Relationships between nitrogen removal processes and functional microorganisms in the rhizosphere soil in a horizontal surface flow constructed wetland

2019 ◽  
Vol 70 (11) ◽  
pp. 1603 ◽  
Author(s):  
Yinuo Zhu ◽  
Jing Li ◽  
Zhangjie Cai ◽  
Wei Li ◽  
Yinru Lei ◽  
...  
Keyword(s):  
Nitrogen Removal ◽  
Constructed Wetland ◽  
Rhizosphere Soil ◽  
C:N Ratio ◽  
Surface Flow ◽  
Horizontal Surface ◽  
Nitrification Rate ◽  
Nirs Gene ◽  
Potential Nitrification ◽  
Removal Processes

Plant species could significantly affect the nitrogen removal processes mediated by microorganisms in constructed wetlands. However, the links between nitrogen removal processes in the rhizosphere and the related functional microorganisms in a horizontal surface flow constructed wetland in winter remain poorly understood. In this study we collected 24 rhizosphere soils from Typha orientalis and Phragmites australis to evaluate potential nitrogen removal activities, namely the potential nitrification rate (PNR) and denitrification enzyme activity (DEA), and their relationship with functional genes (i.e. nitrate reductase, nirS, and ammonia mono-oxygenase, amoA, of ammonia-oxidising archaea, AOA, and ammonia-oxidising bacteria, AOB) in denitrifiers and nitrifiers in winter. DEA and PNR were significantly higher in the rhizosphere soil of T. orientalis than P. australis, which was due to the higher abundance of nitrifiers and denitrifiers in the rhizosphere of T. orientalis. AOB were the major predictor of PNR in rhizosphere soil of T. orientalis, whereas AOA were more important for P. australis. In addition, denitrifiers containing the nirS gene were found to be the main drivers of DEA, and AOA and AOB also contributed to the denitrification process in the rhizosphere soil of both plants. Furthermore, the abundance of nitrifiers was significantly affected by the C:N ratio, soil organic matter and moisture, whereas the abundance of denitrifiers was affected by soil moisture and pH.

scholarly journals Effect of the Influent Substrate Concentration on Nitrogen Removal from Summer to Winter in Field Pilot-Scale Multistage Constructed Wetland–Pond Systems for Treating Low-C/N River Water

2021 ◽  
Vol 13 (22) ◽  
pp. 12456
Author(s):  
Tao Wang ◽  
Liping Xiao ◽  
Hongbin Lu ◽  
Shaoyong Lu ◽  
Xiaoliang Zhao ◽  
...  
Keyword(s):  
River Water ◽  
Constructed Wetlands ◽  
Nitrogen Removal ◽  
Constructed Wetland ◽  
Substrate Concentration ◽  
Removal Rate ◽  
Carbon Sources ◽  
River Estuary ◽  
Pilot Scale ◽  
Surface Flow

The quality of micropolluted water is unstable and its substrate concentration fluctuates greatly. The goal is to predict the concentration effect on the treatment of nitrogen in a river with an actual low C/N ratio for the proposed full-scale Xiaoyi River estuary wetland, so that the wetland project can operate stably and perform the water purification function effectively in the long term. Two pilot-scale multistage constructed wetland–pond (MCWP) systems (S1 and S2, respectively) based on actual engineering with the same “front ecological oxidation ponds, two-stage horizontal subsurface flow constructed wetlands and surface flow constructed wetlands (SFCWs) as the core and postsubmerged plant ponds” as the planned process were constructed to investigate the effect of different influent permanganate indexes (CODMn) and total nitrogen (TN) contents on nitrogen removal from micropolluted river water with a fixed C/N ratio from summer to winter in the field. The results indicate that the TN removal rate in the S1 and S2 systems was significant (19.56% and 34.84%, respectively). During the process of treating this micropolluted water with a fixed C/N ratio, the influent of S2 with a higher CODMn concentration was conducive to the removal of TN. The TN removal rate in S2 was significantly affected by the daily highest temperature. There was significant nitrogen removal efficiency in the SFCWs. The C/N ratio was a major determinant influencing the nitrogen removal rate in the SFCWs. The organic matter release phenomenon in SFCWs with high-density planting played an essential role in alleviating the lack of carbon sources in the influent. This research strongly supports the rule that there is seasonal nitrogen removal in the MCWPs under different influent substrate concentrations, which is of guiding significance for practical engineering.

Intermittent Aeration for Nitrogen Removal in Small Oxidation Ditches

1990 ◽  
Vol 22 (3-4) ◽  
pp. 131-138 ◽  
Author(s):  
Hiroyuki Araki ◽  
Kenichi Koga ◽  
Katsuto Inomae ◽  
Tetsuya Kusuda ◽  
Youichi Awaya
Keyword(s):  
Nitrogen Removal ◽  
Cycle Time ◽  
Test Plant ◽  
Nitrification Rate ◽  
Oxidation Ditch ◽  
Intermittent Aeration ◽  
Tank Model ◽  
Scale Test ◽  
Total Nitrogen Removal ◽  
Removal Processes

An intermittent aeration method is available for nitrogen removal in a small oxidation ditch. The purpose of this study is to establish a basis for design and operation of the oxidation ditch with the intermittent aeration method. Discussions on the essential process parameters depending on cycle time tc, aerobic period ta, specific nitrification rate vn and specific denitrification rate vd were carried out by using a continuous-flow stirred-tank model. It is shown theoretically that an optimum range of the aerobic time ratio (ta/tc) for nitrogen removal exists in the region of 1/v n* to 1-1/vd*. From evaluating an amount of leaking nitrogen in the intermittent aeration, the cycle time is proved to be minimized. Experiments in a full scale test plant were conducted to affirm the validity of the proposed basis. It is confirmed that the total nitrogen removal efficiency of 90% is achieved and the estimated removal efficiencies by this basis agree well with the experimental data. The newly proposed basis and parameters for nitrogen removal using the intermittent aeration method are available for not only an oxidation ditch but also other nitrogen removal processes by single sludge systems.

scholarly journals Nitrogen removal from summer to winter in a field pilot-scale multistage constructed wetland-pond system

2020 ◽  
Author(s):  
Liping Xiao ◽  
Tao Wang ◽  
Hongbin Lu ◽  
Shaoyong Lu ◽  
Jiaxin Li ◽  
...  
Keyword(s):  
Removal Efficiency ◽  
Total Nitrogen ◽  
Nitrogen Removal ◽  
Constructed Wetland ◽  
Pilot Scale ◽  
Surface Flow ◽  
Treatment Unit ◽  
Pond System ◽  
Load Rate ◽  
Plant Harvesting

Abstract Background Single-stage constructed wetlands (CWs) has a single ecological service function and is greatly affected by temperature, which are general in removal of total nitrogen. Multistage hybrid CWs were proven to capable of enhancing removal of nitrogen. Therefore, this study aimed to explore the variation in nitrogen removal in the combined CWs-pond process from summer to winter and the contribution of plant harvesting and the functions of bacteria to nitrogen removal. Methods A pilot-scale multistage constructed wetland-pond system (MCWP) with the process of "the pre-ecological oxidation pond + the two-level horizontal subsurface flow constructed wetland (HSCW) + the surface flow constructed wetland (SFCW) and the submerged plant pond (SPP)" was used to treat actual polluted river water in the field. During the 124 days of operation, the nitrogen concentrations in the units influent and effluent of the system were measured every two days, and the plant height in HSCWs and SFCW was measured once per month. When the system operated stably to the 72nd day, the substrates in the CWs were sampled to analyze the bacterial community structure and composition. Results The concentration of total nitrogen (TN) in the MCWP gradually decreased from 3.46 mg/L to 2.04 mg/L, and the average removal efficiency of TN was approximately 40.74%. The SPP performed the best among all units, and the TN removal efficiency was as high as 16.08%. The TN removal efficiency was significantly positively affected by the daily highest temperature. A formula between the total TN removal efficiency and the highest temperature was obtained by nonlinear fitting. The TN removal load rate in the HSCWs was 2.7–3.7 times that of the SFCW. Furthermore, the TN transformed by Iris pseudacorus L. accounted for 54.53% in the SFCW. Conclusion We found that the significant positive correlation between the daily highest temperature and the total TN removal rate a field MCWP system. The SFCW, as an advanced treatment unit, increased the proportion of nitrogen removed by plant harvesting. The bacteria completed the nitrogen cycle in the SFCW, which had high-density planting, through a variety of nitrogen removal pathways.

Pollutant removal within hybrid constructed wetland systems in tropical regions

2009 ◽  
Vol 59 (2) ◽  
pp. 233-240 ◽  
Author(s):  
T. Y. Yeh ◽  
C. H. Wu
Keyword(s):  
Total Nitrogen ◽  
Nitrogen Removal ◽  
Constructed Wetland ◽  
Metal Removal ◽  
Nitrate Nitrogen ◽  
Aerobic Oxidation ◽  
Heavy Metal Removal ◽  
Surface Flow ◽  
Pollutant Removal ◽  
Oxidation Pond

Hybrid constructed wetlands have received tremendous interests for water quality enhancement due to insufficient sewage treatment and groundwater deterioration in Taiwan. The main objectives of this study were to investigate pollutant removal efficiencies and mechanisms within field-scale hybrid natural purification systems. The studied hybrid constructed wetland systems include an oxidation pond, two serial surface flow wetlands with a cascade in between, and a subsurface flow wetland receiving secondary treated dormitory sewage. The average SS, BOD and COD percent removal efficiency was 86.7, 86.5 and 57.8%, respectively. The ratio of BOD to COD decreased from 0.65 in the initial aerobic compartment to 0.21 in anoxic parts of the systems, indicating most biological degradable materials were decomposed in the aerobic oxidation pond and surface flow wetlands. Heavy metal removal percentages of copper and zinc were 72.9 and 68.3%, respectively. Sedimentation and plant uptake are the possible sinks for metals retention. Significant phosphorus removal was not achieved in this study. Total Kjeldahl nitrogen (TKN) and ammonium decreased from 4.08 to 1.43 and 3.74 to 1.21 mg/L, respectively, while nitrate nitrogen increased from 1.91 to 3.85 mg/L within the aerobic oxidation pond and surface flow wetlands. This result demonstrated nitrification occurring within aerobic compartments. The nitrate nitrogen continued to decrease from 3.85 to 1.43 mg/L within the anoxic subsurface wetlands mainly through denitrification transformation. Total nitrogen removal was from 7.61 to 3.61 mg/L, with the percentage removal of total nitrogen around 52.6%. The primary nitrogen removal and transformation mechanisms within the studied wetland systems were nitrification within aerobic followed by denitrificaiton within anaerobic systems. The emergent macrophytes enhance aeration through oxygen transferring that attributing the higher organic matter removal and nitrification rate. The hybrid wetland systems are viable options of pollutants transformation and removal in tropical countries, while tertiary wastewater systems are too costly or unable to operate. Effluent of purified systems can comply with local surface water criteria rendering for groundwater recharge.

scholarly journals A Better MLE Nitrification Process Adopted from STOAT Simulation Experiments

2021 ◽  
Vol 43 (6) ◽  
pp. 443-452
Author(s):  
Taewook Kim ◽  
Sunjoo Cho ◽  
Sung-Hyun Kwon ◽  
Daechul Cho
Keyword(s):  
Nitrogen Removal ◽  
Water Conservation ◽  
Reduction Rate ◽  
Ammonia Concentration ◽  
Nitrification Rate ◽  
Process Variables ◽  
Simulation Experiments ◽  
Nitrification Process ◽  
Do Concentration ◽  
Removal Processes

Objectives : Nitrogen removal processes are very important in terms of water conservation. Among them, the MLE process has been difficult to optimize because it has many variations and required experiences in operation.Methods : In this work, we quantitatively analyzed the nitrification of the MLE process using the STOAT simulation program. In particular, we attempted to improve nitrification rate even at lower water temperatures.Results and Discussion : As a result, more than 93% ammonia was nitrificated when the water temperature was above 20℃, and a lower reduction rate of ammonia was observed when the temperature was below 15℃. Simulations applying three process variables (MLSS, DO concentration, and RAS) were carried out once or several times to increase nitrogen removal efficiency at 10℃, and the most efficient variable was ‘RAS increase’(55% reduction of ammonia).Conclusions : For more efficient nitrification rate, simultaneous increases in RAS and DO were required. In this case, the ammonia concentration in the effluent dropped by 61.4% and it was desirable to increase the MLSS return volume for T-N concentration reduction.

Enhancement of nitrogen removal via addition of cattail litter in surface flow constructed wetland

2018 ◽  
Vol 204 ◽  
pp. 205-211 ◽  
Author(s):  
Suqing Wu ◽  
Lei Gao ◽  
Jianya Gu ◽  
Weili Zhou ◽  
Chunzhen Fan ◽  
...  
Keyword(s):  
Nitrogen Removal ◽  
Constructed Wetland ◽  
Surface Flow

Enhancement of nitrogen removal in subsurface flow constructed wetlands employing a 2-stage configuration, an unsaturated zone, and recirculation

1995 ◽  
Vol 32 (3) ◽  
pp. 59-67 ◽  
Author(s):  
Kevin D. White
Keyword(s):  
Constructed Wetlands ◽  
Nitrogen Removal ◽  
Constructed Wetland ◽  
Subsurface Flow ◽  
Great Promise ◽  
Effluent Recirculation ◽  
Wetland Treatment ◽  
Subsurface Flow Constructed Wetlands ◽  
Inlet Zone ◽  
Bod Removal

Constructed wetland technology is currently evolving into an acceptable, economically competitive alternative for many wastewater treatment applications. Although showing great promise for removing carbonaceous materials from wastewater, wetland systems have not been as successful at nitrification. This is primarily due to oxygen limitations. Nitrification does occur in conventional wetland treatment systems, but typically requires long hydraulic retention times. This paper describes a study that first evaluated the capability of subsurface flow constructed wetlands to treat a high strength seafood processor wastewater and then evaluated passive aeration configurations and effluent recirculation with respect to nitrogen treatment efficiency. The first stage of a 2-stage wetland treatment system exhibited a relatively short hydraulic retention time and was designed for BOD removal only. The second stage wetland employed an unsaturated inlet zone and effluent recirculation to enhance nitrification. Results indicate that organic loading, and thus BOD removal, in the first stage wetland is key to optimal nitrification. Passive aeration through an unsaturated inlet zone and recirculation achieved up to 65-70 per cent ammonia nitrogen removal at hydraulic retention times of about 3.5 days. Inlet zone configuration and effluent recirculation is shown to enhance the nitrogen removal capability of constructed wetland treatment systems.

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