Effective Nitrogen Removal Research Articles

Revealing mechanisms of triclosan on the removal and distribution of nitrogen and phosphorus in microalgal-bacterial symbiosis system

Microalgal-bacterial symbiosis (MABS) system performs synergistic effect on the reduction of nutrients and carbon emissions in the water treatment process. However, antimicrobial agents are frequently detected in water, which influence the performance of MABS system. In this study, triclosan (TCS) was selected to reveal the effects and mechanisms of antimicrobial agents on MABS system. Results showed that the removal efficiencies of chemical oxygen demand, NH4+-N and total phosphorus decreased by 3.0%, 24.0% and 14.3% under TCS stress. In contrast, there were no significant decrease on the removal effect of total nitrogen. Mechanism analysis showed that both the growth rate of microorganisms and the nutrients retention capacity of extracellular polymeric substances were decreased. The intracellular accumulation for nitrogen and phosphorus was promoted due to the increased cytomembrane permeability caused by lipid peroxidation. Moreover, microalgae were dominant in MABS system with ratio between microalgae and bacteria of more than 5.49. The main genus was Parachlorella, with abundance of more than 90%. Parachlorella was highly tolerant to TCS, which might be conductive to maintain its survival. This study revealed the nutrients pathways of MABS system under TCS stress, and helped to optimize the operation of MABS system.

Action Mechanism of Bacillus on Microalgae During Nitrogen Metabolism in Urban Tailwater

To improve deep denitrification of black and odorous water and improve the quality of surface water, we studied the characteristics of nitrogen metabolism and denitrification of urban tailwater by microalgae (Z), Bacillus (Y), and Bacillus microalgae (ZY). The results showed that there was a good removal effect of ammonia nitrogen of group Z and group ZY in urban tailwater. The degradation rate of both groups reached 95%. The best effect on the removal of nitrite nitrogen was of group Z in urban tailwater. The combined action of Bacillus and Micrococcus played a relatively strong and stable effect on the conversion of nitrite nitrogen to nitrate nitrogen in the nitrogen cycle reaction. Bacillus could effectively remove nitrate nitrogen and improve the removal efficiency of nitrate nitrogen by microalgae. Best removal effect of nitrate nitrogen was observed in group ZY in urban tailwater, with a degradation rate as high as 99%, in which the nitrate nitrogen was removed almost completely. The Bacteria with high proportions in Z were Chroococcidiopsis_PCC_7203 (24.38%), uncultured_bacterium-g_norank_f_A4b (23.65%), Exiguobacteriu (7.09%), Leptolyngbya_PCC-6306(9.41%), and Bacillus (1.99%). The bacteria with high proportions in ZY were Brevibacillus (22.94%), Clostridium (8.78%), and Bacillus (4.88%), and the proportion of Chroococcidiopsis_PCC_7203 was only 7.84% in ZY, which was considerably lower than that in Z samples. The conclusions were as follows:microalgae could effectively remove ammonia nitrogen in the system. Bacillus and microalgae had very good removal effect of ammonia nitrogen and nitrate nitrogen. During the nitrogen removal of black and odorous water by algae, the Bacillus inhibited the excessive growth of microalgae and prevented eutrophication and black odor in water. This study can provide data support for the deep treatment of urban tail water and prevention of surface water eutrophication.

Enhanced nutrients removal and microbial mechanisms in a pilot-scale anaerobic-oxic-anoxic (A/O/A) system: Synergistic roles of denitrifying polyphosphate accumulating organisms and endogenous denitrifiers

The realization of low-cost and high-standard nutrients removal are not acquired effectively in conventional pre-denitrification biological nitrogen removal processes (e.g., anaerobic/anoxic/oxic (A/A/O) process) for the treatment of domestic sewage. In this study, a pilot-scale bioreactor system based on the synergism of denitrifying phosphorus removal (DPR) and endogenous denitrification (ED) was proposed for advanced nutrients removal, which was operated under alternating anaerobic/oxic/anoxic (A/O/A) mode with no extracellular carbon source in the anoxic stage. The results showed that A/O/A and A/A/O systems were successfully established and operated in four stages with different mixed liquor suspended solid (MLSS, I: 3.32 ± 0.25 g/L, II: 5.89 ± 0.94 g/L, III: 8.66 ± 0.51 g/L, IV: 9.11 ± 5.72 g/L). Compared with the A/A/O system, the A/O/A system showed significantly higher nitrogen and phosphorus removal effectiveness within hydraulic retention time of 10 h. At MLSS of 8.66 ± 0.51 g/L, the A/O/A system could achieve simultaneously efficient removal of COD (91.47% ± 2.06%, 2.97 ± 0.26 mg COD/(g MLSS·h)), NH4+-N (97.27% ± 1.23%, 0.37 ± 0.06 mg NH4+-N/(g MLSS·h)), TN (89.94% ± 1.47%, 0.45 ± 0.03 mg TN/(g MLSS·h)), and PO43--P (96.67% ± 0.88%, 0.04 ± 0.01 mg PO43--P/(g MLSS·h)), and the effluent concentrations of COD, NH4+-N, TN, and PO43--P were 24.0 ± 3.1, 0.9 ± 0.4, 4.4 ± 0.6, and 0.13 ± 0.03 mg/L, respectively. In addition, microbial community results indicated that denitrifying polyphosphate accumulating organisms and endogenous denitrifiers synergistically enhanced the nutrients removal capacity in the A/O/A system. Overall, this work provides new insight for further scaling and optimization of the A/O/A system.

Influence of Sediment, Plants, and Microorganisms on Nitrogen Removal in Farmland Drainage Ditches

The removal of nitrogen from water is a consequence of the synergistic action of plant uptake, sediment sorption, and microbial decomposition. However, there is a lack of long-term experimental studies on the effects of each component in the process of nitrogen removal. In this study, we investigated the effect of sediment, plants, and microorganisms on nitrogen removal by setting up three systems: water–sterilized sediment, water–sediment, and water–sediment–plant. The nitrogen removal effect followed the following rank order of effectiveness: the “water–sediment–plant” system > the “water–sediment” system > the “water–sterilized sediment” system. The ditch sediment had a strong enrichment effect for nitrogen. In addition, the migration rate of nitrogen in the sediment with different depths was different. The ammonia-nitrogen migration rate in the sediment showed an increasing trend with time and depth. The nitrate-nitrogen migration process in the sediment showed a trend of enrichment toward the middle layer (15.0–25.0 cm). Aquatic plants and microorganisms can promote the removal of nitrogen in water, with the average purification rates of 13.92% and 19.92%, respectively.

Isolation and Identification of a Carbon-Fixing Bacteria Strain and Its Efficiency for Nitrogen and Phosphorus Removal from Viaduct Rainwater

In order to explore bacteria resources that are applicable for purification of viaduct rainwater, a carbon-fixing bacteria strain numbered 1C-1 was isolated from the sediment of a viaduct rainwater tank. The strain was identified through morphological characteristics and 16S rDNA sequences. The effects of three main factors (the simulated viaduct rainwater concentration, the carbon source dosage, and the inoculation amount) on the nitrogen and phosphorus removal rate of the strain were tested using simulated viaduct rainwater. Based on this, the nitrogen and phosphorus removal efficiencies for the actual viaduct rainwater were verified. The results showed that the strain belonged to Streptomyces sp. Under different simulated viaduct rainwater concentrations, the strain exhibited relatively high efficiency for nitrogen and phosphorus removal at the original concentration of simulated viaduct rainwater; other conditions remaining unchanged, the purification efficiency was relatively high when the glucose dosage was 800 mg, and the removal rates of ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) were 71.48%, 47.86%, and 10.43%, respectively; other conditions remaining unchanged, the purification efficiency was relatively high when the inoculation amount was 1%, and the removal rates of NH4+-N, TN, and TP reached 58.62%, 58.35%, and 27.32%, respectively. Under the above optimal process conditions of an original concentration of viaduct rainwater, a carbon source dosage of 800 mg, and an inoculation amount of 1%, the strain removed 92.62%, 6.98%, and 6.16% of NH4+-N, TN, and TP, respectively from the actual viaduct rainwater; more interestingly, the removal rates of NH4+-N and TN were 43.26% and 78.02%, respectively, even without carbon source addition. It seems that there is no need for carbon source addition to remove nitrogen from the actual viaduct rainwater for the strain. To sum up, the carbon-fixing bacteria 1C-1 presents an obvious nitrogen and phosphorus removal effect (especially for nitrogen) for viaduct rainwater treatment and has application potential.

Anaerobic starvation realizes partial nitrification and starts anammox bacteria self-enrichment in mainstream municipal sewage treatment in a low filling ratio sequencing batch reactor

The initiating and stable preservation of partial nitrification (PN) and achievement of anammox bacteria self-enrichment in domestic sewage is a purposeful subject. In this article, an originality tactics of anaerobic starvation for 100 days was adopted for rapidly achieving PN in actual wastewater, the nitrite accumulation rate (NAR) improved from 4.95% to 81.73% in 18 days. After anaerobic starvation was stopped, the stable PN effect furnished enough stroma for the growth of anammox bacteria. The abundance of Candidatus Brocadia grew from 0% to 0.42% in floc sludge and 0.43% in blank biofilm, which promoted nitrogen removal effect. Anaerobic starvation continuing 74 days generated further decrease in the abundance of Nitrobacter and Nitrospira of nitrite-oxidizing bacteria (NOB), indicating that anaerobic starvation can restore the destroyed partial nitrification. In conclusion, this article furnished a low-cost method for achieving anammox bacteria self-enrichment in mainstream municipal wastewater in 10% filling ratio without chemicals addition.

Evolution of aniline degradation and nitrogen removal performance in electro-enhanced sequence batch reactor under salinity stress: Sludge characteristics and microbial diversity

To explore the influence mechanism of different concentrations of salinity on the electro-enhanced aniline biodegradation system, a control group and experimental groups (0%-NaCl, 0.5%-NaCl, 1.5%-NaCl, 2.5%-NaCl, 3.5%-NaCl) were established. The experimental results showed that the electric field strengthened the denitrification performance, while salinity had little effect on the degradation efficiency of aniline and chemical oxygen demand (COD). The removal rate of TN reached 79.6% and 74.9% in 0.5%-NaCl and 1.5%-NaCl, respectively, which were superior than 0%-NaCl. As salinity increased, the nitrogen removal effect was negatively affected. Microbial diversity analysis indicated that the microbial community structure was uniform in the control group, 0%-NaCl, and 0.5%-NaCl, with the dominant genus OLB8 ensuring the nitrogen removal performance. In contrast, in the 2.5%-NaCl and 3.5%-NaCl experimental groups, the organic degrading bacteria were still active, while nitrifiers and denitrifiers were severely damaged. In conclusion, this study suggested that low concentrations of salinity can improve the decontamination performance of the electro-enhanced aniline biodegradation system, while high concentrations of salinity could lead to the collapse of the decontamination mechanism.

Stable isotopes of nitrate (δ15N and δ18O) as functional indicators of nitrogen processing in constructed wetlands

The effectiveness of nitrogen removal in wetlands relies heavily on the biological processes that control its removal. Here, we used δ15N and δ18O of nitrate (NO3−) to assess the presence and the dominance of transformation processes of nitrogen in two urban water treatment wetlands in Victoria, Australia over two rainfall events. Laboratory incubation experiments were undertaken in both light and dark to measure the isotopic fractionation factor of nitrogen assimilation (by periphyton and algae) and benthic denitrification (using bare sediment). Highest isotopic fractionations were observed for nitrogen assimilation by algae and periphyton in the light, 15ε = −14.6 to −25 ‰ while the 15ε = −1.5 ‰ in bare sediment, consistent with that of benthic denitrification. Transect water samplings of the wetlands showed different rainfall patterns (discrete versus continuous) affect the removal capability of the wetlands. During the discrete event sampling, the observed 15ε of NO3− (an average of 3.0 to 4.3 ‰) within the wetland falls between the experimental 15ε of benthic denitrification and assimilation; coinciding with the decrease in NO3− concentrations, suggesting that both denitrification and assimilation were important removal pathways. Depletion of δ15N-NO3− throughout the whole wetland system also suggested the influence of water column nitrification during this time. In contrast, during continuous rain events, no fractionation effect was observed within the wetland and was consistent with limited NO3− removal. The difference in fractionation factors within the wetland during different sampling conditions suggested that nitrate removal was highly likely limited by changes in overall nutrient inputs, residence time and water temperature which impeded biological uptake or removal. These highlight that consideration of sampling condition is crucial when assessing the efficacy of a wetland in removing nitrogen.

Deep Treatment of Tailwater by Aerobic Denitrifying Bacteria Enhanced Biofilter

The high concentration of total nitrogen in the tailwater discharged from some wastewater treatment plants is relatively high, which is easy to cause eutrophication in the receiving water bodies. In this study, the aerobic denitrifying bacteria were combined with denitrifying biofilter through bioreinforcement technology. The aerobic denitrifying bacteria strains W30 and Z66 isolated from activated sludge were used to construct a complex bacterial agent to strengthen the denitrifying biofilter, and the enhanced nitrogen removal effect of the complex bacterial agent was investigated, and the microbial community structure in the system after bioreinforcement was analyzed by high-throughput sequencing technology. The results showed that strain W30 was identified as Pannonibacter and strain Z66 as Pseudomonas by 16S rDNA sequencing analysis. The bioreinforced denitrification biofilter had a fast start-up rate of membrane hanging, and the removal rate of total nitrogen (TN) increased by 9. 36% under natural oxygenation compared with that under aeration; the single-factor test of carbon/nitrogen ratio (C/N) and hydraulic retention time (HRT) determined C/N=4. 27 and HRT=1. 0 h as the optimal working conditions of the filter cell; the highthroughput sequencing results further showed that the percentages of Pannonibacter and Pseudomonas in the denitrifying biofilter decreased from 0. 49% and 2. 56% at the beginning of operation to 0. 073% and 0. 18% after 130 days of operation. A stable denitrification system was formed with Thauera, Dechlorobacter, Exiguobacterium and other genera.

Study on the performance of anodic desulfurization and cathodic denitrification coupled electricity generation in microbial fuel cell

Sulfide autotrophic denitrification microbial fuel cell was set up and the two reaction processes of desulfurization in anode chamber and denitrification in cathode chamber were separated to study nitrogen and sulfur removal effect and electricity generation capacity. The results showed that simultaneous desulfurization in anode chamber and nitrate removal in cathode chamber was feasible. The removal load of sulfide and nitrate almost increased with the increase of their concentrations under the experiment operation conditions. Higher sulfide concentration in a certain range was beneficial to generate electricity. The change of nitrate concentration in the cathode chamber had less effect on sulfide removal efficiency and electricity production performance of microbial fuel cell, which was mainly depended on the influent sulfide concentration in the anode chamber. The maximum sulfide and nitrate removal loads were 0.36 kg∙m−3∙d−1 and 0.07 kg∙m−3∙d−1 respectively, with a maximum power density of 144.03 mW∙m−3. The external resistance affected the quantities and varieties of reaction products in the anode chamber and the cathode chamber. Lower external resistance was beneficial to improve the efficiency of nitrate removal in the cathode chamber. The microbial community structure of the anode chamber in sulfide autotrophic denitrification MFC was similar to that of sulfide autotrophic denitrification SBR, whose main functional bacterial genera were Clostridium, Thiobacillus and Rhodobacteraceae. However, the functional bacteria in the cathode chamber were completely different, whose dominant bacteria included Thiobacillus, Bacillus, Flavobacteriaceae, Acinetobacter, Sphingomonas and Paracoccus. The research results provided a new idea and method for the sulfur- and nitrogen-containing wastewater treatment.

Pilot-scale aerobic granular sludge reactors with granular activated carbon for effective nitrogen and phosphorus removal from domestic wastewater

Aerobic granular sludge (AGS) is a breakthrough biotechnology of 21st century and an innovative alternative to activated sludge for treating wastewater. Concerns on long-start up periods for development of AGS and stability of granules are impeding its widespread implementation for treating low-strength domestic wastewater especially in tropical climate conditions. Addition of nucleating agents have been shown to improve development of AGS while treating low-strength wastewaters. There are no previous studies on AGS development and biological nutrient removal (BNR) in the presence of nucleating agents during treatment of real domestic wastewater. This study investigated AGS formation and BNR pathways while treating real domestic wastewater in a 2 m3 pilot-scale granular sequencing batch reactor (gSBR) operated without and with granular activated carbon (GAC) particles. The gSBRs were operated under tropical climate (T ≈ 30 °C) for >4-years to evaluate the effect of GAC addition on granulation, granular stability and BNR at pilot-scale. Formation of granules was observed within 3 months. MLSS values of 4 and 8 g/L were recorded within 6 months in gSBRs without and with GAC particles, respectively. The granules had an average size of 1.2 mm and SVI5 of 22 mL/g. Ammonium was mainly removed through nitrate formation in the gSBR without GAC. But, ammonium was removed by short-cut nitrification via nitrite due to washout of nitrite oxidizing bacteria in the presence of GAC. Phosphorus removal was much higher in gSBR with GAC due to the establishment of enhanced biological phosphorus removal (EBPR) pathway. After 3 months, the phosphorus removal efficiencies were at 15 % and 75 %, respectively, without and with GAC particles. The addition of GAC led to moderation in bacterial community and enrichment of polyphosphate-accumulating organisms. This is the first ever report on pilot-scale demonstration of AGS technology in the Indian sub-continent and GAC addition on BNR pathways.

Stimulation on microbial nitrogen metabolism by iron under PFAS exposure drives effective nitrogen removal in constructed wetland

Constructed wetlands (CWs) have been employed for treatment of perfluoroalkyl substances containing wastewater. However, suppression on operation performances of CWs was inevitable, particularly on nitrogen removal. In this study, 10–30 mg/L nano zero-valent iron (nZVI) was introduced into CWs because of its potential for driving effective nitrogen removal via promoting functional microbes. Perfluorooctanoic acid (PFOA) exposure led to reduction of ammonia (NH4+-N) transformation, but stimulated nitrate (NO3−-N) removal by up to 83.12 %. With PFOA exposure, 10 mg/L nZVI caused the most significant improvement on NH4+-N removal, with maximum increase of 3.65 %. By contrast, 30 mg/L nZVI was prone to alleviate NO3−-N accumulation by 14.19–24.22 % compared to control group. Lower dosage of nZVI (10–20 mg/L) increased activity of five nitrogen cycling enzymes by 31.42–315.18 % in maximum. Whereas, 30 mg/L nZVI led to limited promotion or even inhibition on these enzymes. Analogously, stimulation on nitrifying, anammox, and denitrifying bacteria, as well as functional key genes were more obvious by nZVI at lower concentration. Besides, nZVI reduced functional gene of dissimilatory nitrate reduction to ammonium and related bacteria, increasing NH4+-N removal indirectly. The most promotion on nitrate dependent Fe oxidation bacteria like Paracoccus could explain improvement on NO3−-N removal by 30 mg/L nZVI.

Liquid-gas phase transition enables microbial electrolysis cell to treat organic pollution and synchronously remediate nitrate-contaminated groundwater via hydrogenotrophic denitrification

Groundwater denitrification is challenged by a lack of electron donors and usually requires additional energy input or chemical agents. MEC can convert organic pollution into clean electron donor (hydrogen) through a gas-liquid phase transition. In this study, the MEC was combined with permeable bio-reactive barrier (PRB) as a hybrid system to achieved simultaneous organic waste removal, hydrogen production and groundwater remadition via long-distance hydrogenotrophic denitrification by biogas. The semi-hydrophobic PTFE-coated granular activated carbons (GAC) and hydrophilic GAC were filled as two kinds of biocarriers in PRBs, in which the hydrophobic PTFE surface coating improved hydrogen utilization. The PTFE-coated GAC maked the denitrification performance of PRB insensitive to hydrogen partial pressure within the tested range of 0.01–0.04 MPa and achieved effluent nitrate concentration of <20 mg L−1 within 12 h (The Water Quality Standard for Drinking Water Sources in China). The gas production in MECs was actively pumped to PRBs and spontaneously achieve negative pressure on the MEC side and positive pressure on the PRB side. The actively pumping of biogas induced negative pressure in MEC and positive pressure in PRB. The negative pressure improved current density by 18.6 ± 0.7% in MECs and the MEC-PRB hybrid system achieved a nitrate removal of 85.0 ± 0.8% in actual groundwater with an effluent concentration of 15.0 ± 0.8 mg L−1 at 72 h. This work demonstrated the feasibility of matching MEC and PRB as a novel hybrid system for organic pollution degradation and effective nitrogen removal in electron-donor-lacking groundwater.

A Novel Layered and Advanced Nitrogen Removal Filter with Gravel and Embedded Bio-Organic Carrier Based on Autotrophic and Heterotrophic Pathways

Given increasingly prominent environmental issues, there is a pressing need to satisfy more stringent emission standards for wastewater treatment plants (WWTP) while concurrently prioritizing energy conservation; a new up-flow layered nitrogen removal filter was constructed on a laboratory scale using gravel (for the bottom and top layers) and embedded bio-organic carriers (for the middle layer) containing microorganisms as fillers to treat the secondary effluent by introducing a portion of raw water. This study investigated the nitrogen removal effectiveness and transfer pathways of synthetic wastewater at varying mixing ratios, promoted the enrichment of Anammox Bacteria (AnAOB) by embedding microorganisms, and analyzed the microbial community structure using high-throughput sequencing techniques. The findings showed that the highest total nitrogen (TN) removal efficiency was achieved with chemical oxygen demand (COD), ammonia (NH4+-N), and nitrate (NO3−-N) contents in the mixture at 77, 10, and 8 mg·L−1, respectively, with an average efficiency of 89.42%. NO3−-N was mostly removed through denitrification (heterotrophic), while NH4+-N was eliminated by partial nitrification (PN) and anaerobic ammonium oxidation (Anammox, autotrophic). According to high-throughput sequencing results, denitrifying bacteria such as Thauera (1.30–6.96%), Flavobacterium (0.18–0.40%), and Parcubacteria (0.14–0.32%) were present in all the filter layers, and Anammox bacteria such as Candidatus_Kuenenia were predominant in the middle layer at a 0.88% abundance, with the aid of organic carriers.

Nitrogen Metabolism and Flora Characteristics of Bacteria Algae Complex System

In order to denitrify the urban tail water deeply and control the eutrophication of surface water, the molecular biology methods were used to study the nitrogen metabolism performance of the denitrification complex flora and the algal-bacteria symbiotic system. The results showed that the nitrogen metabolism complex flora was high ammonification and denitrification performance. The removal effect of ammonia nitrogen of group JZ was very well in urban tailwater, and the degradation rate was as high as 95%. The removal effect of total nitrogen of group JZ was better than that of group J in the experimental water distribution. High-throughput sequencing showed that the main dominant flora and proportion of group J were Firmicutes 44.53%, Proteobacteria 43.41%, Actinobacteria 5.37%, Bacteroidetes 3.04%, and Chloroflexi 1.35%. The main dominant bacterial groups in the group JZ were 33.89% Cyanobacteria, 25.34% Chloroflexi, 19.38% Proteobacteria, 10.02% Firmicutes, and 4.20% Acidobacteria. The dominant species in group J were compared with those in group JZ; the proportions were 82% and 18% in Firmicutes, 69% and 31% in Proteobacteria, 1% and 99% in Cyanobacteria, 5.1% and 95% in Chloroflexi, 73% and 27% in Actinobacteria. It was concluded that the removal effect of ammonia nitrogen of group JZ was high in the urban tailwater. With the addition and growth of Micrococcus in group J, the nitrogen metabolism flora in group JZ changed accordingly, so as to adapt to the environment in which the dominant algae formed. It forms a new nitrogen metabolism system of bacteria and algae with Micrococcus. This research provides a theoretical and data basis for the application of algal-bacterial co-metabolism systems.

Effective removal of nitrogen and phosphorus from a black-odorous water by novel oxygen-loaded adsorbents

Black-odorous water, caused by hypoxia and overloading of nitrogen and phosphorus, is ubiquitous in global urban rivers. In this study, we developed oxygen-loaded adsorbents by loading oxygen into activated carbon, Attapulgite, Phoslock, and Muscovite via vacuum-pressure swing method, and investigated their aeration and removal efficiency of phosphate, ammonia nitrogen, and total nitrogen in black-odorous water. Results showed that the addition of oxygen-loaded coal-based columnar activated carbon (OCC) or oxygen-loaded Muscovite (OM) alone could increase the dissolved oxygen (DO) concentration at the sediment–water interface to more than 6 mg·L-1 on the first day, and OCC could maintain the high level of oxidation–reduction potential (ORP) (up to + 327 mV) for 15 days. Most oxygen-loaded adsorbents remarkably reduced phosphate in water, essentially from 0.27 mg·L-1 to < 0.05 mg·L-1. Additionally, ammonia nitrogen and total nitrogen were reduced by more than 50 % by adding materials after oxygen loading treatment. The 16 s RNA results showed that Dechloromonas was dominant in abundance, and the reduction of nitrogen was mainly affected by microbial activity. Our results provided a series of oxygen-loaded adsorbent materials with potential engineering applications for rapid treatment of urban black-odorous water.

Efficient H2O2 production from urine treatment based on a self-biased WO3/TiO2-Si PVC photoanode and a WO3/CMK-3 cathode

Urine accounts for only 1% of municipal wastewater volume but contributes 80% of nitrogen, which has become one of the challenges for existing wastewater treatment plants. Herein, we proposed a novel approach based on a self-biased WO3/TiO2-Si PVC photoanode and a WO3-modified mesoporous carbon (CMK-3) cathode (WO3/CMK-3) to produce significantly high-value chemical H2O2 from urine treatment with effective total nitrogen removal. The central idea of the design is to achieve a feasible reversal of the thermodynamic trend of O2 reduction to H2O2 from a non-spontaneous to a strongly spontaneous process by combining it with a urine treatment reaction that releases large amounts of chemical energy in the photoelectrocatalytic (PEC) system. The results indicated that the H2O2 production was boosted remarkably by urine disposal reaction (5.13 mg cm−2 h−1) with a faradaic efficiency of 72%, and the WO3/CMK-3 cathode showed 6.1 and 2.5 times higher H2O2 production activity than the common gas diffusion electrode and carbon felt electrode, respectively. Moreover, urine was degraded effectively into N2 with a total nitrogen removal of 91.4% within 120 min, and the kinetic constant of urine degradation was 0.0397 min−1, which was 15.4 times that of the blank. The results of ESR and quenching experiments demonstrated that the amine group of urine selectively and rapidly converted into N2 by Cl•. This study provides new insights into efficient urine disposal and synchronous H2O2 production.

Influence of double-layer filling structure on nitrogen removal and internal microbial distribution in bioretention cells

The nitrogen removal effect of traditional bioretention cells on runoff rainwater is not stable. The nitrogen removal effect of bioretention cells can be improved by setting up a layered filling structure, but the effect of changes in filling structure on the nitrogen removal process and microbial community characteristics is still unclear. Two types of porosity fillers were set up in the experiment, and a homogeneous bioretention cell and three bioretention cells with layered fillers were constructed by changing the depth range of the upper and lower layers to analyze the influence of the pore variation of different depth fillers on the nitrogen removal process and microbial community characteristics. The experimental results showed that, compared with the homogeneous filing structure, the layered filling structure can strengthen the adsorption of NH4+-N and the conversion of NO3−-N, so as to increase the removal rates of NH4+-N and NO3−-N by 20.71–81.56% and 9.25%–78.19%, respectively. Although the low porosity filler structure will reduce the nitrification activity and urease activity by 48.63%–66.68% and 8.00%–20.64% respectively, it can increase the denitrification activity by 19.14%–31.92%, thus significantly reducing the nitrate content in the filler. The low porosity filler structure can affect the growth and reproduction of various phylum bacteria such as Proteobacteria, Chloroflexi, Acidobacteria, and genus bacteria such as Nitrospira, Ellin6067, Rhizobacter, Pseudomonas, which can improve the diversity and richness of microorganisms.

Study of Ammonia Removal Efficiency and Process Regulation Strategy of Biological Aerated Filter in Treating Low-Temperature Micropolluted Urban Landscape Water

To explore the treatment performance of a biological aerated filter (BAF) for exogenous pollutants in low-temperature landscape water, a laboratory and pilot system were constructed in urban rivers in the alpine region of northern China, and the key influencing factors such as pH, hydraulic load, air–water ratio, and temperature were studied. The results showed that the operation parameters of the BAF need to be controlled to achieve good nitrogen removal effect. Based on the hazard identification of ammonia nitrogen in landscape water effluent, the critical control points of the BAF process were determined, and corresponding control strategies were formulated. By adjusting operation parameters and other measures, hazards can be identified and overcome with reasonable accuracy. Therefore, the effluent ammonia nitrogen and concentration can be kept within the limits of the law. Double-layer aerated organisms can operate stably at normal temperature, in a transition period, and at low temperature period. The average removal rate of ammonia nitrogen in the three periods can reach 83.29%, 68.53%, and 56.55%, respectively, and the effluent quality can meet the requirements of landscape water during operation.

Novel nitrogen removal process in marine aquaculture wastewater treatment using Enteromorpha ferment liquid as carbon

The process performance of partial denitrification of a novel anaerobic fermentation integrated fixed-film activated sludge (IFAS-AFPD) of Enteromorpha was studied. The response surface method was used to determine the optimal reaction conditions, and the operation experiment was carried out under the optimal conditions. The results showed that the nitrogen removal effect was the best when the salinity was 12.2 g•L−1, the Carbon-Nitrogen ratio (C/N) was 4, the pH was 8.5, and the Nitrite Accumulation Rate, Nitrate Removal Rate, Chemical Oxygen Demand Utilization Rate could reach 77%, 89% and 51%. Experimental results have shown that the NAR of the Enteromorpha ferment liquid system could be maintained at about 74%, which was noteworthy higher than that of the sodium acetate (CH3COONa) system at 42%; Microbial community analysis showed that Enteromorpha ferment liquid was more beneficial to the growth of Bacteroidetes than CH3COONa.