Nutrient removal mechanisms in constructed wetlands and sustainable water management

1999 ◽  
Vol 40 (2) ◽  
pp. 121-128 ◽  
Author(s):  
K. Sakadevan ◽  
H. J. Bavor
Keyword(s):  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Agricultural Runoff ◽  
First Year ◽  
Hydraulic Loading ◽  
P Concentration ◽  
N Removal ◽  
Influent Water ◽  
Second Year ◽  
Total P

Constructed wetland systems are used to treat domestic and industrial wastewater and agricultural runoff. In this field study the influence of hydraulic loading, retention time, water column depth and phosphorus (P) concentrations of influent wastewater on P and nitrogen (N) removal was examined in experimental constructed wetland systems. Five constructed wetlands with a surface area of 150 m2, were developed in the field. Results showed that P concentrations of water from outlets of all five systems decreased (from as low as 11% decrease for the system which received wastewater with average P concentration of 8.2 mg P L−1 to as high as 48.9% decrease for the system which received wastewater with average P concentration of 3.58 mg P L−1) compared to the influent water. The N concentrations in the outlet water were also decreased in all five systems (from as low as 26.3% decrease to as high as 77.5% decrease) compared to the influent water. The total P and N in the wetland sediment increased in the first year in all five systems but were unchanged at the end of the second year. The study showed that low hydraulic loading and greater retention times positively enhanced removal of P and N from wastewater in constructed wetland systems.

Long-term nitrogen compound removal trends of a hybrid subsurface constructed wetland treating milking parlor wastewater throughout its 7 years of operation

2015 ◽  
Vol 73 (5) ◽  
pp. 1018-1024 ◽  
Author(s):  
J. Harada ◽  
T. Inoue ◽  
K. Kato ◽  
H. Izumoto ◽  
X. Zhang ◽  
...  
Keyword(s):  
Constructed Wetland ◽  
Nitrogen Compound ◽  
Total Carbon ◽  
Removal Rates ◽  
N Removal ◽  
Transformation Mechanisms ◽  
Water Recirculation ◽  
Second Year ◽  
Northern Japan

This study evaluated the nitrogen compound removal efficiency of a hybrid subsurface constructed wetland, which began treating milking parlor wastewater in Hokkaido, northern Japan, in 2006. The wetland's overall removal rates of total nitrogen (TN) and ammonium (NH4+-N) improved after the second year of operation, and its rate of organic nitrogen (Org-N) removal was stable at 90% efficiency. Only nitrate (NO3−-N) levels were increased following the treatment. Despite increased NO3−-N (maximum of 3 mg-N/L) levels, TN removal rates were only slightly affected. Removal rates of TN and Org-N were highest in the first vertical bed. NH4+-N removal rates were highest in the second vertical bed, presumably due to water recirculation and pH adjustment. Concentrations of NO3−-N appeared when total carbon (TC) levels were low, which suggests that low TC prevented complete denitrification in the second vertical bed and the final horizontal bed. In practice, the beds removed more nitrogen than the amount theoretically removed by denitrification, as calculated by the amount of carbon removed from the system. This carbon-nitrogen imbalance may be due to other nitrogen transformation mechanisms, which require less carbon.

Ammonium removal in constructed wetlands with recirculating subsurface flow: removal rates and mechanisms

1995 ◽  
Vol 32 (3) ◽  
pp. 193-202 ◽  
Author(s):  
F. J. Sikora ◽  
Tong Zhu ◽  
L. L. Behrends ◽  
S. L. Steinberg ◽  
H. S. Coonrod
Keyword(s):  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Removal Rate ◽  
N Uptake ◽  
Subsurface Flow ◽  
N Removal ◽  
Air Water Interface ◽  
Scirpus Cyperinus ◽  
Macrophyte Growth ◽  
Discernible Difference

From June 1993 through February 1994, the removal of NH4-N was evaluated in constructed wetlands at the TVA constructed wetland research facility in Muscle Shoals, AL. The objectives were to determine rates for NH4-N removal and speculate on potential mechanisms for removal. Nine constructed wetland cells were used with approximate dimensions of 9.1 × 6.1 × 0.6 m3 and a recirculating subsurface flow system in a gravel base. Treatments consisted of an unplanted (WO=control) and two polycultural planting schemes (P1=Scirpus acutus, Phragmites communis and Phalaris arundinacea; P2=Typha sp., Scirpus atrovirens georgianus and Scirpus cyperinus) replicated 3 times. Salt solutions were added and recirculated in each cell resulting in initial concentrations of 50 and 300 mg l−1 of NH4-N and COD, respectively, when fully diluted with wetland water. Salts were added to wetlands approximately every 6 weeks with the first addition on June 1, 1993 and the last addition on February 9, 1994 for a total of 6 time periods (times I, II, III, IV, V and VI). The COD of the waters was removed at rates ranging from 5.5 to 10 g/m2/d during times I through IV with no discernible difference amongst the planting treatments. Wetland cells with P1 were more efficient at removing NH4-N (1.1 g/m2/d) than P2 (0.6 g/m2/d) or WO (0.5 g/m2/d) at time I with differences decreasing by time IV (0.3 to 0.7 g/m2/d). During the winter (times V and VI), there were no differences in NH4-N removal amongst planting treatments with an average removal rate of 0.35 g/m2/d. There was a seasonal change in NH4-N removal in all the treatments, with the change most noticeable in the planted cells. The removal of NH4-N in WO was speculated to be due to a combination of sorption onto gravel, microbial assimilation, and nitrification at the air-water interface. The extra NH4-N removal in the planted cells diminished in the winter because the removal was most likely due to a combination of enhanced nitrification from O2 transport and NH4-N uptake mediated by seasonal macrophyte growth.

The Study on the Correlation between Removal Rate of Pollutants and its Influencing Factors in Xinxue River Constructed Wetland of China

2011 ◽  
Vol 374-377 ◽  
pp. 932-936
Author(s):  
Qun Miao ◽  
Chao Wang ◽  
Xiao Jie Cao ◽  
Yu Ting Gu ◽  
Jing Jing Sun
Keyword(s):  
Water Temperature ◽  
Total Nitrogen ◽  
Constructed Wetland ◽  
Significant Positive Correlation ◽  
Removal Rate ◽  
Significant Negative Correlation ◽  
Positive Correlation ◽  
N Removal ◽  
Analysis Theory ◽  
Influent Water

Based on the monitoring data of February~December 2009 from Xinxue River Constructed Wetland, the regression analysis theory was used to establish mathematical models to determine the correlationship among the removal rate of pollutants, pollutant concentration, water temperature and influent water inflow, and optimize the operation parameters of the wetland. The multivariate linear regression equation was established with Statistical analysis software (SPSS). According to the correlation coefficient of the equation: the NH3-N removal has a significant positive correlation with water temperature, and a significant negative correlation with influent flow, total nitrogen removal has a significant positive correlation with water temperature, COD removal has a significant positive correlation with COD influent concentration. In addition, veracity of the model was also checked by contrasting the measured and analog data of March~June 2010 from the wetland. The results show that this model has a desired effect to estimate the removal rate and effluent concentration of COD and NH3-N, but undesirable to total nitrogen.

scholarly journals The Use of Constructed Wetland for Mitigating Nitrogen and Phosphorus from Agricultural Runoff: A Review

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 476
Author(s):  
Jiayu Li ◽  
Bohong Zheng ◽  
Xiao Chen ◽  
Zhe Li ◽  
Qi Xia ◽  
...  
Keyword(s):  
Plant Species ◽  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Lemna Minor ◽  
Hydrilla Verticillata ◽  
Agricultural Runoff ◽  
Structure Design ◽  
Ceratophyllum Demersum ◽  
Nitrogen And Phosphorus ◽  
Emergent Plants

The loss of nitrogen and phosphate fertilizers in agricultural runoff is a global environmental problem, attracting worldwide attention. In the last decades, the constructed wetland has been increasingly used for mitigating the loss of nitrogen and phosphate from agricultural runoff, while the substrate, plants, and wetland structure design remain far from clearly understood. In this paper, the optimum substrates and plant species were identified by reviewing their treatment capacity from the related studies. Specifically, the top three suitable substrates are gravel, zeolite, and slag. In terms of the plant species, emergent plants are the most widely used in the constructed wetlands. Eleocharis dulcis, Typha orientalis, and Scirpus validus are the top three optimum emergent plant species. Submerged plants (Hydrilla verticillata, Ceratophyllum demersum, and Vallisneria natans), free-floating plants (Eichhornia crassipes and Lemna minor), and floating-leaved plants (Nymphaea tetragona and Trapa bispinosa) are also promoted. Moreover, the site selection methods for constructed wetland were put forward. Because the existing research results have not reached an agreement on the controversial issue, more studies are still needed to draw a clear conclusion of effective structure design of constructed wetlands. This review has provided some recommendations for substrate, plant species, and site selections for the constructed wetlands to reduce nutrients from agricultural runoff.

scholarly journals The Elliot Ditch Constructed Wetlands

2007 ◽  
Vol 2 (3) ◽  
pp. 79-87
Author(s):  
Aaron A Zambo
Keyword(s):  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Agricultural Runoff ◽  
Load Reduction ◽  
Nitrogen And Phosphorus ◽  
Detention Time ◽  
Wetland System ◽  
Contaminant Load

The purpose of this experiment was to determine the contaminant load reduction incurred using a constructed wetland with an average hydraulic detention time of five days in treating agricultural runoff. The main contaminants present in the runoff were nitrogen and phosphorus from agricultural fertilizers. The findings of the experiment show that significant contaminant load reduction results can be achieved with a detention time, of as little as five days, in a properly constructed wetland system.

scholarly journals Wetland Technologies for Nursery and Greenhouse Compliance with Nutrient Regulations

HortScience ◽  
2013 ◽  
Vol 48 (9) ◽  
pp. 1103-1108 ◽  
Author(s):  
Sarah A. White
Keyword(s):  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Public Awareness ◽  
Subsurface Flow ◽  
Agricultural Runoff ◽  
Surface Flow ◽  
Treatment Wetlands ◽  
Treatment Technology ◽  
Subsurface Flow Constructed Wetlands ◽  
Floating Treatment Wetlands

The need to protect our water resources and increasing public awareness of the importance of cleaner water for ecological and human health reasons are driving regulations limiting nutrient release from traditionally exempt, non-point source agricultural contributors. Modification of production practices alone may not be adequate to meet regulated nutrient criterion limits for irrigation and stormwater runoff entering surface waters. Three constructed wetland technologies are well suited to help agricultural producers meet current and future regulations. The first two technologies, surface- and subsurface-flow constructed wetlands, have been in use for over 40 years to cleanse various types of wastewater, whereas floating treatment wetlands are an emerging remediation technology with potential for both stormwater and agricultural runoff treatment applications. The mechanisms driving removal of both nitrogen (N) and phosphorus (P) in constructed wetland systems are discussed. Surface-flow constructed wetlands remediate N contaminants from both container nursery and greenhouse production wastewater, whereas P remediation is variable and tied most closely to active plant growth as the constructed wetland ages. Subsurface-flow constructed wetlands effectively remediate N from production wastewater and can be tailored to increase consistency of P remediation through selection of P-sorbing root-bed substrates. Floating treatment wetlands effectively remediate both N and P with a designed surface area of a pond covered depending on the target effluent concentration or regulated total maximum daily load. The choice of treatment technology applied by growers to meet regulated water quality targets should be based on both economic and site-specific considerations.

scholarly journals A tracer study in a vertical flow constructed wetland treating septage

2018 ◽  
Vol 15 (3) ◽  
pp. 345-353 ◽  
Author(s):  
Jason Jie Xiang Bui ◽  
Yee Yong Tan ◽  
Fu Ee Tang ◽  
Carrie Ho
Keyword(s):  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Retention Time ◽  
Evaluation Method ◽  
Hydraulic Retention Time ◽  
Vertical Flow ◽  
Content Type ◽  
Hydraulic Loading ◽  
Hydraulic Behaviour ◽  
Vertical Flow Constructed Wetland

Purpose This study aims to investigate the hydraulic behaviour of a pilot-scale, two-staged, vertical flow constructed wetland (VFCW) for septage treatment, in terms of factors such as hydraulic retention time and hydraulic loading rate and its influence on the treatment dynamics. Because of intermittent feeding mode of VFCW systems and variation in its loading, its hydraulic behaviour is highly variable and need to be understood to optimize its treatment performance. Design/methodology/approach Tracer test were carried out using bromide ion with varying hydraulic loading rates (HLR) of 6.82 cm/d, 9.09 cm/d and 11.40 cm/d (i.e. equivalent to 75 L/d, 100L/d and 125 L/d). Tracer data is then analysed using the Residence Time Distribution (RTD) method. Findings RTD analysis showed that the increase in HLR increases the average hydraulic retention time (HRT). Subsequently, the increase in HLR results in a lower recovery of effluent, resulting in poor productivity in treatment. The study also showed that the removal of nitrogen and organic matter improved with increasing HRT. However, observations show no correlation between HRT and total solids removal. Originality/value A performance evaluation method (by tracer) is proposed to understand the hydraulics of flow in constructed wetlands, which has not been widely studied. Additionally, the dynamics of treatment in VFCWs treating septage may also be revealed by the tracer method. The study can be applied to any constructed wetlands designed for treatment of wastewater, septage or sludge.

Role of plant uptake on nitrogen removal in constructed wetlands located in the tropics

1997 ◽  
Vol 36 (12) ◽  
pp. 1-8 ◽  
Author(s):  
Thammarat Koottatep ◽  
Chongrak Polprasert
Keyword(s):  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Plant Uptake ◽  
Aquatic Vegetation ◽  
Initial Density ◽  
Free Water ◽  
N Removal ◽  
N Assimilation ◽  
Removal Efficiencies

Major interactive components of the constructed wetlands such as aquatic vegetation, substratum, water, microorganisms and animals play significant roles in the treatment of wastewaters. For nitrogen (N) removal, a sequential nitrification/denitrification reaction and plant uptake are two major treatment mechanisms, while NH3 volatilization is considered to be insignificant under the liquid pH lower than 8. In this research, both laboratory- and pilot-scale constructed wetlands were operated in the free water surface (FWS) mode. In order to investigate the role of plant uptake of N, narrow-leave cattails (Typha augustifolia) were planted at the initial density of 35 rhizomes/m2. Based on N mass balance, approximately 50% of the total nitrogen (TN) loaded into the constructed wetlands, operating at the hydraulic retention time (HRT) of 2–10 days, was accounted for by the amount of N assimilation into the plant tissues, resulting in the total kjeldahl nitrogen (TKN) and chemical oxygen demand (COD) removal efficiencies of 40–70% and 71–83%, respectively. To further investigate the role of plant uptake, the cattail plants harvested at the intervals of 2, 4, 8, and 12 weeks of operation resulted in the TN removal efficiencies of 73, 78, 86 and 80%, respectively. The constructed wetland unit having the plant harvesting interval of 8 weeks yielded the N plant uptake of 7.1–7.5 kg/(ha.day) amounting to 66–71% of the TN input. Some biogeochemical parameters such as oxidation-reduction potential (Eh) and dissolved oxygen (DO) in the constructed wetland beds suggested the occurrence of anoxic and reduced conditions which were favorable for the N removal processes such as plant uptake, ammonification, and nitrification/denitrification.

Hydraulic performance of a mature wetland treating milkhouse wastewater and agricultural runoff

2009 ◽  
Vol 59 (12) ◽  
pp. 2455-2462 ◽  
Author(s):  
S. Speer ◽  
P. Champagne ◽  
A. Crolla ◽  
C. Kinsley
Keyword(s):  
Constructed Wetlands ◽  
Constructed Wetland ◽  
Preferential Flow ◽  
Agricultural Runoff ◽  
Hydraulic Performance ◽  
Tracer Study ◽  
Hydraulic Efficiency ◽  
Vegetation Density ◽  
Tracer Studies ◽  
Density Profiles

A tracer study is an efficient method of determining flow dynamics within a constructed wetland. In previous studies, a number of tracer studies have been carried out on various constructed wetlands covering a wide range of configurations. From these tracer studies it is evident that all constructed wetlands perform differently and generally with less efficiency than assumed by theoretical design computations. During the summer of 2004, a tracer study was performed on a constructed wetland located in Embrun, Ontario (Canada) treating milkhouse wastewater and agricultural runoff to determine its actual hydraulic performance. Sediment height and vegetation density profiles were also obtained and examined to explain the preferential flow pathways that were observed during the tracer analysis. It was determined that the constructed wetland had an effective treatment area representing 79% of the total area, and that the hydraulic efficiency of the system was 74%. Examination of the sediment height and vegetation density profiles resulted in no evidence of physical pathways that could be attributed to the establishment of preferential flow. The hydraulic efficiency was therefore attributed to the inflow and outflow layout of the constructed wetland cell, combined with wind induced mixing.

Pesticide retention in the watershed and in a small constructed wetland treating diffuse pollution

2005 ◽  
Vol 51 (3-4) ◽  
pp. 143-150 ◽  
Author(s):  
K. Haarstad ◽  
B.C. Braskerud
Keyword(s):  
Constructed Wetland ◽  
Chemical Properties ◽  
First Year ◽  
Order Stream ◽  
Balance Study ◽  
Aquatic Life ◽  
First Order ◽  
Second Year ◽  
One Year ◽  
Mass Balance Study

Loss of pesticides is likely from watersheds where pesticides are used. The herbicides propachlor, linuron and metamitron, and the fungicides propiconazole, fenpropimorph and metribuzin and metalaxyl, were applied on an arable soil plot. A mass balance study showed that approximately 96% of the applied pesticides disappeared within the watershed. Three pesticides remained as residuals in the soil profile one year after the application. The 4% of the pesticides that were lost from the watershed gave peak concentrations, appearing immediately after spraying, reaching levels that can be hazardous to aquatic life. The constructed wetland situated in the first-order stream generally managed to lower the peak concentrations significantly. For the summer season, retention varied from 12 to 67% the first year. The second year, we observed both loss and retention. Increasing the wetland surface from 0.2% to 0.4% of the watershed area increased the average retention with 21% units the first year and 9% units the second year. Chemical properties of the pesticides could explain some of the behaviour in the watershed and in the wetland.

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