively; CSC-CW remained high TIN removal efficiency (from 74.7 ± 20.2 % to 93.4 ± 1.9 %) while SC-CW had significant lower values when HRT = 6 h (29.8 ± 30.1 %). Mass balance and high-throughput sequencing analysis revealed that mixotrophic denitrification at the sulfur layer and simultaneous nitrification-denitrification (SND) at the rhizosphere played the major role in N removal from CSC-CW (> 95 %). GAC addition facilitated the growth of Iris pseudacorus with the final fresh weight increased from 33.9 gFW ind−1 to 82.3 gFW ind−1 in CSC-CW and 82.7 gFW ind−1 in SC-CW. This study optimizes the practical application of S0-based CWs amended with GAC for N removal from carbon-limited wastewater.