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Intermittent sand filters (ISFs) are widely used in rural areas to treat domestic and dilute agricultural wastewater due to their simplicity, efficacy and relative low cost. However, filter clogging reduces their operational lifetime and sustainability. To reduce the potential of filter clogging, this study examined pre-treatment of dairy wastewater (DWW) by coagulation with ferric chloride (FeCl3) prior to treatment in replicated, pilot-scale ISFs and monitored their performance over an entire milking season (301 days). Over the study duration and at the end of the study, the extent of clogging across hybrid coagulation-ISFs was quantified and the results were compared to ISFs treating raw DWW without a coagulation pre-treatment, but otherwise operated under the same conditions. During operation, biomass growth/extent of clogging was higher in ISFs treating raw DWW, which were fully clogged after 280 days of operation. The hybrid coagulation-ISFs remained fully operational until the end of the study. Examination of the filter media in both filter types showed that the ISFs treating raw DWW lost approximately 85% of their initial infiltration capacity in the uppermost layer due to biomass build-up versus 40% loss for hybrid coagulation-ISFs. Furthermore, ISFs treating raw DWW retained more organic matter and proportionally higher amounts of phosphorus, nitrogen and sulphur than the pre-treated DWW, with values decreasing with depth below the filter surface. Overall, hybrid coagulation-ISFs are likely to sustain infiltration capacity for a longer period than filters treating raw wastewater; therefore, requiring smaller surface area for treatment and minimal maintenance. The authors would like to acknowledge Teagasc for the grant of a Walsh Fellowship to the first author [funding number: RMIS-0386]. The authors appreciate the help of technical staff: Seamus McShane, Adrian Hawe, Tomas Condon & John Paul Murphy (Teagasc Moorepark), Denis Brennan (Teagasc Johnstown Castle), and Emma McDermott (Centre for Microscopy and Imaging, University of Galway). peer-reviewed

The rewetting of degraded peatlands has been adopted as a method to address climate change. Concerns have been raised about the effects of peat inundation and drying cycles, in more extreme climate events, on the potential release of nitrogen (N) species, in particular ammonium (NH4-N), once rewetted, as well as the physico-chemical and biological properties of the peat. This study used intact peat cores to measure the impact of two different cycles of peat inundation and drying (1 month and 2 month) over a total study duration of 56 weeks on the (1) NH4-N, nitrate-N (NO3-N) and dissolved reactive phosphorus (DRP) in the soil pore water; (2) microbial community structure; (3) physico-chemical properties of the peat; and (4) the structure of the peat, and therefore its ability to mitigate flood risks and storm surges. The study found that rewetted cores released NO3-N in the pore water up to a concentration of 6.25 mg L-1, but had no appreciable impact on NH4-N, which remained below 1.7 mg L-1 over the study duration. DRP moved quickly though the upper layers of the cores, but physico-chemical analysis suggested it was adsorbed to more iron-rich soil, which was present at depths below 0.4 m in the cores. Time intervals between inundation produced no significant difference on the forms of inorganic N released, nor did it compact the soil or change the microbial community structure. The depth of the water table, however, had a significant impact on inorganic N release, particularly NO3-N, which indicates that this N species, and not NH4-N, may be problematic in rewetted peatlands. The authors acknowledge the assistance of Stephen Monteverde and Dr Siubhán Comer. The authors would like to thank the European Commission and the Irish Environmental Protection Agency (EPA) (Project reference number 2019-W-MS-42) for funding the collaborative international consortium (WATERPEAT) financed under the Water JPI 2018 Joint Call of the WaterWorks2017 ERA-NET Cofund. This project is funded under the EPA Research Programme 2014-2020. The EPA Research Programme is a Government of Ireland initiative funded by the Department of Communications, Climate Action and Environment. It is administered by the Environmental Protection Agency, which has the statutory function of co-ordinating and promoting environmental research. peer-reviewed 2024-11-02

With more than 40 countries currently proposing to boost their national bioeconomies, there is no better time for a clarion call for a new bioeconomy, which, at its core, tackles the current disparities and inequalities in phosphorus (P) availability. Existing biofuel production systems have widened P inequalities and contributed to a linear P economy, impairing water quality and accelerating dependence on P fertilizers manufactured from finite non-renewable phosphate rock reserves. Here, we explore how the emerging bioeconomy in novel, value-added, bio-based products offers opportunities to rethink our stewardship of P. Development of integrated value chains of new bio-based products offer opportunities for co-development of P-refineries to recover P fertilizer products from organic wastes. Advances in material sciences are exploiting unique semiconductor and opto-electrical properties of new P allotropes (2D Black Phosphorus and Blue Phosphorus). These novel P materials offer the tantalising prospect of step-change innovations in renewable energy production and storage, in biomedical applications, and in biomimetic processes, including artificial photosynthesis. They also potentially offer an antidote to the P paradox that our agricultural production systems have engineered us into, and expand the future role of P in securing sustainability across both agroecological and technological domains of the bioeconomy. However, there remains a myriad of social, technological and commercialization hurdles to be crossed before such an advanced circular P bioeconomy could be realized. The emerging bioeconomy is just one piece of a much larger puzzle of how to achieve more sustainable and circular horizons in our future use of phosphorus. HPJ was supported by the NERC National Capability projects NEC06851 and NEC07000. peer-reviewed

Landspreading of sewage sludge remains the most economical and practical means for its disposal, with some countries, such as Ireland, disposing up to 90% to land. Its nitrogen, phosphorus and metal content make it an effective fertiliser replacement. However, there are potentially serious issues associated with its use in agriculture. These range from impacts on the environment through surface losses of nutrients, metals, pharmaceuticals and personal care products (PPCPs), and emerging contaminants, as well as build-up of contaminants in the soil and transfer to the human food chain. This paper details the main findings of an Irish Environmental Protection Agency (EPA)-funded study which investigated these issues. This study characterised treated sewage sludge ( biosolids ) from wastewater treatment plants employing different means of sludge treatment, examined surface losses of various physico-chemical parameters following land application, measured metal uptake by ryegrass, and modelled the potential impacts on human health. This study was funded by the Irish EPA (Project reference number 2012-EH-MS-13). non-peer-reviewed

The responses of waterbodies to agricultural programmes of measures are frequently delayed by hydrological time lags through the unsaturated zone and groundwater. Time lag may therefore, impede the achievement of remediation deadlines such as those described in the EU Water Framework Directive (WFD). Omitting time lag from catchment characterisation renders evaluation of management practices impossible. Time lag aside, regulators at national scale can only manage the expectations of policy-makers at larger scales (e.g. European Union) by demonstrating positive nutrient trajectories in catchments failing to achieve at least good status. Presently, a flexible tool for developing spatial and temporal estimates of trends in water quality/nutrient transport and time lags is not available. The objectives of the present study were first to develop such a flexible, parsimonious framework incorporating existing soil maps, meteorological data and a structured modelling approach, and to secondly, to demonstrate its use in a grassland and an arable catchment (~10 km2) in Ireland, assuming full implementation of measures in 2012. Data pertaining to solute transport (meteorology, soil hydraulics, depth of profile and boundary conditions) were collected for both catchments. Low complexity textural data alone gave comparable estimates of nutrient trajectories and time lags but with no spatial or soil series information. Taking a high complexity approach, coupling high resolution soil mapping (1:10,000) with national scale (1:25,000) representative profile datasets to This research was funded by the Teagasc Walsh Fellowship Scheme. peer-reviewed 2018-12-10

The removal efficiency of carbon (C) and nitrogen (N) in constructed wetlands (CWs) is very inconsistent and frequently does not reveal whether the removal processes are due to physical attenuation or whether the different species have been transformed to other reactive forms. This paper aims to address this knowledge gap by reviewing the biogeochemical dynamics and fate of C and N in CWs and their potential impact on the environment, and by presenting novel ways in which these knowledge gaps may be eliminated. Nutrient removals in CWs vary with the type of CW, vegetation, climate, season, geographical region and management practices. Horizontal flow CWs tend to have good nitrate (NO3-) removal, as they provide good conditions for denitrification, but cannot remove ammonium (NH4+) due to limited ability to nitrify NH4+. Vertical flow CWs have good NH4+ removals, but their denitrification ability is low. Surface flow CWs decrease nitrous oxide (N2O) emissions but increase methane (CH4) emissions; subsurface flow CWs increase N2O and carbon dioxide (CO2) emissions, but decrease CH4 emissions. Mixed species of vegetation perform better than monocultures in increasing C and N removal and decreasing GHG emissions, but empirical evidence is still scarce. Lower hydraulic loadings with higher hydraulic retention times enhance nutrient removal, but more empirical evidence is required to determine an optimum design. A conceptual model highlighting the current state of knowledge is presented and experimental work that should be undertaken to address knowledge gaps across CW, vegetation and wastewater types, hydraulic loading rates and regimes, and retention times, is suggested. We recommend that further research on process-based C and N removal and on the balancing of end products into reactive and benign forms is critical to the assessment of the environmental performance of CWs. peer-reviewed

Book chapter [no abstract available] EPA ireland (Project reference number 2012-EH-MS-1); EU COST Action Water_2020

Journal article Denitrification bioreactors, typically containing woodchips, are artificial sinks used to remediate nitrate (NO3-) losses on agricultural landscapes. Analysis of these bioreactors frequently considers their efficacy in terms of only a single contaminant (for example, NO3-), but does not consider other losses ammonium (NH4+), phosphorus (PO43-), methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O). In this study, laboratory-scale denitrifying bioreactors operated at hydraulic retention times (HRTs) ranging from 4 to 22 d, containing either lodgepole pine woodchips (LPW), lodgepole pine needles (LPN), barley straw (BBS) or cardboard, were investigated to elucidate operational optima considering three scenarios using: (1) only NO3- net fluxes (2) NO3-, NH4+ and PO43- combined fluxes (3) all fluxes (water and gaseous) combined. At the end of the experiment, after up to 745 days of operation, the bioreactors were destructively sampled for microbial analysis. In Scenario 1, there was a net removal in the bioreactors, which generally performed best at shorter HRTs. In Scenario 2, there was a net release of contaminants from all bioreactors, which substantially increased in Scenario 3. Total greenhouse gas emissions were highest for the cardboard bioreactors (296 g CO2-eq m-2 d-1) at the longest HRT, and were dominated by CH4 emissions. Highest N2O emissions emanated from LPN and LPW bioreactors, which also had a greater proportion of denitrifiers than the other bioreactors. Overall, considering all three scenarios, LPN bioreactors were the best performing at all HRTs. However, the long-term availability of its carbon source may be limited, as there was an 80% reduction over a 560 d period. Department of Agriculture, Fisheries and Food - Research Stimulus Programme 2007 (RSF 07 525) peer-reviewed

http://ojs.aishe.org/index.php/aishe-j/article/view/154 The aim of this study was to investigate the impact of student volunteers on community organizations and to identify deficits in training within service learning modules which, if addressed, could enable community organizations to benefit more from student volunteers. An anonymous survey aimed to measure students impact, as perceived by host community organizations, relative to non-student volunteers and paid staff, and to investigate if their impact and the types of work they undertook was correlated with organization attributes. The perceived impact of student volunteers on the organization mission was high, but the nature of their work was functional and not academic in nature. Host organizations felt that student preparedness, prior to their engagement, could be enhanced by members of the organizations either addressing the student body within a classroom context, or by playing a role in the design of modules which may have an impact on their area of focus. peer-reviewed

Journal article This study compared the performance of three aggregate layerings, commonly used in the construction of unbound forest roads in Ireland, when they were subjected to repeated loading in a new large-scale test rig. These layerings comprised (i) a layer of uncrushed, granitic, sandy gravel - a good quality road aggregate (ii) a layer of shale - a poor quality aggregate, and (iii) a layer of crushed limestone an excellent quality aggregate with a wet mix macadam (WMM) grading on top of a poor quality shale sub-base layer . The repeated load testing rig was designed and constructed to test different surface or completion layering thicknesses of the aggregates over a common formation or subgrade material of silty sandy soil. This testing was achieved by surface loading the aggregates through a 200 mm-diameter rubber pad - attached to a hydraulic actuator on the test rig - for up to 150,000 load applications. The subgrade pressures and surface deflections were measured at applied stresses of 500 kPa, 750 kPa and 1000 kPa. The good quality granitic aggregate performed much better than the poor quality shale aggregate under the repeated loading and is suitable as a completion material for use in unbound forest roads. The shale aggregate can be used in unbound forest roads as a sub base material. peer-reviewed

The application of biochar produced from wood and crop residues, such as sawdust, straw, sugar bagasse and rice hulls, to highly weathered soils under tropical conditions has been shown to influence soil greenhouse gas (GHG) emissions. However, there is a lack of data concerning GHG emissions from soils amended with biochar derived from manure, and from soils outside tropical and subtropical regions. The objective of this study was to quantify the effect on emissions of carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) following the addition, at a rate of 18 t ha-1, of two different types of biochar to an Irish tillage soil. A soil column experiment was designed to compare three treatments (n=8): (1) non-amended soil (2) soil mixed with biochar derived from the separated solid fraction of anaerobically digested pig manure and (3) soil mixed with biochar derived from Sitka Spruce (Picea sitchensis). The soil columns were incubated at 10 oC and 75 % relative humidity, and leached with 80 mL distilled water, twice per week. Following 10 weeks of incubation, pig manure, equivalent to 170 kg nitrogen ha-1 and 36 kg phosphorus ha-1, was applied to half of the columns in each treatment (n=4). Gaseous emissions were analysed for 28 days following manure application. Biochar addition to the soil increased N2O emissions in the pig manure-amended column, most likely as a result of increased denitrification caused by higher water filled pore space and organic carbon (C) contents. Biochar addition to soil also increased CO2 emissions. This was caused by increased rates of C mineralisation in these columns, either due to mineralisation of the labile C added with the biochar, or through increased mineralisation of the soil organic matter. peer-reviewed

The effectiveness of chemical amendment of pig slurry to ameliorate phosphorus (P) losses in runoff is well studied, but research mainly has concentrated only on the runoff pathway. The aims of this study were to investigate changes to leachate nutrient losses, soil properties and greenhouse gas (GHG) emissions due to the chemical amendment of pig slurry spread at 19 kg total phosphorus (TP), 90 kg total nitrogen (TN), and 180 kg total carbon (TC) ha-1. The amendments examined were: (1) commercial grade liquid alum (8% Al2O3) applied at a rate of 0.88:1 [Al:TP] (2) commercial-grade liquid ferric chloride (38% FeCl3) applied at a rate of 0.89:1 [Fe:TP] and (3) commercial-grade liquid poly-aluminium chloride (PAC) (10% Al2O3) applied at a rate of 0.72:1 [Al:TP]. Columns filled with sieved soil were incubated for 8 mo at 10oC and were leached with 160 ml (19 mm) distilled water wk-1. All amendments reduced the Morgan s phosphorus and water extractable P content of the soil to that of the soil-only treatment, indicating that they have the ability to reduce P loss in leachate following slurry application. There were no significant differences between treatments for nitrogen (N) or carbon (C) in leachate or soil, indicating no deleterious impact on reactive N emissions or soil C cycling. Chemical amendment posed no significant change to GHG emissions from pig slurry, and in the cases of alum and PAC, reduced cumulative N2O and CO2 losses. Chemical amendment of land applied pig slurry can reduce P in runoff without any negative impact on nutrient leaching and GHG emissions. Future work must be conducted to ascertain if more significant reductions in GHG emissions are possible with chemical amendments. peer-reviewed

Losses of phosphorus (P) from soil and slurry during episodic rainfall events can contribute to eutrophication of surface water. However, chemical amendments have the potential to decrease P and suspended solids (SS) losses from land application of slurry. Current legislation attempts to avoid losses to a waterbody by prohibiting slurry spreading when heavy rainfall is forecast within 48h. Therefore, in some climatic regions slurry spreading opportunities may be limited. The current study examined the impact of three time intervals (TIs) (12, 24 and 48h) between pig slurry application and simulated rainfall with an intensity of 11.0±0.59 mm h-1. Intact grassed soil samples, 1 m long, 0.225 m wide and 0.05 m deep, were placed in runoff boxes and pig slurry or amended pig slurry was applied to the soil surface. The amendments examined were: (1) commercial grade liquid alum (8% Al2O3) applied at a rate of 0.88:1 [Al: total phosphorus (TP)] (2) commercial-grade liquid ferric chloride (38% FeCl3) applied at a rate of 0.89:1 [Fe:TP] and (3) commercial-grade liquid poly-aluminium chloride (PAC) (10 % Al2O3) applied at a rate of 0.72:1 [Al:TP]. Results showed that an increased TI between slurry application and rainfall led to decreased P and SS losses in runoff, confirming that the prohibition of land-spreading slurry if heavy rain is forecast in the next 48h is justified. Averaged over the three TIs, the addition of amendment reduced all types of P losses to concentrations significantly different (p

peer-reviewed

An economic analysis was performed on treatment options for pig manure in Ireland. Costs were based on a 500 sow integrated pig farm producing 10,500 m3 of manure per year at 4.8 % dry matter. The anaerobic digestion of pig manure and grass silage (1:1; volatile solids basis) was unviable under the proposed tariffs, with costs at Euro 5.2 m-3 manure. Subsequent solid-liquid separation of the digestate would cost an additional Euro 12.8 m-3 manure. The treatment of the separated solid fraction by composting and of the liquid fraction by integrated constructed wetlands, would add Euro 2.8 and Euro 4.6 m-3 manure, respectively to the treatment costs. The cost analysis presented showed that the technologies investigated are currently not cost effective in Ireland. Transport and spreading of raw manure, at Euro 4.9 m-3 manure (15 km maximum distance from farm) is the most cost effective option. Department of Agriculture Food and Fisheries peer-reviewed

The use of digital resources in higher education has risen significantly over the last ten years and will continue to do so for the foreseeable future. The challenge for educational instructors is in determining how to utilise digital resources effectively; the basis for this should not be their availability alone, but rather their ability to enhance the student learning experience and achieve desired learning outcomes. This paper describes the successful widespread integration of digital resources in the undergraduate teaching of civil engineering at the National University of Ireland, Galway. Various types of digital resources, including animations, videos, design software and case studies, are utilised. The recently completed Engineering building is itself a digital resource. Designed as a living laboratory, the building¿s structure, energy systems and internal environment are heavily instrumented and the structural, environmental and energy datasets are used as teaching tools. The higher education teaching of Engineering differs significantly from that of other disciplines, such as the Arts or Humanities, in that engineering degrees are typically subject to a strict accreditation process by the national professional engineering body. In Ireland, this body (Engineers Ireland) prescribe six programme outcomes for Level 8 engineering degree programmes. The learning outcomes of individual course modules must therefore map onto one or more of these prescribed programme outcomes. The aim of this paper is to elucidate how digital resources have been used successfully by academic staff in the teaching of civil engineering subjects to help achieve professional accreditation criteria whilst also providing a more engaging student learning experience. peer-reviewed

The use of digital resources in higher education has risen significantly over the last ten years and will continue to do so for the foreseeable future. The challenge for educational instructors is in determining how to utilise digital resources effectively; the basis for this should not be their availability alone, but rather their ability to enhance the student learning experience and achieve desired learning outcomes. This paper describes the successful widespread integration of digital resources in the undergraduate teaching of civil engineering at the National University of Ireland, Galway. Various types of digital resources, including animations, videos, design software and case studies, are utilised. The recently completed Engineering building is itself a digital resource. Designed as a living laboratory, the building’s structure, energy systems and internal environment are heavily instrumented and the structural, environmental and energy datasets are used as teaching tools. The higher education teaching of Engineering differs significantly from that of other disciplines, such as the Arts or Humanities, in that engineering degrees are typically subject to a strict accreditation process by the national professional engineering body. In Ireland, this body (Engineers Ireland) prescribe six programme outcomes for Level 8 engineering degree programmes. The learning outcomes of individual course modules must therefore map onto one or more of these prescribed programme outcomes. The aim of this paper is to elucidate how digital resources have been used successfully by academic staff in the teaching of civil engineering subjects to help achieve professional accreditation criteria whilst also providing a more engaging student learning experience.

peer-reviewed Land application of dairy slurry can result in incidental losses of phosphorus (P) to runoff in addition to increased loss of P from soil as a result of a buildup in soil test P (STP). An agitator test was used to identify the most effective amendments to reduce dissolved reactive phosphorus (DRP) loss from the soil surface after land application of chemically amended dairy cattle slurry. This test involved adding slurry mixed with various amendments (mixed in a beaker using a jar test flocculator at 100 rpm), to intact soil samples at approximate field capacity. Slurry/amended slurry was applied with a spatula, submerged with overlying water and then mixed to simulate overland flow. In order of effectiveness, at optimum application rates, ferric chloride (FeCl2) reduced the DRP in overlying water by 88%, aluminium chloride (AlCl2) by 87%, alum (Al2(SO4)3·nH2O) by 83%, lime by 81%, aluminium water treatment residuals (Al-WTR; sieved to

Dairy soiled water (DSW) is produced on dairy farms through the washing-down of milking parlours and holding areas, and is generally applied to land. However, there is a risk of nutrient loss to surface and ground waters from land application. The aim of this study was to use aerobic woodchip filters to remove organic matter, suspended solids (SS) and nutrients from DSW. This novel treatment method would allow the re-use of the final effluent from the woodchip filters to wash down yards, thereby reducing water usage and environmental risks associated with land spreading. Three replicate 100 m(2) farm-scale woodchip filters, each 1 m deep, were constructed and operated to treat DSW from 300 cows over an 11-month study duration. The filters were loaded at a hydraulic loading rate of 30 L m(-2) d(-1), applied in four doses through a network of pipes on the filter surface. Average influent concentrations of chemical oxygen demand (COD), SS and total nitrogen (TN) of 5750 +/- 1441 mg L-1, 602 +/- 303 mg L-1 and 357 +/- 100 mg L-1, respectively, were reduced by 66, 86 and 57% in the filters. Effluent nutrient concentrations remained relatively stable over the study period, indicating the effectiveness of the filter despite increasing and/or fluctuating influent concentrations. Woodchip filters are a low cost, minimal maintenance treatment system, using a renewable resource that can be easily integrated into existing farm infrastructure. (C) 2011 Elsevier Ltd. All rights reserved. peer-reviewed

The aim of this study was to investigate the composting of separated pig manure solids with or without a variety of bulking agents at a low initial C/N ratio (12.5-23.3). Compost stability was investigated using an oxygen uptake rate (OUR) test and compost maturity was investigated using a germination index test. All treatments showed typical patterns of compost temperature. Temperatures above 60 degrees C were achieved by Day 2, followed by a thermophilic phase (50-60 degrees C), which lasted for 1 to 2 weeks followed by a cooling phase. The stability of one of treatments which did not contain any bulking agent - OUR of 25 mmol O-2 kg(-1) OM hour(-1) - was negatively affected by its initial high water content (69%). The addition of a bulking agent and initial water content below 60% were necessary to compost the separated solid fraction of pig manure at a low initial C/N ratio. Irish Department of Agriculture Food and Fisheries - Research Stimulus Fund Programme (RSFP) - National Development Plan 2007-2013 peer-reviewed

peer-reviewed The main threats to soils outlined in the pending Soil Framework Directive (SFD) are: contamination, loss of organic matter, erosion, compaction, sealing, salinization and desertification. The first four threats are pertinent to agricultural systems in Atlantic Europe, but vary in their extent between countries depending on the spatial soil distribution. Loss of soil biodiversity has not been included as a potential threat in the SFD due to lack of information that is currently available both spatially and temporally to facilitate any legislation to protect it. This paper gives emphasis to the four main threats outlined above associated with Agricultural systems in Atlantic Europe. Each soil threat is discussed in relation to the agricultural management calendar for cultivated and grazed grassland soils. The paper discusses current soil protection policies and possible changes to such legislation with the adoption of the SFD by member states.

Nutrient loss from agricultural sources to water continues to be a national challenge. Diffuse pollution from agricultural sources is considered to be the primary cause of slight-to-moderate water pollution in Ireland, but agricultural point sources, such as farmyards, are often not considered due to their scattered spatial distribution and small areal extent. Agricultural point sources tend to be small and localised hot spots of nutrients and, therefore, can be efficiently treated using environmental technologies developed for wastewater and contaminated land treatment. A small area associated with soiled water irrigation, on a 4.27 ha case study site at Teagasc, Johnstown Environmental Research Centre, Ireland, was identified, where groundwater nitrate-nitrogen (NO3-N) concentration exceeds the maximum admissible drinking water concentration of 11.3 mg N L-1. A continuous, shallow permeable reactive barrier may be suitable to remediate point source pollution at this site. A methodology, based on site and groundwater characterisation, successfully located a site for a permeable reactive barrier. peer-reviewed

The aim of this study was to examine the seasonal variation in biomass, total nitrogen (Tot-N) and total phosphorus (Tot-P) content of Phragmites australis in a 3-cell free-water surface (FWS) constructed wetland in western Ireland and to investigate the effects of harvesting on their biomass and nutrient content. One cell of the wetland was divided into two plots: one plot, measuring 80 m2, was completely harvested on the 16th June, 2005, while the other plot, the control plot, remained uncut throughout the study duration. At approximately monthly intervals over an 8-month study duration, completely randomised 0.64m2 areas within each plot were harvested to water level and the shoot biomass and nutrient content were measured. In the control plot, the plant biomass, Tot-N and Tot-P content peaked in August. In the June-cut plot, the shoot biomass, total nitrogen (Tot-N) and total phosphorus (Tot-P) content peaked in September. The mean rate of dry matter production (RPD), defined as the mean daily rate of dry matter production per unit area per day between harvests, attained maximum rates of 12.8g m-2d-1 and 4.2g m-2d-1 for the control and June-cut plots, respectively, indicating that annual harvesting of emergent vegetation may not have any beneficial effect on biomass production or nutrient content under Irish climatic conditions. peer-reviewed

Highway surface runoff contains pollutants such as total suspended solids (TSS), hydrocarbons, de-icing salts, and heavy metals. Treatment methods for highway runoff include storage/treatment facilities, such as constructed wetlands (CWs), detention ponds, or sedimentation tanks; stormwater infiltration facilities, such as soakaways, trenches, or basins; and filter strips and swales. These facilities are commonly referred to as SuDS - Sustainable Drainage Systems.The treatment of highway runoff using CWs is widely used in America, Australia and most of Europe. CWs are a suitable choice for the treatment of highway runoff, due to their relative low cost and good efficiency in treating contaminants such as TSS, organic matter, heavy metals, as well as hydrocarbons and inorganic salts. This review paper aims to characterise highway surface runoff, quantify the removal mechanisms of influent pollutants, evaluate the performance of CWs in the treatment of highway runoff, discuss their design criteria, and compare their performance with other treatment methods. peer-reviewed

In Ireland, agricultural activities have been identified as major sources of nutrient input to receiving waters and it has been estimated that these activities contribute 75.3% of the nitrogen (N) and 33.4% of the phosphorus (P) in these waters. Strategy at European level focuses on the prevention of nutrient loss by improved farm management. However, it does not focus on nutrient remediation or incidental nutrient loss of farmyard manures to surface and groundwater. This review describes the impact of agriculture on the environment in Ireland and examines emerging technologies for agricultural wastewater treatment. An integrated approach at pre-treatment and field stages for nitrate (NO3) remediation and P control is recommended. peer-reviewed

peer-reviewed Nutrient loss from agricultural sources to water continues to be a national challenge. Diffuse pollution from agricultural sources is considered to be the primary cause of slight-to-moderate water pollution in Ireland, but agricultural point sources, such as farmyards, are often not considered due to their scattered spatial distribution and small areal extent. Agricultural point sources tend to be small and localised hot spots of nutrients and, therefore, can be efficiently treated using environmental technologies developed for wastewater and contaminated land treatment. A small area associated with soiled water irrigation, on a 4.27 ha case study site at Teagasc, Johnstown Environmental Research Centre, Ireland, was identified, where groundwater nitrate-nitrogen (NO3-N) concentration exceeds the maximum admissible drinking water concentration of 11.3 mg N L-1. A continuous, shallow permeable reactive barrier may be suitable to remediate point source pollution at this site. A methodology, based on site and groundwater characterisation, successfully located a site for a permeable reactive barrier.

Journal article Intermittent sand filtration is a common and effective method for treating septic tank effluent. However, if the loading rate is too high, clogging and ponding of the sand filter surface layer can occur due to the accumulation of excessive biomass and the deposition of suspended solids. This ponding limits the practicality of sand filtration as it makes it necessary to take the filter out of service for maintenance. The objective of this study was to develop and test, on-site, a new hybrid filter system that would reduce the risk of clogging at an organic loading rate substantially greater than the maximum recommended loading rate for intermittent sand filters. The system comprised a 0.6 m deep horizontal flow biofilm reactor (HFBR) over a 0.85 m deep stratified sand filter. The HFBR consisted of a stack of 20 horizontal corrugated polyvinyl chloride sheets, at 32 mm vertical spacings. The sheets were arranged so that the wastewater flowed over and back along alternate sheets down through the stack. The main biofilm growth formed on these sheets. The hybrid filter was loaded with septic tank effluent from an office/garage complex at the rate of 206 L/m(2) day for a period of 400 days in two phases. During the first phase, the effluent volume of 600 L/day was applied in 24 doses/day for 10 min/dose, and during the second phase in 6 doses/day for 40 min/dose. Biofilms in the HFBR substantially reduced the organic and suspended solids loads that reached the sand filter surface and allowed an average total biochemical oxygen demand (BODT) loading rate, based on HFBR plan area, of 37 g BODT/m(2) day to be applied to the system without clogging. This rate was substantially greater than the maximum recommended loading rate of 24 g BODT/m(2) day for intermittent sand filters. During both loading phases a BODT removal of 94% was achieved and nitrification was nearly complete. The average effluent BODT was 12 +/- 4 mg/L during both phases. The hybrid filter system appeared to perform better in terms of suspended solids handling and nitrification during the more frequent dosing phase. The hybrid filtration system offers a more compact alternative to intermittent sand filtration on its own with little risk of clogging. peer-reviewed

Journal article This laboratory study examined the use of various wood materials as a carbon source in horizontal flow filters to denitrify nitrate-nitrogen (NO3-N) from a synthetic wastewater. The filter materials were: sawdust ( Pinus radiata), sawdust and soil, sawdust and sand, and medium-chip woodchippings and sand. Two influent concentrations of NO3-N, 200 mgL(-1) and 60 mgL(-1), loaded at 2.9 to 19.4 mg NO3-N kg(-1) mixture, were used. The horizontal flow filter with a woodchippings/sand mixture and an influent NO3-N concentration of 60 mgL(-1), which operated over a study duration of 166 days, performed best, yielding a 97% reduction in NO3-N at steady-state conditions. Teagasc (Walsh fellowship) peer-reviewed

A stratified sand filter column, operated in recirculation mode and treating synthetic effluent resembling high-strength dairy wastewaters was studied over a 342-d duration. The aim of this paper was to examine the organic, total suspended solids (TSS) and nutrient removal rates of the sand filter, operated in recirculation mode, under incrementally increasing hydraulic and organic loading rates and to propose a field filter-sizing criterion. Best performance was obtained at a system hydraulic loading rate of 10 L m(-2) d(-1); a higher system hydraulic loading rate (of 13.4 L m(-2) d(-1)) caused surface ponding. The system hydraulic loading rate of 10 L m(-2) d(-1) gave a filter chemical oxygen demand (COD), TSS, and total kjeldahl nitrogen (TKN) loading rate of 14, 3.7, and 2.1 g m(-2) d(-1), respectively, and produced consistent COD and TSS removals of greater than 99%, and an effluent NO(3)-N concentration of 42 mg L(-1) (accounting for an 86% reduction in total nitrogen (Tot-N)). As the proportional surface area requirement for the sand filter described in this study is less than the recommended surface area requirement of a free-water surface (FWS) wetland treating an effluent of similar quality, it could provide an economic and sustainable alternative to conventional wetland treatment.

Journal article A laboratory sequencing batch biofilm reactor (SBBR), operated for a period of 158 days, was used to treat domestic-strength synthetic effluent. The biofilm. reactor comprised a bulk fluid reactor, a biofilm plastic module, a synthetic wastewater feed tank, and pneumatic devices with pneumatic controls. The reactor cycle time was 8 h, and its operation consisted of five phases: feeding (59 min), mixing (1 min), anoxic/anaerobic (3 h), aerobic (3 h), and settling (1 h). At total chemical oxygen demand (CODT) loading rates of 8.8 g CODT m(-2) d(-1) and 1.2 kg CODT m(-3) d(-1), expressed in terms of the plastic module surface area and reactor volume, respectively, the SBBR had average removal rates of 8.3 g CODT m(-2) d(-1) and 1.1 kg CODT m(-3) d(-1), or 94%. Total orthophosphorus (M-PT) and filtered orthophosphorus (PO4-P-F) removals were 44% and 50%, respectively. peer-reviewed

Globally, agriculture urgently needs alternative sources of phosphorus (P). Presently, global agriculture is over-reliant on inorganic mineral P fertilisers sourced from finite mining sources. This is especially relevant in the European Union (EU), since Europe lacks natural rock phosphate deposits. There are many alternative organic sources of P, which could be used at low cost in agriculture to grow crops. For example, as one of the largest agricultural-food sectors in EU, the dairy processing industry generates large amounts of P-rich dairy processing sludge (DPS), which can be further processed into secondary-raw-material-based fertilising products, referred to as STRUBIAS (STRUvite, BIochar, or incineration AShes). As DPS and DPS-derived STRUBIAS products have the potential to be used as bio-based fertilisers, to encourage farmers to choose such fertiliser alternatives and stimulate their access to the market, the EU has implemented changes to the Fertiliser Regulations. To date, few studies have focused on the potential of these products to be used as agricultural fertilisers, which has hindered their incorporation in agricultural nutrient management planning. This thesis aims to address the knowledge gaps associated with their agronomic performance and potential environmental risks when reused as fertilisers in agriculture. Specifically, the aims of this thesis were to: (1) quantify the nutrient and metal content of a range of DPS and DPS-derived products (2) compile a database and develop a MS ExcelTM calculator programme to provide farmers with a quick and safe way to reuse these products (3) determine the mineral fertiliser equivalent value (MFE) of a range of these products when used to grow ryegrass and spring wheat, and (4) examine how the different application rate (optimal versus high) and calculation methods (with and without chemical fertiliser response curves) affect MFE results, which, in turn, will enable a standard approach to be used in fertilisation. 2025-03-09

Dairy farms produce dairy soiled water (DSW) during the milking process, which consists of a mixture of water, cow faeces, urine, milk, detergents, and sediment. Land spreading is the most common disposal method for DSW. However, when applied at rates that exceed the nutrient demand of the herbage, or when applied under unfavourable soil and weather conditions, land application of DSW can result in pollutant loss to associate receiving water bodies (ground and surface waters). 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 (OM), suspended solids (SS), P, and pathogens. Such chemicals are already being used on Irish farms. For example they have been shown to be effective at reducing gaseous emissions during storage of slurry and DSW and indeed preventing P losses in runoff from subsequent land application of these wastes to fields. To date, a combination of a coagulation process and CWs or ISFs have not been used to treat DSW. The present research introduces a novel coagulation step before wastewater is treated by CWs or ISFs. 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. In addition, this step would negate the need for CWs to expand in size as their P remediation capacity would be maintained at a high level. This is likely to increase the uptake of such systems on farms in the future. 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), were 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 legally discharged to receiving waters, or recycled to wash farm yards, protecting water quality and saving water, respectively. In parallel, the sludge portion generated from the coagulation process, can be applied to land as a bio-based fertilizer without adverse impacts on the grass growth, and with the added benefit that there would be a substantially lower risk of nutrient losses from such a fertilizer to waters. This management approach could eliminate or reduce the pollution risk along surface pathways to waters, and minimise the overall net cost compared to land application of raw DSW (without treatment). Future research should focus on the life cycle and circularity assessment of these hybrid systems.

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 greater understanding of 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, at 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 management and legislative issues related to discharge consents for on-farm treated agricultural wastes and to selected use of manure amendments.

The provision of high quality, potable water in a sustainable and effective manner is a key challenge for water engineers, scientists, and policy makers. Urbanisation and industrial development, along with population growth, intensification of agriculture and climate change, has increased the strain on current potable water supplies in the developed world, not only in terms of supply, but also by way of introducing new contaminants into the abstraction waters. Emerging contaminants, alongside increasingly stringent environmental legislation, make the maximum allowable concentrations for various contaminants within potable water more difficult to achieve. Although the situation is improving, over 660 million people worldwide still do not have access to improved water supplies. Sustainable and robust solutions that ensure effective water treatment for a variety of contaminants, while also being low cost and low maintenance, are required. Metals and nutrients continue to enter source water supplies by anthropogenic and natural sources. While metals can be damaging to human health, nutrients can lead to excessive microbial activity. The presence of organic matter in source waters also challenges water treatment plants (WTPs), as disinfectants used post-treatment can trigger a reaction with organic matter to create toxic by-products. These can develop both in the WTP and along the distribution network, and long-term exposure can be detrimental to human health. This is a major problem in Ireland and elsewhere, and to date, no cost-effective and sustainable solution has been found. Various technologies are being developed to target problem contaminants, including coagulation systems, gas transfer systems, oxidation technologies, and membranes. Although these may be effective, they may also require high capital investment, be subject to fouling, and require expert maintenance. In addition, costly treatment systems are not feasible for smaller water treatment facilities and developing countries. Instead, a move towards more traditional contaminant removal and retention mechanisms, such as adsorption and filtration, may be more sustainable. Such technologies, in tandem with the use of alternative filter media, such as waste products and locally sourced material, can improve the sustainability of WTPs while not negatively impacting performance. This study aimed to address the issue of contaminant removal, by designing a filter that could fit into the current model of a WTP, and which could remove a variety of contaminants including metals, nutrients, and disinfection by-product precursors. The technology incorporated the use of waste materials to reduce cost and maintain sustainability, and was comprehensively tested at laboratory-scale and pilot-scale. A number of waste products and local materials were first tested at bench-scale, using a variety of common water contaminants to assess their adsorptive capacities. The media tested included coarse sand, zeolite, granular activated carbon (GAC), pyritic fill, Bayer residue, bottom ash, fly ash, and granular blast furnace slag. Following this, laboratory-scale stratified filters were constructed, comprising some of the most successful media from the bench-scale study: fly ash, Bayer residue, zeolite, sand, and GAC. The filters were evaluated for treatment performance and media clogging potential. The results obtained from the laboratory-scale study led to a re-design for the pilotscale study, which was operated at a WTP that used lake water as its potable water source. The WTP was chosen as it had a history of formation of disinfection byproducts. Two filter configurations were examined under intermittent and constant loading rates, and comprised combinations of sand, Bayer residue, GAC, and pyritic fill. While each of the alternative designs proved more successful than a standard sand filter, a filter configuration comprising sand, GAC, and pyritic fill, proved most effective in dissolved organic carbon removal under a continuous loading regime. These studies show that waste products can be used in filtration technologies, where adsorption is a key mechanism, thereby reducing overall capital and maintenance requirements. Adsorption isotherms are instrumental in the design of bespoke filters, and this study found that it is possible to target the removal of specific contaminants, depending on the constituents of the source water. This study presents a simple, lowmaintenance design to reduce the concentration of key contaminants in potable water, and addresses a major problem for WTPs.

Time lag is the delay between the implementation of water quality mitigation measures and observed effects on water quality. This delay arises as a result of the long hydrological/hydrogeological pathways between nutrient sources and water receptors (Fenton et al., 2011; Sousa et al., 2013). Although time lag is an intrinsic component of nutrient transport through the vertical pathway (through the unsaturated zone), which has been identified as a controlling factor on the response to programmes of mitigation measures (POM). However, it is not currently accounted for within the European Union Water Framework Directive (EU-WFD) (EC, 2000), nor is there any established and accepted method of time lag assessment or prediction within the Republic of Ireland. This represents not only a knowledge gap from a theoretical perspective, but also a major limitation for assessing the efficacy of current measures on water quality (Schulte et al., 2006), ascertaining the implementation of legislative requirements (Wall et al., 2012), and developing appropriate policies for future iterations of this directive (Schröder et al., 2004; Bournaoui and Grizzetti, 2014). Although reporting periods within the EU-WFD are fixed at three- to six-year intervals (2012-2015, 2021 and 2027) (EC, 2000), time lag may frequently exceed these periods, leading to a perceived failure of either the POM or their implementation (Fenton et al., 2011). 2020-02-05

peer-reviewed Doctoral thesis 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. 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. Irish Research Council

Drainage of peatlands has been part of forestry practice since the early 20th century. In Ireland and the UK, approximately 800,000 ha of peat catchments were drained and afforested between the 1950s and 1990s. A large number of these forests are now approaching maturity and the rate of forest harvesting will undergo a rapid increase in the near future. Nutrient release following harvesting of upland blanket peat forests in western Ireland has become a significant environmental concern, as these forests drain into ecologically valuable, oligotrophic, salmonid rivers. Therefore, the objectives of this study were to assess the mechanisms of release and transport of phosphorus (P) and nitrogen (N) from harvested peatland forests and the effectiveness of various mitigation methods to decrease nutrient export from them. A litterbag study was used to investigate the decomposition and P and N release dynamics of harvest residue needles on different peat sites and a laboratory incubation study assessed the mobilization of P and N from peat due to a rise in water table. Laboratory flume and mini-catchment experiments investigated the effect of harvest residue brash windrows on nutrient export from harvested blanket peatlands and nutrient retention efficiency of blanket peatland buffer areas. The results suggest that P is easily released from decaying harvest residue needles, whereas N is mostly retained or accumulated during the initial stages of decomposition. Therefore, the release of N from harvest residue needles is not a likely source of the increased N export following clear-cutting, but harvest residues may contribute to P losses. High water tables produced anoxic conditions in upper peat layers and resulted in P mobilization from moderately decomposed, nutrient-poor, Irish blanket peat and highly decomposed, nutrient-rich, Irish blanket peat. In peats from Finland, P mobilization occurred only from nutrient-poor, ombrotrophic peats, and not from nutrient-rich, minerotrophic peats. A high water table also caused higher mobilization of ammonium-N (NH4+-N) from nutrient-rich peats compared to nutrient-poor peats. These results suggest that water-logged conditions may cause different patterns of nutrient release from different types of peats depending on their biogeochemical characteristics.The release of P from brash windrows in blanket peat catchments is a significant source of P to receiving waters. Although brash windrows do not release N during the early stages of their decomposition, the decomposition of brash may enhance N leaching and export, probably by enhancing microbial activity and soil N mineralization below brash. The removal of harvest residues and whole-tree harvesting could be an efficient means of decreasing N and P release and transport to water courses from blanket peat catchments. Conventionally-designed buffer areas, with and without seeded grasses, may have limited effect on P retention from through-flow waters in blanket peat catchments, as frequent high flow episodes, typical in blanket peat areas, are disadvantageous for effective P retention. Alternatively, a mini-buffers method, comprising brash mats and windrows positioned perpendicular to the slope, as opposed to along the main slope, and with the strips between the brash windrows seeded with native grasses, is proposed. In contrast to conventional buffer areas, a grassed or non-grassed mini-buffers method might be a feasible means of decreasing P export to water courses from harvested blanket peat sites.

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. 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.

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. 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 v 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.

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. 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.

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. First, 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.