Ammonia Nitrogen Removal Efficiency Research Articles

Nitrogen removal performance and needed area estimation of surface-flow constructed wetlands using a probabilistic approach

Pollutant concentrations in influents into constructed wetlands (CWs) are highly fluctuating and may vary over several orders of magnitude, leading to large uncertainties in removal performance assessment when using pollutant concentrations in the influent and effluent directly. Incorporating a probabilistic approach into removal performance assessment and needed area estimation of CWs could advantage decision making regarding wastewater treatment and engineering applications. A series of three-stage surface-flow CWs (SFCWs) were constructed for treating ammonium-rich swine wastewater. The surface removal rate and removal efficiency of ammonium nitrogen in the SFCWs using the probabilistic approach were 0.27–3.23 g m−2 d−1 and 43.0–99.9% (95% confidence interval (CI)), which were consistent with the deterministic approach (95% CI: 0.24–3.18 g m−2 d−1 and 70.4–99.9%). The needed SFCW area was estimated as 6.6 (95% CI: 1.4–17.8) to 29.7 (95% CI: 6.4–80.1) m2 for required removal efficiency from 40% to 90% for 0.18 m3 d−1 swine wastewater with different strengthens. For specific removal efficiency of 90%, the needed CW areas was 13.9 (95%CI: 4.9–42.7), 25.1 (95%CI: 5.9–66.0), 33.5 (95%CI: 13.5–87.1), and 40.8 (95%CI: 16.2–89.4) m2 for influent ammonium loading rate of 0.18–2.7, 2.7–14.4, 14.4–36, and 36–60 g d−1, respectively. The first-order removal constant of ammonium nitrogen decreased logarithmically with increasing influent and effluent concentration/loading rate in the SFCW units (p < 0.001), which was responsible for the needed SFCW areas covering a wide range. The reliability analysis confirmed the results from the probabilistic approach were appropriate. The present study shed new lights on the performance evaluation and design of CWs for treating wastewater with highly-fluctuating concentrations using a probabilistic approach.

Simultaneous removal of phosphate and ammonium nitrogen from agricultural runoff by amending soil in lakeside zone of Karst area, Southern China

The loss of phosphorus(P) and nitrogen from agricultural non-point source(ANPS) is one of the main causes of eutrophication in rivers, lakes and reservoirs in the Karst region, southern China. The lakeside buffer zone has proven to be effective in reducing the input of ANPS pollutants. However, the interception efficiency of natural soil for P and ammonia nitrogen is insufficient to control ANPS pollution. In this study, natural zeolite(NZ), aluminium modified clay(AMC) and lanthanum modified bentonite(LaMB) were used to amend the natural soil collected in the lakeside zone of Kelan Reservoir, Guangxi, China. An experimental study was conducted to examine the dissolved inorganic P(DIP) and ammonia nitrogen removal efficiency and fixation mechanism of three amended soils under simulation conditions. The results showed that natural soil had a high fraction of clay and silt (particle size<20μm; 75.2 %), and had a high removal rate of >95 % for the DIP at the beginning of the experiment. With the intermittent input of farmland drainage, the P removal rate of natural soil from runoff decreased gradually. Compared with the control group, P removal rates of AMC- and LaMB amended soils remained at a high level within 46 days, with means of 93.6 % and 93.9 %. However, NZ amended soil has a weak interception capacity of runoff P pollutant. The chemical sequential extraction showed that AMC increased soil P capacity by forming NaOH-P and NaHCO3-P, while LaMB by forming NaOH-P, NaHCO3-P and Residual-P. In addition, LaMB amended soil can simultaneously remove ammonia from farmland runoff, with the removal rate of 89.3 %. AMC- and LaMB amended soils are proved to be potential and effective technologies for ANPS pollution control. This study provide an important basis for the treatment of ANPS pollutants and the construction of lakeside buffer zone in eutrophic watershed.

Influences of plant species and radial oxygen loss on nitrous oxide fluxes in constructed wetlands

Constructed wetlands have been used as a green technology to treat wastewaters for several decades. However, constructed wetlands are considered to be great sources of nitrous oxide, a potent greenhouse gas contributing to global warming. Plants play an important role in the nitrogen cycling in wetland ecosystems. To investigate the effects of wetland plants on nitrous oxide fluxes through radial oxygen loss and nutrient removal, integrated vertical flow constructed wetlands were used and planted with three wetland plants (Canna indica L. (C. indica), Acorus calamus L. (A. calamus) and Scirpus validus Vahl (S. validus)). The results showed that integrated vertical flow constructed wetlands were significant sources of nitrous oxide fluxes. However, the nitrous oxide fluxes from the C. indica, A. calamus and S. validus wetlands differed substantially, ranging from 0.05 ± 0.01 to 1.80 ± 0.34, 0.08 ± 0.00 to 0.62 ± 0.20, and 0.03 ± 0.00 to 0.27 ± 0.01 mg N2O-N/m2/h, respectively, and had a similar tendency of seasonal variations: summer > autumn > spring > winter. The nitrous oxide fluxes from the down-flow cells were higher than those from the up-flow cells in every season. Among the three plant species, S. validus was most efficient in removing total nitrogen and ammonium nitrogen while minimizing nitrous oxide fluxes, and could be utilized preferentially as wetland plant. The radial oxygen loss of species has a seasonal tendency: summer > autumn > spring > winter. The nitrous oxide fluxes had positive significant correlations with temperatures, ammonium nitrogen and total nitrogen removal efficiencies and radial oxygen loss. These results contributed to linear prediction and reduction for nitrous oxide fluxes in constructed wetlands.

Start-up of the Simultaneous Nitrification, Anammox, and Denitrification (SNAD) Reactor and Efficacy of a Small Amount of Organic Carbon

In perspective of the issue of how to begin simultaneous nitrification, anammox, and denitrification (SNAD) rapidly, the sequencing batch biofilm reactor (SBBR) was adopted to enrich ammonia-oxidizing bacteria (AOB) and anammox bacteria (AnAOB) rapidly and to inhibit nitrite-oxidizing bacteria (NOB) after three phases (67 days) of culture, and the impacts of different low carbon-nitrogen ratios (COD/N) on denitrification performance of the process were investigated. The results showed that preventing the accumulation of nitrite (NO2−-N) was the key to start SNAD successfully. The removal efficiencies of ammonia nitrogen (NH4+-N) and total nitrogen (TN) in the system can reach more than 99% and 90%, respectively. Corresponding to COD/N = 0, 1 and 2, removal efficiencies of NH4+-N were 99.6%, 99.5%, and 98.5% respectively and removal efficiencies of TN were 93.8%, 97.2%, and 98.1%, respectively; the total nitrogen removal rate (TNRR) was greater than 0.29 kg N m−3 day−1. It indicates that the presence of a small amount of COD is beneficial to the denitrification of NO3−-N without affecting the effect of simultaneous nitrification and anaerobic ammonium oxidation, which further improves the efficiency of nitrogen removal. High-throughput sequencing analysis showed that the ratios of AOB, AnAOB, and denitrifying bacteria were 7.3%, 20.1%, and 7.66%, respectively. Candidatus Kuenenia was the only genus of the SNAD reactor with anaerobic ammonium oxidation. AOB, Anammox, and heterotrophic denitrifying bacteria were present in the system, while ammonia oxidation and anaerobic ammonium oxidation played a dominant role in the denitrification process.

Sustainable ammonia-contaminated wastewater treatment in heterotrophic nitrifying/denitrifying microbial fuel cell

Abstract Air-cathode microbial fuel cells (ACMFCs) have a remarkable potential in wastewater treatment for scalable-scale and sustainable operation. In this study, a heterotrophic nitrifying/denitrifying air-cathode microbial fuel cell (HND-ACMFC) was investigated with ammonia-contaminated wastewater in long-term operation. Over an operational period of 197 d, high removal efficiencies of chemical oxygen demand (COD, 91%), ammonia (99%), and total nitrogen (TN, 95%) were achieved stably and repeatedly, with continuous bioelectricity production of 0.72 A/m3 and maximum power density of 100 mW/m3. Microbial community structure analysis showed that majority of the dominated bacteria were affiliated with Thauera, Nitrosomonas, Arcobacter, Pseudomonas, Clostridium, and Geobacter, which are identified as nitrogen-removing bacteria (NRB) and/or electrochemically active bacteria (EAB). Scanning electron microscopic analysis demonstrated the presence of a considerable number of bacteria attached to the two electrodes, even in the air-exposed part of the biocathode. Moreover, energy input/output evaluation showed that the maximum normalized energy recovery still reached 0.12–0.21 kWh/kg COD when ammonia nitrogen was depleted efficiently. These results demonstrate that HND-ACMFC is a possible approach to accomplish simultaneous wastewater treatment and energy recovery, and also enhances the activity of functional microorganisms. Hence, HND-ACMFC may benefit the sustainable treatment of ammonia-contaminated wastewater by using MFC technology in view of economical configuration/operation and high performance.

Total Ammonia Nitrogen (TAN) Removal Efficiency in Recirculating Aquaculture Systems by using Sponge-Bed Trickling Filter

Total Ammonia Nitrogen (TAN) Removal Efficiency in Recirculating Aquaculture Systems by using Sponge-Bed Trickling Filter

Enhanced total nitrogen removal performance in a full scale Orbal oxidation ditch by a novel step aeration mode

Two aeration modes, namely point aeration and step aeration, were proposed and implemented in a full scale Orbal oxidation ditch, and nitrogen removal performance was studied. The results showed that nitrogen removal performance under point aeration mode depended on oxygen supply control. Highest total nitrogen (TN) removal efficiency of 73.2% was achieved when oxygen input in the outer, middle and inner channel accounted for 50, 25 and 25% of total oxygen supply, respectively. With the same oxygen supply, both aeration modes demonstrated complete nitrification with over 97% ammonia nitrogen removal efficiencies. However, TN removal efficiency was 78.8% under step aeration mode, which was higher than that under point aeration. The pyrosequencing results indicated that microbial community composition was affected by aeration modes and step aeration mode was beneficial to the enrichment of denitrifiers. The greater diversity and relative abundance of denitrifiers enhanced TN removal under step aeration mode.

Characteristic on pollutant removal and extracellular polymeric substances distribution in different periods of an up-flow biological aerated filter

The up-flow biological aerated filter (UBAF) reactor was established to explore the pollutant removal and the extracellular polymeric substances (EPS) distribution at the initial stage of biofilm, maturity of biofilm, and stable operation periods. The parallel factor (PARAFAC) model was applied to analyze the three-dimensional fluorescence characteristics of EPS. Canonical correlation analysis (CCA) was used to study the correlation between the distribution of EPS and pollutant removal. The results showed that the removal efficiency of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total phosphorus (TP) at the maturity of biofilm were higher than other periods, and reached to 95.68%±0.87%, 73.48%±4.32%, and 63.80%± 14.27%, respectively. The operation period had a significant correlation with EPS distribution. All of biofilm samples detected four kinds of fluorescent substance of tryptophan-like (C1), protein-like (C2), humilic acid (C3), and humic acids-like (C4). The CCA result showed that NH4+-N removal had a very significant positive correlation with EPS concentration and composition (R≥0.9261).

Modified carbon nitride as an efficient adsorbent for ammonia nitrogen with low concentration

AbstractThe adverse effects of excessive ammonia on aquatic ecosystem have provoked the development of efficient methods for its removal. Here, we present a thermal copolymerization of melamine and sodium hydrogen carbonate and successfully introduce oxygen groups into the structure of g‐C3N4, which is applied to low‐concentration ammonia removal. Oxygen groups are introduced into g‐C3N4 and increase its surface electron negativity. When the initial concentration of ammonia nitrogen is 18.74 mg L−1, the lowest concentration of it after adsorption is 1.43 mg L−1, and the ammonia nitrogen removal efficiency is 92.3%. The main reason for our material high performance on adsorption ammonium may be ascribed to deprotonated carboxylic acid, which has the ability to adsorb positively charged ammonium ions.

Effect of periodic temperature shock on nitrogen removal performance and microbial community structure in plug-flow microaerobic sludge blanket

The positive effects nitrogen removal capability in a plug-flow microaerobic sludge blanket at low temperature are confirmed by inducing periodic high temperature shocks. This method enables enhancement of metabolic activity and an optimized bacterial community structure of microbes under the conditions of low C/N ratio and temperature. The control reactor was operated at a constant temperature of 20 °C, and the plug-flow microaerobic sludge blanket was subjected to a high temperature shock treatment with three cycles for 94 d. Starting with the initial temperature of 20 °C, after three cycles at temperature (30 °C) shock, the removal efficiencies of ammonium and total nitrogen at the terminal period increased to 68.0% and 54.7% from 51.1% to 35.6%, respectively. The activity and relative abundance of ammonia oxidizing bacteria, nitrite oxidizing bacteria, and anammox bacteria, dominated by Candidatus Brocadia at low temperature, were accordingly enhanced after periodic temperature shocks.

Preliminary Research on Synergetic Removal of Phosphorus and Nitrogen by Aeration and Adsorption

Zhao, L.; Gong, D.; Li, L.; Lin, L.; Du, Q.; Qiao, Q.; Guo, W.; Tang, X., and Li, Q., 2019. Preliminary research on synergetic removal of phosphorus and nitrogen by aeration and adsorption. In: Guido-Aldana, P.A. and Mulahasan, S. (eds.), Advances in Water Resources and Exploration. Journal of Coastal Research, Special Issue No. 93, pp. 291–297. Coconut Creek (Florida), ISSN 0749-0208.Eutrophication of lakes, estuaries and coastal waters is one of the global environmental issues and removal of phosphorus and nitrogen from the water is the most direct way for eutrophication control for those water bodies. The synergistic removal effects of phosphorus and nitrogen by aeration and adsorption in water under different aeration intensities and aeration patterns were investigated in the present research. The results indicated that aeration and adsorption simultaneously used had a synergistic effect on the removal of phosphate in water, over 90% of orthophosphate was removed jointly, which was significantly greater than the summational removal rate (<50%) of aeration and adsorption alone. However, such synergistic effect did not reflect in the removal of ammonia nitrogen. Similar ammonia nitrogen removal efficiency was exhibited in intermittent aeration and continuous aeration group under different aeration patterns. Therefore, intermittent aeration can be utilized for the energy consumption reduction of the further experiment. The combination of aeration and adsorption has definite advantages in the phosphate removal in water. However, further in-depth research is needed in the synergistic removal of ammonia nitrogen by adsorption and aeration. The results of present research can provide some technical references for eutrophication control in lakes, estuaries and coastal waters.

Pilot study of nitrogen removal from landfill leachate by stable nitritation-denitrification based on zeolite biological aerated filter

A pilot (about 1 m3/d) process consisting of pre-denitrification and zeolite biological aerated filter (ZBAF) was established and run for nitrogen removal of landfill leachate. The results showed that stable nitritation and denitrification was achieved for landfill leachate with removal efficiency of Chemical Oxygen Demand (CODCr), ammonium and total nitrogen (TN) of 53.2 ± 3.0%, 93.5 ± 2.4% and 74.7 ± 9.4%, respectively. Based on the ammonium adsorption equilibrium by zeolite, stable free ammonia could be maintained for inhibition of nitrite oxidizing bacteria (NOB) and dominance of ammonia oxidizing bacteria (AOB) in ZBAF, resulting in efficient nitritation with a nitrite accumulation ratio higher than 90.0% and an average nitrite production rate of 1.387 kg NO2−-N m−3 day−1. High-throughput sequencing analysis further revealed enrichment of AOB and elimination of NOB in ZBAF. Compared to two-stage anoxic-oxic process, the pilot-scale process could save approximate 5000 mg/L glucose (about 3.10 US dollar/m3) with almost similar TN removal performance. All results obtained demonstrated the feasibility of the pilot process, which might be highly promising for the nitritation and denitrification of low C/N landfill leachate in the future.

Enhanced Nutrient Removal and Microbial Community Structure in a Step-feed A2/O Process Treating Low-C/N Municipal Wastewater

To resolve the issue of insufficient influent carbon sources in existing municipal wastewater treatment plants (WWTPs) in China, a pilot-scale step-feed A2/O process was used to treat low-C/N (C/N<5) municipal sewage with five different inflow distribution ratios. In this study, the effects of influent flow distribution on the removal efficiencies of chemical oxygen demand (COD), ammonium nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) were investigated. The results showed that optimal removal efficiencies of 89.41% for COD, 95.30% for NH4+-N, 83.00% for TN, and 90.09% for TP were obtained at an inflow QPA:QAN:QA distribution ratio of 0.1:0.2:0.3. The activated sludge exhibited excellent settleability characteristics, showing a sludge volume index (SVI)<120 mL·g-1 with an average volatile suspended solids (VSS) total suspended solids (TSS) ratio of 0.84 (Phase 5), and no filamentous bacteria bulking occurred during the 120-day experiment. Moreover, the microbial community structure in the oxic zone was detected by high-throughput sequencing. The results demonstrated that excellent nutrient removal and sludge settling performance of the system were closely related to the enrichment of six types of heterotrophic bacteria, four types of denitrifying bacteria, five types of polyphosphate-accumulating organisms (PAOs), and two types of zoogloea and the elimination of three types of filamentous bacteria.

The effects of refractory pollutants in swine wastewater on the growth of Scenedesmus sp. with biofilm attached culture

Microalgae have been widely used for treatment of swine wastewater. However, the research on combined treatment of refractory pollutants ammonia nitrogen, Cu (II) and antibiotics from swine wastewater was still scattered. This study, the growth and removal efficiency of NH4Cl, CuSO4, tetracycline, norfloxacin and sulfadimidine with selected Scenedsmus sp. was investigated by biofilm attached culture. The results showed that low concentration of ammonia nitrogen had little effect on algae growth. The highest biomass productivity was 6.2 g/(m2d) at the concentration of NH4Cl of 50.0 mg/L, which was similar to that of a standard growth medium BG 11. Cu (II) concentration of 1.0 mg/L could accelerate the growth of Scenedsmus sp., and the highest biomass was 57.2 g/m2 in 8 days. Moreover, the highest biomass mean values was 59.5 g/m2, 57.1 g/m2, and 58.1 g/m2, respectively, when tetracycline concentration was 20.0 mg/L, norfloxacin concentration was 100.0 mg/L and sulfadimidine concentration was 10.0 mg/L. The removal efficiency of ammonia nitrogen, copper, tetracycline, norfloxacin and sulfadimidine with Scenedsmus sp. at their optimal initial concentration by biofilm attached culture was 85.2%, 64.6%, 74.6%,71.2%, and 62.3%, respectively. This study provides a theoretical basis for the purification of refractory substances from swine wastewater.

Nitrification of low concentration ammonia nitrogen using zeolite biological aerated filter (ZBAF)

This study focuses on nitrification through a biological aerated filter (BAF) that is filled with a zeolite medium at low concentrations of ammonia. The zeolite medium consists of natural zeolite powder. The BAF is operated under two types of media, which are a ball-type zeolite medium and expanded poly propylene (EPP) medium. Nitrification occurred in the zeolite BAF (ZBAF) when the influent concentration of ammonia nitrogen was 3 mg L-1, but the BAF that was filled with an EPP medium did not experience nitrification. The ammonia nitrogen removal efficiency of ZBAF was 63.38% and the average nitrate nitrogen concentration was 1.746 mg/L. The ZBAF was tested again after a comparison experiment to treat pond water, and municipal wastewater mixed pond water. The ZBAF showed remarkable ammonia-nitrogen treatment at low concentration and low temperature. During this period, the average ammonia nitrogen removal efficiency was 64.56%. Especially, when water temperature decreased to 4.7℃, ammonia nitrogen removal efficiency remained 79%. On the other hand, the chemical-oxygen demand (COD) and phosphorus-removal trends were different. The COD and phosphorus did not show as efficient treatment as the ammonia-nitrogen treatment.

Advanced Denitrification of Municipal Wastewater Achieved via Partial ANAMMOX in Anoxic MBBR

Anoxic MBBR is a process to achieve advanced denitrification from municipal wastewater. Here, anoxic MBBR was applied as a post-denitrification SBR to achieve advanced denitrification by partial anammox (anaerobic ammonium oxidation). During a 250-day operation, denitrification performance gradually improved and the total nitrogen concentration of the effluent was approximately 5 mg·L-1. The average nitrate, ammonia, and total inorganic nitrogen removal efficiencies were (97.7±2.9)%, (93.3±2.9)%, and (94.3±2.7)%, respectively, between day 211 and 250. The simultaneous removal of ammonia and nitrate was observed in the anoxic reactor. Analysis of the ammonia removal pathway revealed that assimilation and nitrification were poor in the anoxic MBBR. The anammox activity test and the denitrification performance showed that anammox occurred and played a not insignificant role in the anoxic MBBR. The results of real-time quantitative PCR showed that anammox bacteria enriched in anoxic MBBR, especially in the anoxic carrier biofilms, where the abundance of anammox bacteria increased from 4.37×107 copies·g-1 to 2.28×1010 copies·g-1. This study demonstrates that anoxic carrier biofilms may have potential applications in anammox bacterial enrichment to enhance denitrification from municipal wastewater.

Start-up of oxygen-limited autotrophic partial nitrification-anammox process for treatment of nitrite-free wastewater in a single-stage hybrid bioreactor

ABSTRACT This study presents effective ammonium removal from nitrite-free ammonium-rich synthetic wastewater through combined partial nitrification (PN) and anammox processes in a multi-zone hybrid airlift bioreactor (BioCAST). Removal efficiencies of ammonia-nitrogen and total nitrogen up to 85.6% and 81.2%, respectively, were achieved shortly after the start-up of bioreactor treating the nitrite-free ammonium-rich synthetic wastewater with ammonium concentrations of 10–350 mg/L. The hybrid (containing suspended and attached biomass) and multi-zone design of the bioreactor with different dissolved oxygen levels, along with the inoculation with anammox-containing sludge were the main factors in the successful start-up of the bioreactor. Nitrate accumulation problem due to the fast growth of nitrite-oxidizing bacteria in the bioreactor was controlled by two operating strategies including lowering the HRT from 4 days to 2 days and controlling the dissolved oxygen concentration in the aerobic zone of the bioreactor between 0.9 and 1.2 mg/L. Moreover, the 16S rRNA gene analysis confirmed that the partial nitrification of ammonia to nitrite occurred by Nitrosomonas sp. primarily in the suspended biomass in the aerobic zone, while the conversion of nitrite to N2 occurred by Candidatus Brocadia species in the anoxic zone. This study showed the effective removal of ammonium from a nitrite-free wastewater by providing a proper HRT, controlling the DO concentration between 0.9 and 1.2 mg/L in the aerobic zone, and preventing biomass loss using both suspended and attached microbial cultures in different zones of the bioreactor.

Evolution and resistance of a microbial community exposed to Pb(II) wastewater

This study investigated the treatment performance of activated sludge on Pb(II)-containing wastewater, including contaminant removal efficiency, extracellular polymeric substances, pbrT gene content and the microbial community. The average removal efficiencies of ammonia nitrogen, chemical oxygen demand, total phosphorus, total nitrogen and Pb(II) were 40% ± 4%, 91% ± 3%, 95% ± 3%, 51% ± 5% and 92% ± 9% during the stable operation stage, respectively. Moreover, the extracellular polymeric substance -protein contents increased significantly from day 0 to day 60 (p < 0.05). The most abundant fluorescent component in extracellular polymeric substances was a humic acid-like substance, and its fluorescence intensity increased significantly from day 0 to day 60 (p < 0.05). Adsorption of negatively charged organic functional groups in extracellular polymeric substances was identified as a major component of the removal of Pb(II). Most of the denitrifying bacteria associated with nitrogen removal showed an increasing trend during the acclimation stage, which may have resulted in high total nitrogen removal efficiency. In addition, pbrT uptake protein was found to be responsible for the uptake of Pb(II) into cells. The abundance of the pbrT gene showed a downward trend (p < 0.05) after adding Pb(II), probably because expression of the pbrT gene was inhibited under Pb(II) stress. Sphingopyxis containing the pbrT gene was the dominant resistance genus, and its relative abundance increased significantly (p < 0.05) from day 0 to day 60. This study provided a theoretical basis for the treatment of Pb(II)-containing wastewater.

Using the Modified Sugarcane Bagasse Cellulose Cation Membrane as a Separator in the Electrodialysis Device for Ammonia Nitrogen Removal

Bulk modification was applied to synthesize modified sugarcane bagasse cellulose (MSBC) cation exchange membrane using in electrodialysis device for the removal of ammonia nitrogen wastewater. The effect of MSBC mass fraction and pore forming agent in casting solution on membrane physico-chemical properties was studied. XRD showed that the crystal lattice of cellulose in membrane transformed from cellulose I to cellulose II, and the FT-IR displayed that there were no new functional groups after the membrane formation. With the increase of MSBC, the moisture content and swelling degree of the membrane decreased, but the mechanical strength increased and the IEC increased from 0.68 to 1.05 mmol/g. With the increase of pore-forming agent, the moisture content, swelling degree and increased in varying degrees, but the mechanical strength decreased, it is worth noting that ion exchange capacity (IEC) has increased from 0.31 to 1.35 mmol/g as the amount of pore agent is four times that of MSBC. The influence of initial concentration of ammonia nitrogen wastewater, voltage and electrolysis time on the removal rate of ammonia nitrogen was investigated. The results showed that the removal efficiency of ammonia nitrogen was higher when the initial concentration was 1500–2000 mg/L, and the removal rate of ammonia nitrogen can be up to 90.12% under the condition of the voltage is 10 V and the electrolysis time is 7 h. This implied that the cation exchange membranes prepared from MSBC can be produced that can be appliedin wastewater treatment.

Effect of the particle size on the ammonia removal rate and the bacterial community composition of bioflocs

The total ammonia nitrogen (TAN) removal efficiency and bacterial community composition of bioflocs with <50-μm particle size, > 50-μm particle size and un-sieved bioflocs were investigated in the current study. The initial ratio of dissolved organic carbon to TAN (DOC/TAN) in the three groups were about 14:1. No significant difference was found in the removal rate of TAN, average concentrations of TAN and nitrite nitrogen among the three groups (P > 0.05). The C/N (w/w) ratio of the > 50-μm bioflocs was significantly higher than those of the other groups. No significant differences were found in the crude protein content in the bioflocs among the three groups. The development of the bacterial community compositions of the bioflocs was analyzed by Illumina MiSeq sequencing analyses. Most OTUs were shared among the three groups at all the sampled time points. With the increase in the relative abundance of phylum Firmicutes, that of phylum Proteobacteria, Chorolexi, and Bacteroidetes decreased in all the three groups. The phylum Firmicutes and genus Bacillus were predominant in all the sampled time points. At the end of the experiment, genus Bacillus accounted for 81% in the < 50-μm group, 82% in the > 50-μm group, and 75% in the un-sieved group.