Use of zeolite for nutrient retention and a slow-release fertiliser

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

Funder: UL

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., 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

A novel method to protect the environment from nutrient losses arising from forestry

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

Funder: IRC

Principal Investigator: Dr 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. 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

Novel Bioleaching-Bioprecipitation Process for Recovery of Valuable Metals from Petroleum Refinery Spent Catalyst

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

Funder: IRC

Principal Investigators: Dr 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., 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

Lag Time: extending achievement of Water Framework Directive water quality timelines beyond 2015 without implementation

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., 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.

Measurement and modelling of health impacts arising from the landspreading of biosolids

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

Funder: EPA (STRIVE)

Principal Investigators: Dr Mark Healy (NUI Galway) Dr 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.

Journal papers:

  1. 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
  2. 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
  3. 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.
  4. 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
  5. 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
  6. 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
  7. 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
  8. 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.

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., 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.

2. 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

2. 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

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. Biosolids presentation

Chemical amendments to pig slurry to reduce nutrient release in surface runoff

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

Funder: IRCSET

Principal Investigator: Dr Mark Healy (NUI Galway) Dr 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., 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
  2. 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
  3. 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.
  4. 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.

Assessment of the suitability of co-mixed and composted separated solids of pig manure after anaerobic digestion for use

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

Funder: Teagasc (Walsh Fellowship)

Principal Investigator: Dr Mark Healy (NUI Galway) Dr Peadar Lawlor (Teagasc)

Budget (€): 72,000

Objective:

Landspreading of pig manure in quantities greater than that required by plants can result in pollution of ground and surface water bodies. Recent regulations have placed restrictions on the application of manure to land, while further more stringent restrictions will come into force in the coming years. To comply with  these regulations, it is estimated that pig farmers will require approximately 50% more spreadlands for manure application in 2017 than is the case in 2012. This will increase the cost of landspreading pig manure and, therefore, alternative viable  on-farm treatment options for pig manure are urgently required. Composting and pyrolysis of the separated solid fraction of pig manure may be a solution to this problem.

Results:

A  composting  experiment  was  designed  to  identify  the  most  effective  readily available bulking agents to produce stable and mature compost from the separated solid fraction of pig manure. Of the bulking agents investigated, sawdust was found to be the best, due to its large surface area and small particle size. A second composting experiment was then designed to investigate the required ratio of sawdust addition to pig manure. Two ratios of separated pig manure  solids-to-sawdust  (w/w)  were examined: 4:1 and 3:2. It was found that the lower ratio of sawdust addition produced stable compost, while the decreased sawdust requirement also reduced costs. An economic analysis, conducted to determine the viability of separation and composting of pig manure in Ireland, suggested that pig manure composting is not currently viable due to the high cost of separation, but may become viable in the future if a cheaper method of separation is used, and if oil prices continue to rise.

A pyrolysis experiment was designed to produce and characterise biochar, bio-liquid and gas from pig manure, and to examine the impact of the addition of different rates of sawdust on the energy yield. Increasing the sawdust content in the wood/manure mixture increased the resultant biochar and gas heating values, but reduced bio-liquid heating values. The nutrient concentrations of the biochar were reduced with increasing sawdust content in the wood/manure mixture. The effect of composting the feedstock before pyrolysis was also examined. An energy balance was conducted on the processes of separation, composting and pyrolysis of pig manure. A positive net energy yield was produced from these technologies with the addition of sawdust to the manure. Composting the feedstock before pyrolysis reduced the net energy yield.

The effect of amending soil with two types of biochar, produced from pig manure and wood, on nutrient leaching, soil properties and greenhouse gas emissions, was also examined. Both types of biochar affected the nitrogen (N) cycling process within the soil, which, in turn, reduced nitrate (NO3-) leaching and increased nitrous oxide (N2O) emissions. Emissions of carbon dioxide (CO2) were higher in the biochar-amended soils due to a higher rate of mineralization. The soil water, organic matter, carbon (C) and N contents were impacted when both types of biochar were added. The biochar produced from pig manure released phosphorus (P), and resulted in higher P contents both in the soil and in the leachate.

This study showed that composting and pyrolysis can be used as alternatives to landspreading of pig manure. However, at present, neither of these treatment methods is currently viable for on-farm implementation.  Composting is a proven technology and can be quickly implemented at farm-scale, but using the techniques of this study, the  cost  of  slurry  separation  with  a  decanter  centrifuge  would  be  prohibitively expensive. However, composting of pig manure following a cheaper method of separation should be investigated, and may be economically viable. Pyrolysis of separated pig manure may be an alternative to landspreading in the future. However, farm-scale studies would be first required to investigate whether the laboratory results of the present study can be replicated on a larger scale. The current method of landspreading pig manure remains the most feasible manure treatment option at the current time. This study showed that the application  of biochar to soil can reduce nutrient leaching, and may be an effective method of reducing surface and ground water contamination after landspreading of pig manure. However, further studies are required to examine different soil types, biochar types and application rates.

Outputs:

Journal papers:

  1. Troy, S.M., Lawlor, P.G., O’ Flynn, C.J., Healy, M.G. 2014. The effect of biochar addition on nutrient leaching and soil properties of tillage soil amended with pig manure. Water, Air and Soil Pollution 225(3): 1900. Troy_Wat_Air_Soil
  2. Troy, S.M., Lawlor, P.G., O’ Flynn, C.J., Healy, M.G. 2013. Impact of biochar addition to soil on greenhouse gas emissions following pig manure application. Soil Biology and Biochemistry 60: 173-181.  Troy_Soil Biol Biochem
  3. Troy, S.M., Nolan, T., Leahy, J.J., Lawlor, P.G., Healy, M.G., Kwapinski, W. 2013. Effect of sawdust addition and composting of feedstock on renewable energy and biochar production from pyrolysis of anaerobically digested pig manure. Biomass and Bioenergy 49: 1 – 9. PDF here
  4. Troy, S.M., Nolan, T., Kwapinski, W., Leahy, J.J., Healy, M.G., Lawlor, P. 2012. Effect of sawdust addition on composting of separated raw and anaerobically digested pig manure. Journal of Environmental Management 111: 70 – 77.
  5. Nolan, T., Troy, S.M., Gilkinson, S., Frost, P., Xie, S., Zhan, X., Harrington, C., Healy, M.G., Lawlor, P.G. 2012. Economic analysis of pig manure treatment options in Ireland. Bioresource Technology 105: 15-23. 
  6. Nolan, T., Troy, S.M., Healy, M.G., Kwapinski, W., Leahy, J.J., Lawlor, P.G. 2011. Characterization of separated pig manure composted with a variety of bulking agents at low initial C/N ratios. Bioresource Technology 102: 7131-7138.

Conference papers:

  1. Troy, S., Nolan, T., Lawlor, P., Leahy, J.J., Healy, M.G., Kwapinski, W. 2012. Influence of sawdust addition and pre-composting on energy production from pig manure pyrolysis. ESAI Colloquium, University College Dublin, 8-10 March, 2012.
  2. Troy, S., Nolan, T., Lawlor, P., Leahy, J.J., Healy, M.G., Kwapinski, W. 2011. Influence of the addition of different carbon rich bulking agents and composting on the characteristics of pig manure char. ESAI Colloquium, University College Cork, April, 2011.
  3. Troy, S.M., Nolan, T., Healy, M.G., Lawlor, P.G. 2011. Effect of manure to sawdust ratio on the composting of separated solids from anaerobically digested pig manure. Agricultural Research Forum Conference. 14-15 March, Tullamore, Co. Offaly.
  4. Nolan, T., Troy, S., Healy, M.G., Lawlor, P.G. 2011. Characterization of compost produced from separated pig manure and a variety of bulking agents at low initial C/N ratios. Agricultural Research Forum Conference. 14-15 March, Tullamore, Co. Offaly.

Assessment of the impacts of forest operations on the ecological quality of water (Hydrofor)

‌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. 12th 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)

Novel agri-engineering solutions for amelioration of surface and groundwater at critical source areas

‌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. 5th 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. 16th 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.

Alum (aluminium sulphate) addition for the control of soluble phosphorus in runoff from grasslands

Start date: 01/09/98          End date: 21/10/11

Funder: Teagasc (Walsh Fellowship)

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

Budget (€): 72,000

Objective:

Phosphorus (P) loss from grassland to a waterbody can adversely affect water quality. Land application of dairy cattle slurry can result in incidental P losses to runoff in addition to increased chronic P losses from soil as a result of a build-up in Soil Test P (STP). A literature review identified chemical amendment of dairy cattle slurry as a possible mitigation measure to prevent such losses. This study comprised laboratory and field-scale experiments, which investigated the effectiveness and feasibility of chemical amendments in reducing P solubility, taking into account for the first time their pollution swapping potential.

Results:

A  controlled  agitator  experiment  was  designed  to  identify  the  most  effective chemical amendment to reduce Dissolved Reactive Phosphorus (DRP) release to water overlying grassed soil cores, which received un-amended and amended dairy cattle slurry. In addition to effectiveness, the feasibility of these amendments was determined based on several criteria: estimated cost of amendment, amendment delivery to farm, addition of amendment to slurry, and slurry spreading costs due to any volume increases. The four best amendments based on effectiveness and feasibility, at optimum application rates were: ferric chloride (FeCl2), which reduced the DRP in overlying water by 88%, aluminium chloride (AlCl3) (87%), alum (83%) and lime (81%). These amendments were then added to slurry immediately before it was surface applied to grassed soil in runoff boxes, which were subjected to simulated rainfall events. Analysis of overland flow showed that PAC (Poly-Aluminium Chloride, a commercially available form of AlCl3) was the most effective amendment for decreasing DRP losses in runoff following slurry application, while alum proved to be the most effective for total P (TP) and particulate P (PP) reduction. The incidental loss of metals (aluminium (Al), calcium (Ca) and iron (Fe)) in runoff during all experiments was below the maximum allowable concentrations (MAC) for receiving waters.

Once the effectiveness of the amendments under laboratory conditions were quantified, their pollution swapping‘ potential  was  examined.  A  laboratory-scale  gas  chamber experiment was conducted to examine emissions of ammonia (NH3), nitrous oxide (N2O), methane (CH4) and carbon dioxide (CO2). After considering pollution swapping in conjunction with amendment effectiveness, the amendments recommended for a micro plot study were, from best to worst: PAC, alum and lime. This component of the study investigated how soil and chemically amended slurry interactions affect amendment effectiveness under field conditions. The results of this micro-plot study validated the results from the laboratory-scale studies. Alum and PAC reduced average flow-weighted mean concentration (FWMC) and total loads of DRP, dissolved un-reactive phosphorus (DUP), PP and TP in runoff, while amendment of slurry with lime at the rate examined in this study  was  not  effective  at  reducing  P  losses. Alum amendment  significantly increased average FWMC of ammonium-N (NH4-N) in runoff water during the first rainfall event after the slurry was applied (an 84% increase). This indicates that chemical amendment of dairy cattle slurry conducted on a large scale could increase soluble N losses. Finally, a 9-month incubation experiment was conducted using five Irish grassland soils to examine the effect of amendments on the long-term plant availability of P in soil and the effect of soil type on the stability of reductions in P solubility. The study showed that, with the exception of FeCl2, the chemical amendments reduced water extractable phosphorus (WEP) without affecting STP.

This study showed that amendments are effective and that there is no major risk of pollution swapping associated with alum and PAC. This is a significant finding as there is now potential to use amendments strategically, in combination with existing POM (programme of measures), to mitigate P losses. The next step will be to examine the use of chemical amendments at catchment-scale. It is hoped that there will be economic incentives given to farmers to reduce nutrient losses. It is possible that P mitigating methods, such as chemical amendment of dairy cattle slurry, may be used strategically within a catchment to bind P in cow and pig slurries.

Outputs:

Journal papers:

  1. Brennan, R.B., Healy, M.G., Fenton, O., Lanigan, G. 2014. The effect of chemical amendment of dairy cattle slurry on greenhouse gas and ammonia emissions. PLoS One 10(6): e0111965. doi: 10.1371/journal.pone.0111965 Brennan_PLoS One
  2. Brennan, R.B., Wall, D., Fenton, O., Grant, J., Sharpley, A.N., Healy, M.G. 2014. The impact of chemical amendment of dairy cattle slurry before land application on soil phosphorus dynamics. Communications in Soil and Plant Analysis 45(16): 2215 - 2233. Brennan_Soil_Pl
  3. Brennan, R.B., Healy, M.G., Grant, J., Ibrahim, T., Fenton, O. 2012. Incidental phosphorus and nitrogen loss from grassland plots receiving chemically amended dairy cattle slurry. Science of the Total Environment 441: 132 – 140. Brennan_Plot
  4. Brennan, R.B., Fenton, O., Grant, J., Healy, M.G. 2011. Impact of chemical amendment of dairy cattle slurry on phosphorus, suspended sediment and metal loss to runoff from a grassland soil. Science of the Total Environment 409: 5111-5118. Brennan_flume
  5. Brennan, R.B., Fenton, O., Rodgers, M., Healy, M.G. 2011. Evaluation of chemical amendments to control phosphorus losses from dairy slurry. Soil Use and Management 27(2): 238-246. Brennan_SUM

Conference papers:

  1. Brennan, R.B., Fenton, O., Grant, J., Healy, M.G. 2011. Mitigating incidental DRP losses from land application of dairy cattle slurry using chemical amendments. Agricultural Research Forum Conference. 14-15 March, Tullamore, Co. Offaly.
  2. Brennan, R.B., Fenton, O., Healy, M.G. 2010. Chemical amendment of dairy cattle slurry for control of phosphorus in runoff from grasslands. A05 symposium on emerging technologies to remove phosphorus. ASA-CSA-SSSA International Meetings, Long Beach, CA. 31 October – 4 November, 2010.
  3. Brennan, R.B., Fenton, O., Healy, M.G. 2010. Evaluation of chemical amendments to control soluble phosphorus losses from dairy cattle slurry. In: E. Turtola, P. Ekholm, W. Chardon (eds). MTT Science 10. Novel methods for reducing agricultural nutrient loading and eutrophication: Meeting of COST 869, 14-16 June, Jokioinen, Finland. p. 18. 
  4. Brennan, R.B., Fenton, O., Rodgers, M., Healy, M.G. 2010. Chemical amendment of dairy cattle slurry for control of phosphorus in runoff from Irish grasslands. SEGH 2010. 27 June – 2 July, 2010. National University of Ireland, Galway.
  5. Brennan, R.B., Fenton, O., Rodgers, M., Healy, M.G. 2010. The addition of chemical amendments to dairy cattle slurry for the control of phosphorus in runoff from grasslands. BSAS/WPSA/Agricultural Research Forum Conference. Queen’s University, Belfast. 12-14 April, 2010.

Determination of the nutrients and metals in runoff from grassland treated with biosolids and meat and bone meal

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

The erodibility and phosphorus loss potential of a selection of Irish tillage soils

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 (Pm) in determining environmental risk, it would appear to be impractical and costly to run two soil P tests side by side given that Pm 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 Pm 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.

Treatment of dairy soiled water using an aerobic woodchip filter and a sand filter

‌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

Mitigation techniques for the treatment of nutrient losses from agricultural systems in Ireland

Start date: 1/9/07          End date:30/8/10

Funder: Teagasc

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

Budget (€): c. 100,000

Objective:

Agriculture management is a landscape issue impacting on water quality. The Water Framework Directive (WFD) aims to achieve ‘at least good status’ in ground and surface waters by 2015. Good status means both ‘good ecological status’ and ‘good chemical status’. Implementation of mitigation measures called “programmes of measures” (POM) to prevent nutrient loss must be in place by 2012. In Ireland, the Nitrates Directive is the basic POM in place. While the WFD aims to prevent nutrient losses from agricultural activities, it does not account for nutrients already lost in runoff or through leaching to shallow groundwater. The aim of this study was to investigate P and nitrogen (N) mitigation techniques suitable for Irish conditions.

 

Results:

For P mitigation, iron ochre originating from copper- sulphur (Cu - S) mines in Avoca, Co. Wicklow was investigated. This was the first time internationally that a metal mining ochre was fully characterised. A maximum P adsorption capacity of 16 to 21 g P kg-1 was determined. Kinetics experiments showed that P adsorption occurred quickly - 97% within 5 min. To investigate the site-specific maximum P adsorption capacity, samples of ochre were analysed for iron (Fe) mineralogy. X-ray diffraction exhibited an Fe mineralogy consisting of jarosite, minor amounts of ferrihydrite and the end product goethite. Goethite was the dominant Fe mineral present on site. The absence of schwertmannite in the Avoca sample restricted the available surface area for adsorption, thereby reducing the maximum P adsorption capacity. In the Avoca samples, P adsorption to oolites and diatoms was present. Inductively coupled plasma mass spectroscopy (ICP-MS) and bulk energy-dispersive X-ray spectroscopy (EDX) investigations exhibited potentially toxic concentrations of Fe, zinc (Zn), lead (Pb), arsenic (As) and copper (Cu). When added to soil, ochre sequestered enough P to protect a waterbody from P losses, but toxic levels of metal release was problematic.

For N mitigation, a permeable reactive barrier (PRB), comprising carbon-rich media such as woodchip, was chosen for investigation. As a nitrate plume migrates through the reactive media, nitrate is transformed to the gaseous phase, thereby protecting a down-gradient sensitive receptor. A 4.2 ha site with known nitrate shallow groundwater pollution from a dirty water irrigator was chosen. Using site and 

groundwater characterisation techniques and geochemistry data from 17 piezometers over a 2-yr period, the location of a PRB on site was determined. Contaminant mass flux calculations showed attenuation on site, but did not point to any transformational processes. Using this data together with denitrification rates from soil and woodchip and soil samples, the dimensions of the PRB were calculated and a location was identified. On the same site, another approach investigated the spatial distribution of nitrate and chloride on site. This showed that saturated hydraulic conductivity (ks) and distance from source were significant parameters for shallow groundwater nitrate prediction. For chloride, ks and elevation (m AOD) were significant. The addition of denitrification parameters to the predictive model identified that parameters such as N2/Argon (Ar) ratio, redox potential and nitrous oxide (N2O) agreed best with the nitrate distribution on site. The second methodology enabled large savings as it showed that natural attenuation on site was sufficient to protect a sensitive receptor.

In PRB research, denitrification potential within the reactive media of a PRB changes over time, but methodological constraints make the quantification of this potential unfeasible. A new methodology was developed to address this. Using δ15N/δ18O isotopes, eight wells were divided into indicative ‘high denitrification’ and ‘low denitrification’ wells. Two ‘low denitrification’ wells with high nitrate concentration were amended with woodchip to enhance denitrification. Water samples were retrieved from all wells using a low-flow syringe and analysed for N2/Ar ratio using Membrane Inlet Mass Spectrometry. Results showed that there was good agreement with respect to denitrification identification between stable isotope, chemical (N2/Ar ratio and dissolved organic C (DOC)) and physio-chemical (dissolved oxygen, temperature, conductivity and pH) parameters. Such techniques were able to pick up on small changes in denitrification potential.

Overall the P control technology chosen was effective at P sequestration but could not be used due to high metal losses. For N remediation a number of knowledge gaps were developed, which allowed a more accurate method of identifying areas of natural attenuation on site. Further research should now focus on pollution swapping using column and field scale denitrification bioreactors.

 

 

Outputs:

Journal papers:

  1. 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.
  2. 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.
  3. Fenton, O., Richards, K.G., Kirwan, L., Healy, M.G. 2009. Factors affecting nitrate distribution in shallow groundwater under a beef farm in south eastern Ireland. Journal of Environmental Management 90: 3135-3146. 
  4. Fenton, O., Healy, M.G., Richards, K. 2009. Methodology for the location of a subsurface permeable reactive barrier for the remediation of point source pollution on an Irish farm. Tearmann 6: 29 - 44.
  5. *Fenton, O., Healy, M.G., Rodgers, M., O hUallacháin, D. 2009. Site-specific P absorbency of ochre from acid mine drainage near an abandoned Cu-S mine in the Avoca-Avonmore catchment, Ireland. Clay Minerals 44: 113-123. 
  6. Fenton, O., Healy, M.G., Rodgers, M. 2009. Use of ochre from an abandoned metal mine in the south east of Ireland for phosphorus sequestration from dairy dirty water. Journal of Environmental Quality 38: 1120 – 1125.

 

Conference papers:

  1. 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. 5th International Nitrogen Conference. 3-7 December, New Delhi, India.
  2. Fenton, O., Richards, K., Healy, M.G., Kirwin, L. 2009. Factors affecting the spatial distribution of nitrate in shallow groundwater on a beef farm in South Eastern Ireland. Agricultural Research Forum, 12-13 March, 2009, Tullamore, Co. Offaly.
  3. 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.
  4. Fenton, O., Rodgers, M., Healy, M.G. 2008. Phosphorus retention in synthetic and dairy soiled water amended with Avoca-Avonmore catchment ochre. Agricultural Research Forum, 10-13 March, 2008, Tullamore, Co. Offaly.
  5. Fenton, O., Healy, M.G., Rodgers, M. 2007. Assessing the performance of phosphorus retention using an Avoca-Avonmore catchment ochre, Ireland. Groundwater Quality 2007 Conference, Fremantle, Western Australia, 2-7 December, 2007.
  6. Fenton, O., Healy, M.G. 2007. Preliminary steps in the location of a groundwater remediation system. 7th Irish Agricultural Economics Society meeting. Tullamore, Co. Offaly. 12th March, 2007. ESAI Environ Proceedings 108(4): 52 – 58.