Completed Projects

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Start date: 01/10/18           End date: 31/09/22

Funder: Teagasc

Principal Investigator: Prof Mark Healy and Dr Alma Siggins (University of Galway), Dr Pat Tuohy, Dr Daire O' Huallachain and Prof Owen Fenton (Teagasc)

Budget (€): 96,000

Summary:

Constructed wetlands (CWs) and intermittently loaded sand filters (ISFs) have been investigated for the treatment of agricultural wastewaters, and have been shown to provide efficient and sustainable treatment of DSW. Nevertheless, the large surface area requirements for treatment, poor long term phosphorus (P) removal, and media clogging are the main limitations of these systems. The addition of chemical coagulants to DSW, such as aluminium and ferric salts, have been found to be effective in clarifying DSW and removing organic matter, suspended solids (SS), P, and pathogens. To date, a combination of a coagulation process and CWs or ISFs have not been used to treat DSW. The hypothesis of this thesis is that the addition of a coagulation process as a pre-treatment step could improve the performance of CWs and ISFs, and overcome the shortcomings of the individual capacities of these systems. Therefore, the objective of this thesis was to investigate the combined capacities of coagulation-CWs and coagulation-ISFs and compare the results to the individual capacities of conventional CWs and ISFs.

To achieve this objective, an optimum chemical coagulant, mixing time, and dosage was identified in improving effluent quality of DSW. Following this, replicated pilot-scale hybrid CWs and ISFs, each employing a preliminary coagulation process using ferric chloride (FeCl₃), was operated for a 43-wk period on a dairy farm (representing an entire milking season in Ireland). Conventionally designed CWs and ISFs were used as study controls. The hybrid systems performed better and were able to operate effectively at higher hydraulic loading rates than conventional CWs and ISFs. The performance of the hybrid systems exceeded that of the conventional systems, obtained removal efficiencies ≥ 99 % for all measured water quality parameters (chemical oxygen demand, SS, P, nitrogen and turbidity), and complied with EU directives concerning urban wastewater treatment. The effluent quality from the conventional ISFs deteriorated over the timeframe of the study until clogging occurred, while the hybrid ISFs continued to perform effectively without any evidence of clogging or P breakthrough. Examination of the filter media in both filter types showed that conventional ISFs retained more biomass than hybrid coagulation-ISFs. Conventional ISFs lost approximately 85% of their initial infiltration capacity in the uppermost layer due to biomass build-up versus 40% loss for hybrid ISFs.

Overall, hybrid coagulation-CW/ISFs are a promising technology that require a small area (75% reduction in footprint in comparison to conventional systems) and minimal maintenance, and produce excellent effluent quality. The final effluent from the hybrid system may be may be legally discharged to receiving waters, or may be recycled to wash farm yards, saving water. In parallel, the sludge portion generated from the coagulation process, can be applied to amend soil properties with no adverse impacts on the grass growth, providing an agronomic value as an organic fertilizer, and reducing the risk of nutrient losses. This management approach could eliminate the pollution risk, and minimise overall net cost compared to land application of raw DSW.

Outputs:

Mohamad, A.Y.A., Tuohy, P., Healy, M.G., Fenton, O., O'hUallachain, D., Siggins, A. 2024. Effects of coagulation on chemical and microbial properties of water-soil-plant systems of constructed wetlands. Chemosphere 362: 142745. Ahmed_Chemosphere 

Mohamed, A.Y.A., Siggins, A., Healy, M.G., O hUallachain, D., Fenton, O., Tuohy, P. 2020. Appraisal and ranking of poly-aluminium chloride, ferric chloride and alum for the treatment of dairy soiled water. Journal of Environmental Management 267: 110567.Mohamed et al. JEM‌

Mohamad, A.Y.A., Siggins, A., Healy, M.G., Fenton, O., O hUallachain, D., Tuohy, P. 2022. A novel hybrid coagulation-constructed wetland for the treatment of dairy wastewater. Science of the Total Environment 847: 157567 Mohamed et al. STOTEN

Mohamad, A.Y.A., Siggins, A., Healy, M.G., Fenton, O., O hUallachain, D., Tuohy, P. 2022. A novel hybrid coagulation-intermittent sand filter for the treatment of dairy wastewater. Journal of Cleaner Production 369: 133234 Mohamed et al. J. Clean. Prod.

Mohamed, A.Y.A., Tuohy, P., Healy, M.G., Ó hUallacháin, D., Fenton, O., Siggins, A. 2023. Effects of wastewater pre-treatment on clogging of an intermittent sand filter. Science of the Total Environment 876: 162605. Ahmed_STOTEN_2023

Start date: 01/10/19    End date: 31/09/22

Funder: Marie Skłodoswka Curie Innovative Training Network

Principal Investigators: Prof Mark Healy (NUI Galway), Prof Owen Fenton (Teagasc)

Background:

Phosphorous (P) is essential for life, but it is a finite resource. The industrialization of food production in order to feed a rapidly expanding population is giving rise to serious leakage of P through the global agricultural food system. This is particularly pertinent in the dairy industry, where losses of P are causing environmental damage and ultimately putting food safety at risk. About 2-3% of the incoming milk for dairy processing is lost during cleaning operations, via washing steps and through occasional milk spills.4 The production of dairy products such as cheese and yogurt gives rise to P-rich dairy processing waste (DPW), and as a whole, the dairy industry is the EU’s largest industrial food wastewater contributor and one of the main sources of P-rich industrial effluent.5,6 The recent abolition of EU milk quotas (2015) has resulted in a 2.8% annual growth in milk production with a corresponding increase in DPW.7 If the management of DPW does not improve, then leakage of nutrients will continue to intensify, leading to environmental problems such as the eutrophication of water bodies by P run-off from soil.

To date, finding a solution to reusing P from DPW, other than direct land spreading of dairy wastewater sludge, has been hampered by a lack of available technology, suitably trained personnel and a market for the products. To stimulate innovation in technologies for producing substitutes for mined phosphate rock from P-rich wastes, the EU has proposed changes to the Fertilizers Regulations, which would permit CE labeling of waste-based fertilizers in order to ease their access to the single market11. This opens opportunities for the dairy processing industry to innovate by adapting technologies and new waste management strategies to minimize P leakage while benefiting from emerging market opportunities. To ensure the long-term economic and environmental sustainability of these non-mineral fertilizer products, they will need to provide plant crops with required nutrients and should not negatively impact on the environment or adversely affect the safety of food or animal feedstuff.

To achieve the goal of phosphorus recovery for new fertilizers from DPW, we must conduct robust scientific investigations, develop and test new technologies, train a new generation of researchers, re-configure current DPW processes, and share information and findings with industry, policymakers, standards bodies, and regulators. Our proposed multi-disciplinary, intersectoral research programme will directly address this need.

REFLOW will provide a unique opportunity for researchers to obtain the knowledge and skills needed to develop and deploy new technologies for socially and environmentally responsible innovative management of DPW, and to stimulate new markets for recycled P. This ETN will provide advanced training to a new generation of high-achieving early-stage researchers through a structured PhD programme, focused on three overall research goals.

1. To develop and demonstrate processes for the recovery and reuse of phosphorous (P) products from DPW;

2. To establish their fertilizer value and optimum application rates through laboratory protocols and field trials;

3. To address the environmental, social, food safety and economical challenges, ultimately finding marketdriven solutions for the new processes and fertilizer products.

Objectives: To model the fate and transport of P in novel fertilizers from DPW, added to soil and its impact on P soil cycling processes. Undertake batch, column and field plot experiments using soils from a long term P trial: Monitor the fate and transport of 33P radiolabelled DPW fertilizers added to soils (scintillation counter) in incubation and column experiments using intact soil cores from baseline soils that have never received P and soils that have undergone build-up and depletion cycles. Measure leaching losses from column experiments; At plot scale, P fractions and available P trends over a full grass growth year will be established on baseline plots and plots receiving fertilizers from DPW to establish changes in available P concentrations at varying application at rates, measured in conjunction with grass growth mesurements; Results from the incubation, column and plot scale experiments will be synthesised to model chemical and biological interactions between P derived from dairy waste and native soil P.

 Outputs:

Shi, W., Healy, M.G., Ashekuzzaman, S.M., Daly, K., Leahy, J.J., Fenton, O. 2021. Dairy processing sludge and co-products: a review of present and future re-use pathways in agriculture. Journal of Cleaner Production 314: 128035.

Shi, W., Fenton, O., Ashekuzzaman, S.M., Daly, K., Leahy, J.J., Khalaf, N., Chojacka, K., Numviyimana, C., Warchol, J., Healy, M.G. 2024. Fertiliser equivalent value of dairy processing sludge-derived STRUBIAS products using ryegrass (Lolium perenne L.) and spring wheat (Triticum aestivum). Jouurnal of Plant Nutrition and Soil Science 10: 1 - 10. Shi (J. Pl. Nutr.) 

Hu, Y., Khomenko, O., Shi, W., et al. 2021. Holistic review of dairy processing sludge and secondary STRUBIAS products used in agriculture. Frontiers in Sustainable Food Systems 5: 763020. Wenxuan_frontiers paper

Shi, W., Fenton, O., Ashekuzzaman, S.M., Daly, K., Leahy, J.J., Khalaf, N., Hu, Y., Chojnacka, S., Numyiyimana, C., Healy, M.G. 2022. An examination of maximum legal application rates of dairy processing and associated STRUBIAS fertilising products in agriculture. Journal of Envirnomental Management 301: 113880. Wenxuan JEM

Shi, W., Healy, M.G., Ashekuzzaman, S.M., Daly, K., Fenton, O. 2022. Mineral fertiliser equivalent value of dairy processing sludge and derived bichar using ryegrass (Lolium perenne L.) and spring wheat (Triticum aestivum). Journal of Environmental Management 321: 116012 Shi et al. JEM_2022

Start date: 01/09/19      End date: 30/06/22

Funder: H2020 - Water Joint Programming Initiative

Principal Investigator: Prof Mark Healy and Dr Oisin Callery

Objective:

Peatland are important in several regions as they contribute to many ecosystem services such as drinking water provision, biomass production and flood retention. When peatlands are drained, negative environmental impacts include reduced surface water quality, loss in biodiversity and green house gas emission. Peatland water management must consider ways to: i) reduce water-related environmental impacts, ii) produce crops and biomass, iii) limit subsidence and soil loss, iv) prevent fire during droughts, v) viable solutions for restoration and after use of degraded sites. Water management must consider different type of peatlands, different land use options, climate, and socio-economic settings. As peat subsides, acid sulphate soil may be exposed with time (from below peatlands). In coastal lowlands, acid surges and salt water intrusion add to the complexity of water management. To limit impacts on surface water and to reach environmental and sustainable development goals; water and land protection on peat soils should be better developed. The potential mitigation options depend on several issues such as land use, peatland type, hydrological setting, climate, geology and the socio-economic setting. Several recommendations for future peatland management have been discussed, suggested and/or required by authorities and NGOs. The options suggested often involve water management with effects on land use and therefore on local communities, land owners and biomass producers. The options outlined should be scientifically sound and tested in practice. Lack of effective, simple and robust water management options to achieve the policy goals result in stakeholders’ frustration, lack of compliance and poor environmental practice guided by an “opportunity driven strategy” rather than “conservation of ecosystem services” approach. This proposal aims to develop the scientific knowledgebase on   peatlands and water management for different types of peatlands found in peat rich areas of Northern Europe and Indonesia. The work is organized in 5 work packages (WPs) devoted to: i) Analysis of peatland use impacts on hydrology and water quality, ii) Solutions for efficient water management and water quality control, iii) Tools for integrated land and water management on peat soils, iv) Stakeholder involvement and communication to outline best management options, v) Project management and coordination. A database on peat soil hydrology, water management options and a toolbox on methods for water management will be developed with educational material for capacity building in different regions. This will allow stakeholders to make water management plans on local and catchment scale that meet multiple policy goals and allow a transition for smarter water and land management and suitable solutions to future decision-making.

Outputs: 

Journal papers:

Healy, M.G., Siggins, A., Molloy, K., Potito, A.P., O'Leary, D., Daly, E., Callery, O. 2023. The impact of alternating drainage and inundation cycles on geochemistry and microbiology of intact peat cores. Science of the Total Environment 858: 159664.  Healy et al., STOTEN (2023)

Monteverde, S., Healy, M.G., O'Leary, D., Daly, E., Callery, O. 2022. Management and rehabilitation of peatlands: the roles of water chemistry, hydrology, policy, and emerging monitoring methods to ensure informed decision making. Ecological Informatics 69: 101638. Monteverde et al. 2022 

O'Leary, D., Brown, C., Healy, M.G., Regan, S., Daly, E. 2023. Observations of intra-peat variability using multiple spatially coincident remotely sensed data sources and machine learning. Geoderma 430: 116348. O'Leary et al. 2023

Conference presentations:

O'Leary, D., Monteverde, S., Callery, O., Healy, M.G., Brown, C., Daly, E. 2020. Defining peatland zones using self-organising map clustering on airborne radiometric data and OS digital elevation model. Irish Quaternary Association Annual Symposium. Nove, 27, 2020. 

O'Leary, D., Healy, M.G., Callery, O., Brown, C., Daly, E. 2020. Defining potential peatland managment zones using unsupervised self-organising map clustering on airborne ratiometric data. Session #B025-07. AGU Fall Meeting, 1-17 December.

Start date: 1/5/16           End date: 31/9/20

Funder: Teagasc

Principal Investigators: Prof Mark Healy (NUI Galway), Prof Gary Lanigan and Dr William Burchill (Teagasc), and Dr Barbara Amon (ATB, Germany)

Budget (€): 88,000

Objective:

Nitrogen contained in slurry is an important source of N on Irish farms. However, a large proportion of this N can be lost from slurry via ammonia (NH₃) gas emissions. These emissions are also detrimental to the environment. Agriculture contributes 98 % of the total NH₃ emissions in Ireland. The cattle sector is by far the largest source of these emissions, comprising 72% of total emissions, with these emissions arising principally during animal housing and slurry storage (48%). This is important given that Irish livestock numbers are expected to grow post quote while EU national NH₃ emissions targets are set to be more stringent up to 2030. Slurry storage emissions is one potential area were NH₃ emissions can be reduced on Irish farms. However, little is known about the extent of slurry storage emissions in Ireland and the effectiveness of strategies to reduce NH₃ emissions under Irish conditions. 

The objectives of this MSc will be to assess the effect of a number of potential strategies to reduce emissions from slurry storage. The effect of these strategies will be quantified using twelve concrete slurry storage tanks (volume of 1 m³) at a purpose built slurry storage facility.  A dynamic chamber approach will be used to estimate NH₃ loss with gaseous emissions measured at the chamber inlets and outlets using a photoacoustic gas analyser and/or acid trapping. This will allow the simultaneous measurement of NH₃, methane, nitrous oxide and carbon dioxide, and will allow assessment of NH₃ loss and any positive or negative feedback these strategies have on greenhouse gas emissions.

Outputs:

Kavanagh, I., Burchill, W., Healy, M.G., Fenton, O., Krol, D., Lanigan, G.J. 2019. Mitigation of ammonia and greenhouse gas emissions from stored cattle slurry using acidifiers and chemcial amendments. Journal of Cleaner Production 237: 117822.  Kavanagh et al. J. Cleaner Prod.

Kavanagh, I., Fenton, O., Healy, M.G., Burchill, W., Lanigan, G., Krol, D. 2021. Mitigating ammonia and greenhouse gas emissions from stored cattle slurry using agricultural waste, commerically available products, and a chemical acidifier. Journal of Cleaner Production 294: 126251. Kavanagh et al. 2021

Start date: 01/11/16           End date: 31/10/19

Funder:  Marie Skłodoswka Curie Innovative Training Network

Principal Investigator: Prof Mark Healy (NUI Galway), Prof Owen Fenton (Teagasc)

Abstract:

Intensification of agriculture in the European Union has resulted in nutrient losses from farms, which have contributed to a deterioration in water quality. As soil in drainage water ditch networks has limited capacity to attenuate nutrients leaving farms, efforts to reduce nutrient loads have been unsuccessful. Therefore, innovative solutions and experimental approaches are needed to intercept nutrients in ditches before final discharge to receiving waters. The existing ditch networks on farms may offer an opportunity for implementation of nutrient attenuation measures, by combining the natural attenuation capacity of the ditch with in-ditch engineered structures containing media capable of adsorbing nutrients. Although these structures have gained in popularity as a mitigation option, their configuration or optimal placement in the landscape has not yet been fully considered. The selection of appropriate media depends on the type of nutrient losses, the nutrient loads, media adsorption capacity and lifetime. In addition, the identification of an optimal location for the placement of in-ditch engineered structures is crucial for successful implementation as such structures are capable of only removing a proportion of nutrient loads exiting the farm, so the natural attenuation capacity of the ditch is important to further reduce the load.This thesis proposes two innovative mitigation techniques to remove both nitrogen (N) and phosphorus (P) in an agricultural drainage system: an in-ditch engineered system filled with reactive media and a natural solution which utilises soil chemistry of the ditch network for nutrient removal.

In order to develop the first technique, a novel, internationally applicable decision support tool (DST) was developed to select locally sourced media for single or dual mitigation of N and P. The developed DST was validated in several case studies and it was then used to select an optimal combination of media for the removal of ammonium (NH₄⁺) and P in water draining from an intensive dairy farm in south-east Ireland. Normally, large-scale column tests need to be conducted to develop design criteria for engineered structures, but as these are time consuming and expensive, rapid small-scale column tests (RSSCTs) were used, for the first time, to assess the media performance and longevity in simultaneous N and P removal in comparison with large-scale columns. The adsorption capacity and lifetime of the selected media in large- and small-scale column studies were consistent and the generated data using RSSCTs were successfully used to model P and N removals in the large-scale filters. This indicated that RSSCTs may be used to accurately and quickly develop design criteria for in-ditch engineered structures.

In the second technique, the natural P remediation capacity of the ditch network of the study site was investigated with a view to identifying the optimum location for the placement of an engineered structure and to examine the capacity of a ditch in retaining or mobilising P. Experimental analyses indicated that the ideal location for installation of an in-ditch structure was at the point where a sharp increase in nutrient concentration was observed, which was due  to discharges from the farm yard. The results also showed that P inputs into the drainage network accumulated in the sediments and bankside over time. This not only contributed to degradation of water quality leaving this farm, but the stored nutrients in the ditch network, as a result of decades of application, had also changed the chemistry of sediments to act as a secondary source of P, adding to the already polluted water.

Arising from the findings of this thesis, in order to limit nutrient losses from intensive farms into drainage waters, implementation of an enhanced remediation technique is essential where natural attenuation is insufficient to eliminate pollution. An efficient mitigation measure starts with characterisation of the type of nutrient losses and then the development of appropriate in-ditch engineered structures filled with media to remove the identified nutrients. However, cognisance must also be taken of potential pollution swapping as a result of using the media, appropriate structure dimension and optimal location, and the nutrient remediation or immobilisation capacity of the ditches. This thesis provides a design framework that will contribute to sustainable, environmentally friendly farm management.

 Outputs

Journal papers:

Ezzati, G., Healy, M.G., Christianson, L., Daly, K., Fenton, O., Feyereisen, G., Thornton, S., Callery, O. 2020. Use of rapid small-scale tests for simultaneous prediction of phoshorus and nitrogen retention in large-scale filters. Journal of Water Process Engineering 37: 101473. Ezzati et al. J. Wat. Proc. Engin.‌

Ezzati, G., Fenton, O., Healy, M.G., Christianson, L., Feyereisen, G.W., Thornton, S., Chen, Q., Fan, B., Ding, J., Daly, K. 2020. Impacts of P inputs on source-sink P dynamics of sediment along an agricultural ditch network. Journal of Environmental Management 257: 109988. ‌Ezzati et al. JEM_2020

Ezzati, G., Healy, M.G., Christianson, L., Feyereisen, G.W., Thornton, S., Daly, K., Fenton, O. 2019. Developing and validating a decision support tool for media selection to mitigate nutrients in drainage waters. Ecological Engineering: X 2: 100010. ‌Golnaz_Ecol Eng

Chagnan, E., Thornton, S.F., Rolfe, S.A., Wells, N.S., Knoller, K., Murphy, J., Tuohy, P., Daly, K., Healy, M.G., Ezzati, G., von Chanier, J., Fenton, O. 2019. An integrated assessment of nitrogen source, transformation and fate within an intensive dairy system to inform managemnet change. Plos One 14(7): e0219479. Clagnan paper‌‌‌

Conference papers:

Ezzati, G., Healy, M.G., Daly, K., Christianson, L., Feyereisen, G., Thornton, S., Fenton, O. 2017. Feasbility matrix to identify locally sourced mixed media to mitigate agricultural pollutants in land drainage. ASA, CSSA, SSSA International Annual Meeting. Oct 22 - 25, Tampa, Florida.

Start date: 01/02/19       End date: 31/01/21

Funder: EPA

Principal investigator: Dr Liam Morrison (NUI Galway), Prof Mark Healy (CoI)

Objective:

This project will combine Earth Observation technologies, in situ monitoring of water quality and seaweed tides, and laboratory experiments in order to: i) identify the most important pressures affecting these estuaries; ii) generate useful information about the ecological status and water quality to inform policy; and iii) develop solutions to reach a good ecological status and improve ecosystem services. All these aims will be accomplished through the development of five work packages: WP1 will assess water quality in water catchments; WP2 will monitor the development of green tides using satellite images; WP3 will provide information to predict the effectivity of management actions in a global change context (i.e. climate change; eutrophication; and emergent pollutants) based on laboratory experiments; WP4 will develop ex-situ cultivation protocols for different seagrasses to restore seagrass meadows or use seagrasses as biomonitors; WP5 will create a net of volunteers to improve the monitoring of green tides in those estuaries (i.e. water quality, bloom extent and internal C:N in seaweed tissue). Additionally, a sixth WP will be focused on the communication of the results and in the development of a protocol for good practices to reduce nutrient losses in agriculture.

Outputs:‌

Karki, S., Bermejo, R., Wilkes, R., Mac Monagail, M., Daly, E., Healy, M.G., Hanafin, J., McKinstry, A., Morrison, L. 2021. Mapping spatial distribution and biomass of intertidal Ulva blooms using machine learning and earth observation. Frontiers in Marine Science 8:633128.  Karki et al. 2021 

Start date: 1/7/17           End date: 31/6/19

Funder: H2020-Marie Skłodowska-Curie Actions (MSCA) Individual Fellowship

Principal Investigators: Prof. Mark Healy, Dr Florence Abram, Dr Alma Siggins

Budget (€): 187,866

Objective:

Waste disposal and treatment is a major source of contamination of soils, surface and groundwater, and accounts for 35% of the 1.1 million contaminated sites in Europe. Leaching of the organic solvent trichloroethylene (TCE) into groundwater has been identified as a primary issue with unlined landfills, affecting up to 70% of leachates tested. Mainly used as a metal degreaser and dry-cleaning reagent, TCE is difficult to treat; current treatment methods, such as anaerobic digestion or air stripping, are ineffective and/or expensive. This project will investigate the use biochar, or other appropriate media, for treatment of TCE contaminated water via two technologies - permeable reactive interceptors (PRIs) and permeable contaminant retaining filter (PCRF) bags. This novel, low-cost solution will address the requirements of European Union (EU) legislation, including the Water Framework Directive (WFD).

Outputs:

Siggins, A., Abram, F., Healy, M.G. 2020. Pyrolysed waste materials show potential for remediation of trichloroethylene-contaminated water. Journal of Hazardous Materials 390: 121909‌ Siggins et al. J. Haz. Mat.

Siggins, A., Thorn, C., Healy, M.G., Abram, F. 2021. Simultaneous adsorption and biodegradation of trichloroethylene occurs in a biochar packed column treating contaminated landfill leachate. Journal of Hazardous Materials 403: 123676.  Siggins et al. 2021 ‌

Start date: 1/12/13           End date: 30/11/18

Funder: DAFM/Teagasc

Principal Investigator: Prof Mark Healy (NUI Galway and Dr Karen Daly (Teagasc) (on Teagasc Walsh Fellow). Project investigators: Dr Karen Daly (Teagasc), Mary Ryan (Teagasc), Prof. Phil Jordan (UU), Dr Donnacha Doody (AFBI), Prof Mark Healy (NUI Galway)

Budget (€): 105,940

Objective:

The overall objective of this research is to provide evidence-based strategies for nutrient management on farms in sensitive catchments.  The evidence will be derived from a research agenda examining the optimum use and management of nutrients as a Source and the hydrological Pathways controlling the delivery of this source to surface waters.  This Ph.D. research will focus on the predominant soils and current nutrient management in case-study catchments. The overall objective of the work is to optimise phosphorus (P) use on the predominant soil types in case study catchments so that farmers can continue to farm, yet, minimise the risk of P loss to waters. The case-study catchments selected for this work are likely to have a high proportion of peat soils and previous research on phosphorus in these soils has highlighted significant differences in their P chemistry compared to mineral soils, specifically,  low sorption capacity for phosphorus and poor P retention in these soils. These findings have implications for sustainable use of fertiliser and slurry in these areas.  There is a gap in our knowledge on the efficient use and management of nutrients on high organic matter soils, and this project will integrate agronomic experiments with rainfall simulator work to describe P assimilation and transport of applied nutrients to these soils.  The work in this study will focus on the predominant mineral and peat soils in the selected case-study catchments.

Outputs:

Journal papers:

Gonzalez Jimenez, J.L., Daly, K., Roberts, W.M., Healy, M.G. 2019. Split phosphorus applications as a strategy to reduce incidental phosphorus losses in surface runoff. Journal of Environmental Management 242: 114-120. Gonzalez et al. 2019_JEM

Golnazez Jimenez, J.L., Healy, M.G., Daly, K. 2019. Effects of fertiliser on phosphorus pools in soils with contrasting organic matter content: a fractionation and path analysis study. Geoderma 338: 128-135. Gonzalez et al. Geoderma

Golzalez Jimenez, J.L., Healy, M.G., Roberts, W.M., Daly, K. 2018. Contrasting yield responses to phosphorus applications on mineral and organic soils from extensively managed grasslands: implications for P management in high ecological status catchments. Journal of Plant Nutrition and Soil Science 181: 861 - 869. Gonzalez et al. J. Pl Sci Nutr

Conference papers:

Gonzalez-Jimenez, J.L., Healy, M.G., Roberts, W.M., Daly, K. 2016. Grass yield and phosphorus fractions in organic soils. Organic Phosphorus in the Environment: Solutions for Phosphorus Security Conference. Sept. 5-9, Lake District, England.

‌‌‌Start date: 01/09/15                                    End date: 31/08/18

Funder: EPA

Principal investigators: Dr Ronan Courtney (University of Limerick), Dr Mark Healy (NUI Galway)

Objective:

This project aims to illustrate the value contained in bauxite residue. It aims to: unlock the volume of various rare earths from bauxite residue and increase the range and yields of recovered raw materials, illustrate the re-use potential of bauxite residue, push Ireland to the forefront in the area of raw materials processing technologies.

Outputs:

Journal papers:

Cusack, P.B., Callery, O., Courtney, R., Ujaczki, E., O'Donoghue, L.M.T., Healy, M.G. 2019. The use of rapid, small-scale column tests to determine the efficiency of bauxite as a low-cost adsorbent in the removal of dissolved reactive phosphorus. Journal of Environmental Management 241: 273-283. Cusack et al. JEM_2019

Cusack, P.B., Healy, M.G., Ryan, P.C., Burke, I.T., O' Donoghue, M.T., Ujaczki, E., Courtney, R. 2018. Enhancement of bauxite residue as a low-cost adsorbent for phosphorus in aqueous solution, using seawater and gypsum treatments. Journal of Cleaner Production 179: 217 - 224. Cusack et al. 2018

Cusack, P.B., Healy, M.G., Callery, O., Di Carlo, E., Ujaczki, E., O'Donoghue, L.M.T., Courtney, R. 2022. An investigation into the growth of lolium pereen L. and soil properties following soil amendment with phosphorus-saturated bauxite residue. Bulletin of Environmental Characterisation and Toxicology. https://doi.org/10.1007/s00128-022-03514-6. Cusack et al. 2022

Cusack, P.B., Courtney, R., Healy, M.G., O'Donoghue, L.M.T., Ujaczki, E. 2019. An evaluation of the general composition and critical raw material content of bauxite resiude in a storage area over a twelve-year period. Journal of Cleaner Production 208: 393-401. Cusack_J. Cleaner Prod._charact.

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Start date: 1/12/15           End date: 30/11/17

Funder: EPA

Principal Investigator: Dr Eoghan Clifford and Prof Mark Healy 

Objective:

In the last 30 years, there have been significant advances in waste and landfill management practices in response to EU Directives. These have led to changes in leachate composition, volumes produced and treatability. Furthermore, increasingly stringent wastewater discharge requirements mean that the co-treatment of leachate in municipal/ urban wastewater treatment plants (UWWTPs) can now be a challenge for some UWWTPs. Key challenges faced by UWWTP operators treating landfill leachate include high nitrogen/ammonium concentrations in leachate and the increased cost of treating wastewater to increasingly stringent standards. It is anticipated that the requirement to meet these standards will drive UWWTP operators to consider their incoming load profile and the impacts on final standards required.

The aims of this project were to: characterise the volumes and composition of leachate from landfills in Ireland; survey UWWTP and landfill operators and to conduct a technical review of how leachate is handled by MWWTPs; examine the co-treatment of leachate in UWWTPs specifically the impact of leachate loading regime or rate of leachate addition on UWWTP performance and quantify the hydraulic and mass (expressed as mass ammonium-nitrogen) loading of landfill leachate (as a percentage of the total influent loading rate) above which the performance of a UWWTP may be inhibited; analyse the costs of on-site (at landfill) and off-site treatment of landfill leachate 

Outputs:

Journal papers:

Brennan, R.B., Clifford, E., Devroedt, C., Morrison, L., Healy, M.G. 2017. Treatment of landfill leachate in municipal wastewater treatment plants and impacts on effluent ammonium concentrations. Journal of Environmental Management 188: 64 – 72. 

Brennan, R.B., Healy, M.G., Morrison, L., Hynes, S., Norton, D., Clifford, E. 2016. Management of landfill leachate: the legacy of European Union directives. Waste Management 55: 355 – 363. Brennan et al. Waste Management

‌Start date: 01/04/13           End date: 31/03/15

Funder: EPA (STRIVE)

Principal Investigators: Dr Mark Healy (NUI Galway) Prof Owen Fenton (Teagasc) Dr Enda Cummins (UCD)

Budget (€): 179,775

Background and summary of main findings:

Treated sewage sludge, commonly referred to as ‘biosolids’, is the organic by-product of urban waste water treatment. When appropriate treatment is applied, it may be reused as an agricultural fertiliser. Despite this benefit, there are several issues associated with the reuse of municipal sewage sludge in agriculture. While many of these are issues of perception, there is considerable concern over the presence of metals, nutrients, pathogens, pharmaceutical and personal care products (PPCPs), and other endocrine-disrupting and synthetic compounds in biosolids, which may cause environmental and human health problems.

The main aims of this research were to (1) quantify the range of concentrations of metals and two of the most abundant PPCPs in the world, the antimicrobials triclosan (TCS) and triclocarban (TCC), in biosolids from a range of wastewater treatment plants (WWTPs) in the Republic of Ireland (2) undertake a field-scale experiment to assess losses of nutrients (nitrogen and phosphorus), metals, TCS and TCC, and microbial matter (total and faecal coliforms) following successive rainfall events on grassland onto which biosolids had been applied, and to compare the results with another commonly spread organic fertiliser, dairy cattle slurry (DCS) (3) to measure the uptake of metals by ryegrass for a period of time after the application of biosolids (4) conduct a risk assessment of potential hazards of human health concern based on the experimental data.

Three types of biosolids commonly used in Ireland were examined as part of this study: anaerobically digested, lime stabilised (LS) and thermally dried (TD). Biosolids and DCS were surface applied in accordance with the legislation in Ireland. A rainfall simulator was used to generate surface runoff over three successive events (24 hr, 48 hr and 360 hr) after a single application.

The metals in the biosolids from the WWTPs examined were below the maximum allowable concentrations of metals for use in agriculture in the European Union (EU). Some priority metals such as antimony and tin, which are potentially harmful to human health, were identified in some of the samples analysed. As these parameters are not currently regulated, this means that a number of toxic metals, which are up to 40 times higher than their baseline concentrations in soils, are being applied to land without regulation. In the WWTPs examined, concentrations of TCS and TCC were 0.61 and 0.08 µg g^-1, which were below the concentrations for these parameters measured in other countries. Similar to the findings for metals, the possibility exists that these potentially harmful, unregulated contaminants, for which no international standards currently exist for recycling in agriculture, may accumulate in the soil upon repeated application.

When losses of nutrients, metals, and indicator microorganisms arising from biosolid-amended plots were compared with slurry treatments, biosolids did not pose a greater risk in terms of losses along the surface runoff pathway. The concentrations of TCS and TCC in surface runoff were also mainly below the limits of detection (90 ng L^-1 for TCS, 6 ng L^-1 for TCC). Furthermore, there was no significant difference in metal bioaccumulation of the ryegrass between plots that received biosolids and those that did not cover the study duration.

A literature review identified contaminants of concern based on relevant risk factors, persistence, bioaccumulation and toxicity (PBT). The contaminants identified were persistent organic contaminants (POPs), pharmaceuticals and PPCPs. A suite of 16 contaminants identified in the literature were further analysed in a risk ranking model to include health based risk endpoints. A probabilistic model was constructed in Excel 2010 (incorporating @Risk 6.0) to estimate human exposure to organic contaminants that are contained within biosolids destined for land application. Nonylphenols ranked the highest across all environmental compartments. The use of these contaminants is heavily restricted in the EU; however, because of their persistence, bioaccumulation and toxicity of these compounds in the environment remains a concern. Triclosan and TCS also ranked high, and may be considered as a potentially greater risk, as their use is not restricted and they are known to cause adverse health effects.

An exposure assessment model was further developed for both metals and E. coli. The model considered exposure to metals and E. coli through surface water abstracted for drinking taking account of surface runoff, dilution and water treatment effects. The likelihood of illness arising from exposure and the severity of the resulting illness was evaluated. Different dose-response relationships were characterised for the different pollutants with reference Lifetime Average Daily Dose (LADD) and Hazard quotient (HQ) used for metals, whilst a worst-case negative exponential dose-response model was used for E. coli. Of all the scenarios considered (three biosolids treatments), and with regards to the LADD, results showed that mean copper exposure concentrations for children were highest in all three rainfall events (mean values 2.07 × 10^-2, 2.07 × 10^-2 and 1.18 × 10^-2 µg kg^-1 bw d^-1) corresponding to the LS treatment. This was followed by adult copper exposure concentrations (mean value 1.80 ×10^-2, 1.31 × 10^-3 and 9.21 × 10^-3 µg kg^-1 bw d^-1, for all three rainfall events). The results for the hazard quotient showed that, of all the scenarios considered, the metal copper and the biosolid treatment LS had the highest HQ for children for all three rainfall events with mean child HQ values 5.59 × 10^-4, 4.09 × 10^-4 and 3.18 × 10^-4 respectively, followed by mean adult HQ values of 4.87 × 10^-4, 3.54 × 10^-4 and 2.49 × 10^-4, respectively. However, these were still below the threshold value of risk (HQ < 0.01, no existing risk).

The results for viable E. coli consumed show that one of the sludges examined (an anaerobically digested sludge originating from a WWTP in the UK (ADUK)) was highest for the first and second rainfall events with mean exposure values 5.20 × 10^-1 MPN/100 ml and 2.34 ×10^-1, MPN/100 ml, respectively. The results for the probability of illness for healthy and immunocompromised populations showed that the biosolid treatment ADUK (first and second rainfall event) among immunocompromised populations (Ic) had the greatest probability of illness/d with mean probability values of 3.68×10^-3 and 2.1 × 10^-3 illness/d, respectively. The results indicate that the risk of illness was negligible for healthy individuals; however, care is required with immunocompromised individuals where the annual risk was greater than the threshold risk of illness (10^-4) as set by the USEPA.

The overall conclusion from this study is that although, in general, land applied biosolids pose no greater threat to water quality than dairy cattle slurry and cattle exclusion times from biosolids-amended fields may be overly strict (within the context of current exclusion criteria), a matter of concern is that unlegislated metals and PPCPs, found to be present in biosolids originating from a selection of WWTPs examined in this study, may be inadvertently applied to land. With multiple applications over several years, these may build up in the soil and may enter the food chain, raising concerns over the continued application of biosolids to land in Ireland. 

Outputs:

Final report:

Healy, M.G., Fenton, O., Cummins, E., Clarke, R., Peyton, D., Fleming, G., Wall, D., Morrison, L., Cormican, M. 2017. Health and water quality impacts arising from the landspreading of biosolids. EPA Strive Report no. 200. EPA, Co. Wexford. http://epa.ie/researchandeducation/research/researchpublications/researchreports/research200.html

Journal papers:

1. Clarke, R., Healy, M.G., Fenton, O., Cummins, E. 2018. Quantitative risk assessment of antimicrobials in biosolids applied on agricultural land and potential translocation into food. Food Research International 106: 1049 - 1060. Rachel_Food Res Internat
2. Healy, M.G., Fenton, O., Cormican, M., Peyton, D.P., Ordsmith, N., Kimber, K., Morrison, L. 2017. Antimicrobial compounds (triclosan and triclocarban) in sewage sludges, and their presence in runoff following land application. Ecotoxicity and Environmental Safety 142: 448 - 453. Healy PPCP
3. Clarke, R., Peyton, D., Healy, M.G., Fenton, O., Cummins. E. 2017. A quantitative microbial risk assessment model for total coliforms and e. coli in surface runoff following application of biosolids to grassland. Environmental Pollution 224: 739 - 750. Rachel_Env Poll
4. Mahon, A.M., O'Connell, B., Healy, M.G., O'Connor, I., Officer, R., Nash, R., Morrison, L. 2017. Microplastics in sewage sludge: effects of treatment. Environmental Science and Technology 51: 810 - 818. Mahon et al.
5. Clarke, R., Peyton, D., Healy, M.G., Fenton, O., Cummins, E. 2016. A quantitative risk assessment for metals in surface water following the application of biosolids to grassland. Science of the Total Environment 566-567: 102-112. Clarke et al. STOTEN
6. Healy, M.G., Ryan, P.C., Fenton, O., Peyton, D.P., Wall, D., Morrison, L. 2016. Bioaccumulation of metals in ryegrass (Lolium perenne L.) following the application of lime stabilised, thermally dried and anaerobically digested sewage sludge. Ecotoxicology and Environmental Safety 130: 303 - 309.  Ecotox. Env. Safety
7. Peyton, D.P., Healy, M.G., Fleming, G.T.A., Grant, J., Wall, D., Morrison, L., Cormican, M., Fenton, O. 2016. Nutrient, metal and microbial loss in surface runoff following treated sludge and dairy cattle slurry application to an Irish grassland soil. Science of the Total Environment 541: 218 - 229. Dara_STOTEN
8. Healy, M.G., Fenton, O., Forrestal, P.J., Danaher, M., Brennan, R.B., Morrison, O 2016. Metal concentrations in lime stabilised, thermally dried and anaerobically digested sewage sludges. Waste Management 48: 404 -408. Metals_biosolids paper
9. Clarke, R., Healy, M.G., Fenton, O., Cummins, E. 2016. A quantitative risk model to evaluate emerging contaminants in biosolid amended land and potential transport to drinking water. Human and Ecological Risk Assessment 22(4): 958-990. Clarke et al. 2016_Hum Ecol Risk

Book chapters:

1. Healy, M.G., Clarke, R., Peyton, D., Cummins, E., Moynihan, E.L., Martins, A., Beraud, P., Fenton, O. 2015. Resource Recovery from sludge. p. 139 - 162. In (K. Konstantinos, K.P. Tsagarakis, Eds.): Sewage treatment plants: economic evaluation of innovative technologies for energy efficiency. IWA, London. Healy et al. biosolids_IWA

2. Colón, J., Alarcón, M., Healy, M.G., Namli, A., Ponsá, S., Dilek Sanin, F., Taya, C. 2017. Producing sludge for agricultural applications. p. 292 – 314. In: (J.M. Lema, S. Suarez Martinez, Eds.) Innovative wastewater treatment and resource recovery technologies. IWA, London. Colon et al. COST

Conference papers:

1. Healy, M.G. 2018. Reuse of sewage sludge in agriculture. 1st meeting of the Interreg-NWE project, ReNu2Farm. June 22, IT Carlow. (Keynote). InterReg presentation

2. Healy, M.G. 2018. Presence of emerging contaminants in treated sludges and their potential impacts on the environment. European Biosolids and Organic Resources Conference. November 13 - 14, Leeds, UK. (Invited presentation).

3. Healy, M.G., Fenton, O., Cummins, E., Clarke, R., Peyton, D.P., Fleming, G.T.A., Wall, D., Morrison, L., Cormican, M. 2016.  Investigations into potential risks associated with the use of treated municipal sludge on agricultural land. European Biosolids and Organic Resources Conference. Nov 15 - 16, Edinburgh, Scotland.

4. Healy, M.G., Morrison, L., Forrestal, P.J., Peyton, D., Fleming, G.T.A., Danaher, M., Wall, D., Cormican, M., Fenton, O. 2015. Characterisation of metal concentrations in treated municipal sludge in Ireland and impacts on runoff water quality following land application. International Conference on Solids Wastes 2015: Knowledge Transfer for Sustainable Resource Management. Hong Kong SAR, China. 19 - 23 May, 2015. Hong Kong presentation

5. Healy, M.G., Peyton, D., Fleming, G., Danaher, M., Morrison, L., Wall, D., Grant, J., Cormican, M., Fenton, O. 2014. Measurement of surface runoff of mixed contaminants arising from the landspreading of treated sewage sludge. ASA, CSSA, and SSSA International Annual Meeting. Nov 2-5, Long Beach, CA. ASA presentation

6. Healy, M.G., Fenton, O., Cummins, E., Clarke, R., Peyton, D.P., Fleming, G.T.A., Wall, D., Morrison, L., Cormican, M. 2016. Investigations into potential risks associated with the use of treated municipal sludge on agricultural land. European Biosolids and Organic Resources Conference. Nov 15 - 16, Edinburgh, Scotland. Biosolids presentation

‌Start date: 1/2/14           End date: 31/1/18

Funder: EPA

Principal Investigator: Prof Mark Healy and Prof Mike Gormally (University of Galway)

Budget (€): 73,500

Natural wetlands (NWs) are one of the most economically and ecologically important habitats on Earth, currently comprising about 6% of the world’s surface area. They provide many ecosystem services including the supply of fresh water, food and building materials, water quality improvement, biodiversity support and flood mitigation. The loss of NWs (> 50%) globally over the past two centuries has, however, greatly reduced their facilitation in water purification and wastewater treatment. For this reason, various types of artificial wetlands (constructed wetlands; CWs) have been designed to assist in the removal of a range of pollutants from wastewaters, and accordingly, improve water quality.

Constructed wetlands have several advantages in comparison to conventional wastewater treatment systems. They are a sustainable, green system requiring lower operation and maintenance costs. In addition, the vegetation in CWs assists in many important pollutant removal mechanisms including sedimentation, filtration and plant uptake of metals and nutrients. However, a paucity of information exists on metal and nutrient accumulations within vegetation in CWs, with many studies focusing on concentrations only. As a result, best practices for the harvesting of CW vegetation as a means of metal / nutrient removal, is lacking. This study addresses this significant knowledge gap in CW performance via biomass harvesting of CW vegetation. The additional benefits to biodiversity provided by CWs have received comparatively less attention than their capacity in wastewater treatment. This provides the incentive for the second aim of this study where the biodiversity value of CWs in comparison to that of NWs is assessed. For the first time, the suitability of terrestrial habitats surrounding CWs and NWs for the protected smooth newt is compared, with a view to recommending newt-friendly changes to existing and future CW design. Similarly, marsh flies (Diptera: Sciomyzidae) which are recognised bioindicators of wetlands, are used to quantify, for the first time, the value of CWs to aerial invertebrate diversity. This study also assesses the impacts of water quality and the habitats surrounding CWs on marsh flies since no systematic study has examined this to date.

The results of the study show that the concentrations and accumulations of metals and nutrients in CW vegetation follow contrasting seasonal patterns. Some metals and nutrients measured in the belowground (BG) biomass were greater than 80% of the more commonly measured aboveground (AG) biomass suggesting that analysis of emergent shoots only may significantly underestimate the metal and nutrient uptake and capacity of CW vegetation. Based on the results of the study, it is important to schedule harvesting at specific times of the year to coincide with maximum accumulations of specific metals and nutrients in CW plants. The study also shows that CWs present an opportunity to compliment biodiversity in the locations in which they are placed. The results of a Habitat Suitability Index (HSI) whereby each CW and NW received a score, concluded that appropriate management of the areas immediately surrounding CWs can provide habitat for the protected smooth newt and recommendations to improve new and existing CWs as newt-friendly habitat were crafted. Marsh fly assemblages are similarly influenced by habitats surrounding CWs. In addition, the potential value of CWs to marsh fly conservation is evidenced by over one third of the Irish sciomyzid fauna being represented in the eight CWs in this study, including four species listed as scarce or threatened in the UK.

In conclusion, the results of this study have reinforced the motion which suggests that CW treatment performance is better when plants are present, due to the uptake capacity and accumulation of metals and nutrients into the CW vegetation. The results has elucidated the seasonal patterns of metals and nutrients in AG and BG biomass in a temperate oceanic climate, and provides recommendations on removal via vegetation harvesting, which could prevent potential pollution events in receiving waters. In addition, CWs can now be viewed as crucial in providing habitat to species of conservation concern such as the smooth newt, and scarce and threatened sciomyzid flies, that may be otherwise absent in the surrounding landscape in which CWs are placed. Extensive recommendations to include minor modifications to the future design and management of CWs for smooth newts and marsh flies are provided, which can also be applied to enhance CWs for other wildlife groups and species of conservation concern.

Outputs:

Performance database of wetlands in Ireland: http://wetlands.nuigalway.ie

Journal papers:

Mulkeen, C.J., Williams, C.D., Swaney, W.T., Healy, M.G., Gormally, M.J. 2024. Sciomyzidae (Diptera) assemblages in constructed and natural wetlands: implications for constructed wetland design. Wetlands 44:5. Mulkeen et al. (Wetlands) 

Mulkeen, C.J., Williams, C.D., Gormally, M.J., Healy, M.G. 2017. Seasonal patterns of metals and nutrients in Phragmites australis (Cav.) Trin. ex Steudel in a constructed wetlands in the west of Ireland. Ecological Engineering 107: 192 - 197.  Mulkeen et al. 2017_veg paper

Mulkeen, C.J., Gibson-Brabazon, S., Carlin, C., Williams, C.D., Healy, M.G., Mackey, P., Gormally, M.J. 2017. Habitat suitability assessment of constructed wetlands for the smooth newt (Lissotriton vulgaris [Linnaeus, 1758]): A comparison with natural wetlands. Ecological Engineering 106: 532-540.  Mulkeen et al. (habitat paper)

Maher, C.A., Carey, J.G.J., Mulkeen, C.J., Williams, C.D., Knutson, L.V., Healy, M.G.,, Gormally, M.J. 2018. Diagnostic definitions and figures of male and female Tetanocera punctifrons and T. latifolia, new records of T. punctifrons in Ireland, and notes on biology (Diptera, Sciomyzidae). Dipterists Digest 24: 129 - 145. ‌ Maher et al.

Conference papers:

Mulkeen, C.J., Gormally, M.J., Healy, M.G. 2017. The power of plants in constructed wetlands. 14th International Phytotechnologies Conference. September 25 - 29, Montreal, Canada.

Mulkeen, C.J., Healy, M.G., Gormally, M.J., Williams, C.D. 2014. Biodiversity richness and water quality in natural and constructed wetlands: what can Scimyzids tell us? 8th International Congress of Dipterology, Potsdam, Amsterdam, August, 2014.

Start date:  01/10/12         End date: 31/01/17

Principal Investigator: Dr Mark Healy (NUI Galway) Prof Owen Fenton (Teagasc)

Objectives and main findings:

Agricultural activity is a major source of nutrient emissions to surface and ground waters and a significant contributor to greenhouse gas emissions. Despite legislation to improve terrestrial water quality, prescribed targets are not being met. This is against a background of more intensive farming practices such as concentrated animal feeding operations, which have led to large volumes of manures being generated in relatively small areas and spread at rates that exceed plant nutrient demand. The competing demands of providing more food from the same land area, while simultaneously reducing environmental impacts, is a major challenge. While many mitigation measures to reduce nutrient losses, such as crop and land management, have been put forward, these alone will not achieve the necessary improvements in water and air quality. The main nutrients of concern are phosphorus (P), which mainly contributes to coastal and freshwater eutrophication, and nitrogen (N), which has adverse impacts on human and livestock health through leaching to groundwater. Increased losses of carbon (C) also adversely impact the atmosphere through greenhouse gas emissions. New techniques which are sustainable, economical, and which do not negatively impact the atmosphere, aquatic ecosystems or human and animal health, are therefore required to reduce this form of non-point agricultural pollution. Similarly, a deeper understanding into the removal mechanisms and factors affecting the performance of existing treatment technologies, such as aerobically operated farm filters, is needed. 

This laboratory-based study examined the effectiveness of applying combined zeolite and either polyaluminum chloride (PAC) or alum amendments to reduce losses of N, P, C and suspended solids (SS) from surface applied dairy and pig slurries, and dairy soiled water (DSW), when subjected to varying interval rainfall events. Traditionally, such studies aimed to reduce only P in the surface runoff; however, this study aimed to identify an optimal amendment to the slurries and DSW to simultaneously reduce N, P, C and SS. Once an optimal rate of amendment was determined, their impact – if any – on leaching losses of N, P and C, and on emissions of carbon dioxide (CO₂) and methane (CH₄), were quantified. Separately, a passive filter study using woodchip and sand media to investigate the impacts of media depth, organic loading rates (OLRs), and media type to treat DSW, was also undertaken.

The study concluded that combined use of zeolite and chemical amendments when mixed with dairy and pig slurries and DSW, reduced losses of N, P and SS in surface runoff to a much greater extent than those from unamended slurries. The combined amendments were most effective when mixed with dairy slurry, followed by pig slurry, and were least effective when used with DSW. The impact of the amendments was correlated with the dry matter (DM) content of the slurries and the relative effectiveness of the amendments to flocculate P, N and SS-enriched slurry particles. Although the amendments were also effective in reducing C losses, their use may not be economically viable, given the relatively low amounts of C measured in runoff from unamended slurries compared with the amounts applied. Use of the combined amendments did not reduce leaching losses of N, P and C, or gaseous emissions of CO₂ and CH₄ from pig slurries and DSW, when compared to unamended slurries. While they reduced leaching losses of C from dairy slurries, they also increased CO₂ emissions. The greatest short term threat of nutrient leaching and gaseous emissions of CO₂ and CH₄ was posed by pig slurry, in both amended and unamended forms.

Intermittently loaded woodchip filters were assessed to be more economically and environmentally effective in treating DSW than sand filters; however, their removal mechanism for all contaminants was physical as opposed to biological. While the sand filters nitrified DSW effluent [43±18 mg nitrate-N (NO₃-N) L^-1] for the first 85 days of operation, concentrations reduced thereafter to 7.2±1.6 mg NO₃-N L^-1. The woodchip filters did not nitrify the effluent, even at relatively low loadings of 35 g chemical oxygen demand (COD) m^-2 d^-1. The final filtered effluent from both sand and woodchip filters, however, was above the concentrations at which it may be legally discharged to receiving waters. Options for its reuse may be to use the treated effluent in irrigation and, in time, to incorporate the spent timber residue into the soil.

The potential of mixing zeolite and chemical amendments with agricultural slurries to mitigate environmental impacts must be considered in the context of traditional conservation and nutrient management practices, which would appear to be the most cost effective strategies over the long term. The N, P, and C mitigation measures described in this study may provide more immediate water quality benefits, in particular at severely overloaded ‘legacy’ sites or ‘critical source areas’, where manure additions are already restricted to crop removal rates. Prior to use of the new techniques described in this study, a cost-benefit analysis of applying amendments to organic wastes, and to on-farm filter treatment of DSW will be essential in the context of whole-farm and watershed-scale nutrient management. Such an analysis should only be carried out after long term field-scale studies, and should also address legislative issues related to discharge consents for on-farm treated agricultural wastes and to selected use of manure amendments.

Outputs:

Journal papers:

Murnane, J.G., Fenton, O., Healy, M.G. 2018. Impacts of zeolite, alum and polyaluminium chloride amendments mixed with agricultural wastes on soil column leachate, and CO2 and CH4 emissions. Journal of Environmental Management 206: 398 - 408.  Murnane et al. 2018

Murnane, J.G., Brennan, R.B., Healy, M.G., Fenton, O. 2016. Zeolite combined with alum and aluminium chloride (PAC) mixed with agricultural slurries reduces carbon losses in runoff from grassed soil boxes. Journal of Environmental Quality. In press. John_JEQ_Carbon paper

Murnane, J.G., Brennan, R.B., Healy, M.G., Fenton, O. 2016. Assessment of intermittently loaded woodchip and sand filters to treat dairy soiled water. Water Research 103: 408 - 415.  Murnane et al. Wat Res

Murnane, J.G., Brennan, R.B., Healy, M.G., Fenton, O. 2015. Use of zeolite with alum and PAC amendments to mitigate runoff losses of P, N and suspended solids from agricultural wastes applied to land. Journal of Environmental Quality 44: 1674 - 1683. Murnane et al. 2015_JEQ

‌

Start date: 01/12/13           End date: 31/10/17

Funder: IRC

Principal Investigator: Prof Mark Healy (NUI Galway)

Budget (€): 95,991

Objective:

Approximately 800,000 hectares of blanket peat catchments were afforested between the 1950s and 1990s in Ireland and the UK. Most of these forests are now approaching their harvesting and regeneration phase. Harvesting activities can result in the export of harmful nutrients from forest catchments and, if they reach surface waters, can cause severe pollution problems. As many of these forests are in ecologically sensitive areas, which attract large numbers of tourists, potential damage to waters (and reputation) could have serious environmental and financial consequences for areas that depend solely on tourism. To date, forest guidelines propose the use of grass areas between the forest and streams, but these are inadequate to stop highly mobile, dissolved nutrients from travelling over the peat surface or through the peat (which has limited ability to adsorb them). This project proposes the use of various amendments - added to the soil surface, in small trenches perpendicular to the flow, or added to the residue (‘brash’) material – to mitigate the flow of nutrients to receiving waters. These experiments, which have never been attempted in a forestry context, will be conducted at laboratory-scale and at field-scale.

Outputs:

Journal papers:

Callery, O., Healy, M.G. 2019. A novel method to rapidly assess the suitability of water treatment residual and crushed concrete for the mitigation of point and nonpoint source nutrient pollution. Resources, Conservation and Recycling:x 2, August 2019, 100010.  Oisin_Res. Cons. Recycl. paper 

Callery, O., Healy, M.G. 2017. Predicting the propagation of concentration and saturation fronts in fixed-bed filters. Water Research 123: 556 - 568.  Callery and Healy, 2017

Callery, O., Healy, M.G., Rognard, F., Barthelemy, L., Brennan, R.B. 2016. Evaluating long-term performance of low-cost adsorbents using small-scale adsorption column experiments. Water Research 101: 429 - 440.  Oisin_Wat Res

Callery, O., Brennan, R.B., Healy, M.G. 2015. Use of amendments in a peat soil to reduce phosphorus losses from forestry operations. Ecological Engineering 85: 193 - 200. Callery et al. 2015

‌Start date: 1/2/16           End date: 31/1/18

Funder: IRC

Principal Investigators: Prof Mark Healy, Dr Liam Morrison, and Dr Ashish Pathak (IRC Researcher)

Budget (€): 91,140

Objective:

Petroleum refinery industries generate significant quantities of spent catalyst as a waste product. Spent catalysts contain appreciable concentrations of valuable metals such as molybdenum (Mo), nickel (Ni), cobalt (Co) and vanadium (V), and hence can be considered as an “artificial ore”. Conventionally, metal extraction from spent refinery catalyst is achieved by hydrometallurgy or pyrometallurgy. However, current methods of metal extraction such as hydrometallurgy and pyrometallurgy, are highly energy demanding. They also generate secondary waste and their downstream processing cost is high. Therefore, there is need to develop more sustainable and environmentally friendly biotechnological methods for treating the spent refinery catalyst. In recent years, bioleaching has been developed as an eco-friendly and efficient method for recovering these valuable metals from petroleum refinery spent catalyst.

The aim of this project is to develop a novel, integrated leaching-precipitation process to recover valuable metals (Ni, V, Mo, Co etc.) from waste petroleum refinery catalyst using a novel and unique combination of bioleaching and bio-precipitation. Bioleaching by sulfur-oxidizing and/or iron-sulfur oxidizing bacteria (Acidithiobacilli) will be followed by precipitation of the leachate metals as insoluble sulfides by sulfate-reducing bacteria.

Journal papers:

Pathak, A., Healy, M.G., Morrison, L. 2018. Changes in the fractionation profile of Al, Ni and Mo during bioleaching of spent hydroprocessing catalysts with acidithiobacillus ferroxidans. Journal of Environmental Science and Health, Part A: Toxic/Hazardous Substances and Environmental Engineering 53 (11): 1006-1014. Pathak et al. J. Env. Sci and Health

Pathak, A., Morrison, L., Healy, M.G. 2017. Catalytic potential of selected metal ions for bioleaching, and potential techno-economic and environmental issues: a critical review. Bioresource Technology 229: 211 - 221.  Pathak et al. 2017

Start date: 1/6/18          End Date: 31/5/22

Funder: Marie Skłodowska-Curie Innovative Training Network

Principal Investigator: Prof Mark Healy (NUI Galway), Mr Mark Bowkett (T.E. Laboratories Ltd.), Prof Owen Fenton (Teagasc)

Objective:

INSPIRATION (managing soil and groundwater impacts from agriculture for sustainable intensification) is a multidisciplinary European Training Network composed of 26 partners in 9 European countries, which aims to develop low-technology management practices, monitoring approaches, modelling and decision-making tools, and innovative technology applications in the field of sustainable agriculture by a combination of fundamental and applied science (www.inspirationitn.eu). The research focuses on understanding and predicting the environmental fate of nutrient and organic pollutants from agricultural practices and managing their impact on soil, water and climate systems to ensure sustainable production. It links lab- to catchment-scale studies of biogeochemical processes with field-scale evaluation of novel monitoring and management concepts, using state-of-the-art methods. The network will provide high-quality research training to young scientists, through 15 fully-funded Early-Stage Researcher (PhD level) fellowships. The network includes leading research groups, regulators, advisory bodies, water utilities, consulting firms, commercial R&D and multinationals. The project has an international advisory group and will undertake a comprehensive programme of knowledge transfer and outreach activities with other scientific networks and professional bodies in this field. 

This is an industry-based PhD and the project will focus on the mitigation of soil and groundwater impacts from agriculture using mixed waste media. The main objectives of the PhD will include the following:
1. Identification of locally sourced raw materials across partner countries used in isolation or in combination that have the capacity to mitigate mixed contaminants and are safe to recycle back on land. 
2. Evaluation of performance and biochar and other potential media in this application.
3. Development of methodology to measure NKP and other contaminants in the media. Passive sampling and microfluidic technologies will be considered.
4. Development of in-process monitoring to provide information for modelling on lab pilot plant.
5. Field deployment of measuring technology to monitor performance of media in a field application.

Outputs:

Arenas-Montano, V., Fenton, O., Moore, B., Healy, M.G. 2021. Evaluation of the fertiliser replacement value of phosphorus-saturated filter media. Journal of Cleaner Production 291: 125943. ‌Arenas-Montano_2021

Start date: 01/11/12           End date: 31/10/15

Funder: Teagasc Walsh Fellowship

Principal Investigator: Drs Mark Healy and Tiernan Henry (NUI Galway) Dr Owen Fenton (Teagasc)

Budget (€): 72,000

Objective:

Implementation of agricultural nutrient programmes of measures (POM) within the Water Framework Directive (WFD) by 2012 and achievement of ‘at least’ good water quality status by 2015 does not consider management legacy and hydrological/hydrogeological “lag time” processes in catchments. Lag time occurs as nutrient leaching pathways between soils, groundwater and rivers are generally long and complex, and the pathways vary depending on soil/subsoil type, bedrock geology/hydrogeology, and climatic factors such as rainfall. For groundwater nitrate, the components of lag time are: nutrient concentration leaving the rooting zone, unsaturated zone travel time, aquifer nutrient concentration, aquifer flushing time to below the nitrate-N threshold concentration of 37.5 mg L^-1, horizontal saturated travel time to a surface waterbody, travel time through the hyporeic zone, and nutrient attenuation along this pathway. In Ireland, the Nitrates Directive is the agricultural POM currently in place to achieve WFD water quality goals. Recently completed research currently under review provided initial estimation of lag time for Ireland using a range of model parameters taken from the literature and this showed that the earliest change in water quality due to measures introduced in 2012 will be 2019. Other changes will not take effect until after 2027. The proposed research will provide more Irish specific estimates of lag time and will generate internationally important methods for its estimation. This project aims to address this issue and to protect Irish farmers against potentially restrictive implementation of further POM before the 2015 reporting deadline.

Results:

A literature review was conducted in which the controlling factors on tu were identified, and various approaches to simulating water and solute transport using unsaturated zone numerical models were examined. Subsequently, an investigation was conducted to determine the consequences for tu estimates made using a popular model (Hydrus 1D) depending on whether low-complexity (texture and bulk density) or high-complexity (the soil water characteristic curve (SWCC)) soil input data are used. It was found that high-complexity data improved model performance, but for trend assessment, low-complexity data suffice. The position of the nutrient source relative to the receptor was found to influence model requirements, with high-complexity data becoming more critical in locations where source and receptor are close.

Having identified the utility of low- and high-complexity input data, the impact of four common soil textural analysis (low-complexity data) methods were assessed. It was found that there were only minor differences in tu estimates (<0.03 yrs), irrespective of whether laser diffraction, hydrometer, or pipette methods were used. The hand texturing method performed poorest, indicating superior performance of any of the three laboratory methods. Regarding high-complexity input data, the impact of various temporal rules concerning the time to hydraulic equilibrium when constructing an SWCC using the centrifuge method was statistically assessed. This simple but novel approach allows the impact of experimental duration on SWCCs of specific soils to be determined. A methodological toolkit to estimate tu was developed using soil data available from the Irish Soil Information System. Using this toolkit, tu was estimated for a grassland and an arable catchment. In both catchments, tu estimates frequently exceeded three years, and were almost 10 years for the deepest soils, indicating that the targets of the EU-WFD may not be achievable until the second reporting period. Trend estimates were verified using potassium bromide (KBr-) tracer tests in each catchment. The toolkit approach satisfactorily indicated trend ranges for most scenarios when compared to the in situ tracer study.

This toolkit may be employed specifically in catchments exhibiting poor or declining water quality in order to anticipate future improvements, and on a national scale, to aid in the design of judicious policies and effective monitoring campaigns.

Outputs:

Journal papers:

Vero, S.E., Basu, N.B., Van Meter, K., Richards, K.G., Mellander, P.E., Healy, M.G., Fenton, O. 2018. Review: the environmental status and implications of the nitrate time lag in Europe and North America. Hydrogeology Journal 26: 7 - 22. Vero et al. 2018

Vero, S.E., Healy, M.G., Henry, T., Creamer, R.E., Ibrahim, T.G., Forrestal, P.J., Richards, K.G., Fenton, O. 2016. A methodological framework to determine optimum durations for the construction of soil water characteristic curves using centrifugation. Irish Journal of Agriculture and Food Research 55(2): 91 - 99. Vero et al. IJAFR

Vero, S.E., Healy, M.G., Henry,  T., Creamer, R.E., Ibrahim, T.G., Richards, K.G., Mellander, P.E., McDonald, N.T., Fenton, O. 2017. A framework for determining unsaturated zone time lags at catchment scale. Agriculture Ecosystems and Environment 236: 234 - 242 Vero_Ag_Ecosyst_Env

Vero, S.E., Ibrahim, T.G., Creamer, R.E., Grant, J., Healy, M.G., Henry, T., Kramers, G., Richards, K.G., Fenton, O. 2014. Consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates. Journal of Contaminant Hydrology 170: 53 - 67.  Vero et al. J. Cont. Hydrol.

Conference papers:

Vero, S.E., Creamer, R.E., Healy, M.G., Henry, T., Forristal, P., Richards, K.G., Fenton, O. 2015. Achieving equilibrium in the soil water characteristic curve: an ‘effective’ approach. ASA, CSSA, and SSSA International Annual Meeting. Nov 13 – 19, Minneapolis, MN. 

Vero, S.E., Ibrahim, T.G., Creamer, R.E., Grant, J., Healy, M.G., Henry, T., Kramers, G., Richards, R.G., Fenton, O. 2015. Effects of meteorological and soil data on unsaturated time lag estimates. Agricultural Research Forum, Offaly, Ireland. 1 March, 2015.

Vero, S.E., Creamer, R., Henry, T., Healy, M.G., Ibrahim, T., Richards, K., Fenton, O. 2014. Unsaturated time lag: managing the expectations of policymakers using numerical models. ASA, CSSA, and SSSA International Annual Meeting. Nov 2 - 5, Long Beach, CA.

Vero, S.E., Creamer, R., Healy, M.G., Henry, T., Ibrahim, T., Richards, K., Fenton, O. 2014. Hydraulic equilibrium: is it ever reached? ASA, CSSA, and SSSA International Meeting. Nov 2 - 5, Long Beach, CA.

Start date:    01/09/10      End date: 31/08/13

Funder: IRCSET

Principal Investigator: Prof Mark Healy (NUI Galway) Prof Owen Fenton (Teagasc)

Budget (€): 72,000

Objective:

In Ireland, the pig industry is concentrated in a small number of counties. Pig farms typically have a high stocking rate. Therefore, the disposal of slurry in a cost-effective and environmentally-responsible way is a serious issue for farmers. Slurry is commonly applied to land, but this may not be possible if the land is at, or approaching, phosphorus (P) saturation. As pig farmers dispose of slurry in the vicinity of their properties, most of the nearby land is at P saturation, so alternative treatment methods need to be utilised (e.g. constructed wetlands, anaerobic digestion, filtration) or the slurry needs to be transported to another location. These alternatives are not currently financially viable in Ireland. Existing legislation (S.I. 610 of 2010) and recent changes in the implementation of legislation governing the timing and quantities of slurry that may be applied to land, means that pig farmers will no longer be able to exceed the maximum legal application rate to land (from January 2017). European policy aiming to intensify pig production will only accentuate this problem. If pig farmers are forced, in exceptional circumstances, to land apply slurry to unsuitable land, surface and subsurface losses of nutrients and suspended solids (SS) may occur. This could be potentially problematic if the land is located in a critical source area (CSA), an area that is highly likely to pollute receiving waters.

In these circumstances, a possible novel solution is to chemically amend the pig slurry prior to landspreading. This would mean that pig farmers may, in exceptional circumstances, utilise the land in the vicinity of their farms for landspreading, without releasing excessive nutrients and SS into receiving waters. However, knowledge gaps exist concerning the type of amendments to be used, the characteristics of the soil on which they can be most effectively used, and their impact on incidental (short-term) and chronic (long-term) losses of nutrients, SS and greenhouse gas (GHG) to surface and subsurface water and the atmosphere. Therefore, the aims of this project were to: (1) identify the most appropriate chemical amendments, and their addition rates, to reduce P losses in runoff from pig slurry based on effectiveness, cost and feasibility; (2) investigate the impacts of these chemical amendments on nutrient losses in leachate, soil properties and GHG emissions; and (3) identify suitable soil types on which to landspread chemically-amended pig slurry.

Results:

Laboratory bench-scale experiments were designed to identify the amendments which had the potential to reduce P in overland runoff and to quantify the stoichiometric rates at which to add them to the slurry. Based on effectiveness, cost and feasibility, the amendments identified were alum, which reduced dissolved reactive phosphorus (DRP) in overlying water by 86%, poly-aluminium chloride (PAC) (73%) and ferric chloride (FeCl₃) (71%). Following these bench-scale experiments, rainfall simulation experiments were conducted to quantify the impact of chemical amendments to slurry on surface runoff losses at various time intervals from the time of application. Poly-aluminium chloride performed best in these experiments. For the first time, the effect of these amendments on GHG emissions, soil properties and leachate was also examined. Chemical amendment did not adversely affect GHG emissions, soil properties or leachate from pig slurry, but FeCl₃ increased nitrous oxide (N₂O) and carbon dioxide (CO₂) losses. Finally, a 3-mo incubation experiment was conducted using a range of soil types to examine the effect of amendments on the long-term plant availability of P in soil and P solubility. Alum reduced more water extractable P than PAC, but also resulted in less plant available P. Considering cost, surface runoff and subsurface leachate losses, GHG emissions and impacts on soil chemistry, PAC was found to be the most suitable amendment with which to chemically amend pig slurry.

There is the potential, in combination with existing programmes of measures, to employ chemical amendment as a measure to mitigate the environmental impact arising from the landspreading of pig slurry. This should be conducted in targeted areas of the CSA and should take into account soil type and its chemical properties. Before implementation, these tests must first be validated in long-term testing at field-scale over a wide variety of soil types, and include repeated application and incorporation. At present, there is no provision in legislation for chemical amendments to be used as a mitigation measure in the land application of pig slurry, but if they are to be utilised, a regulatory framework will need to be introduced by the relevant bodies.

Outputs:

Journal papers:

1. O' Flynn, C.J., Fenton, O., Wall, D., Brennan, R.B., McLaughlin, M.J., Healy, M.G. 2018. Influence of soil phosphorus status, texture, pH and metal content on teh efficacy of amendments to pig slurry in reducing phosphorus losses. Soil Use and Management 69(2): 1 - 8. O' Flynn et al. SUM
2. O’ Flynn, C.J., Healy, M.G., Lanigan, G.J., Troy, S.M., Somers, C., Fenton, O. 2013. Impact of chemically amended pig slurry on greenhouse gas emissions, soil properties and leachate. Journal of Environmental Management 128: 690-698. PDF here
3. O’ Flynn, C.J., Healy, M.G., Wilson, P., Noekstra, N.J., Troy, S.M., Fenton, O. 2013. Chemical amendment of pig slurry: control of runoff related risks due to episodic rainfall events up to 48 hours after application. Environmental Science and Pollution Research 20: 6019 – 6027. Con ESPR paper
4. O’ Flynn, C.J., Fenton, O., Wilson, P., Healy, M.G. 2012. Impact of pig slurry amendments on phosphorus, suspended sediment and metal losses in laboratory runoff boxes under simulated rainfall. Journal of Environmental Management 113: 78 – 84.
5. O’ Flynn, C.J., Fenton, O., Healy, M.G. 2012. Evaluation of amendments to control phosphorus losses in runoff from pig slurry applications to land. CLEAN – Soil, Air, Water 40(2): 164-170.  

Conference papers:

1. O’ Flynn, C.J., Healy, M.G, Fenton, O. 2013. Chemical amendment of pig slurry prevents P loss in runoff – but don’t forget to examine the gaseous emissions! ESAI Colloquium, NUI Galway, January 31 – February 1, 2013.
2. O’ Flynn, C.J., Fenton, O., Wilson, P., Healy, M.G. 2012. Impact of slurry amendments to control phosphorus losses in laboratory runoff boxes under simulated rainfall. ESAI Colloquium, University College Dublin, 8-10 March, 2012.
3. O’ Flynn, C.J., Fenton, O., Wilson, P., Healy, M.G. 2012. Impact of pig slurry amendments to control phosphorus losses in laboratory runoff boxes under simulated rainfall. Agricultural Research Forum Conference. March 12-13. Tullamore, Co. Offaly.

‌Start date: 01/05/08          End date: 30/04/13

Funder: EPA/COFORD (STRIVE)

Principal Investigator: Dr Mark Healy (for NUI Galway)

Budget (€): 1,999,446

Objective:

Ireland’s forest cover stands at approximately 10%, or 700,000 ha, of the total surface area of the island and it is estimated that almost 60% of this forestry is on peat. Forestry on peatland throughout the world is now moving towards a ‘progressive management approach’, which incorporates sustainable timber production alongside multiple uses such as habitat restoration, ecological regeneration and the minimisation of any potentially negative effects to the surrounding environment. However, the legacy of blanket peatland forestry, planted in the 1950s, must be dealt with, as most of this forestry is now at harvestable age and current and future recommended best management practices (BMPs) for forestry operations must consider soil and water quality, environmental impacts and greenhouse gas (GHG) emissions. The aim of this project was to investigate the short and long-term changes in nutrient and sediment releases, watertable (WT) fluctuations, and GHG emissions arising from harvesting (clearfelling) of forested peatlands in the west of Ireland.

Results:

The study was located in three sites: (1) the Altaconey (Altahoney) forest, which comprised a regenerated riparian peatland buffer clearfelled 5 years before the present study, a recently clearfelled coniferous forest, and a standing mature coniferous forest (2) a virgin peat site and (3) a paired catchment study in the Glennamong forest. The Altaconey forest was instrumented with a network of piezometers, one of which was automated, for WT and water quality measurement, a rain gauge, and open-bottomed collars for gas flux measurement. Water, soil and gas measurements, the latter of which were also collected at the VP site, were taken regularly over a 2 ¼ -year study duration (12 months before clearfelling, 15 months after). Two paired catchments in the Glennamong forest, one a study control (no clearfelling) and the other clearfelled, and each with an area of approximately 10 ha, were instrumented for water quality and flow measurement.

Management changes such as drainage, fertilisation, afforestation and subsequent clearfelling of forested peatlands influences WT position, nutrient load transfer to shallow groundwater, and GHG emissions from soil respiration. In the Altaconey forest, there was an immediate rise in the WT after clearfelling, but this had no significant impact on the concentrations of total oxidized nitrogen (TON), nitrate nitrogen (NO₃^--N) or dissolved reactive phosphorus (DRP), the latter of which was more impacted by degrading logging residues (brash material) than by WT fluctuations. However, fluctuations in WT did influence concentrations of ammonium-nitrogen (NH₄⁺-N), which was highest under the standing mature coniferous forest, an area with the deepest WT. Nitrogen (N) and phosphorus (P) discharges to the adjacent watercourse in excess of maximum admissible concentrations were negligible due to the low lateral saturated conductivity and the high inherent natural attenuation capacity of the peat.

Fluctuations in the WT also affected GHG emissions from soil respiration and sequestration, as clearfelling of the forest at Altaconey produced significant increases in carbon dioxide (CO₂) (11±2 kg CO₂-C ha^-1 d^-1 before clearfelling to 19±2 kg CO₂-C ha^-1 d^-1 after clearfelling) and methane (CH₄) emissions (22±14 g CH₄-C ha^-1 d^-1 to 163±99 g CH₄-C ha^-1 d^-1), but a decrease in nitrous oxide (N₂O) emissions (1.7 g N₂O-N ha^-1 d^-1 to 0.7 g N₂O-N ha^-1 d^-1).

Elevated levels of nutrients and suspended sediment (SS) in surface waters are frequently associated with forestry clearfelling operations for up to 4 years. Despite significant rises in nutrients and SS at the Glennamong study site and changes to some water parameters, the implementation of BMP, where possible, and the quick execution of a site restoration plan comprising silt traps and water management on extraction racks, appeared to negate excessive nutrients and SS export to the adjoining watercourse.

Outputs:

Final report:

Kelly-Quinn, M., Bruen, M., Harrison, S., Healy, M.G., Clarke, J., Drinan, T., Feeley, H.B., Finnegan, J., Graham, C., Regan, J., Blacklocke, S. 2016. Assessment of the impacts of forest operations on the ecological quality of water (Hydrofor). EPA Synthesis Report No. 169. EPA, Co. Wexford. Hydrofor EPA

Journal papers:

1. Finnegan, J., Regan, J.T., Fenton, O., Lanigan, G.J., Brennan, R.B., Healy, M.G. 2014. The short-term effects of management changes on watertable position and nutrients in shallow groundwater in a harvested peatland forest. Journal of Environmental Management 142: 46 - 52. Finnegan et al. JEM
2. Finnegan, J., Regan, J.T., O’ Connor, M., Wilson, P., Healy, M.G. 2014. Implications of applied best management practices for peatland forest harvesting. Ecological Engineering 63: 12-26. Joanne_Ecol_Eng_2014_BMP
3. Finnegan, J., Regan, J.T., de Eyto, E., Ryder, L., Tiernan, D., Healy, M.G. 2012. Nutrient dynamics in a peatland forest riparian buffer zone and implications for the establishment of planted saplings. Ecological Engineering 47: 155 – 164.  PDF here ‌

Conference papers:

1. Finnegan, J., Regan, J.T., McCabe, B., Healy, M.G. 2012. Use of brash mats for clearfelling of forestry on peat: an Irish perspective. p. 8 – 16. The International Peat Congress (IPC), Stockholm, 3-8 June, 2012.
2. Finnegan, J., Regan, J.T., Healy, M.G. 2011. Assessment of impacts of forest operations on the environment. 12^th International Conference on Environmental Science and Technology (CEST). 8-10 September, Rhodes Island, Greece.
3. Finnegan, J., Regan, J.T., Healy, M.G. 2011. Assessment of impacts of forest operations on the environment. ESAI Colloquium, University College Cork, April, 2011. (winner – best presentation)

‌Start date: 01/12/07          End date: 01/06/12

Funder: Department of Agriculture, Fisheries and Food (Research Stimulus Fund)

Principal Investigator: Dr Owen Fenton (Project Co-ordinator) Dr Mark Healy

Budget (€): 611,296

Objective:

This study investigated novel methods to treat subsurface and surface waters.

Results:

This project has shown that denitrifying bioreactors are adaptable for Irish purposes i.e. as end of pipe solution to clean drainage discharges and natural drainage outlets such as springs. They also have the capacity to create pollution swapping of design criteria are not adapted properly but when sequential units are placed in tandem can mitigate against mixed pollution sources. From an international point of view this project has placed bioreactors in a more important position scientifically i.e. within gaseous and water research. From a buffer strip point of view this project shows that hydrology must be considered the effective operation of vegetated buffer strips and this is solely dependent on location. This project shows that chemical amendment of soil water and runoff works but is expensive and other forms of mitigation should be sought.

The overall impact in the agri-sector could be huge if this blueprint is rolled out to the next stage i.e. implementation. This could have huge consequences as presently large areas of the country are being drained or existing drainage networks are being modernized. At present as drainage discharge enters waterways un-attenuated. An adaptable system in sequence with either a vegetated buffer strip or phosphorus sobbing material could be an option for the future to prevent both P and N losses to surface and ground waters.

Outputs:

Journal papers:

1. Fenton, O., Healy, M.G., Brennan, F.P., Thornton, S.F., Lanigan, G.J., Ibrahim, T.G. 2016. Holistic evaluation of field-scale denitrifying bioreactors as a basis to improve environmental quality. Journal of Environmental Quality 45(3): 788-795.  JEQ_bioreactors
2. Healy, M.G., Barrett, M., Lanigan, G., Serrenho, A., Ibrahim, T.G., Thornton, S.F., Rolfe, S.A., Huang, W.E., Fenton, O. 2014. Optizing nitrate removal and evaluating pollutoin swapping trade-offs from laboratory denitrification bioreactors. Ecological Engineering 74: 290 - 301. Ana_bioreactor
3. Fenton, O., Healy, M.G., Brennan, F., Jahangir, M.M.R. Lanigan, C.J., Richards, K.G., Thornton, S.F., Ibrahim, T.G. 2014. Permeable reactive interceptors – blocking diffuse nutrient greenhouse gases losses in key areas of the farming landscape. Journal of Agricultural Science 152: S71 - S81. Fenton et al._2014_J. Ag. Sci.
4. Ibrahim, T.G., Fenton, O., Richards, K.G., Fealy, R.M., Healy, M.G. 2013. Loads and forms of nitrogen and phosphorus in overland flow and subsurface drainage on a marginal land site in south east Ireland. Biology and Environment: Proceedings of the Royal Irish Academy 113B(2): 169-186.  
5. Serrenho, A., Fenton, O., Murphy, P.N.C., Grant, J., Healy, M.G. 2012. Effect of chemical amendments to dairy soiled water and time between application and rainfall on phosphorus and sediment losses in runoff. Science of the Total Environment 430: 1-7. Ana_STOTEN
6. Fenton, O., Kirwan, L., O’ Uallacháin, D., Healy, M.G. 2012. The effectiveness and feasibility of using ochre as a soil amendment to sequester dissolved reactive phosphorus in runoff. Water, Air and Soil Pollution 223(3): 1249-1261.
7. Healy, M.G., Ibrahim, T.G., Lanigan, G., Serrenho, A., Fenton, O. 2012. Nitrate removal rate, efficiency and pollution swapping potential of different organic carbon media in laboratory denitrification bioreactors. Ecological Engineering 40: 198-209. Ana_Ecol_Eng
8. Fenton, O., Healy, M.G., Henry, T., Khalil, M.I., Grant, J., Baily, A., Richards, K.G. 2011. Exploring the relationship between groundwater geochemical factors and denitrification potentials on a dairy farm in south east Ireland. Ecological Engineering 37: 1304-1313.
9. Fenton, O., Serrenho, A., Healy, M.G. 2011. Evaluation of amendments to control phosphorus losses in runoff from dairy soiled water. Water, Air and Soil Pollution 222: 185-194. Fenton_Ana
10. Fenton, O., Healy, M.G., Schulte, R.P.O. 2008. A review of remediation and control systems for the treatment of agricultural wastewater in Ireland to satisfy the requirements of the Water Framework Directive. Biology and Environment: Proceedings of the Royal Irish Academy 108B(2): 69 – 79.

Conference papers:

1. Serrenho, A.J., Fenton, O., Lanigan, G., Healy, M.G. 2011. Nitrate removal capacity and greenhouse gas emissions from laboratory-scale permeable reactive barriers. Agricultural Research Forum Conference. 14 - 15 March, Tullamore, Co. Offaly.
2. Fenton, O., Healy, M.G., Baily, A., Henry, T., Khalil, M.I., Serrenho, A.J., Richards, K.G. 2010. Investigating denitrification hotspots in groundwater using δ¹⁵N/δ¹⁸O  isotopes and membrane inlet mass spectrometry. 5^th International Nitrogen Conference. 3-7 December, New Delhi, India.
3. Serrenho, A.J., Fenton, O., Rodgers, M., Healy, M.G. 2010. Laboratory study of a denitrification system using a permeable reactive barrier. BSAS/WPSA/Agricultural Research Forum Conference. Queen’s University, Belfast. 12-14 April, 2010. 
4. Haria, A., Fenton, O., Kenny, S., Rodgers, M., Healy, M.G. 2009. Drainflow and its impact on surface runoff with respect to nutrient transport from agricultural grasslands. 16^th Nitrogen workshop, University of Turin, Italy, 28 June – 1 July, 2009.
5. Fenton, O., Healy, M.G., Schulte, R.O. 2008. A review of remediation and control systems for the treatment of agricultural wastewater in Ireland to satisfy the requirements of the Water Framework Directive. Teagasc Grassland and EU Water Framework conference, 12 – 14 November, 2008, Teagasc, Johnstown Castle, Co. Wexford.

Start date:  01/09/09         End date: 31/08/12

Funder: IRCSET

Principal Investigator: Dr Mark Healy (NUI Galway) Dr Owen Fenton (Teagasc)

Budget (€): 72,000

Objective:

Biosolids are the by-product of urban wastewater treatment. When spread on arable land or grassland, and provided that they are treated to the approved standards, they may offer an excellent source of nutrients and metals required for plant and crop growth. Application of biosolids to agricultural land can be relatively inexpensive in countries such as the Republic of Ireland and the USA, as such by-products are defined as wastes. Meat and bone meal (MBM), derived from the processing of residues from the slaughtering of farmyard animals, is also a potential fertiliser replacement, but its re-use in agriculture in Ireland is currently restricted.

The amount of sewage sludge being applied to land in the European Union (EU) has dramatically increased. This is as a result of various directives, which advocate the re-use of sludge and limit the disposal of biodegradable municipal waste via landfill. In addition, the minimisation, recycling and recovering of waste is one of the six key goals outlined by the EPA. In Ireland, the application rate of biosolids to land is governed by statutory instrument (S.I.) 610 of 2010, which sets out nutrient (phosphorus (P) and nitrogen (N)) limits for various crops. These guidelines do not consider the relationship between biosolid application rates and surface runoff of nutrients, suspended sediment (SS), or metals. Therefore, the aims of this research were to: (1) to develop a simple, novel method to calculate the maximum legal application rate of biosolids (anaerobically digested (AD), thermally dried (TD) and lime stabilised (LS)) and two types of MBM (high ash and low ash content, MBM HA and MBM LA, respectively) to land (2) to quantify the potential of dissolved reactive phosphorus (DRP) release to surface water following land application in a bench-scale experiment (3) to determine the potential for nutrient and metal release following successive rainfall events on land onto which biosolids or MBM had been applied, and (4) to investigate, over an 11-wk study period, the impact of their land application on soil properties and P availability to plants.

Results:

Following development of an MS Excel™-based programme (objective 1), a controlled agitator test showed that AD biosolids and high ash and low ash-content MBM may be applied to land within maximum legal application limits without any adverse risk of runoff of P or metals (objective 2). These results were largely verified at laboratory-scale (objective 3), but the results indicated that, considering potential DRP and metal loss to surface runoff, AD biosolids may be the most viable option. Re-constituted soil columns, treated with either biosolids or MBM applied at the maximum legal application rate were used to address objective 4. The addition of biosolids or MBM LA had no significant impact on the plant available phosphorus (measured as Morgan’s Phosphorus, Pm) or water extractable phosphorus (WEP) content of the soil. The addition of MBM HA resulted in increased Pm and WEP in the top soil layer of the soil, but values measured were well below optimal agronomic levels. However, this study was preliminary in nature and further work would have to be completed over longer study durations than the present study before a full analysis of the efficacy of biosolids or MBM may be determined.

This study showed that, in general, biosolids and MBM release low amounts of nutrients and metals into receiving waters. However, their re-use in agriculture ultimately depends on their efficacy as a viable alternative to organic or artificial fertilisers. Long-term studies investigating their impact on surface runoff and leaching, greenhouse gas emissions, and crop growth at field-scale are needed.

Outputs:

Journal papers:

1. Lucid, J.D., Fenton, O., Grant, J., Healy, M.G. 2014. Effect of rainfall time interval on runoff losses of biosolids and meat and bone meal when applied to a grassland soil. Water, Air and Soil Pollution 225(8): 2042. PDF here
2. Lucid, J.D., Healy, M.G., Fenton, O. 2013. Estimation of maximum biosolids and meat and bone meal application to a low P index soil and a method to test for nutrient and metal losses. Water, Air and Soil Pollution 224: 169 – 186.  PDF here

Start date: 01/08/06           End date: 31/07/09

Funder:

Principal Investigator: Dr Mark Healy (NUI Galway) Dr Owen Fenton (Teagasc)

Budget (€): 72,000

Objective:

Arable cropping, due to its intensive nature, can leave soil with reduced ground cover and impaired soil structure, making it vulnerable to erosion under heavy rainfall. Runoff containing suspended sediment (SS) and nutrients, particularly phosphorus (P), from agricultural fields is considered to be one of the main causes of water quality impairment. To date, in Ireland, no study has investigated erosion and associated P loss from tillage soils when subjected to high intensity rainfall, even though international research indicates significantly higher P export coefficients from this land use than from grassland. As a result, only agronomic nutrient advice is available and this has been adopted into current legislation. Research was therefore necessary to assess the potential P losses arising from complying with the legislation. This objective was addressed in the first part of the study using two simulated rainfall experiments. A related objective involving the development of a screening methodology to identify tillage fields with erosion risk and soil quality problems was addressed in the second part.

Results:

The aim of the first part of the study was to quantify the amount of dissolved reactive phosphorus (DRP), total phosphorus (TP), particulate phosphorus (PP) and SS released in runoff from five tillage soils with varying soil test P (STP) when subjected to a rainfall intensity of 30 mm hr^-1 applied in three successive events. Soil physical and chemical parameters, slope, and time interval between storm events were ranked in order of importance for the prediction of P and SS releases, and a runoff dissolved phosphorus risk indicator (RDPRI) was developed to identify the STP for Irish tillage soils above which there may be a potential threat to surface water quality.  The effect of soil type on the flow weighted mean concentration (FWMC) of DRP (p = 0.013) depended on both slope and time between rainfall events. The effect of soil type depended only on surface slope for the FWMCs of SS (p = 0.044), TP (p = 0.014) and PP (p = 0.022) in surface runoff. Increasing the overland flow rate over the soil surface in the presence of rainfall had the effect of increasing the concentrations of SS, PP and TP (but not DRP) in surface runoff (p < 0.05) across all soils. An increase in extractable soil P resulted in an increase in concentrations of DRP in surface runoff (p < 0.05) across all soils. Of the five methods used to extract soil P in these experiments, water extractable P (WEP) was identified as having the greatest potential to be used as an indicator of the risk of P movement from soil into runoff water. However, despite its apparent advantage over Morgan’s Phosphorus (P_m) in determining environmental risk, it would appear to be impractical and costly to run two soil P tests side by side given that P_m gives a good approximation for both agronomic and environmental purposes.

Combining the results of both experiments (rainfall only and rainfall and overland flow) indicated that if the current agronomic optimum P_m range for tillage soils of 6.1 - 10 mg L^-1 is maintained by tillage farmers through adherence to recommended P application rates, then the risk of runoff with DRP concentrations in excess of the level at which eutrophication is likely to occur (0.03 mg molybdate reactive phosphorus (MRP) L^-1) should be minimal.

Ireland has a valuable resource in terms of its land and soil quality, and promoting sustainable soil management is one of the areas of action included in Food Harvest 2020, the national strategy for the development of the agri-food sector. Agricultural activities that can negatively impact on soil quality must be tackled if Ireland is to meet the ambitious growth targets set out in this vision. Therefore, in the second part of the study, the five soils above, and a sixth soil, were assessed in their natural field conditions to determine their erosion risk and soil quality status. At each study site, detailed soil classification results and visual soil assessments were used in conjunction with observed erosion levels to select the most appropriate indicators for assessing erosion risk and soil quality status. Parameters selected include: texture, slope, erosion features, structure, ponding, potential rooting depth, soil organic matter (SOM), average annual rainfall and current land use. Assessment of these indicators at each study site using the user friendly grading system developed here, made it possible to correctly identify the sites where the erosion risk was high. This work showed that adoption of an erosion and soil quality screening method by tillage farmers and advisory specialists in Ireland will enable the quantification of the extent of erosion risk and soil quality degradation on farms. This will allow remediation measures to be prioritised for the most vulnerable sites, which is likely to result in cost and resource savings for farmers and advisory services.

Outputs:

Journal papers:

1. Regan, J.T., Rodgers, M., Healy, M.G., Kirwan, L., Fenton, O. 2010. Determining phosphorus and sediment release rates from five Irish tillage soils. Journal of Environmental Quality 39: 185-192. Regan_JEQ
2. Regan, J.T., Fenton, O., Healy, M.G. 2012. A review of phosphorus and sediment release from Irish tillage soils, the methods used to quantify losses and the current state of mitigation practice. Biology and Environment: Proceedings of the Royal Irish Academy 112B(1): 157-183. Regan_Tillage_review

Conference papers:

1. Regan, J., Healy, M.G., Rodgers, M., Fenton, O. 2008. Sediment and nutrient loss from five Irish tillage soils at two rainfall intensities. EUROSOIL conference, 25 – 29 August, 2008, Technical University, Vienna, Austria.
2. *Regan, J., Rodgers, M., Healy, M.G., Fenton, O., Walsh, M. 2008. Soil erosion and nutrient loss from Irish tillage soils. Agricultural Research Forum, 10-13 March, 2008, Tullamore, Co. Offaly.
3. Regan, J., Rodgers, M., Healy, M.G., Fenton. O. 2008. Sediment loss and surface runoff from Irish tillage soils. ESAI Colloquium, Dundalk IT, February, 2008.

‌Start date: 1/9/08           End date:30/8/11

Funder: Teagasc (Walsh Fellowship)

Principal Investigator: Dr Mark Healy (NUI Galway) Dr Padraig French/Dr Paul Murphy (Teagasc)

Budget (€): c. €100,000

Objective:

The milking process produces dairy soiled water (DSW) that contains variable concentrations of nutrients. The most common method of disposal is by application to land. However, this practice can result in the pollution of nearby receiving water bodies. It is proposed that aerobic woodchip filters would decrease contaminant concentrations of nutrients in DSW. A laboratory-based experiment investigated woodchip as a filter medium to treat DSW. Subsequently, farm-scale filters investigated the system under normal farm conditions. The effectiveness of two types of sand filters (SFs), single-layer and stratified, were compared to treat effluent from the farm-scale woodchip filters.

Results:

0.5, 1, and 1.5 m-deep laboratory filters (n=3) containing Sitka Spruce (Picea sitchensis (Bong.) Carr.) treated DSW at two loading rates: 280 g suspended solids (SS) m-2 d-1 (S1) and 840 g SS m-2 d-1 (S2). Average chemical oxygen demand (COD), SS and total nitrogen (TN) decreases of 95, 99 and 88 %, respectively, were achieved and the effect of depth was negligible. Based on these findings, three replicated farm-scale 1 m-deep filters, each with a surface area of 100 m2, were constructed and loaded at 30 L m-2 d-1 for 11 months. Average decreases of 65, 84 and 60 % for COD, SS and TN, respectively, were achieved. Three replicated single-layer SFs and stratified SFs were operated for 82 days and loaded at 20 L m-2 d-1 with the effluent from the farm-scale filters. Average influent COD, SS and TN concentrations were decreased by an average of 39, 52 and 36 % for the single-layer SFs and 56, 62 and 57 % for the stratified SFs, respectively.

These results demonstrate the potential use of woodchip as a filter medium for treating DSW to produce an effluent for re-use in washing yards, or for application to land as an organic fertiliser. This would reduce water usage and the environmental risks associated with land spreading. Woodchip filters are a low cost, minimal maintenance treatment system, using a renewable resource, which can be easily integrated into existing farm infrastructure.

Outputs:

Journal papers:

1. Ruane, E.M., Murphy, P.N.C., French, P., Healy, M.G. 2014. Comparison of a stratified and a single-layer laboratory sand filter to treat dairy soiled water from a farm-scale woodchip filter. Water, Air and Soil Pollution 225: 1915 Ruane et al. 2014
2. Ruane, E.M., Murphy, P.N.C., Healy, M.G., French, P., Rodgers, M. 2011. On-farm treatment of dairy soiled water using aerobic woodchip filters. Water Research 45: 6668-6676.  PDF here

Start date: 1/9/15           End date: 31/8/18

Funder: NUI Galway

Principal Investigator: Dr Bryan McCabe and Dr Mark Healy (NUI Galway), and Dr Owen Fenton (Teagasc)

Budget (€): c. €60,000

Objective:

The soil water characteristic curve (SWCC) describes the volumetric water content of a soil at a given matric potential. The SWCC allows elucidation of solute transport timescales. Contexts in which the SWCC may be successfully used include the determination of ‘lag time’ between good agricultural practices and the determination of travel times of contaminated plumes arising from industrial practices. The proposed research work aims to use the centrifugal method to determine solute transport in different soil types and in different contexts.

Outputs: