Removal Rates Of NH4 Research Articles

Treatment of fishery wastewater by co-culture of Thalassiosira pseudonana with Isochrysis galbana and evaluation of their active components

Microalgae can synthesize their own active substances by absorbing nitrogen, phosphorus in wastewater to provide the nourishing bait for the aquatic organisms, when purifying the aquaculture wastewater. This research Thalassiosira pseudonana (Tp) and Isochrysis galbana (Ig) were selected to treat fishery wastewater and then evaluation of their active components. The results showed that the highest biomass productivity of Tp and Ig was 0.11 g·L−1·day−1 and 0.14 g·L−1·day−1, respectively, at the optimal initial inoculum biomass of 0.4 g·L−1. Furthermore, the two strains were co-cultured in different initial inoculum volume ratios, and the highest biomass was at the volume ratio of 1:1. With the most suitable inoculum biomass and volume ratio, the removal rates of NH4+-N, TN and TP were 80.65%, 85.29% and 92.75%, respectively. Moreover, the cells after wastewater treatment showed high contents of carbohydrate, protein, and lipid, which were 36.62%, 8.72% and 23.11%, respectively. This study showed that co-culturing Thalassiosira pseudonana with Isochrysis galbana to treat fishery wastewater is feasible, and algae cells have high nutritional value, which may provide a feasible technology for ecological protection and resource utilization of aquaculture.

Effect of Hydraulic Residence Time on Removal Efficiency of Pollutants in Subsurface Flow Constructed Wetlands and Analysis of Denitrification Mechanism

This study used vertical and horizontal subsurface constructed wetlands with continuous inflow, to compare and analyze the effects of four hydraulic residence times on the removal efficiency of conventional pollutants. Using the optimal hydraulic retention time, the two types of wetlands were examined in terms of the stromal layer nitrification, denitrification, and ammonia oxidation abundance of functional genes, as well as the intensity of nitrification and denitrification. In addition, redundancy analysis and variance decomposition analysis were used to determine the main factors affecting nitrogen removal in the two kinds of wetlands, so that targeted improvement measures can be suggested. The best removal efficiency of conventional pollutants (COD, TP, TN, and NH4+-N) was achieved with a hydraulic retention time of 24 h, resulting in a removal rate of more than 70%. With a 24 h retention time, the removal rate of NH4+-N and TN and the intensity of nitrification and denitrification exhibited a gradually decreasing trend along the flow direction. Among the three functional genes, the abundance of denitrification functional genes (nirS) was much higher than that of nitrification functional genes (nxrA) and ammonia oxidation functional genes (AOB-amoA). In this study, the nitrogen removal ability of the two subsurface flow constructed wetlands was jointly affected by environmental factors and microbial factors, among which microbial factors contributed the most to nitrogen removal (55% and 48%). In addition, the removal rates of TN and NH4+-N were proportional to DO, specific surface area of substrate, COD concentration, as well as nitrification and denitrification functional genes, but inversely proportional to pH. Therefore, in order to improve the nitrogen removal efficiency of both systems, the amount of dissolved oxygen and carbon sources in the substrate layer should be increased, while the pH value should be appropriately reduced. Moreover, the horizontal subsurface constructed wetland significantly improves the nitrogen removal efficiency of the system, as the substrate layer has a larger specific surface area. This study provides a theoretical basis for the design of constructed wetlands and the selection of an optimal hydraulic residence time. Quantitative analysis of nitrogen removal pathways is of great significance for understanding the nitrogen removal mechanism and improving the nitrogen removal rate in constructed wetlands.

Enrichment of Antibiotic Resistant Bacteria and Antibiotic Resistance Genes by Sulfamethoxazole in the Biological Treatment System of Mariculture Wastewater

Although antibiotics are heavily used in mariculture, only a small portion of the added antibiotics is absorbed. Little is known about the response process of antibiotics, antibiotic resistant bacteria, and antibiotic resistance genes to antibiotic-containing wastewater entering a wastewater treatment system. In this study, an anoxic/aerobic moving bed biofilm reactor (A/O-MBBR) was used to treat marine aquaculture wastewater containing sulfamethoxazole (SMX). The antibiotics and resistance genes in the reactor were then evaluated under selective SMX pressure, and the changing abundance patterns and the response of microbial communities and cultivable resistant bacterial populations were further explored. The results show that with an influent SMX concentration of 500 μg ·L-1 and a hydraulic retention time of 8 h, SMX had a slight effect on the removal rate of NH4+-N and NO2--N, following which the performance gradually recovered. During this stage, SMX removal reached approximately 32%, with more than 78% of SMX removed from the hypoxic zone. The resistance gene was more significantly enriched in the hypoxic zone than in the aerobic zone. In the hypoxic zone, the absolute abundance of gene sul1 increased by 2.43 log, whereas that of gene sul2 increased by 1.71 log. In the region, the absolute abundance of sul1 increased by 1.17 log, whereas that of sul2 increased by 0.91 log. Resistant plate culture and high-throughput sequencing showed that the genus Pseudoalteromonas was the most dominant culturable resistant bacteria in the reactor. The genus Pseudomonas predominated in the uncultured resistant bacteria in the reactor. This study showed that marine aquaculture wastewater containing SMX promotes the enrichment of resistance genes, causing the abundance of some resistant bacteria to increase significantly.

Performance of hybrid-constructed floating treatment wetlands in purifying urban river water: A field study

Floating treatment wetlands (FTWs) are a new management method for improving urban stormwater runoff. However, most studies have been performed at laboratory, micro, and meso scales. Therefore, it is necessary to evaluate the purification effect of the ecological floating bed in urban water bodies under in situ conditions. The purpose of this study was to compare the treatment potential of two types of hybrid-constructed FTWs for urban river water, and to quantify the effects and concentration radii of dissolved oxygen (DO), water temperature (T), nitrate nitrogen (NO3−-N), ammonia nitrogen (NH4+-N), and total phosphorus (TP) under different rainfall conditions. The difference analysis in the first rainfall stage (p < 0.05) indicated that FTWs with multiple plant species (FTW-A) and FTWs with a single species (FTW-B) had significantly better treatment potential than the blank control for all water quality parameters except T. The second stage study showed that the hybrid system could effectively purify the river water during the rainfall period, and the effect of FTW-A was higher than that of FTW-B. After the initial rainfall, DO decreased, NH4+-N and TP concentrations increased, the removal rate of NH4+-N decreased to 55.88%–58.33%, and the removal rate of TP decreased to 5.00%–10.53%. During continuous rainfall, the removal rate of NH4+-N remained between 16.28% and 63.89%, while the removal rate of TP fluctuated, reaching 26.32%, although the final concentration of TP was not removed during the experimental period. Meanwhile, the hybrid constructed FTW continuously increased the DO concentration; however, denitrification was inhibited, resulting in ineffective removal of nitrate and nitrogen in the water body. Further study on the influence radius of two types of FTWs on DO, T, NO3−-N, NH4+-N, and TP found that the influence radius of FTWs varied with the concentration of each parameter. For the same parameter, the influence radius of FTWs with multiple plant species and FTWs with a single species was RFTW-A ≥ RFTW-B. In this study, the purification effect of hybrid-constructed FTW in urban water was evaluated, which provided guidance and support for the FTW site layout of actual river courses in the future.

Bio-clogging mitigation in vertical subsurface flow constructed wetlands using rhamnolipids-citric acid compound

Sustainable operation of constructed wetlands (CWs) is challenging due to bio-clogging caused by the excessive aggregation of extracellular polymeric substances (EPS) in substrate interspaces. In this study, rhamnolipids (RLs) and citric acid (CA) were used as solubilizers in situ with the influent to mitigate bio-clogging in CWs for the first time. Four lab-scale CWs with vertical subsurface flow were set to validate the efficiency of CA-RLs. After solubilization treatment with CA-RLs, the effective porosity of CWs restored to about 83.0% of the initial. RLs could solubilize and disperse blockage, and CA further promote the effects by destroying the stable structure of EPS. The surface contact angle became larger after CA-RLs treatment, as did the absolute zeta potential of EPS, attributed to the solubilization of hydrophobic EPS. CA-RLs inhibited the surface adhesion of cells and dissociated EPS into small particles, reduced the aggregation ability of EPS. The EEM-PARAFAC analysis showed solubilization treatment increased the tryptophan-like or protein-like components in effluent. Furthermore, the rehabilitative porosity after CA-RLs solubilization treatment provided suitable conditions for the growth of denitrifiers (especially Rhodopseudomonas and Rubrivivax), conducive to recover the performance of CWs. After bio-clogging mitigation, the removal rates of NH4+-N (25–30%) and COD (50–55%) in CWs gradually recovered to 55–70% and 70–75%, respectively. These findings provided a better understanding of the bio-clogging characteristics, which were helpful to mitigate bio-clogging in CWs.

Pilot-Scale Airlift Bioreactor with Function-Enhanced Microbes for the Reduction of Refinery Excess Sludge.

A pilot-scale airlift bioreactor (ALBR) system was built and operated continuously for refinery excess sludge (RES) reduction. Combined ALBR and function-enhanced microbes (composed of photosynthetic bacteria and yeast) were integrated into the system. The pilot-scale ALBR was operated for 62 days, and the start-up time was 7 d. Continuous operation showed that the sludge reduction efficiency was more than 56.22%, and the water quality of the effluent was satisfactory. This study focused on investigating the effects of hydraulic retention time (HRT) on the stability of the system and the effect of sludge reduction. Under different HRT conditions of 40, 26.7, 20, and 16 h, the sludge reduction rates reached 56.22%, 73.24%, 74.09%, and 69.64%, respectively. The removal rates of chemical oxygen demand (COD) and total nitrogen (TN) decreased with decreasing HRT, whereas the removal rate of NH4+-N increased. The removal rate of total phosphorus (TP) was approximately 30%. Results indicate that the ALBR and function-enhanced microbe system can reduce sludge and treat sewage simultaneously, and the effluent is up to the national emission standard. Addition of function-enhanced microbes can promote the degradation of petroleum hydrocarbon substances in the sludge, especially alkanes with low carbon numbers. This study suggests that the optimal HRT for the system is 16 h. The total operation cost of the ALBR combined with the function-enhanced microbe system can be reduced by 50% compared with the cost of direct treatment of the RES system.

Transformation of N and S pollutants and characterization of microbial communities in constructed wetlands with Vallisneria natans

The simulated constructed wetland with Vallisneria natans was studied for the migration and transformation of dissolved oxygen, nitrogen and sulfur pollutants and characterization of microbial community under different concentrations (7.5, 15, 22.5, 30 mgN/L) of NH4+-N. Results indicated that the recovery rate of DO was 0.027–0.07 mg/h, and the removal rate of NH4+-N was over 90%. Meanwhile, S2− was generated into different forms when the DO and the sulfate concentration were below 1 mg/L and over 100 mg/L, respectively. In addition, 16S rRNA sequencing analysis showed that after 30 days, the microbial diversity in both sediments declined, while that in the biofilms of leaves increased by 16.42%. Overall, Vallisneria natans can change microbial communities by releasing oxygen and provide attachment system to form biofilms. When Cinlet(NH4+-N) < 22.5 mgN/L, Cinlet(SO42−) < 135 mg/L, Vallisneria natans can effectively prevent water quality deterioration and strengthen the in-situ self-purification ability of water.

Integration of Algal Biofuel Production with Municipal Wastewater Treatment: a Review

The integration of algae-based wastewater treatment and biofuel production has been of growing research interest in recent years. This article reviewed recent researches in algae biofuel production and the integration of algal wastewater treatment and biofuel production. The methods to algal biofuel production, biofuel productivity, and removal rate of treated municipal wastewater were summarized in this review. Chlorella is largely used, especially in biodiesel and bioethanol production. Spirulina is more often used to produce biogas. The removal rate of NH4+-N can be high in this integration. The most common biofuel products in this integration are biomethane and lipid. Traces of the integration are numerous on laboratory basis and limited in commercial use for now. The barrier to apply it from lab to commercial use may include a high cost during algae harvesting as well as land use and availability. Possible solutions and research gaps are outlined in this article.

Enrichment and domestication of a microbial consortium for degrading aniline

In this study, a microbial consortium was enriched and acclimated to degrade aniline by the aerobic bioreactor. The system achieved a high degradation efficiency of aniline (over 99%) within a short period. Meanwhile, the removal rate of NH4+-N was up to 33.3%. The dominant populations of Comamonas and Zoogloea were critical for maintaining the removal performance. Ortho-cleavage and meta-cleavage pathways were responsible for degrading aniline. Our work presented that the microbial consortium could effectively treat aniline, and provided a potential alternative for eliminating aniline.

Study on Start-up Performance of Anammox Process

Anammox, as one of the most revolutionary new denitrification technologies so far, has broad application prospects. In order to explore the start-up process of the anaerobic ammonia oxidation process, the experiment was conducted to domesticate anaerobic sludge in an up-flow anaerobic sludge bed reactor. The results showed that the reactor reached a stable operation stage from the 95th day to the 112th day. The removal rate of NH4 +-N and the removal rate of NO2 −-N were stabilized at 94.12% and 97.70%, respectively. According to the removal of NH4 +-N and NO2 −-N in the reactor, the start-up process can be divided into 4 stages, and there is denitrification and synergistic anaerobic ammonia oxidation in the reactor.

A New Type of Ecological Floating Bed Based on Ornamental Plants Experimented in an Artificially Made Eutrophic Water Body in the Laboratory for Nutrient Removal.

In this study, a new type of ecological floating bed (NT-EFB) employing ornamental plants (either Spathiphyllum floribundum, Hydrocotyle sibthorpioids, Chlorophytum comosum or Peperomia obtusifolia) was designed to purify confected eutrophic water for 39days. The growth characteristics of the plants and the effect of water treatment were analyzed and compared. The results showed that: (1) all the four ornamental plants examined survived well in the eutrophic water and an increase of plant biomass was observed; (2) the degradation efficiency of TOC by adding plants was about 85.0%; (3) the removal rate of NH4+-N was about 97.0%; (4) all the four plants can be used as floating bed plants to treat eutrophic water and Hydrocotyle sibthorpioids had the best growth characteristics and treatment efficiency. The study provides an adequate reference for the treatment of eutrophication using ecological floating beds.

Effect of Fe on Nitrogen Removal Rate and Microbes of Anammox

With the anammox sludge as the inoculation sludge, the effect of different concentrations of Fe2+ and Fe3+ on the denitrification performance of the anammox reaction was explored by setting a control experiment.The results showed that when the Fe2+ concentration was 0.08mmol/l, the reactor had the best removal efficiency, the removal rate of NH4+-N was 89.14% after 60h, and the removal rate of NO2--N was 85.9%. The positive effect of Fe3+ on the anammox reaction was similar to that of Fe2+. From reading the literature, it can be known that Fe has a positive impact on anammox microorganisms in three aspects by promoting microbial enrichment, promoting the production of functional enzymes, and promoting microbial granulation.

Catalytic ozonation of NH4+-N in wastewater over composite metal oxide catalyst

Large amounts of water containing-ammonium nitrogen (NH4+-N) have attracted increasing attention. Catalytic ozonation technology, involving the generation of hydroxyl radical (·OH) with strong oxidation ability, was originally utilized to degrade organic-containing wastewater. In this paper, Ce/MnOx composite metal oxide catalysts prepared with different preparation conditions were used to degrade wastewater containing inorganic pollutant (NH4+-N). The as-prepared catalyst features were characterized using X-ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and H2-temperature programmed reduction (H2-TPR) techniques. The results show that the catalyst, prepared by conditions with precipitant Na2CO3 and Ce/Mn molar ratio 1:2 calcined at 400 °C for 3 h in pH 11.0, displays the optimal performance, with the removal rate of NH4+-N and selectivity to gaseous nitrogen, 88.14 wt% and 53.67 wt%, respectively. The effects of several operating factors including solution pH, initial NH4+-N concentrations and scavengers were evaluated. In addition, XRD patterns of catalyst with the best performance and the comparative study on decontamination of NH4+-N by various processes (O3, catalyst and catalyst/O3) show that the primary metal oxides are CeO2 and MnO2 in Ce/MnOx composite metal oxide catalysts, which have a synergistic effect on the catalytic ozonation of NH4+-N, and the new phase MnO2 plays a great role. After 5 consecutive use cycles, the degradation efficiency is declined slightly, and can still achieve better than 70 wt% over 1 h reaction. Additionally, the application of catalytic ozonation for actual wastewater on the removal rate of NH4+-N was investigated. Possible mechanism and degradation pathway of NH4+-N were also proposed. In a word, the application of CeO2–MnO2 composite metal oxide catalysts in catalytic ozonation can be regarded as an effective, feasible and promising method for the treatment of NH4+-N.

Removal of nitrogen from rainwater runoff by bioretention cells filled with modified collapsible loess

The construction of bioretention facilities in collapsible loess areas faces some problems such as low infiltration rate of rainwater runoff and system blockage, which seriously affect the treatment effect of bioretention cell on rainwater runoff. According to the different filler matrix, three bioretention cells with improved filler were constructed, the 1# bioretention system was filled with 50% of the construction waste mixed with 50% loess, and the 2# bioretention system was filled with 50% concrete sand mixed with 50% loess, the 3# bioretention system was filled with 45% concrete sand +10% wood chips +45% loess mixed in the bioretention cell. The results show that the removal rate of NH4+-N is the highest when the height of the inundation zone of the bioretention cell is 600 mm (more than 98%). The change of hydraulic load and submerged zone height had a significant effect on the removal rate of NO3−-N in bioretention cell (P < 0.05). The removal rate of NO3−-N in the bioretention cell decreased with the increase of hydraulic load, and the bioretention cell had the highest removal rate of NO3−-N (48.85%) under low hydraulic load conditions. The removal rate of NO3−-N in the bioretention cell increased with the increase of the height of the inundation area, and the removal rate of NO3−-N was the highest when the inundation area height of the bioretention cell was set at 600 mm (98.33%). The improved bioretention cell has a better effect on NH4+-N treatment during the wet period, and the NH4+-N concentration of the effluent is below 0.4 mg/L. The NO3−-N concentration in the effluent of the three improved bioretention cells during the wet period differed greatly. Among them, the bioretention cells using sawdust modified fillers had the highest removal rate of NO3−-N. The collapse amount of the three improved bioretention cells was below 0.5 cm, and the permeability coefficients were above 2 cm/h. The experiment proves that the three methods to improve the collapsible loess filler can be applied to the construction of the bioretention cell in the collapsible loess area so that the bioretention technology can be effectively promoted in the loess area. This experiment has great significance to the construction of bioretention cells in the loess area.

Spontaneous formation and mechanism of anaerobic ammonium oxidation (anammox) bacteria in swine wastewater treatment system

The anaerobic ammonium oxidation (anammox) process is a new and cost-effective green technology for inorganic nitrogen removal in wastewater treatment plants (WWTPs). Red activated sludge granules were found in a swine wastewater treatment system of Guangdong Province using two-stage A/O processes. In order to test the anammox process in the wastewater treatment system, both practical and simulation experiments were conducted, including water quality determination, nitrogen balance, 15N isotope tracing and 16S rRNA sequencing. The results showed that inorganic nitrogen and NH4+-N were removed from the first-stage aerobic tank by 94% and 99.99%, respectively. Anammox granules formed under a DO of 0.19–0.54 mg/L, C/N of 0.60, and COD <300 mg/L. In the laboratory experiment, the removal rates of NH4+-N and NO2−-N by the red granules (50 g) were 18.14 mgN·L−1·h−1 and 18.99 mgN·L−1·h−1, respectively, confirming that the anammox process was involved. Candidatus Brocadia was the main anammox bacteria, accounting for 16.5% of the relative abundance among nitrogen removal bacteria in the red granules, cooperating with denitrifying bacteria (DNB) and ammonia oxidizing bacteria (AOB) in removing nitrogen. Anammox bacteria occur naturally in swine wastewater treatment systems and provide promising evidence for future direct application of this technology in treating swine wastewater at full scale.

Enhanced removal of NH4 + in bioretention by sludge biochar

Both bioretention and sludge biochar have better effects to the removal of nitrogen and phosphorus removal in water. Combining them coulid improve the effect of bioretention on NH4 +. After applying sludge biochar, the adsorption effect of filler on NH4 + was improved. When the sludge biochar was applied to the filler, on the top of the submerged area in the tank, the removal rate of NH4 + could reach 88.62%∼94.48%.

Co-occurrence of microplastics and triclosan inhibited nitrification function and enriched antibiotic resistance genes in nitrifying sludge

As more and more microplastics (MPs) and triclosan (TCS), which are added in consumer products, enter wastewater treatment plants with sewage, there are concerns about the impacts of the co-occurrence of MPs and TCS on biological wastewater treatment. In this study, the co-effects of four 1 mg/L MPs (polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC) and polyamide (PA)) and 0.5 mg/L TCS on nitrification were investigated in lab-scale nitrifying sequencing batch reactors (SBRs) (SBR-PE, SBR-PS, SBR-PVC and SBR-PA) relative to control which received no MPs (SBR-CK). The removal rates of NH4+-N and TCS in SBR-CK were around 100% and 92%, respectively. Compared with SBR-CK, no measurable inhibition was observed on nitrification in SBR-PE and SBR-PS, however, SBR-PVC and SBR-PA rapidly lost nitrification function during 14 days, which might be due to the reducing of MLSS caused by PVC, PA and TCS co-loading. Furthermore, PS, PVC and PA decreased the removal of TCS. The co-occurrence of TCS and PS, PVC, PA increased extracellular polymeric substances, reduced microbial diversity and shifted microbial communities. Notably, the acrA-03, mexF, fabI, intI1, intI3 and IS613 genes were enriched by MPs and TCS co-loading. Therefore, the removal of MPs and TCS from wastewater should be prioritized.

Start-up of an Integrated Process of Denitrifying Phosphorus Removal Coupled with Partial Nitritation and Anaerobic Ammonium Oxidation

An integrated process uses an anaerobic baffled reactor combined with a fully mixed reactor (ABR-CSTR) as a test carrier for low-carbon, high-ammonia nitrogen (NH4+-N ≥ 200 mg·L-1) wastewater under continuous flow operating conditions; the normal anaerobic sludge in different compartments is subjected to domestication and cultivation to realize denitrifying phosphorus removal, partial nitritation, and anaerobic ammonium oxidation, thereby achieving the coupling effect of the three. Partial nitritation was successfully achieved in the A4 (CSTR) section by the strategy of limited oxygen (dissolved oxygen DO=0.8 mg·L-1) and intermittent aeration (exposure ratio=30 min:30 min) after 30 days. Subsequently, a strategy of shortening the hydraulic retention time (HRT) was adopted to achieve a stable operation of partial nitritation, and a stable influent substrate of NO2--N/NH4+-N 1.0-1.1 was provided for anaerobic ammonium oxidation. The anaerobic ammonium oxidation function was achieved after 154 days in the A5 and A6 compartments. The removal rates of NH4+-N and NO2--N were 94% and 97%, respectively, and the NO3--N concentration in the effluent was stable at 22 mg·L-1. The denitrifying phosphorus removal function was successfully achieved in the A1-A3 compartments by using NOx--N in the reflux as an electron acceptor. The removal rate of PO43--P was 77%. The integrated process was successfully coupled through 175 days, achieving simultaneous removal of C, N, and P.

Cow manure anaerobic fermentation effluent treatment by oxygen-based membrane aerated biofilm reactor

After cow manure undergoes anaerobic fermentation process, it still contains several pollutants such as nitrogen, phosphorus, and organic matter. If not treated properly, these pollutants would cause secondary pollution. Membrane-aerated biofilm reactor (MABR) has been widely used to handle the wastewater with high concentration contaminants. In this study, MABR was utilized to treat the cow manure anaerobic fermentation effluence (CMAFE). In order to avoid incomplete biofilm being affected by high concentration of CMAFE, a gradient dilution of CMAFE was employed. The removal rates of NH4+-N and COD were achieved up to 90% and 85%, respectively, in different dilution ratios. RDA demonstrated that NH4+-N removal was in a full-nitrification process in higher dilution ratio (Stage 1 and 2) but in short-nitrification in lower dilution ratio (Stage 4). The gradient dilution did not affect the biofilm growth. The Inner biofilm contained higher amounts of extracellular polymeric substance (EPS) than the Outer biofilm, which reduced the impact of high-concentration CMAFE on the internal aerobic bacteria, especially nitrifying bacteria. Concerning bacteria abundance, a significant modification occurred in the biofilm compared to raw sludge, demonstrating that MABR had a great potential in CMAFE treatment.

Preparation and characterization of a copper phosphotungstate/titanium dioxide (Cu-H3PW12O40/TiO2) composite and the photocatalytic oxidation of high-concentration ammonia nitrogen

Currently, the majority of wastewater with a high concentration of ammonia nitrogen (NH4+/NH3) is treated using biological methods, which have poor biodegradability and low removal efficiency. In this paper, a composite photocatalyst of copper phosphotungstate/titanium dioxide (Cu-H3PW12O40/TiO2) was prepared by sol-gel hydrothermal synthesis, and the composite catalyst was characterized by X-ray diffraction (XRD), UV–vis-diffuse reflectance spectroscopy (UV-VIS-DRS), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS)、scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The photocatalytic oxidation of a high-concentration NH4+/NH3 solution was carried out under ultraviolet (UV) light to explore the effects of different influencing factors on the photocatalytic effect and to optimize the reaction conditions. The prepared composite catalyst exhibited higher photocatalytic activity than that of TiO2. When the initial concentration of the solution was 300 mg·L−1, the initial pH was 11, the catalyst concentration was 1.5 g·L−1, the loading level of Cu-H3PW12O40 was 40%, and the aeration rate was 1.5 L·min−1, the removal rate of NH4+/NH3 by the composite photocatalyst could reach >80%. Very little NO2− and NO3− were produced, and N2 was the main product.