Removal of nitrogen in constructed wetlands with horizontal sub-sureface flow: a review

Vymazal, Jan; Kröpfelová, Lenka

doi:10.1672/08-216.1

“…When comparing different studies, the removal efficiency varies considerably, which makes it difficult to assess the extent to which wetland creation is an efficient measure to reduce eutrophication. Several previous studies [10][11][12][13][14][15][16][17][18] (cited in the protocol for this systematic review [19]) have indicated that removal differences between wetlands are related to a number of different factors such as inflow concentration, load variations, hydraulic retention time, temperature, hydraulic efficiency, and type of wetland. This calls for a systematic review of removal rates and how they are influenced by the wetland characteristics, loading differences, and environmental factors.…”

Section: Introductionmentioning

confidence: 99%

How effective are created or restored freshwater wetlands for nitrogen and phosphorus removal? A systematic review

Land

¹

,

Granéli

²

,

Grimvall

³

et al. 2016

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Background: Eutrophication of aquatic environments is a major environmental problem in large parts of the world. In Europe, EU legislation (the Water Framework Directive and the Marine Strategy Framework Directive), international conventions (OSPAR, HELCOM) and national environmental objectives emphasize the need to reduce the input of nutrients to freshwater and marine environments. A widely used method to achieve this is to allow water to pass through a created or restored wetland. However, the large variation in measured nutrient removal rates in such wetlands calls for a systematic review. Methods:Searches for primary studies were performed in electronic databases and on the internet. One author performed the screening of all retrieved articles at the title and abstract level. To check that the screening was consistent and complied with the agreed inclusion/exclusion criteria, subsets of 100 articles were screened by the other authors. When screening at full-text level the articles were evenly distributed among the authors. Kappa tests were used to evaluate screening consistency. Relevant articles remaining after screening were critically appraised and assigned to three quality categories, from two of which data were extracted. Quantitative synthesis consists of meta-analyses and response surface analyses. Regressions were performed using generalized additive models that can handle nonlinear relationships and interaction effects.Results: Searches generated 5853 unique records. After screening on relevance and critical appraisal, 93 articles including 203 wetlands were used for data extraction. Most of the wetlands were situated in Europe and North America. The removal rate of both total nitrogen (TN) and total phosphorus (TP) is highly dependent on the loading rate. Significant relationships were also found for annual average air temperature (T) and wetland area (A). Median removal rates of TN and TP were 93 and 1.2 g m −2 year −1 , respectively. Removal efficiency for TN was significantly correlated with hydrologic loading rate (HLR) and T, and the median was 37 %, with a 95 % confidence interval of 29-44 %. Removal efficiency for TP was significantly correlated with inlet TP concentration, HLR, T, and A. Median TP removal efficiency was 46 % with a 95 % confidence interval of 37-55 %. Although there are small differences in average values between the two quality categories, the variation is considerably smaller among high quality studies compared to studies with lower quality. This suggests that part of the large variation between studies may be explained by less rigorous study designs. Conclusions:On average, created and restored wetlands significantly reduce the transport of TN and TP in treated wastewater and urban and agricultural runoff, and may thus be effective in efforts to counteract eutrophication. However, restored wetlands on former farmland were significantly less efficient than other wetlands at TP removal.

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“…Horizontal subsurface flow (HSSF) CWs have long been used for treatment of domestic and municipal wastewater. Nowadays however, there is the increasing trend of using HSSF CW for other types of wastewater including industrial, agricultural, and landfill leachates [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Bacterial Community Abundance and Structure in Horizontal Subsurface Flow Wetland Mesocosms Treating Municipal Wastewater

Oopkaup

¹

,

Truu

²

,

Nõlvak

³

et al. 2016

Water

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Dynamics of bacterial community abundance and structure of a newly established horizontal subsurface flow (HSSF) pilot-scale wetland were studied using high-throughput sequencing and quantitative polymerase chain reaction (PCR) methods. Bacterial community abundance increased rapidly within one month and stabilised thereafter in three replicate HSSF constructed wetland (CW) mesocosms. The most dominant phylum was Proteobacteria, followed by Bacteroidetes in wetland media biofilms and Firmicutes in influent wastewater. CW bacterial community diversity increased over time and was positively related to the wastewater treatment efficiency. Increase in the abundance of total bacteria in the community was accompanied with the abundance of denitrifying bacteria that promoted nitrate and nitrite removal from the wastewater. During the 150-day study period, similar patterns of bacterial community successions were observed in replicate HSSF CW mesocosms. The data indicate that successions in the bacterial community in HSSF CW are shaped by biotic interactions, with a significant contribution made by external abiotic factors such as influent chemical parameters. Network analysis of the bacterial community revealed that organic matter and nitrogen removal in HSSF CW could be, in large part, allocated to a small subset of tightly interconnected bacterial species. The diversity of bacterial community and abundance of denitrifiers were good predictors of the removal efficiency of ammonia, nitrate and total organic C in HSSF CW mesocosms, while the removal of the seven-day biochemical oxygen demand (BOD 7 ) was best predicted by the abundance of a small set of bacterial phylotypes. The results suggest that nitrogen removal in HSSF CW consist of two main pathways. The first is heterotrophic nitrification, which is coupled with aerobic denitrification and mediated by mixotrophic nitrite-oxidizers. The second pathway is anaerobic denitrification, which leads to gaseous intermediates and loss of nitrogen as N 2 .

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“…Vymazal and Kroepfelova [6] described the removal of nitrogen in horizontal sub-surface flow constructed wetlands (HF CWs) for various types of wastewater. The survey included more than 900 annual means from more than 300 systems in 36 countries that were categorized into municipal, industrial, agricultural, and landfill leachate.…”

Section: Introductionmentioning

confidence: 99%

How effective are created or restored freshwater wetlands for nitrogen and phosphorus removal? A systematic review protocol

Land

¹

,

Granéli

²

,

Grimvall

³

et al. 2013

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Background: Eutrophication of aquatic environments is a major environmental problem in large parts of the world. In Europe, EU legislation (the Water Framework Directive and the Marine Strategy Framework Directive), international conventions (OSPAR, HELCOM) and national environmental objectives emphasize the need to reduce the input of plant nutrients to freshwater and marine environments. A widely used method to achieve this is to let water pass through a constructed or restored wetland (CW). However, the large variation in measured nutrient removal rates in such wetlands calls for a systematic review. The objective of this review is to quantify nitrogen and phosphorus removal rates in constructed or restored wetlands and relate them to wetland characteristics, loading characteristics, and climate factors. Wetlands are created to treat water from a number of different sources. Sources that will be considered in this review include agricultural runoff and urban storm water run-off, as well as aquaculture wastewater and outlets from domestic wastewater treatment plants, with particular attention to the situation in Sweden. Although the performance of wetlands in temperate and boreal regions is most relevant to the Swedish stakeholders a wider range of climatic conditions will be considered in order to make a thorough evaluation of climatic factors.

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Removal of nitrogen in constructed wetlands with horizontal sub-sureface flow: a review

Cited by 51 publications

References 42 publications

How effective are created or restored freshwater wetlands for nitrogen and phosphorus removal? A systematic review

How effective are created or restored freshwater wetlands for nitrogen and phosphorus removal? A systematic review

Dynamics of Bacterial Community Abundance and Structure in Horizontal Subsurface Flow Wetland Mesocosms Treating Municipal Wastewater

How effective are created or restored freshwater wetlands for nitrogen and phosphorus removal? A systematic review protocol

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