TN Removal Rate Research Articles

Urea removal for ultrapure water production by VUV/UV/chlorine under acidic aqueous conditions: Facile elimination and efficient denitrification

Urea in the ultrapure water production process threatens semiconductor manufacturing. This work proposed a urea removal strategy involving the VUV/UV/chlorine process in an acidic solution to achieve high-efficiency urea removal. VUV/UV/chlorine could thoroughly remove urea of 2 mg/L within 9 min at pH 3. A TN removal rate of 70% and a dissolved organic carbon removal rate of 84% were achieved in the urea degradation process. The decrease in pH and the increase in oxidant dosage could improve urea removal efficiency. The presence of chloride anion could improve urea removal by 55–85%. Based on the radical probe and quenching experiments, free radicals accounted for more than 90% of urea removal. •Cl2− and •OH were calculated to contribute approximately 36% and 22%, respectively, to urea removal. •Cl and •ClO together contributed less than 32%. The chlorination of urea was responsible for less than 10% of urea removal. Nitrogen in urea was transformed efficiently into inorganic nitrogen (N2, ammonium, and nitrate with a rough ratio of 6:1:1.1). Organic chlorine products formed in the urea degradation process took up less than 3% in all chlorine element and was converted into chloride anion finally.

Metagenomic analysis revealed the mechanism of extracellular polymeric substances on enhanced nitrogen removal in coupled MABR systems with low C/N ratio containing salinity

A combined membrane-aerated biofilm reactor (MABR) was conducted to treat various C/N ratios with saline wastewater. The influence of C/N on nitrogen removal property, extracellular polymeric substances (EPS) features, bacterial community and relevant functional genes were investigated. Fourier-transform infrared spectrum (FTIR), three-dimensional exaction and emission matrix (3D-EEM) fluorescence spectra and metagenomics analysis were conducted to study the mechanism of EPS for enhanced nitrogen removal at low C/N ratio. The results showed that TN removal rate of the whole MABR system were 73.21%, 69.51% and 67.04%, respectively, with the C/N ratio of 6, 4.5 and 3. MABR-2 biofilms secreted more EPS under low C/N and high-salinity conditions to maintain intracellular and extracellular osmotic pressure balance and to participate in cellular metabolic processes. Meanwhile, under the stimulation of low C/N, MABR-2 system with low influent loading was in a “starvation state”, thus EPS could be utilized by the biofilm of MABR-2 system as carbon source to enhance nitrogen removal. Besides, metagenomics analysis showed that aerobic denitrification and dissimilatory nitrite reduction to ammonia (DNRA) were dominant nitrogen removal pathways in MABR-2 system at low C/N ratio. EPS might participate in related metabolic processes in the electron donors and energy production processes as well as the electron transfer pathways in denitrification system. This work provided a feasible practical application scheme for the enhanced TN removal of low C/N ratio containing salinity.

Performance and mechanism of sacrificed iron anode coupled with constructed wetlands (E-Fe) for simultaneous nitrogen and phosphorus removal.

Three anodic biofilm electrode coupled CWs (BECWs) with graphite (E-C), aluminum (E-Al), and iron (E-Fe), respectively, and a control system (CK) were constructed to evaluate the removal performance of N and P in the secondary effluent of wastewater treatment plants (WWTPs) under different hydraulic retention time (HRT), electrified time (ET), and current density (CD). Microbial communities, and different P speciation, were analyzed to reveal the potential removal pathways and mechanism of N and P in BECWs. Results showed that the optimal average TN and TP removal rates of CK (34.10% and 55.66%), E-C (66.77% and 71.33%), E-Al (63.46% and 84.93%), and E-Fe (74.93% and 91.22%) were obtained under the optimum conditions (HRT 10h, ET 4h, CD 0.13mA/cm2), which demonstrated that the biofilm electrode could significantly improve N and P removal. Microbial community analysis showed that E-Fe owned the highest abundance of chemotrophic Fe(II) (Dechloromonas) and hydrogen autotrophic denitrifying bacteria (Hydrogenophaga). N was mainly removed by hydrogen and iron autotrophic denitrification in E-Fe. Moreover, the highest TP removal rate of E-Fe was attributed to the iron ion formed on the anode, causing co-precipitation of Fe(II) or Fe(III) with PO43--P. The Fe released from the anode acted as carriers for electron transport and accelerated the efficiency of biological and chemical reactions to enhance the simultaneous removal of N and P. Thus, BECWs provide a new perspective for the treatment of the secondary effluent from WWTPs.

Control performance of bioretention system on non-point source pollution in typical Chinese rural areas of Southeastern China

Current work focused on analysis and implementation and of bioretention system in typical rural areas in Southeastern China. These areas are vigorously protected by the Chinese government due to their traditional farming and architectural characteristics that symbolize ancient Chinese civilization. Bioretention system with high pollutant removal capacity and strong environment adaptability might be a suitable technical solution for controlling non-point source pollution in ancient Chinese villages. In lab-scale study, the hydraulic characteristics of the media and the impacts of depth of media layer, depth of saturated zone (SZ), vegetation and extra carbon source (ECS) on pollutant removal efficiency of bioretention system against the current situation of NSP in typical Chinese rural areas (TCRA) were investigated. The results revealed that roots were conducive to maintain the hydraulic conductivity and pollutant removal efficiency of the filter media. The increasing depth of media layer and SZ, vegetation, and ECS could improve pollutant controlling performance of bioretention system. A field-scale bioretention system with optimal configuration determined by lab-scale study was implemented on the site. The average removal rates of TSS, COD, TN and TP of the bioretention system in field study were 81.34%, 41.88%, 37.33% and 71.64%, respectively. Bioretention system could combine with nearby farmland in rural areas without disturbing their original texture, furthermore, proper maintenance and replacement of media and vegetation could significantly improve the performance of bioretention system in TCRAs.

Pretreatment of septic tank wastewater by packed anaerobic baffled reactor: Pollutant degradation and microbial community succession in different compartments

Anaerobic baffled reactor (ABR) is widely used in rural sewage treatment due to its unique structure, strong impact load resistance, and low energy consumption. However, there is a lack of research on pollutant degradation patterns and microbial community succession patterns in each compartment of ABR. In this study, a packed anaerobic baffled reactor (PABR) was constructed. The effects of T and HRT on the pollutant removal performance of PABR were investigated, and the pollutant degradation and microbial community succession in different compartments of PABR were studied. The results show that the removal rates of COD, NH4+-N, and TN of PABR can reach 85.54 ± 1.08%, 16.94 ± 1.01%, and 5.64 ± 1.18% respectively, and PABR has a good pollutant removal effect. With the extension of HRT, the COD removal rate of PABR increases steadily, and the NH4+-N and TN removal rate of PABR increases to a certain extent. The recommended HRT is 72 h. T has a significant impact on the COD removal effect of PABR. The increase of T in a certain range is conducive to the removal of pollutants by PABR. The COD removal rate of PABR decreases gradually along the flow direction, and the removal of organic matter is mainly concentrated in the first compartment. PABR has good removal capacity for CODss and better nitrogen removal capacity compared with traditional ABR. The richness and diversity of the microbial community in PABR increased gradually along the flow direction. The bacterial species in each compartment were similar but the proportion was different, showing the characteristics of multi-stage and separated phase operation. This study provides a new reference for the application of ABR in rural sewage treatment.

Carbon Reduction and Pollutant Abatement by a Bio-Ecological Combined Process for Rural Sewage.

In order to explore the treatment effect of a bio-ecological combined process on pollution reduction and carbon abatement of rural domestic wastewater under seasonal changes, the rural area of Lingui District, Guilin City, Guangxi Province, China was selected to construct a combined process of regulating a pond, biological filter, subsurface flow constructed wetland, and ecological purification pond. The influent water, effluent water, and the characteristics of pollutant treatment in each unit were investigated. The results showed that the average removal rates of COD, TN, and NH3-N in summer were 87.57, 72.18, and 80.98%, respectively, while they were 77.46, 57.52, and 64.48% in winter. There were significant seasonal differences in wastewater treatment results in Guilin. Meanwhile, in view of the low carbon:nitrogen ratio in the influent and the poor decontamination effect, the method of adding additional carbon sources such as sludge fermentation and rice straw is proposed to strengthen resource utilization and achieve carbon reduction and emission reduction. The treatment effect of ecological units, especially constructed wetland units, had a high contribution rate of TN treatment, but it was greatly impacted by seasons. The analysis of the relative abundance of the microbial community at the phylum level in constructed wetlands revealed that Proteobacteria, Acidobacteria, Chloroflexi, Firmicutes, Bacteroidetes, Planctomycetota, and Actinobacteria were the dominant phyla. The relative abundance of microbial communities of Proteobacteria, Chloroflexi, and Acidobacteria decreased to a large extent from summer to winter, while Firmicutes, Bacteroidetes, and Planctomycetota increased to varying degrees. These dominant bacteria played an important role in the degradation of pollutants such as COD, NH3-N, and TN in wetland systems.

Denitrification efficiency, microbial communities and metabolic mechanisms of corn cob hydrolysate as denitrifying carbon source

In this study, the denitrification efficacy of corn cob hydrolysate (CCH) was compared and analyzed with that of glucose and acetate to determine its feasibility as an additional carbon source, and its metabolic mechanism as a denitrification carbon source was investigated in depth. By constructing a denitrification reactor, it was found that the TN removal rate exceeded 97% and the effluent COD remained below 70 mg/L during the stable operation with CCH as the carbon source, and the denitrification effect was comparable to that of the glucose stage (GS) and the acetate stage (AS). The analysis of the microbial community showed that the dominant phylum was Proteobacteria and Bacteroidota, where the abundance of Bacteroidota in the hydrolysate stage (HS) (24.37%) was significantly higher than that of GS (4.89%) and AS (11.93%). And the analysis at the genus level showed the presence of a large number of genera of organic matter hydrolysis and acid production in HS that were almost absent in other stages, such as Paludibacter (12.83%), Gracilibacteria (4.27%), f__Prolixibacteraceae_Unclassified (2.94%). In addition, the higher fatty acid metabolism and lower sugar metabolism of HS during carbon metabolism were similar to the ratio of AS, suggesting that CCH was mainly fermented to acids and then involved in the tricarboxylic acid (TCA) cycle. During nitrogen metabolism, the high relative abundance of narG, nirS, and nosZ ensured the denitrification process. The results of this study were expected to provide a theoretical basis and data support for promoting denitrification from novel carbon sources.

Hydrolysate from the enzymatic treatment of corn cob as a carbon source for heterotrophic denitrification process

The application of hydrolysate obtained from the enzymatic treatment of agricultural waste as a denitrification carbon source is proposed. In this study, comparative experiments on six common agricultural wastes (corn cob, loofah, peanut shell, corn straw, rice straw, and wheat straw) revealed that corn cob released high COD and low relative content of N, and P pollutants and chromaticity, and was most suitable as a raw material for carbon source preparation. The conditions for the preparation of hydrolysate from corn cob were optimized by response surface methodology, and the optimal conditions were pH 5.44, temperature 49.56 °C, enzyme addition of 25 mg, and surfactant content of 0.1 %. The metal elements of the hydrolysate were analyzed and contained a large number of macronutrients (K, Ca, Na, and Mg) and trace elements (Fe, Mn, Co, Ni, Cu, Zn, and Se). The hydrolysate was applied to the denitrification reactor and the effluent TN removal rate reached more than 97 % and COD was below 61 mg/L when the carbon to nitrogen ratio was 5:1. Analysis of the microbial community revealed the presence of a large number of genera involved in the denitrification process and organic matter decomposition such as Thauera (19.08 %), Dechloromonas (7.59 %), and Paludibacter (2.11 %), thus indicating the feasibility of hydrolysate as a carbon source for denitrification. This research is expected to provide new insights into the development of new carbon sources in biological denitrification technologies.

Functional biological anode as electron acceptor for direct oxidation of ammonia nitrogen to N2 in an anaerobic single-chamber reactor

A functional biological anode (nonwoven-wrapped functional microbial carbon felt bag) was constructed to realize the ammonia oxidation to nitrogen gas in a single-chamber anaerobic microbial electrochemical system (MES). The applied potential has a significant impact on oxidation products of ammonia. As the applied potential was reduced from +0.8 V to +0.3 V (vs. Ag/AgCl), the ammonia oxidation rate increased from 65.2% to 94.7% and the TN removal rate increased from almost 0 to 88.0% on the bio-anode. At +0.3 V ammonia could be converted to N2 on the bio-anode and hydrogen is generated on the cathode. The zeolite adsorbent added inside the anodic carbon felt bag was also a key factor to accelerate nitrogen removal in the MES. The dominant genera of SWB02 sp., Nitrospira sp. and Bryobacter sp. played a crucial role in ammonia oxidation according to 16S rRNA analysis. This paper provides a new idea for NH4+-N removal and hydrogen production from wastewater.

Lemnaceae clones collected from a small geographic region display diverse traits relevant for the remediation of wastewater

The Lemnaceae (duckweed) are a family of aquatic plants which can be used as part of a circular economy approach to remediate and valorise wastewater. The suitability of duckweeds relates to their tolerance of wastewater conditions, fast growth rates and valuable biomass. Duckweed species and clones display a wide range of remediation abilities and nutritional composition. In order to find duckweed species and clones best suited for remediation and valorisation of dairy processing wastewater, plant samples were collected from a number of locations around southern Ireland. These species and clones were cultured on a synthetic dairy processing wastewater while growth, TN/TP removal and protein content were assessed. Synthetic dairy wastewater was found to be suitable for remediation by different species and clones. However, significant differences were found in relative growth rate (RGR), TN removal rate and protein content. As per PCA, it was found that species and clones with higher RGR tended to have a lower protein content. Furthermore, nutrient removal rate was not strongly associated with growth and protein content. The results demonstrate that remediation is not positively correlated with valorisation across duckweed species and clones. Thus, clonal selection for duckweed reactors will need to consider the prime objective of remediation i.e. biomass production or wastewater remediation. • Synthetic dairy processing wastewater is suitable medium for duckweed growth. • Significant diversity in remediation relevant traits between Lemnaceae clones. • Nitrogen uptake is only loosely associated with biomass yield. • High protein content is associated with lower growth. • No single duckweed clone is optimal for both remediation and valorisation.

Start-up characteristics and microbial nitrogen removal mechanisms in ANAMMOX systems with different inoculations under prolonged starvation

The characteristics of lab-scale ANAMMOX system for efficient nitrogen removal were tested by different inoculations (anaerobic granular sludge (AGS) + anammox sludge (AMS), R1; AGS alone, R2) in continuous flow reactors following start-up under starvation. TN removal rates were above 90 % in both reactors. Microbial community analysis showed that the nitrogen removal was the combined results of anammox and partial denitrification (PD), Higher microbial growth rate triggered by quorum-sensing (QS) caused R1 to secrete more extracellular polymeric substances (EPS) and promoted the growth of its particle size. However, the overproduction of EPS destroyed the particle structure with time, and led to a deterioration of operational stability in R1. R2 showed better nitrogen removal stability to high nitrogen loading rate (NLR). This was due to higher endogenous organics within R2, which inhibited cell aggregation and EPS overproduction. But undeniably, R1 had higher specific anammox activity (SAA) with higher anammox bacteria (AAOB) abundance (The abundance of Planctomycetota in R1 and R2 were 21.2 %, 7.71 %). The results suggest that the operational stability was influenced by a combination of particle properties and microbial metabolism, and that the inoculation of AGS is more conducive to efficient and economic nitrogen removal in wastewater treatment under starvation.

Constructed Wetland for Sustainable and Low-Cost Wastewater Treatment: Review Article

There is a growing need for more sustainable wastewater treatment technologies to provide non-conventional water sources. Constructed Wetland systems (CW) are viewed as a low-cost treatment technology with proven treatment efficiency. CWS can treat a variety of contaminants using low energy and natural systems by altering various design parameters. There are two configuration types of constructed wetlands: vertical (VF) and horizontal flow CW (HF). Both configurations have been widely adopted in both large and pilot scale studies with proven records of reasonable wastewater treatment efficiency. The current article reviews the recent development of CW technology and highlights the main achievements and successful applications for wastewater treatment at various locations. The review has indicated that a considerable removal efficiency is attained while using engineered CW systems with variable treatment rates for various pollutants. The treatment efficiency is a function of various parameters including wastewater type, scale dimensions, applied plant and the retention time. The review compared the treatment efficiency for both VF and HF and has revealed that various removal rates of BOD, COD, TSS, TN, TP and NH₄ was attained using both configurations. Yet, the removal efficiency in the case of VF was slightly higher compared with the HF with an average treatment level of 77% and 68% was achieved in both systems, respectively. The review revealed that the CW is an effective and sustainable technology for wastewater treatment with the initial influent level, microbial biofilm, detention time, plant species and configuration among the most dominating parameters that are directly controlling the removal rates.

Relationships of pulsed frequency and anammox bacteria growth rate, at low temperatures

ABSTRACT This study explored pulsed frequency that could enhance the anammox bacteria growth rate and TN removal rate at low temperatures (16 ± 1°C). The results showed that the growth rate of anammox bacteria in R1 (1000 Hz) was significantly higher than in R2 (30 Hz) and R3 (106Hz). The relative abundance values of anammox bacteria R1 were higher by 52.21% and 172.41% than R2 and R3, while that of MLSS were as high as 241.07% and 471.36% than R2 and R3, with the nitrogen loading rate was 6.84 kg-N/m³/d. Besides, the dynamics also showed that the specific anammox activity (SAA) and the cellular yield of R1 were higher than R2 and R3. The intermediate frequency could enhance the cell division by stimulating the anammoxosome and reduce the ionic hydration layer to accelerate the ion migration rate, further improving the number of anammox bacteria even at low temperatures. The pulsed frequency could enhance the anammox growth rate and the doubling time is just 5 d.

Treatment Effect of Corncob and Rice Straw Enhanced Subsurface Flow Constructed Wetland on Low C/N Ratio Wastewater

The lack of carbon sources severely inhibits denitrification in wastewater with a low C/N ratio. Corncob and rice straw were chosen as supplementary carbon sources to bring into the wetland system to supplement the carbon sources needed for denitrification, and the enhancing effects of the two carbon sources on nitrogen removal from the wetland were studied. The cumulative release of carbon was in the order of rice straw[(145.17±9.44) mg·g-1]>corncob[(57.41±5.04) mg·g-1] based on the 11-day pure water extraction and release experiment, whereas the cumulative release of nitrogen was in the order of rice straw[(2.31±0.09) mg·g-1]>corncob[(0.66±0.08) mg·g-1]. The average carbon/nitrogen ratios released and accumulated by corncob and rice straw during the observation period were 94.78 and 63.64, respectively. Corncob was more suited as an additional carbon source than rice straw. COD concentrations in the effluent from the corncob and straw constructed wetlands were found to be below 50 mg·L-1 for the 58-day pilot test of subsurface flow constructed wetlands, except on days 8 to 12. The NO3--N removal rates of the corncob-added built wetlands were 93%-99% over the observation period, with good denitrification performance. In comparison, the lowest NO3--N removal rate of the constructed wetland with the addition of rice straw was only 76.8% at the late stage of operation, and the denitrification rate dropped dramatically. The control group removal rates of NO3--N were only 76.2%-77.7%, indicating a clear lack of carbon sources. The accumulation of NO2--N was also induced by a lack of carbon supply. NO2--N effluent concentrations were 2.5-6 times and 6-26 times higher in the constructed wetlands with rice straw and the control groups, respectively, than those in the wetlands constructed with corncob. The addition of corncob resulted in a more substantial reduction in NO2--N content in the constructed wetland than the addition of rice straw (P<0.05). The TN removal rates of wetlands constructed with corncob and rice straw and the control group were 83.75%-93.49%, 76.59%-78.85%, and 67.85%-72.56%, respectively, with significant differences among the three (P<0.01). Finally, pretreatment with dilute alkali heating raised the cumulative carbon release of corncob to (93.73±17.49) mg·g-1 and the carbon/nitrogen ratio to 175.8, significantly improving the carbon release performance of corncob and demonstrating that it is a suitable source of extra carbon.

Nitrogen removal by a strengthened comprehensive floating bed with embedded pellets made by a newly isolated Pseudomonas sp. Y1

ABSTRACT A newly heterotrophic nitrification aerobic denitrification(HN-AD) bacterium Pseudomonas sp. Y1 with highly nitrogen removal ability was isolated from the activated sludge, TN removal rate of which was 99.73%. In this study, two types of different ecology floating bed systems were designed to achieve efficient nitrogen removal in the urban eutrophic landscape water body, one is the comprehensive ecological floating bed(CEFB) system with only Lythrum salicari and the other is the strengthened comprehensive ecological floating bed (SCEFB) system with both Lythrum and embedded pellets made by Y1. The TN removal rates of the CEFB system were 33.82%, 83.84% and 88.91% at 8±1℃, 15±1℃ and 25±1℃, respectively, while the TN removal rates of the SCEFB system increased by nearly 40%, 16% and 11% at the same environment, respectively. The result shows that the SCEFB system can purify the simulated water from surface water body class V to class IV. Thus it has a broad application prospect in the urban eutrophic landscape water body.

The performance and mechanism of iron-modified aluminum sludge substrate tidal flow constructed wetlands for simultaneous nitrogen and phosphorus removal in the effluent of wastewater treatment plants

Aiming at the poor N and P removal performance in the effluent of wastewater treatment plants by constructed wetlands (CWs), aluminum sludge (AS) from water supply plants was used to prepare iron-modified aluminum sludge (IAS), and tidal flow constructed wetlands (TFCWs) using IAS as substrates were constructed. By means of high-throughput sequencing, X-ray diffractometer (XRD), etc., the removal mechanism of N and P in the system and fate analysis of key elements were also interpreted. Results showed that an interlayer structure beneficial to adsorbing pollutants was formed in the IAS, due to the iron scraps entering into the molecular layers of AS. The removal rates of TP and TN by IAS-TFCWs reached 95 % and 47 %, respectively, when the flooding/resting time (F/R) and C/N were 6 h/2 h and 6. During the three-year operation of the IAS-TFCWs, the effluent concentrations of CODCr, NH4+-N, and TP could comply with Class IV Standard of “Environmental Quality Standards for Surface Water” (GB3838-2002). The mechanism analysis showed that the N removal was effectuated through Fe2+ as the electron donor of Fe(II)-driven the autotrophic denitrifying bacteria to reduce nitrate, while the P removal mainly depended on the adsorption reaction between FeOOH in IAS and phosphate. In conclusion, the stable Fe-N cycle in the IAS-TFCWs achieved simultaneous and efficient N and P removal.

Bioaugmentation with Acinetobacter sp. TAC-1 to enhance nitrogen removal in swine wastewater by moving bed biofilm reactor inoculated with bacteria

To enhance the performance of moving bed biofilm reactor (MBBR) inoculated with heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria, bioaugmentation with Acinetobacter sp. TAC-1 was firstly employed and then the treatment performance for real swine wastewater was presented in this study. Results indicated that NH4+-N and TN removal rates of bioaugmented reactor were significantly improved from 16.53 mg/L/h and 16.15 mg/L/h to 24.58 mg/L/h and 24.45 mg/L/h, respectively. The efficient removal performance (NH4+-N 95.01%, TN 86.40%) for real swine wastewater was achieved within 24 h. Microbial analysis indicated that the composition of functional bacteria varied with the introduction of Acinetobacter sp. TAC-1, especially the abundance of Acinetobacter, Paracoccus and Rhodococcus related to the nitrogen removal. Furthermore, bioaugmentation with Acinetobacter sp. TAC-1 increased abundance of enzymes and functional genes (nirS, nirK and norZ) corresponding to denitrification that may be responsible for the enhanced nitrogen removal performance.

A novel completely autotrophic biological treatment process coupled of anammox and sulfur autotrophic (CAS) reactors to remove nitrogen and perchlorate simultaneously

A coupled system of anammox and sulfur autotrophic (CAS) reactors was established to remove ammonia (NH4+-N) and perchlorate (ClO4-) simultaneously in wastewater. The anammox performed NH4+-N removal and the sulfur autotrophs removed nitrate (NO3--N) produced by anammox and ClO4- in influent. When the concentrations of ClO4-, NO3--N and NH4+-N in the CAS were 30–90 mg/L, 100 mg/L and 120 mg/L, respectively, the removal rates of TN and ClO4- by CAS were 99 % and 98 %. The synergistic mechanism of CAS indicated that the secretion of extracellular polymeric substances (EPS) could cope with the impact of ClO4-, so as to ensure the removal performance of NH4+-N and ClO4- and electron transfer system activity (ETSA). High throughput sequencing revealed that the dominant genera were Candidatus Kuenenia, Candidatus Brocadia, Armatimonadetes gp5 and Gp10 in the anammox reactor, and the seven dominant genera were Methyloversatilis, Methylocystis, Ancalomicrobium, Longilinea, Thermogutta, Sulfurimonas and Ferritrophicum in the sulfur autotrophic reactor. The dominant bacteria supported the feasibility of the CAS. Consequently, the CAS provided an effective technical path for the simultaneous removal of NH4+-N and ClO4- in practical application.

Effect of COD/NO3 --N ratio on nitrogen removal performance of partial denitrification coupled anaerobic ammonia oxidation

An one-stage sequencing batch partial denitrification/anammox (PD/A) reactor was used to treat simulated domestic sewage at room temperature. By changing the influent COD/NO3 --N to 3.5, 3.0 and 2.5 respectively, the change of nitrogen concentration in the reaction system was measured to determine the optimal COD/NO3 --N for the operation of PD/A technology. The results showed that during the long-term operation of the reactor, the TN removal rate is the highest when the COD/NO3 --N was 3.5. In the typical cycle, COD/NO3 --N was 3.0, which can reach the highest NTR and highest contribution rate of anammox.

Purification effect of aquatic plant communities in constructed wetland park: a comparative experiment of Tianhe wetland park in China

Constructed wetland parks in urban areas can offer the potential for integrating water conservation and purification. Compared with other treatments, filtering out pollutants by wetland plants is one of the methods used widely for its fast processing time and limited costs. And species allocation plays an important role in the purification process. However, some problems are still waiting for further discussions, such as the purification efficiency in winter due to plant growth rate, etc. Against this background, this paper introduced the Tianhe Wetland Park in China as the site for a comparative experiment, to propose a methodology for testing the purification effect under different plant communities. Through site investigation and lab experiments with water monitoring, the process of water purification by wetland was simulated in the park. After a period of observation and measurement, seven water indexes (pH value, dissolved oxygen, total phosphorus, total nitrogen, ammonia nitrogen, chemical oxygen demand, and turbidity) were selected for the evaluation of water quality to compare the different absorption efficiency by different communities. As a result, the research showed that a configuration of plant community using arboreal, emergent, and submerged plants can carry out a good purification effect during the winter, including Callistemon viminalis, Bischofia javanica, Canna indica, Juncus effusus, Vallisneria natans, and Hydrilla verticillata var. rosburghii. The removal rate of DO, TU, COD, TP, and TN by the designed community can reach 43%, 65%, 45%, 51%, and 62% in sampling sites. Finally, based on the research results, further suggestions for the development of wetlands were proposed to improve park management in the study area.