R Harrington

The Integrated Constructed Wetlands (ICW) concept

The free surface flow Integrated Constructed Wetlands (ICW) concept explicitly combines the objectives of cleansing and managing water flow from farmyards with that of integrating the wetland infrastructure into the landscape and enhancing its biological diversity. This leads to system robustness and sustainability. Hydraulic dissipation, vegetation interception, and evapotranspiration create an additional freeboard at the outlet of each wetland segment and at the point of discharge, thus enhancing hydraulic residence time and cleansing capacity during hydraulic fluxes. The principal design criteria leading to adequate effluent water quality (i.e., molybdate reactive phosphorus less than 1 mg/1) from ICW are that the wetland area needs to be sized by a factor of at least 1.3 times the farmyard area and the aspect ratio for the individual wetland segments (i.e., approximately four cells) needs to be less than 1:2.2 (width to length). Within a year of ICW commissioning, approximately 75% of farmyard runoff was intercepted, leading to improvements in the receiving surface waters of the catchment. Most of the recorded phosphate concentrations after ICW treatment agreed with the Irish Urban Wastewater Treatment Regulation 2001, which can be used as a benchmark to assess ICW treatment performance and which is usually applied unofficially to ICW even if it may appear to be too stringent. A case study of 13 ICW systems suggested that phosphorus exported from an ICW system was similar to the typical background concentrations of phosphorus export rates from land to water.

Integrated Constructed Wetlands (ICW) for livestock wastewater management.

Social, economic and environmental coherence is sought in the management of livestock wastewater. Wetlands facilitate the biogeochemical processes that exploit livestock wastewater and provide opportunities to achieve such coherence and also to deliver on a range of ecosystem services. The Integrated Constructed Wetland (ICW) concept integrates three inextricably linked objectives: water quantity and quality management, landscape-fit to improve aesthetic site values and enhanced biodiversity. The synergies derived from this explicit integration allow one of the key challenges for livestock management to be addressed. An example utilizing twelve ICW systems from a catchment on the south coast of Ireland demonstrates that over an eight year period mean reduction of total and soluble phosphorus (molybdate reactive phosphorus) exceeded 95% and the mean removal of ammonium-N exceeded 98%. This paper reviews evidence regarding the capacity of ICWs to provide a coherent and sustainable alternative to conventional systems.

Assessment of the nutrient removal performance in integrated constructed wetlands with the self-organizing map

The self-organizing map (SOM) model was applied to predict outflow nutrient concentrations for integrated constructed wetlands (ICWs) treating farmyard runoff. The SOM showed that the outflow ammonia-nitrogen concentrations were strongly correlated with water temperature and salt concentrations, indicating that ammonia-nitrogen removal is effective at low salt concentrations and comparatively high temperatures in ICWs. Soluble reactive phosphorus removal was predominantly affected by salt and dissolved oxygen concentrations. In addition, pH and temperature were weakly correlated with soluble reactive phosphorus removal, suggesting that soluble reactive phosphorus was easily removed within ICWs, if salt concentrations were low, and dissolved oxygen, temperature and pH values were high. The SOM model performed very well in predicting the nutrient concentrations with water quality variables such as temperature, conductivity and dissolved oxygen, which can be measured cost-effectively. The results indicate that the SOM model was an appropriate approach to monitor wastewater treatment processes in ICWs.

The potential of integrated constructed wetlands (ICWs) to enhance macroinvertebrate diversity in agricultural landscapes

Integrated Constructed Wetlands (ICWs) constitute an alternative option for the treatment of agricultural wastewater in Ireland. These surface flow systems are formed by interconnected ponds and have the capacity to fit into the landscape and provide habitat for a wide range of biota, including macroinvertebrates that have enormous potential for biodiversity enhancement. For these reasons, five ICW systems were studied. In addition, five natural ponds were investigated to account for the potential of ICW ponds to mimic natural conditions. Nine river sites were also investigated to allow for an evaluation of the catchment biodiversity contribution of the ICW systems. The present study revealed that the last ponds in the chain of these ICW systems are capable of supporting a similar number of taxa as natural ponds. Furthermore, the contribution of the last ponds to the macroinvertebrate diversity at the catchment level was high. ICWs seem to integrate their effluent management and purifying properties with that of biodiversity enhancement and landscape fit. This is the first study to investigate the potential of constructed interconnected ponds, used for wastewater treatment, to enhance biodiversity in agricultural landscapes.

Application of the self-organizing map as a prediction tool for an integrated constructed wetland agroecosystem treating agricultural runoff.

A self-organizing map (SOM) model was applied as a prediction tool for the performance of an integrated constructed wetland (ICW) agroecosystem treating agricultural runoff to protect receiving watercourses. By utilizing the SOM model, the time-consuming to measure expensive biochemical oxygen demand outflow concentrations were predicted well by other inexpensive variables, which were quicker and easier to measure. Correct predictions for the outflow biochemical oxygen demand concentrations were between 89% and 100%. This novel approach allows for the real time control of the outflow water quality of the ICW and potentially also of other treatment system applications. Moreover, the missing values and outliers from the large but incomplete ICW data set were replaced accurately by most likely values determined by the SOM model. This was important because the proportions of unusable entries for chemical oxygen demand, suspended solids and biochemical oxygen demand were very high: 41%, 54%, and 61%, respectively.

Nitrogen removal in an integrated constructed wetland treating domestic wastewater

The nitrogen (N) removal performance of a 3.25 ha Integrated Constructed Wetland (ICW) treating domestic wastewater from Glaslough village in County Monaghan, Ireland, was evaluated in this study. The ICW consists of two sludge ponds and five shallow vegetated wetland cells. Influent and effluent concentrations of two N species, namely, ammonia-nitrogen (NH3-N) and nitrate-nitrogen (NO3-N), which were measured weekly over 2 years, together with hydrology of the ICW provided the basis for this evaluation. The influent wastewater typically contained 40 mg L−1 NH3-N and 5 mg L−1 NO3-N. Concentrations of N in the ICW effluent were typically less than 1.0 mg L−1 for both species. Overall, a total load of 2802 kg NH3-N and 441 kg NO3-N was received by the ICW and a removal rate of 98.0 % and 96.9 %, respectively, was recorded. Average areal N loading rate (245 mg m−2 d−1 NH3-N and 38 mg m−2 d−1 NO3-N) had a significant linear relationship with areal N removal rate (240 mg m−2 d−1 and 35 mg m−2 d−1, respectively) for both species. The areal first-order N removal rate constants in the ICW averaged 14 m yr−1 for NH3-N and 11 m yr−1 for NO3-N. Temperature coefficients (θ) for N reduction in the ICW were lower and less than unity for NO3-N, suggesting that the variability in N removal by the ICW was marginally influenced by temperature.

A review of the potential of surface flow constructed wetlands to enhance macroinvertebrate diversity in agricultural landscapes with particular reference to Integrated Constructed Wetlands (ICWs)

Integrated Constructed Wetlands (ICWs) constitute an alternative way of cleansing water in agricultural areas to conventional water treatment plants. These pond systems integrate their water treatment capabilities with other functions such as biodiversity enhancement, carbon sequestration and landscape fit, by virtue of mimicking natural wetlands. ICWs have shown to have potential to enhance macroinvertebrate diversity in agricultural areas due to their unique design flexibility. We suggest that ICWs characterised by adequate shore sloping and presence of complex habitat mosaics, as well as other design considerations, would maximise the potential of these systems to enhance macroinvertebrate diversity. In addition, it would be highly beneficial to increase the total ICW area and to increase the total number of ponds in a system accordingly from a minimum of four to at least five. This article also highlights the need not only to develop policies that focus on the creation of ICWs but also to foster a number of management practices that rely on the active involvement of farmers. The inclusion of additional ponds in selected ICW systems could be the means to inform local communities as to the importance, attractiveness and conservation value of ponds.

Comparison of macroinvertebrate community structure and driving environmental factors in natural and wastewater treatment ponds

Eutrophication still continues to be an issue of major concern for the protection of water quality, and accordingly, the European Union Water Framework Directive has set a minimum target for all waters where “good status” is defined as a slight departure from the biological community which would be expected in conditions of minimal anthropogenic impact. The use of constructed ponds for wastewater treatment aimed at achieving this target has shown to be an effective alternative to conventional systems in the farm landscape. Their applicability in these areas is of great interest since these ponds have the added potential to combine their wastewater treatment properties with that of biodiversity enhancement. This article focuses on exploring the community structure of both natural and constructed ponds used for wastewater treatment and the driving environmental factors. A total of 15 constructed and 5 natural ponds were sampled for aquatic macroinvertebrates and hydrochemistry in spring and summer 2006. Results showed that the most important factors responsible for the differences in the community structure between these two types of ponds were pH, vegetation structure and pollution levels. These gradients helped to structure a large proportion of the communities with some taxa being associated with the constructed ponds. These results highlight the potential contribution of constructed ponds used for wastewater treatment to the landscape biodiversity. The present findings also open the possibility for a more integrated management of water quality and biodiversity enhancement in farmland areas.

Statistical Modeling of Contaminants Removal in Mature Integrated Constructed Wetland Sediments

AbstractMultiple regression models, principal component analysis, redundancy analysis, and the self-organizing map (SOM) model were applied to assess the effects of physico-chemical parameters on the treatment performance of contaminated wetland sediments in replicate integrated constructed wetland (ICW) mesocosms treating either farmyard runoff or domestic wastewater. Dissolved oxygen concentration and conductivity were correlated with the reduction of ammonia–nitrogen (NH4–N) and/or molybdate reactive phosphorus (MRP), and the redox potential and conductivity were related to chemical oxygen demand (COD) removal. SOM was selected as the prediction model to provide numerical estimations for the performance of ICW mesocosms. The model was validated, indicating that NH4–N, MRP, and COD removal can be predicted by input variables that are quick and cost-effective to measure. The SOM model is an appropriate method for monitoring the performance of mature ICWs as a source of contaminants such as nitrogen and p...

Macroinvertebrate diversity in constructed ponds: community structure and driving environmental factors

Ponds in various parts of Europe have been shown to make a significant contribution to regional diversity (BRONMARK & HANSSON 2002, ÜERTLI et al. 2005) and can support more unique an d more rare species than other waterbody types (WrLLIAMS et al. 2003). A number of studies have emphasized the importance o f creating an d maintaining a variety o f pond types to maximise gamma biodiversity, drawing special attention to environmental factors such as water permanence ( e.g., BIGGS et al. 1994). Despite this, little research has been conducted on the environmenta1 factors that structure and promote macroinvertebrate diversity in ponds. Broos et al. (1994) suggested that seasonal ponds cou1d host rare species not found in other aquatic habitats. In addition, GEE et al. (1997) indicated that 2 small ponds supported more species together than a sing1e larger pond of similar area. Biotic factors also appear to be important; FAIRCHILD et al. (2000) showed that fish in ponds variably affected the number of anisopteran and trichopteran species. Considerably less is known about the macroinvertebrate communities or the environmental factors controlling biodiversity in ponds constructed for effluent treatment. In fact, only 3 studies have explored the macroinvertebrate communities in constructed wetlands and the relationships between these and environmental factors (FAIRCHILD et al. 2000, SPIELES & MnscH 2000, BALCOMBE et al. 2005). W e explored the environmental factors structuring the macroinvertebrate community composition of Integrated Constructed Wetlands (ICWs) from the Anne Valley, Co. Waterford, Ireland (E250600; Nl03750). These results may contribute to the implementation of good design principles to promote biodiversity in future pond creation.