Maximum NH4 Research Articles

Synergistic removal of ammonia nitrogen and hexavalent chromium by the hybrid-system of Acinetobacter baumannii AL-6 and original walnut shell biochar in solution: Mechanism and application

A novel hybrid-system was developed with the Acinetobacter baumannii AL-6 and original walnut shell biochar. Compared with strain AL-6 and biochar, hybrid-system exhibited an excellent synergistic removal ability for ammonia nitrogen (NH4+-N) and hexavalent chromium (Cr(VI)). And the maximum NH4+-N and Cr(VI) removal efficiency of hybrid-system were 93.30 % and 99.63 %, higher than 82.01 % and 56.49 % of strain AL-6, 5.35 % and 14.97 % of biochar, respectively. Strain AL-6 grew well in the presence of biochar and the ammonia oxygenase (AMO) activity of strain AL-6 was improved by adsorption of NH4+-N and Cr(VI) and release of beneficial elements (Ca, K and Mg) on biochar, which enhanced the biodegradation of NH4+-N. Environment persistent free radicals (EPFRs) and oxygen-containing functional groups of biochar could weaken the electron-competition between Cr(VI) and bacteria, biochar, which increased the removal performance of Cr(VI). The hydrophilic functional groups and mesoporous structure of biochar promoted the immobilization capacity of bacteria, which reduced the loose of bacteria from suspended bioreactor. Approximately 84.58 % - 87.97 % of NH4+-N and 1.18 mg·L−1-1.91 mg·L−1 of Cr(VI) were removed by the hybrid-system in sequencing batch reactor (SBR). Particularly, the removal performance of Cr(VI) was significantly improved as the per NH4+-N was degraded with increasing the operational time in SBR.

Potential of ammonium adsorption of coal fly ash-based porous geopolymer granules

Abstract Porous geopolymer materials have been recently used in environmental remediation applications as adsorbents. This study is to investigate the NH4 + adsorption capacity of geopolymer activated from coal fly ash mixing with NaOH, Na2SiO3, and H2O2. The H2O2 with various ratios (0%, 4.5%, and 8.5%) were added into the fly ash pastes as blowing agents. The NH4 + adsorption capacity of these materials was examined concerning the effects of NaOH concentration, H2O2 contents, adsorbent particle sizes, dosages, and NH4 + concentration by batch adsorption test. The results show that adding 4.5% (G45) and 8.5% (G85) of H2O2 developed porous structures in geopolymer granules and their NH4 + adsorption capacity depends on their particle sizes and pore structures. In particular, geopolymer granules with 8.5% H2O2 exhibited higher NH4 + adsorption capacity than lower content of H2O2 in case of particle size of 3.0-8.0 mm. However, pulverized geopolymer still demonstrated the greatest NH4 + adsorption capacity. In addition, both granules G45 and G85 demonstrated a well-fit (R2 = 0.97-0.99) with Langmuir and Freundlich isotherms. The maximum NH4 + adsorption capacity of G85 was 19.86 mg/g, which indicated the NH4 + adsorption potential of porous geopolymer granules generated from waste materials such as coal fly ash.

Thermal Vapor Deposition of a Hydrophobic and Gas-Permeable Membrane on Zirconium Phosphate Cation Exchanger: An Oral Sorbent for the Urea Removal of Kidney Failure.

An oral sorbent with high capacity for NH4+ is desirable in lowering the blood urea level and mitigating the dialysis burden for end-stage kidney disease (ESKD) patients. Zirconium phosphate (ZrP) is an amorphous cation ion exchanger with high NH4+ binding capacity as a sorbent material, but its selectivity to remove NH4+ is limited in the presence of other competing ions in water solution. We previously have developed a gas-permeable and hydrophobic perfluorocarbon coating on ZrP, which improves ZrP's NH4+ selectivity. However, the coating preparation procedure, a wet chemistry approach, is complicated and time-consuming, and more importantly, the large amount of usage of acetone poses a concern for the application of ZrP as an oral sorbent. In this study, we developed a solventless coating protocol that effectively coats ZrP with tetraethyl orthosilicate (TEOS) and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTS) via thermal vapor deposition (TVD) in a simplified manner. X-ray photoelectron spectroscopy (XPS) and contact angle measurements verify the two coatings are successfully deposited on the ZrP surface, and the coating condition was optimized based on an in vitro static binding study. The dynamic binding study of competing ions on Na-loaded ZrP with TVD coatings yields a maximum NH4+ removal (∼3.2 mequiv/g), which can be improved to ∼4.7 mequiv/g if H-loaded ZrP under the same coating condition is used in basic stock solutions. More importantly, both materials barely remove Ca2+ and show excellent acid resistance. The significant improvement in the NH4+ binding capacity and selectivity reported here establishes a highly promising surface modification approach to optimize oral sorbents for ESKD patients.

Synthesis of 4A Zeolite Molecular Sieves by Modifying Fly Ash with Water Treatment Residue to Remove Ammonia Nitrogen from Water

The widespread presence of ammonia nitrogen (NH4+–N) pollutants poses a serious threat to water environment health. In this study, a novel zeolite (WTR–CFA zeolite) with excellent adsorption performance is synthesized using CFA as the raw material and water treatment residue (WTR) as the aluminum source through an ultrasonic–assisted alkali melt hydrothermal method. Compared with traditional CFA–zeolite, WTR–CFA zeolite only generates 4A zeolite with a single crystal phase, and the peak shape is sharp, which results in better crystallization. WTR–CFA zeolite perfectly solves the technical problems of the low utilization rate and poor controllability of the crystal form in traditional artificially synthesized zeolites. The maximum NH4+–N adsorption capacity of WTR–CFA zeolite is 29.80 mg/g, which is higher than that of most adsorbents reported in previous studies. After five cycles of adsorption regeneration, the regeneration efficiency of WTR–CFA zeolite only decreased from 98.84% to 97.12%, which demonstrates excellent environmental value. The adsorption isotherms and kinetics of NH4+–N conform to the Langmuir model and quasi–second order kinetic model, respectively, which indicates that ion–exchange–dominant chemical adsorption plays a major role in the adsorption mechanism. In summary, this study combines the use of CFA and WTR resources with the treatment of aquatic pollution to reduce material synthesis costs, control the crystal structure of WTR–CFA zeolite, and increase adsorption capacity. This approach achieves the goals of “waste treatment and turning waste into treasure”.

Recovering ammonium from real treated wastewater by zeolite packed columns: The effect of flow rate and particle diameter

Nitrogen (N) recovery from wastewater is a desirable way to create a (N) neutral society in view of a circular economy approach. Nitrogen recovery from wastewater by employing adsorption columns filled with zeolite can be a very attractive solution. This study assessed the effect of influent flow rates (namely, 1.6 and 2.3 L h−1) and particle diameters (namely, 0.5–1.0 and 2.0–5.0 mm) of zeolite packed in columns on recovering NH4+ from real domestic treated wastewater (RDTWW). Findings revealed that maximum NH4+ recovery can be achieved by using zeolite with the smallest particle diameter (0.5–1.0 mm) and the highest influent flow rate (2.3 L h-1). The maximum NH4+ adsorption rate was 1.2, 21 and 9.8 mg NH4+ kg-1 h-1 after 205, 32 and 35 h of operation. NH4+ adsorption data were analysed by fitting them to both pseudo-first and pseudo-second order kinetic models. The former model best approximated NH4+ adsorption data. Such a result suggested that the amount of NH4+ adsorbed depended solely on the amount of NH4+ in contact with the zeolite surface. Results successfully established the application of zeolite-packed columns in removing NH4+ from real domestic treated wastewater and the effects of process parameters.

LaNi0.2Cu0.8O3‐δ Perovskites as Electrocatalysts for Electro‐synthesis of Ammonia from Nitrogen Oxyanion

AbstractElectrochemical nitrate reduction to ammonia (NO3RR) has become an attractive alternative way for sustainable ammonia synthesis. The development of electrocatalysts with high activity, stability and Faradaic efficiency is important but challenge due to the complex eight‐electron process. Herein, LaNi0.2Cu0.8O2.77 (LNC) and LaNi0.2Cu0.8O2.53 (LNC−Ar) are demonstrated as electrocatalysts towards NO3RR and the surface reconstruction of the two catalysts was found to have strong effect on the catalytic performance. LNC−Ar shows a superior performance than LNC, with a maximum NH4+ yield of 11.49±1.20 mg h−1 cm−2 and a Faradaic efficiency of 87.10±1.34 % in 0.5 M NO3−, besides, the LNC−Ar remains functionally stable along the long‐time electrolysis. DFT results reveals the reconstructed LaNi0.2Cu0.8O2 (LNCO2) has the best ability to adsorb *NO3, resulting in a better performance towards NO3RR. Further, the better performance on LNC−Ar with more LNCO2 can be well explained. This work opens a new sight on perovskites towards NO3RR and provides an option of active and stable electrocatalyst for sustainable ammonia synthesis.

Ammonium ion removal from aqueous solutions in the presence of organic compounds, using biochar from banana leaves. Competitive isotherm models

BackgroundIndustrial, e.g. food industrial and domestic wastewaters contain huge amount of compounds causing eutrophication, and should be removed with high cost during wastewater treatment. However, these compounds could be utilized as fertilizers too. Biochar can remove a wide range of pollutants from water, such as ammonium, which can be found in relatively high concentration in dairy wastewaters. However, adsorption performance may be affected by the presence of other wastewater pollutants. Thus, this study aims to determine the efficiency of biochar as an adsorbent of ammonium in aqueous solutions in the presence of some selected organic compounds of typical dairy wastewaters such as bovine serum albumin (BSA), lactose, and acetic acid. Methods: The biochar was produced from banana leaves at 300 °C, modified with NaOH, and characterized by Scanning Electron Microscope – Energy Dispersive X-Ray Spectroscopy (SEM-EDX), Fourier-transform infrared spectra (FTIR) analysis, and specific surface area measurements. Batch experiments were carried out to investigate the ammonium adsorption capacity and the ion competitive adsorption mechanism. Significant Findings: Results show that the surface structure of the biochar derived from banana leaves is different from other biochars previously studied; although the specific surface area is not very considerable and despite having nitrogen within the elemental composition, the biochar studied is capable of adsorbing 2.60 mg NH4+/m2, the highest ammonium removal in 2 h occurs at pH 9 and 500 mg biochar dose. Langmuir model in the monolayer phase analysis fits better for all scenarios and the maximum NH4+ adsorption capacity was 0.97 mg/g without organic compounds. In the multilayer adsorption phase, the isotherm model that best fits the data obtained is the Harkins-Jura model without organic compounds. The presence of organic compounds in the aqueous solution significantly impacts the adsorption of ammonium by biochar since it improves the adsorption capacity (1.132 mg/g BSA, 0.975 mg/g lactose, and 1.874 mg/g acetic acid). The Aranovich-Donohue isotherm model fitted the data obtained during ion competitive adsorption experiments well.

Investigation on Basil (Ocimum basilicum L.) and Lavender (Lavandula angustifolia) Cultivation in Aquaponic Aquaculture (Carp, Cyprinus carpio L.)

Aquaponic production system, which creates a sustainable production ecosystem by bringing water, fish, and plants together in a closed system, is a reflection of sustainable economic activities in aquaculture. In this context, the aim of the study was to investigate the cultivation possibilities of carp, lavender, and basil in two different grow beds (water and mollusc shell) created in the aquaponic production system. Basil and lavender as plant material and carp as fish material were used in the study. The experimental design was formed from 12 pots of 90 L volume, and the experiment was continued for 60 days with 3 replications. In the study, reasonably high values for specific growth rate (1.96±0.01 g), condition factor (1.5), and survival rate (97.05%) were obtained in carp. While basil (23.5 cm, 23.5 cm, and 16.5 cm) and lavender (16.57 cm, 15.14 cm end 9.73 cm) grown in water media performed better in terms of plant height, root length, and dry herb yield, the green herb yields of basil (49 cm) and Levander (19 cm) were found to be high for both plants in the mollusc shell media. The maximum NH4, NO3+NO2, and PO4 values were determined as 1.30 mg L-1 (in 3. quarter and fish tank), 40.07 mg/L (in 3. quarter and Levander shell group), and 0.37 mg L-1 (in 1. quarter and basil shell group) respectively.

Alkaline Hydrothermal Treatment of Chabazite to Enhance Its Ammonium Removal and Recovery Capabilities through Recrystallization

The treatment of chabazite (CHA), a natural zeolite, with the alkaline hydrothermal method to improve its ion-exchange capacity is a widely adopted route by environmental scientists for the purpose of better ammonium (NH4+) removal from wastewater. This work addresses a noteworthy trend in environmental science, where researchers, impressed by the increased ion-exchange capacity achieved through alkaline hydrothermal treatment, often bypass the thorough material characterization of treated CHA. The prevalent misconception attributes the improved features solely to the parent zeolitic framework, neglecting the fact that corrosive treatments like this can induce significant alterations in the framework and those must be identified with correct nomenclature. In this work, alkaline-mediated hydrothermally treated CHA has been characterized through X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), solid-state magic-angle spinning nuclear magnetic resonance (MAS-NMR), high-resolution transmission electron microscopy (HRTEM), and energy-dispersive X-ray spectroscopy (EDS) and it is concluded that the treated samples have been transformed into a desilicated, aluminum (Al)-dense framework of analcime (ANA) with a low silica–alumina ratio and with a strikingly different crystal shape than that of parent CHA. This treated sample is further examined for its NH4+ removal capacity from synthetic wastewater in a fixed-bed column arrangement. It achieved a maximum NH4+ removal efficiency of 4.19 meq/g (75.6 mg/g of NH4+), twice that of the parent CHA. Moreover, the regeneration of the exhausted column yielded a regenerant solution, with 94% reclaimed NH4+ in it, which could be used independently as a nitrogenous fertilizer. In this work, the meticulous compositional study of zeolitic materials, a well-established practice in the field of material science, is advocated for adoption by environmental chemists. By embracing this approach, environmental scientists can enhance their comprehension of the intricate changes induced by corrosive treatments, thereby contributing to a more nuanced understanding of zeolitic behavior in environmental contexts.

Simultaneous nitrification/denitrification in a single-chamber stainless steel bioelectrochemical reactor

The removal of nitrogen from wastewater with a low C/N ratio often requires additional carbon sources to address the shortage of electron donors, which increases the cost. We explored a simple and energy effecient means for treating wastewater with a high concentration of ammonia nitrogen under anoxic conditions without the addition of carbon sources. We constructed a stainless steel tube as an anaerobic single-chamber microbial electrolysis cell (MEC) for investigating autotrophic simultaneous nitrification/denitrification (SND). Two different structures (carbon brush vs. stainless-steel) were used to construct biocathodes and compared their performances under different voltages (1.8 V, 1.5 V, 1.2 V) applied by DC power. When voltage was applied at 1.5 V, the removal rates of TN and NH4+-N reached 19.68 ± 0.02 mg L−1 d−1 and 21.04 ± 0.17 mg L−1 d−1, respectively. Simultaneously, it achieved maximum TN and NH4+-N removal over 14 days (44.97 ± 0.28 %, 48.16 ± 0.32 %). These rates were 1.8 and 5 times of that obtained with the conventional carbon brush electrode and open-circuit control. Furthermore, microbial community and SEM analysis indicate that species of Thermomonas, Thibacillus and Thauera were the predominant autotrophic electroactive denitrifying bacteria in the reactors. Overall, we achieved a high rate of nitrogen removal, electron utilization and energy recovery in a single-chamber stainless steel MEC.

Enhancement of alkali- and oxidation-modified biochars derived from water hyacinth for ammonium adsorption capacity

ABSTRACT Wastewater containing high concentrations of ammonium-nitrogen (NH4 +-N) is considered a major concern because its untreated discharge has a variety of adverse effects on the environment and human health. Adsorption using biochars is an easy and cost-effective wastewater treatment method. However, aquatic plants such as water hyacinth for biochar feedstock are considered unsuitable for adsorbent use due to limited NH4 +-N adsorption capacity. In this study, biochar made from water hyacinth was modified with potassium hydroxide (KOH) and hydrogen peroxide (H2O2) to obtain highly efficient adsorbent. This study aimed to enhance NH4 +-N adsorption capacity by KOH- and H2O2-treatments and identify NH4 +-N adsorption mechanism of the modified biochars derived from water hyacinth. The NH4 +-N adsorption of all biochars was dependent on the initial solution pH increasing from pH 2 to 4, then relatively constant from pH 4 to 8. Pseudo-second-order model and Langmuir model were found to be the best fit for NH4 +-N adsorption data. The maximum NH4 +-N adsorption capacity of biochars increased about 8 times (17.1 mg g−1) and 10 times (21.5 mg g−1) after KOH- and H2O2-modification, respectively, compared to pristine biochar (2.14 mg g−1). The main NH4 +-N adsorption mechanisms were suggested as cation exchange for both biochars particularly KOH-modified biochar, and hydrogen bonding by oxygen-containing surface functional groups for H2O2-modified biochar. This study suggested that aquatic plant-based biochar, which has been considered difficult to use, had potential as a promising alternative adsorbent for removing NH4 +-N from wastewater through modification.

Development of a novel three-dimensional biofilm-electrode system (3D-BES) loaded with Fe-modified biochars for enhanced pollutants removal in landfill leachate

Different mass ratio iron (Fe)-loaded biochars (FeBCs) were prepared from food waste and used in the three-dimensional biofilm-electrode systems (3D-BES) as particular electrodes for landfill leachate treatment. Compared to the unmodified biochar (BC), specific surface area of Fe-loaded biochars (FeBC-3 with a Fe: biochar of 0.2:1) increased from 63.01 m2/g to 184.14 m2/g, and pore capacity increased from 0.038 cm3/g to 0.111 cm3/g. FeBCs provided more oxygen-containing functional groups and exhibited excellent redox properties. Installed with FeBC-3 as particular electrode, both NH4+-N and chemical oxygen demand COD removals in 3D-BESs were well fitted with the pseudo-first-order model, with the maximum removal efficiencies of 98.6 % and 95.5 %, respectively. The batch adsorption kinetics experiments confirmed that the maximum NH4+-N (7.5 mg/g) and COD (21.8 mg/g) adsorption capacities were associated closely with the FeBC-3 biochar. In contrast to the 3D-BES with the unmodified biochar, Fe-loaded biochars significantly increased the abundance of microorganisms being capable of removing organics and ammonia. Meanwhile, the increased content of dehydrogenase (DHA) and electron transport system activity (ETSA) evidenced that FeBCs could enhance microbial internal activities and regulate electron transfer process among functional microorganisms. Consequently, it is concluded that Fe-loaded biochar to 3D-BES is effective in enhancing pollutant removals in landfill leachate and provided a reliable and effective strategy for refractory wastewater treatment.

Characterization of the Nitrogen Removal Potential of Two Newly Isolated Acinetobacter Strains under Low Temperature

Excess nitrogen and phosphorus in the water causes several ecological problems for nutrients. Biological nitrogen removal is an economical and efficient way to prevent excessive nitrogen in the environment. For most areas of China, temperatures are usually lower than 20 °C except during the summertime. It is necessary to discover microbes that can efficiently remove nitrogen at low temperatures. In this study, two Acinetobacter strains were isolated from a sample in a wastewater tank in Taizhou for their capabilities to remove NO3−–N and NO2−–N at 15 °C. Heterotrophic nitrification experiments showed that both strains could efficiently remove nitrogen from the culture medium. The maximum removal rates of NH4+–N were 3.15 mg/L·h and 4.74 mg/L·h for heterotrophic nitrification by the strains F and H, respectively. Strain H grew faster and removed both nitrite and nitrate more efficiently than strain F. Genome sequencing showed that strains F and H could be classified into Acinetobacter johnsonii and Acinetobacter bereziniae, respectively. NO2−–N (100 mg/L) was completely removed in 3 days by strain H. The maximum NO3−–N removal rate was 3.53 mg/L·h for strain F. When strain H was cultured in a broth with 200 mg/L NO3−–N, 97.46% of NH4+–N (200 mg/L) was removed in 5 days, and the maximum NH4+–N removal rate was 4.04 mg/L·h. Genomic sequence analysis showed that both the strains lacked genes involved in the denitrification pathway that transforms NO3− into N2. This implies that nitrate or nitrite is removed through the nitrogen assimilation pathway. Genes responsible for nitrate assimilation are clustered together with molybdopterin cofactor biosynthesis genes. Strain H contains fewer resistance genes and transfer elements. All the above data demonstrate that strain H is a promising candidate for nitrogen removal at lower temperatures. But there is still a lot to be done to systematically evaluate the potential of A. bereziniae strain H in treating wastewater at a pilot scale. These include the long-term performance, environmental tolerance, and nitrogen removal efficiency in wastewater. And the application of these Acinetobacter strains in diverse wastewater treatment settings might require careful optimization and real-time monitoring.

Improved simultaneous nitrification–denitrification in fixed-bed baffled bioreactors treating mariculture wastewater: Performance and microbial community behaviors

As mariculture develops, wastewater treatment becomes crucial. In this study, fixed-bed baffled reactors (FBRs) packed with carbon fiber (CFBR) or polyurethane (PFBR) as biofilm carriers were used for mariculture wastewater treatment. Under salinity shocks between 0.10 and 30.00 g/L, the reactors showed efficient and stable nitrogen removal capacities, and the maximum NH4+-N removal rates were 107.31 and 105.42 mg/(L·d) for CFBR and PFBR, respectively, with an initial NH4+-N concentration of 120.00 mg/L. Further, in the independent aerobic chambers of the FBRs for nitrogen removal, taxa enrichment varied depending on the biofilm carrier, and the assembly process was more deterministic in CFBR than in PFBR. Two distinct clusters representing the spatial distribution of the adhering and deposited sludge in CFBR and the front and rear compartments in PFBR were noted. Furthermore, microbial interactions were more numerous and stable in CFBR. These findings improve the application prospects of FBRs in mariculture wastewater treatment.

Rapid simultaneous removal of nitrogen and phosphorous by a novel isolated Pseudomonas mendocina SCZ-2

Nitrogen (N) and phosphorous (P) removal by a single bacterium could improve the biological reaction efficiency and reduce the operating cost and complexity in wastewater treatment plants (WWTPs). Here, an isolated strain was identified as Pseudomonas mendocina SCZ-2 and showed high performance of heterotrophic nitrification (HN) and aerobic denitrification (AD) without intermediate accumulation. During the AD process, the nitrate removal efficiency and rate reached a maximum of 100% and 47.70 mg/L/h, respectively, under optimal conditions of sodium citrate as carbon source, a carbon-to-nitrogen ratio of 10, a temperature of 35 °C, and shaking a speed of 200 rpm. Most importantly, the strain SCZ-2 could rapidly and simultaneously eliminate N and P with maximum NH4+-N, NO3−-N, NO2−-N, and PO43−-P removal rates of 14.38, 17.77, 20.13 mg N/L/h, and 2.93 mg P/L/h, respectively. Both the N and P degradation curves matched well with the modified Gompertz model. Moreover, the amplification results of functional genes, whole genome sequencing, and enzyme activity tests provided theoretical support for simultaneous N and P removal pathways. This study deepens our understanding of the role of HN-AD bacteria and provides more options for simultaneous N and P removal from actual sewage.

Removal of Nutrients from Water Using Biosurfactant Micellar-Enhanced Ultrafiltration

The removal of NH4+, NO3-, and NH3- from wastewater can be difficult and expensive. Through physical, chemical, and biological processes, metals and nutrients can be extracted from wastewater. Very few scientific investigations have employed surfactants with high biodegradability, low toxicity, and suitability for ion removal from wastewater at different pH and salinity levels. This research employed a highly biodegradable biosurfactant generated from yeast (sophorolipid) through micellar-enhanced ultrafiltration (MEUF). MEUF improves nutrient removal efficiency and reduces costs by using less pressure than reverse osmosis (RO) and nanofiltration (NF). The biosurfactant can be recovered after the removal of nutrient- and ion-containing micelles from the filtration membrane. During the experiment, numerous variables, including temperature, pH, biosurfactant concentration, pollutant ions, etc., were evaluated. The highest amount of PO43- was eliminated at a pH of 6.0, which was reported at 94.9%. Maximum NO3- removal occurred at 45.0 °C (96.9%), while maximum NH4+ removal occurred at 25.0 mg/L (94.5%). Increasing TMP to 200 kPa produced the maximum membrane flow of 226 L/h/m2. The concentrations of the contaminating ion and sophorolipid were insignificant in the permeate, demonstrating the high potential of this approach.

Removal of Ammonium Ions from Aqueous Solutions Using Alkali-Activated Analcime as Sorbent

Five alkali-activated analcime (ANA) sorbents (ANA-MK 1, ANA 2, ANA 3, ANA-MK 4, and ANA-MK 5) were developed for ammonium (NH4+) ion removal. Acid treatment and calcination were used as pre-treatments for analcime, and metakaolin (MK) was used as a blending agent in three sorbents. Sorption experiments were performed to evaluate the effects of sorbent dosage (1–20 g L−1), initial NH4+ ion concentration (5–1000 g L−1), and contact time (1 min–24 h). ANA-MK 1, ANA 2, and ANA-MK 4 were the most efficient sorbents for NH4+ ion removal, with a maximum experimental sorption uptake of 29.79, 26.00, and 22.24 mg g−1, respectively. ANA 3 and ANA-MK 5 demonstrated lower sorption capacities at 7.18 and 12.65 mg g−1, respectively. The results for the sorption of NH4+ ions onto the alkali-activated analcime surfaces were modeled using several isotherms. The Langmuir, Freundlich, Sips, and Bi-Langmuir isotherms were the best isotherm models to represent the studied systems. The results of the kinetic studies showed the maximum NH4+ ion removal percentage of the sorbents was ~80%, except for ANA-MK 5, which had a ~70% removal. Moreover, the pseudo-first-order, pseudo-second-order, and Elovich models were applied to the experimental data. The results showed that the sorption process for ANA-MK 1, ANA 2, ANA 3, and ANA-MK 4 followed the Elovich model, whereas the pseudo-second-order model provided the best correlation for ANA-MK 5.

CONSTRUCTION OF NITRIFICATION MODEL WITH NITRIFYING COAL ASH IN AEROBIC TREATMENT OF HIGH STRENGTH WASTEWATER

Nitrifying carriers can provide good settle ability and stable removal efficiency for nitrogen. Models for ammonia removal rate for nitrifying carriers will improve its engineering application. This study was conducted in nitrifying coal ash system with Monod model. Results indicated the maximum NH4+-N removal rate and half-saturation constant of NH4+-N in Monod model were 110.48 mg/L and 59.19 mg/L, respectively. Introduction of the correction coefficients, including pH, temperature and dissolved oxygen (DO) concentration, decreased the average gap between experiment data and simulated data from 6.48 to 2.74 mg N/(L·h). And improved accuracy of the Monod model by 5.11%. The differences between experiment and simulated NH4+-N removal rate ranged from 0.08 mg N/(L·h) to 8.34 mg N/(L·h) when the influent concentration of NH4+-N increased from 443.18 to 1121.29 mg N/L and without organic. Only 0.08% inconsistency between experiment and simulated data occurred in treating wastewater with high-strength ammonia. However, NH4+-N removal rate of the nitrifying coal ash was inhibited about 40% when influent with averaged 173.19 mg COD/L and 37.20 mg N/L, therefore, other factors, the content of nitrifying bacteria for example, need to be introduced into the Monod model when treating organic wastewater.

Comparative assessment on ammonia nitrogen adsorption onto a saline soil-groundwater environment: distribution, multi-factor interaction, and optimization using response surface methodology and artificial neural network.

The adsorption of soil can reduce the leaching of NH4+-N from the external environment into groundwater. The adsorption of NH4+-N is affected by many factors. It is critical to use statistical model to quantitatively describe the effects of interaction between two or more factors on the system response. In this study, HJ-Biplot was used to analyze the correlation characteristics of soil water, salt, and nitrogen, and the response surface methodology and artificial neural network were used to statistically visualize the interaction between factors, including concentration, total dissolved solids (TDS), temperature, and pH. The results showed that the study soil was a typical saline soil, with maximum soil NH4+-N content of 85.45mg/kg. For the adsorption experiments of NH4+-N on saline soils, the effects of factors on the adsorption capacity were assessed using the RSM model. The RSM model was coupled with an ANN to predict the adsorption of NH4+-N by saline soils. The NH4+-N concentration and water pH were both significant at a linear level (p < 0.0001). The interaction between NH4+-N concentration and pH was also more significant (p < 0.01). Under optimal conditions (concentration: 800mg/L; temperature: 24°C; TDS: 637mg/L; pH: 7.83), the NH4+-N adsorption capacity was 1650.2 ug/g, which was in general agreement with the calculated values from the Box-Behnken and RSM model. In addition, a statistical error criterion for the model showed that the RSM-ANN model had greater predictive ability than RSM model.

Simultaneous nitrification and denitrification by controlling current density and dissolved oxygen supply in a novel electrically-induced membrane bioreactor

In this work, a simultaneous nitrification and denitrification (SND) process in a novel electrically-induced membrane bioreactor (eMBR) was established to treat nitrogen (N) and carbon wastewater. The impact of applied current density (CD) on the important operational parameters of the eMBR was also explored. Furthermore, the performance of denitrification and N-removal at various applied CDs (0–23 A/m2) were investigated. Results showed that high biological oxidation of NH4+−N and total nitrogen (TN) removals were attained at an intermittent CD of 12.5 A/m2 with a low aeration (<2.5 mg/L DO) provided by the eMBR system. The maximum NH4+−N and TN removal efficiencies of the eMBR were 98.71% and 83.75%, respectively. The average denitrification rate was enhanced by the adequate application of DC fields to the eMBR with an increase of NO3−−N removal efficiency from 8.3% to 90.5% and SND rate from 40.3% to 96.28%. It is possible that autotrophic and heterotrophic denitrification together contributed to the high performance of the eMBR process and the complete removal of the nitrate, thereby achieving average TN effluent concentrations of <5 mg/L. The eMBR also reached constant and substantial chemical oxygen demand (COD) removal efficiencies of 99.45%. Taken together, such technology presented in this work could potentially decrease energy demands and could lead to the further development of an energy self-sustained N-removal process. The eMBR could be used in a new WWTP design or for retrofitting existing treatment plants.