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Abstract With the intensification of agricultural production in many European countries, more marginal soils with elevated organic matter (OM) content are being brought into cultivation. However, little is known about the transformations in the constituent phosphorus (P) pools of organic soils receiving applications of P fertiliser. Soil P fractions were measured before and after receiving fertiliser in a controlled experiment to determine the change in the soil pools and path analysis was used to evaluate the relationships between P pools. In this study, P deficient soils ranging in OM content from 8 to 76%, were placed in large pots, planted with ryegrass and subjected to P fertiliser applications ranging from 10 to 145 kg ha−1, and monitored over an eight-month study period. High OM soils had a diminished ability to build-up the labile pool from freshly applied P, with relatively low increases up to 200% of the initial value, compared to mineral soils in which the labile pool increased to >2500% of the initial concentration. Additionally, organic soils had higher P uptakes in the grass yield than mineral soils, indicating a higher availability of added P in the soil solution than mineral soils due to their limited sorption ability. In general, there was a reduction in the organic P pool over applications from 0 to 55 kg ha−1, which was indicative of partial mineralization, but was followed by an accumulation of added P over applications from 55 to 145 kg P ha−1. The residual P pools did not build-up with P additions, but data indicated the occurrence of mineralization in most of the soils with decreases of around 40% of the initial concentrations. Organic and residual pools therefore displayed potential to supply P to more labile P pools across all soils of this study. Path analysis indicated that applied P was the only source of labile P in the soil with the highest OM content, leaving it dependent on continuous P applications to supply P for productivity, whereas in the rest of the soils there were interrelations between the non-labile and labile pools. Low pH strongly immobilised the applied P and should be corrected before the initiation of any fertilisation program, even in soils deficient in plant available P. The results demonstrated that P added as fertiliser to organic soils does not accumulate as in mineral soils, which may leave them susceptible to P losses in surface runoff. Therefore, organic soils under agricultural production located in high status catchments should receive low P applications and only during periods with low probability of precipitation to minimise the possibility of P exports to receiving waters. Highlights • Organic soils had limited ability to build-up labile P pool than mineral soils. • Organic and residual P pools were partially mineralized, acting as a source of P. • Low pH promoted immobilisation reactions of P applied, even in P deficient soils. • Added P was removed in higher proportions in organic soils compared to mineral ones. • P fertiliser was the only source of labile P pool in the most organic soil. [ABSTRACT FROM AUTHOR]

This study aimed to quantify leaching losses of nitrogen (N), phosphorus (P) and carbon (C), as well as carbon dioxide (CO 2 ) and methane (CH 4 ) emissions from stored slurry, and from packed soil columns surface applied with unamended and chemically amended dairy and pig slurries, and dairy soiled water (DSW). The amendments to the slurries, which were applied individually and together, were: polyaluminum chloride (PAC) and zeolite for pig and dairy slurry, and liquid aluminium sulfate (alum) and zeolite for DSW. Application of pig slurry resulted in the highest total nitrogen (TN) and nitrate-nitrogen (NO 3 -N) fluxes (22 and 12 kg ha −1 ), whereas corresponding fluxes from dairy slurries and DSW were not significantly ( p < 0.05) higher than those from the control soil. There were no significant ( p < 0.05) differences in leachate N losses between unamended and amended dairy slurries, unamended and amended pig slurries, and unamended and amended DSW. There were no leachate P losses measured over the experimental duration. Total cumulative organic (TOC) and inorganic C (TIC) losses in leachate were highest for unamended dairy slurry (82 and 142 kg ha −1 ), and these were significantly ( p < 0.05) reduced when amended with PAC (38 and 104 kg ha −1 ). The highest average cumulative CO 2 emissions for all treatments were measured for pig slurries (680 kg CO 2 -C ha −1 ) followed by DSW (515 kg CO 2 -C ha −1 ) and dairy slurries (486 kg CO 2 -C ha −1 ). The results indicate that pig slurry, either in raw or chemically amended form, poses the greatest environmental threat of leaching losses and gaseous emissions of CO 2 and CH 4 and, in general, amendment of wastewater with PAC, alum or zeolite, does not mitigate the risk of these losses. [ABSTRACT FROM AUTHOR]

The phenomenon of adsorption is widely exploited across a range of industries to remove contaminants from gases and liquids. Much recent research has focused on identifying low-cost adsorbents which have the potential to be used as alternatives to expensive industry standards like activated carbons. Evaluating these emerging adsorbents entails a considerable amount of labor intensive and costly testing and analysis. This study proposes a simple, low-cost method to rapidly assess the potential of novel media for potential use in large-scale adsorption filters. The filter media investigated in this study were low-cost adsorbents which have been found to be capable of removing dissolved phosphorus from solution, namely: i) aluminum drinking water treatment residual, and ii) crushed concrete. Data collected from multiple small-scale column tests was used to construct a model capable of describing and predicting the progression of adsorbent saturation and the associated effluent concentration breakthrough curves. This model was used to predict the performance of long-term, large-scale filter columns packed with the same media. The approach proved highly successful, and just 24–36 h of experimental data from the small-scale column experiments were found to provide sufficient information to predict the performance of the large-scale filters for up to three months. [ABSTRACT FROM AUTHOR]

This study investigated a novel method of predicting the long-term phosphorus removal performance of large-scale adsorption filters, using data derived from short-term, small-scale column experiments. The filter media investigated were low-cost adsorbents such as aluminum sulfate drinking water treatment residual, ferric sulfate drinking water treatment residual, and fine and coarse crushed concretes. Small-bore adsorption columns were loaded with synthetic wastewater, and treated column effluent volume was plotted against the mass of phosphorus adsorbed per unit mass of filter media. It was observed that the curve described by the data strongly resembled that of a standard adsorption isotherm created from batch adsorption data. Consequently, it was hypothesized that an equation following the form of the Freundlich isotherm would describe the relationship between filter loading and media saturation. Moreover, the relationship between filter loading and effluent concentration could also be derived from this equation. The proposed model was demonstrated to accurately predict the performance of large-scale adsorption filters over a period of up to three months with a very high degree of accuracy. Furthermore, the coefficients necessary to produce said model could be determined from just 24 h of small-scale experimental data. [ABSTRACT FROM AUTHOR]

Landfill leachate is the product of water that has percolated through waste deposits and contains various pollutants, which necessitate effective treatment before it can be released into the environment. In the last 30 years, there have been significant changes in landfill management practices in response to European Union (EU) Directives, which have led to changes in leachate composition, volumes produced and treatability. In this study, historic landfill data, combined with leachate characterisation data, were used to determine the impacts of EU Directives on landfill leachate management, composition and treatability. Inhibitory compounds including ammonium (NH 4 -N), cyanide, chromium, nickel and zinc, were present in young leachate at levels that may inhibit ammonium oxidising bacteria, while arsenic, copper and silver were present in young and intermediate age leachate at concentrations above inhibitory thresholds. In addition, the results of this study show that while young landfills produce less than 50% of total leachate by volume in the Republic of Ireland, they account for 70% of total annual leachate chemical oxygen demand (COD) load and approximately 80% of total 5-day biochemical oxygen demand (BOD 5 ) and NH 4 -N loads. These results show that there has been a decrease in the volume of leachate produced per tonne of waste landfilled since enactment of the Landfill Directive, with a trend towards increased leachate strength (particularly COD and BOD 5 ) during the initial five years of landfill operation. These changes may be attributed to changes in landfill management practices following the implementation of the Landfill Directive. However, this study did not demonstrate the impact of decreasing inputs of biodegradable municipal waste on leachate composition. Increasingly stringent wastewater treatment plant (WWTP) emission limit values represent a significant threat to the sustainability of co-treatment of leachate with municipal wastewater. In addition, the seasonal variation in leachate production poses a risk to effective co-treatment in municipal WWTPs, as periods of high leachate production coincide with periods of maximum hydraulic loading in WWTPs. [ABSTRACT FROM AUTHOR]

This study reports the kinetics and isotherms of the adsorption of five herbicides, MCPA, mecoprop-P, 2,4-D, fluroxypyr and triclopyr, from aqueous solutions onto a range of raw and pyrolysed waste materials originating from an industrial setting. The raw waste materials investigated demonstrated little capability for any herbicide adsorption. Granulated activated carbon (GAC) was capable of the best removal of the herbicides, with >95% removal observed. A first order kinetic model fitted the data best for GAC adsorption of 2,4-D, while a pseudo-first order model fitted the data best for GAC adsorption of fluroxypyr and triclopyr, indicating that adsorption was via physisorption. A pseudo-second order kinetic model fitted the GAC adsorption of MCPA and mecoprop-P, which is indicative of chemisorption. The adsorption of the herbicides in all cases was best described by the Freundlich model, indicating that adsorption occurred onto heterogeneous surfaces. [Display omitted] • Adsorption of herbicides by waste materials and activated carbon investigated. • Activated carbon displayed best adsorption of herbicides. • Adsorption occurred via physisorption or chemisorption. • Adsorption of all herbicides best described by Freundlich model. [ABSTRACT FROM AUTHOR]

As supply chains of chemical fertilisers become more precarious, raw or derived bio-based fertilisers (herein referred to as bio-fertilisers) from the dairy processing industry could be good alternatives. However, their agronomic performance is relatively unknown, and where documented, the method to estimate this value is rarely presented. This pot study investigated aluminium-precipitated and calcium-precipitated dairy processing sludges (Al and Ca-DPS) and DPS-derived biochar as potential bio-fertilisers to grow ryegrass (Lolium perenne L.) and spring wheat (Triticum aestivum). The study aims were to examine how (1) application rate (optimal versus high) and (2) calculation methods (with and without chemical fertiliser response curves) can affect estimates of nitrogen and phosphorus mineral fertiliser equivalence value (N- and P-MFE) and associated agronomic advice. The results from both crops showed that for nitrogen application rates (125 or 160 kg ha−1 for ryegrass and 160 or 240 kg ha−1 for spring wheat) estimates of N-MFE increased for both Al-DPS and Ca-DPS as application rate increased. Dry matter yield response curves produced the highest % N-MFE results (e.g., ryegrass ∼50% and 70% for Al-DPS and Ca-DPS) with other calculation methods producing all similar results (e.g., ryegrass ∼20% for Al-DPS and Ca-DPS). For phosphorus application rates (40 or 80 kg ha−1 for ryegrass and 50 or 80 kg ha−1 for spring wheat), estimates of P-MFE did not increase with application rate. Negative P-MFE values obtained for Ca-DPS and DPS-biochar when growing ryegrass and spring wheat grain, respectively, indicated low plant available phosphorus. Overall, Al-DPS had better performance as a bio-fertiliser when compared to the other products tested. There was no significant difference between the two calculation methods of MFE, which suggests that the determination of MFE could be simplified by using one application as opposed to numerous application rates of fertilisers. Future work should focus on elucidating the N- and P-MFE of a wider range of DPS and STRUBIAS bio-fertilisers, and alternative methods should be investigated that enable a comparison across all bio-fertiliser types. [Display omitted] • Application rate and calculation methods affect agronomic performance outcomes. • High application rates of DPS increased N mineral fertiliser equivalence values. • Al-DPS showed best promise over Ca-DPS and biochar as a bio-based fertiliser. • N-MFE calculated based on dry matter yield was higher than N uptake. • Negative P-MFE values for Ca-DPS and DPS-biochar showed low plant available P. [ABSTRACT FROM AUTHOR]

Cognisant of the negative debate and public sentiment about the land application of treated sewage sludges (‘biosolids’), it is important to characterise such wastes beyond current regulated parameters. Concerns may be warranted, as many priority metal pollutants may be present in biosolids. This study represents the first time that extensive use was made of a handheld X-ray fluorescence (XRF) analyser to characterise metals in sludges, having undergone treatment by thermal drying, lime stabilisation, or anaerobic digestion, in 16 wastewater treatment plants (WWTPs) in Ireland. The concentrations of metals, expressed as mg kg −1 dry solids (DS), which are currently regulated in the European Union, ranged from 11 (cadmium, anaerobically digested (AD) biosolids) to 1273 mg kg −1 (zinc, AD biosolids), and with the exception of lead in one WWTP (which had a concentration of 3696 mg kg −1 ), all metals were within EU regulatory limits. Two potentially hazardous metals, antimony (Sb) and tin (Sn), for which no legislation currently exists, were much higher than their baseline concentrations in soils (17–20 mg Sb kg −1 and 23–55 mg Sn kg −1 ), meaning that potentially large amounts of these elements may be applied to the soil without regulation. This study recommends that the regulations governing the values for metal concentrations in sludges for reuse in agriculture are extended to include Sb and Sn. [ABSTRACT FROM AUTHOR]

Treated municipal sewage sludge (“biosolids”) and dairy cattle slurry (DCS) may be applied to agricultural land as an organic fertiliser. This study investigates losses of nutrients in runoff water (nitrogen (N) and phosphorus (P)), metals (copper (Cu), nickel (Ni), lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr)), and microbial indicators of pollution (total and faecal coliforms) arising from the land application of four types of treated biosolids and DCS to field micro-plots at three time intervals (24, 48, 360 h) after application. Losses from biosolids-amended plots or DCS-amended plots followed a general trend of highest losses occurring during the first rainfall event and reduced losses in the subsequent events. However, with the exception of total and faecal coliforms and some metals (Ni, Cu), the greatest losses were from the DCS-amended plots. For example, average losses over the three rainfall events for dissolved reactive phosphorus and ammonium-nitrogen from DCS-amended plots were 5 and 11.2 mg L − 1 , respectively, which were in excess of the losses from the biosolids plots. When compared with slurry treatments, for the parameters monitored biosolids generally do not pose a greater risk in terms of losses along the runoff pathway. This finding has important policy implications, as it shows that concern related to the reuse of biosolids as a soil fertiliser, mainly related to contaminant losses upon land application, may be unfounded. [ABSTRACT FROM AUTHOR]

Denitrification bioreactors, typically containing woodchips, are artificial sinks used to remediate nitrate (NO 3 − ) losses on agricultural landscapes. Analysis of these bioreactors frequently considers their efficacy in terms of only a single contaminant (for example, NO 3 − ), but does not consider other losses – ammonium (NH 4 + ), phosphorus (PO 4 3− ), methane (CH 4 ), carbon dioxide (CO 2 ) and nitrous oxide (N 2 O). 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 NO 3 − net fluxes; (2) NO 3 − , NH 4 + and PO 4 3− combined fluxes and (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 CO 2 -eq m −2 d −1 ) at the longest HRT, and were dominated by CH 4 emissions. Highest N 2 O 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. [ABSTRACT FROM AUTHOR]

Abstract: Chemical amendment of dairy cattle slurry has been shown to effectively reduce incidental phosphorus (P) losses in runoff; however, the effects of amendments on incidental nitrogen (N) losses are not as well documented. This study examined P and N losses in runoff during three simulated rainfall events 2, 10 and 28days after a single application of unamended/chemically amended dairy cattle slurry. Twenty-five hydraulically isolated plots, each measuring 0.9m by 0.4m and instrumented with runoff collection channels, were randomly assigned the following treatments: (i) grass-only, (ii) slurry-only (the study-control), (iii) slurry amended with industrial grade liquid alum comprising 8% Al2O3, (iv) slurry amended with industrial grade liquid poly-aluminum chloride (PAC) comprising 10% Al2O3, and (v) slurry amended with lime. During the first rainfall event, lime was ineffective but alum and PAC effectively reduced dissolved reactive P (DRP) (by 95 and 98%, respectively) and total P (TP) flow-weighted-mean-concentrations (by 82 and 93%, respectively) in runoff compared to the study-control. However, flow-weighted-mean-concentrations of ammonium–N (NH4–N) in runoff were increased with alum- (81%) and lime-treated (11%) slurry compared to the study-control whereas PAC reduced the NH4–N by 82%. Amendments were not observed to have a significant effect on NO3–N losses during this study. Slurry amendments reduced P losses for the duration of the study, whereas the effect of amendments on N losses was not significant following the first event. Antecedent volumetric water content of the soil or slope of the plots did not appear to affect runoff volume. However, runoff volumes (and consequently loads of P and N) were observed to increase for the chemically amended plots compared to the control and soil-only plots. This work highlights the importance of considering both P and N losses when implementing a specific nutrient mitigation measure. [Copyright &y& Elsevier]

In Ireland, no database detailing the design, influent loading rates or performance of constructed wetlands (CWs) exists. On account of this, they are designed without any protocol based on empirical data. The aim of this paper was to provide the first published data on the performance of free-water surface flow (FWSF) CWs treating primary and secondary-treated municipal wastewater, and agricultural dairy soiled water (DSW) in Ireland. In total, the performance of thirty-four FWSF CWs, comprising fourteen CWs treating primary-treated municipal wastewater, thirteen CWs treating secondary-treated municipal wastewater, and seven CWs treating DSW, were examined. In most CWs, good organic, suspended solids (SS) and nutrient removal was measured. At an average organic loading rate (OLR) of 10 and 9 g biochemical oxygen demand (BOD) m−2 d−1, CWs treating primary and secondary wastewater removed 95 and 84% of influent BOD. Constructed wetlands treating DSW had an average BOD removal of 98%. At average SS loading rates of 6 and 14 g m−2 d−1, CWs treating primary and secondary wastewater had a 96 and an 82% reduction, and produced a final effluent with a concentration of 14 and 13 mg L−1. Constructed wetlands treating DSW produced a final effluent of 34 mg L−1 (94% reduction). Similar to other studies, all CWs examined had variable performance in ammonium-N (NH4 +-N) removal, with average removals varying between 37% (for CWs treating secondary wastewater) and 88% (for CWs treating DSW). Variable ortho-phosphorus (PO4 3−-P) removal was attributable to different durations of operation, media types and loading rates. [Copyright &y& Elsevier]

Abstract: Accumulation of particulate matter and microorganisms present in wastewater as biofilm on the surface of filters can lead to clogging of the media. If clogging of filters occurs, they need to be temporarily decommissioned before they can be operated again. The mechanisms causing clogging may only be delineated through destructive sampling of a filter. The aim of this study was to characterise the build-up of biofilm in the upper layer below the surface of polishing filters intermittently loaded with effluent from a novel horizontal flow biofilm reactor used for the treatment of domestic-strength wastewater. Three filter media were used: crushed glass, sand, and a shallow podzolized soil. The parameters used to measure biofilm build-up were: soil water retention, total phosphorus (Tot-P) content and loss on ignition (LOI). The LOI and Tot-P deposition near the filter surface were lowest in the glass filters. Soil water retention curves indicated that biofilm formation mainly occurred in the uppermost 0.03m depth below the filter surface and gradually decreased with depth. This indicates that measurements of volumetric water content using time domain reflectrometry probes may be used as an in situ proxy for measurements that would normally require the destructive sampling of a filter. [Copyright &y& Elsevier]

Abstract: The performance of a 10L sequencing batch reactor (SBR) treating slaughterhouse wastewater was examined at ambient temperature. The influent wastewater comprised 4672±952mg chemical oxygen demand (COD)/L, 356±46mg total nitrogen (TN)/L and 29±10mg total phosphorus (TP)/L. The duration of a complete cycle was 8h and comprised four phases: fill (7min), react (393min), settle (30min) and draw/idle (50min). During the react phase, the reactor was intermittently aerated with an air supply of 0.8L/min four times at 50-min intervals, 50min each time. At an influent organic loading rate of 1.2g COD/(Ld), average effluent concentrations of COD, TN and TP were 150mg/L, 15mg/L and 0.8mg/L, respectively. This represented COD, TN and TP removals of 96%, 96% and 99%, respectively. Phase studies show that biological phosphorus uptake occurred in the first aeration period and nitrogen removal took place in the following reaction time by means of partial nitrification and denitrification. The nitrogen balance analysis indicates that denitrification and biomass synthesis contributed to 66% and 34% of TN removed, respectively. [Copyright &y& Elsevier]

The dairy industry is one of the largest global producers of wastewater and generates huge volumes of dairy processing sludge (DPS). There are two main types of DPS, lime-treated dissolved air floatation sludge and bio-chemically-treated activated sludge. These sludge types may also be converted to STRUBIAS (STRUvite, BIochar, AShes) products which have potential as fertilizers, secondary feedstocks for phosphate fertiliser granules, and soil amendments. A small number of studies indicate that these products have variable nutrient and metal contents, which differ across sludge and STRUBIAS product types. This is due to many factors such as the type of dairy plants, wastewater treatment process and production technologies. Although such products are land applied, the phosphorus (P) and nitrogen (N) fertilizer equivalency value (FEV) are often unknown and not factored into application rates, and therefore need study under field conditions (across soil and crop types). This review identifies a need to quantify antimicrobial drugs, hormones, pesticides, disinfectants, persistent organic pollutants (POPs), microplastics and nano-particles in all DPS and STRUBIAS types. Where detected, testing should follow the transfer of these contaminants to the soil, crop and water continuum. Further knowledge in the areas identified would enable both agronomic and environmental goals to be met and promote higher uptake of DPS and STRUBIAS re-use in agriculture. • DPS and STRUBIAS used in agriculture as bio-fertilizers and soil amendments. • DPS and STRUBIAS applied to crops but without knowledge of their N and P FEV. • Residues of antimicrobial drugs, hormones and pesticides need testing. • Disinfectant and persistent organic pollutant residues need to be characterised. • Quantification of micro-plastics and nano-particles in waste-soil-crop needed. [ABSTRACT FROM AUTHOR]

Abstract: In Ireland, the most common method of disposal of dairy parlour washings is by land spreading. This treatment method has numerous problems, namely high-labour requirements and the potential for eutrophication of surface and ground waters. Constructed wetlands are commonly used for treatment of secondary municipal wastewaters and they have been gaining popularity for treatment of agricultural wastewaters in Ireland. Intermittent sand filtration may offer an alternative to traditional treatment methods. As well as providing comparable treatment performance, they also have a smaller footprint, due to the substantially higher organic loading rates that may be applied to their surfaces. This paper discusses the performance and design criteria of constructed wetlands for the treatment of domestic and agricultural wastewater, and sand filters for the treatment of domestic wastewater. It also proposes sand filtration as an alternative treatment mechanism for agricultural wastewater and suggests design guidelines. [Copyright &y& Elsevier]

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 10Lm−2 d−1; a higher system hydraulic loading rate (of 13. 4Lm−2 d−1) caused surface ponding. The system hydraulic loading rate of 10Lm−2 d−1 gave a filter chemical oxygen demand (COD), TSS, and total kjeldahl nitrogen (TKN) loading rate of 14, 3. 7, and 2. 1gm−2 d−1, respectively, and produced consistent COD and TSS removals of greater than 99%, and an effluent NO3-N concentration of 42mgL−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. [Copyright &y& Elsevier]

Abstract: A laboratory continuous feed biofilm reactor, comprising a bulk fluid reactor, a biofilm plastic module, a feed tank, and pneumatic devices and controls, was operated for a total period of 257 days, including seeding time, to treat domestic-strength synthetic wastewater under increasing ammonium nitrogen () loading rates, ranging from 0.17±0.01 (0.71±0.06gm−2 d−1) to 0.70±0.02kgm−3 d−1 (2.9±0.1gm−2 d−1). The biofilm plastic module was moved vertically in and out of the wastewater in continuous cycles. The maximum removal rate was reached during the maximum loading phase, when a loading rate of 0.70±0.02kgm−3 d−1 (2.9±0.1gm−2 d−1) was applied to the system. During this loading period, the average removal rate was 0.30±0.10kgm−3 d−1 (1.30±0.40gm−2 d−1). [Copyright &y& Elsevier]

Abstract: The current practice of spray irrigation of dairy parlour wastewaters is laborious and time consuming. Intermittent sand filtration systems may offer an alternative to spray irrigation when designed to remove organic carbon, nitrogen, phosphorus, coliforms and viruses from such wastewaters to allow discharge of the final effluent directly into receiving waters without damage to the environment. In this study two instrumented stratified sand filter columns (0.425 and 0.9m deep, and both 0.3m in diameter) were intermittently loaded for 439 days with synthetic dairy parlour washings at a number of hydraulic and organic loading rates. At a biochemical oxygen demand (BOD) loading of 22gm−2 d−1, over 92% of the BOD and suspended solids in the wastewater was removed in the two filters and nitrification was complete. The 0.9m column had a sustained ability to adsorb the influent phosphorus during the study period; however, the phosphorus adsorption capacity of the 0.425m column began to decrease after approximately 30 days. Biomass, comprising hydrated extracellular polymers (exopolymers) and living and dead cells, accumulated in the 0.9m column; it was assessed by sodium bromide tracer studies and by variations in the sand volumetric water contents using time domain reflectometry (TDR). The biomass growth increased the retention time of the wastewater in the filter media, and occurred mainly at the top of the first sand layer. Intermittent stratified sand filters appear to offer an effective and sustainable treatment process for the removal of BOD from high-strength wastewaters, and for the complete nitrification of ammonium. [Copyright &y& Elsevier]

Land application of dairy soiled water (DSW) is expensive relative to its nutrient replacement value. The use of aerobic filters is an effective alternative method of treatment and potentially allows the final effluent to be reused on the farm. Knowledge gaps exist concerning the optimal design and operation of filters for the treatment of DSW. To address this, 18 laboratory-scale filters, with depths of either 0.6 m or 1 m, were intermittently loaded with DSW over periods of up to 220 days to evaluate the impacts of depth (0.6 m versus 1 m), organic loading rates (OLRs) (50 versus 155 g COD m −2 d −1 ), and media type (woodchip versus sand) on organic, nutrient and suspended solids (SS) removals. The study found that media depth was important in contaminant removal in woodchip filters. Reductions of 78% chemical oxygen demand (COD), 95% SS, 85% total nitrogen (TN), 82% ammonium-nitrogen (NH 4 N), 50% total phosphorus (TP), and 54% dissolved reactive phosphorus (DRP) were measured in 1 m deep woodchip filters, which was greater than the reductions in 0.6 m deep woodchip filters. Woodchip filters also performed optimally when loaded at a high OLR (155 g COD m −2 d −1 ), although the removal mechanism was primarily physical (i.e. straining) as opposed to biological. When operated at the same OLR and when of the same depth, the sand filters had better COD removals (96%) than woodchip (74%), but there was no significant difference between them in the removal of SS and NH 4 N. However, the likelihood of clogging makes sand filters less desirable than woodchip filters. Using the optimal designs of both configurations, the filter area required per cow for a woodchip filter is more than four times less than for a sand filter. Therefore, this study found that woodchip filters are more economically and environmentally effective in the treatment of DSW than sand filters, and optimal performance may be achieved using woodchip filters with a depth of at least 1 m, operated at an OLR of 155 g COD m −2 d −1 . [ABSTRACT FROM AUTHOR]

An intermittent sand filter (ISF) is a simple and cost-effective treatment method that may be adopted on farms to treat dairy wastewater (DWW). However, the use of ISFs has been limited due to the large area required for treatment, and the risk of filter clogging and phosphorus (P) breakthrough, which decrease the operational lifetime. To overcome these limitations, this study uses a novel, pilot-scale coagulation-sedimentation process prior to loading ISFs with DWW. The performance and operational lifetime of this new hybrid coagulation-ISF system was compared to a conventional ISF system in a replicated outdoor pilot-scale experiment over a 43-wk study duration (covering an entire milking season on a farm in Ireland). The hybrid system was able to operate effectively at a higher hydraulic loading rate than a conventional ISF system. The effluent quality from the conventional ISF deteriorated over the timeframe of the study until clogging occurred, while the hybrid system continued to perform effectively without any evidence of clogging or P breakthrough. The hybrid system obtained removal efficiencies ≥99% for all measured water quality parameters (chemical oxygen demand, total suspended solids, total P, ammonium and turbidity), and complied with EU directives concerning urban wastewater treatment. Overall, the hybrid coagulation-ISF is a promising technology that requires a small area (75% reduction in footprint in comparison to a conventional ISF) and minimal operator input, and produces high effluent quality. [Display omitted] • Performance of novel hybrid coagulation-ISF was compared to conventional ISF. • The coagulation-ISF system required only 25% of the conventional ISF size. • The coagulation-ISF system did not experience any clogging or P breakthrough. • The conventional ISF encountered both clogging and P breakthrough. • The coagulation-ISF produced better effluent quality than conventional ISF. [ABSTRACT FROM AUTHOR]

Forestry harvesting on peats is known to result in significant losses of soil phosphorus (P) to adjacent waters, and the issue is becoming an increasingly serious concern as peatland forest stocks mature and reach harvestable age. One potential solution could be the use of low-cost P recovery techniques based on the chemical precipitation and/or adsorption of the dissolved fraction of soil P, which would otherwise be lost. Such recovery techniques have shown promise in similar applications on mineral soils. However, the interaction of peat with P adsorbing materials can significantly alter their adsorptive characteristics, and it is consequentially not known what materials might be suitable for this application. This study compared the performance of six potential soil amendments (aluminum water treatment residual (Al-WTR), crushed concrete, gypsum, magnesium hydroxide, magnesium oxide, and steel wool) in removing P from aqueous solution in the presence of a typical forest peat soil. Comparison of adsorption isotherms plotted from these batch adsorption studies showed that the observed P adsorption maxima of Al-WTR and steel wool were increased by the presence of peat, from 10.6 mg g −1 and 20.4 mg g −1 , to 11.8 mg g −1 and 52.5 mg g −1 , respectively. In contrast, the observed P adsorption maxima of crushed concrete, gypsum, and magnesium oxide were reduced in the presence of peat, by 44%, 87%, and 37%, respectively. The maximum P adsorption achieved by magnesium hydroxide was increased from 29.8 mg g −1 to 59 mg g −1 at an amendment to peat–solid ratio of 1:4, but decreased from 73.9 mg g −1 to 23.6 mg g −1 at an amendment to peat–solid ratio of 1:10. It was concluded that Al-WTR, in particular, shows considerable promise for use as a soil amendment for P immobilization in a peat environment. [ABSTRACT FROM AUTHOR]

Abstract: This study examined the behaviour of two completion aggregates that were placed on a silty sandy formation material and subjected to repeated loading in a large-scale testing rig. The completion aggregates were (i) a good quality limestone, and (ii) a poor quality schist, and are used in the construction of unbound forest roads in Ireland. The schist was tested on its own and in combination with the completion limestone aggregate for up to 150,000 load applications with a maximum loading pressure of 1000kPa. Measurements of surface deflections and formation pressures were made during each test. A combination of a 200mm layer of the limestone aggregate placed on top of a 250mm layer of the schist aggregate produced the lowest permanent deformations, resilient deflections, and resilient pressures under dry and wet undrained conditions. [Copyright &y& Elsevier]

Abstract: This study examined the performance of two aggregates subjected to cyclic loading in a large-scale test rig. The two aggregates examined were: (i) a sandstone from Co. Cork, Ireland and (ii) a limestone shale from Co. Limerick, Ireland. The aggregates were classified and their engineering properties established and compared. Various depths of the aggregates, overlaying a 1-m-deep formation layer, were compacted and subjected to a cyclic loading regime of incrementally increasing pressures of 500, 750 and 1000kPa. Each aggregate was tested for up to 150,000 load applications. The resilient pressures, resilient surface deflections and permanent deformations were measured. The sandstone performed well in a dry state but poorly when wetted up. The shale behaved poorly but the addition of a wet mix macadam (WWM) layer greatly improved its performance. [Copyright &y& Elsevier]

The production of bovine slurry and its subsequent storage are significant sources of ammonia (NH 3) and greenhouse gases (GHGs). Chemical acidification of manures has been shown to significantly reduce these emissions. Waste products, derived from food processing and on-farm practices, may be used as "natural" acidifiers. However, the efficacy of these products in reducing pH and any subsequent emissions are unknown. Commercial "slurry improvers" or "additives" may also be a viable mitigation option; however, their effectiveness is questionable. This study investigated the efficacy and cost of a range of waste and commercial amendments and a chemical acidifier, ferric chloride (FeCl 3), to identify the most effective amendment for NH 3 and GHG emissions reduction. Ammonia abatement potential was observed for 5% sugar beet molasses (67% reduction), 7% apple pulp (49% reduction), and 7% grass silage (38% reduction). Methane (CH 4) emissions were reduced only by spent brewers' grain, sugarbeet molasses, and grass silage effluent at the higher inclusions (i.e. amounts added), with reductions ranging from 15% to 70%. Carbon dioxide (CO 2) emissions were significantly increased with the addition of waste amendments. Commercially available additives had little impact on emissions, with the exception of one treatment, which reduced CH 4 by approximately 10%. Ferric chloride reduced NH 3 emissions by 20%–68%, CH 4 by 6%–65%, and CO 2 by 6%–38%, depending on the inclusion. All waste amendments had low marginal abatement costs ranging from -€0.46 to €0.88 kg−1 NH 3 abated compared to FeCl 3 and commercial amendments (€1.80 to €231 kg−1 NH 3). This incubation experiment demonstrated that a range of on-farm and industry waste streams could be valorised to reduce NH 3 emissions. However, many of these may result in higher CH 4 and CO 2 emissions due to input of labile carbon sources. Therefore, based on the results of the current study, it is recommended that sugarbeet molasses and ferric chloride, at 5% and 1.1% inclusions respectively, be examined in field experiments. [Display omitted] • Farm waste products may be used to reduce NH 3 and GHG emissions. • Ferric chloride and sugarbeet molasses reduced emissions. • A cost saving of ∼ €0.46 kg−1 NH 3 was achieved using waste amendments. • Commercial products were ineffective in abating NH 3 and GHG emissions. [ABSTRACT FROM AUTHOR]

Land spreading of dairy soiled water (DSW) may result in pollution of ground and surface waters. Treatment of DSW through sludge-supernatant separation using chemical coagulants is a potential option to reduce the negative environmental impacts of DSW. The aims of this study were to (1) assess the effectiveness of three chemical coagulants – poly-aluminium chloride (PACl), ferric chloride (FeCl 3) and alum – in improving effluent quality, and (2) assess the properties of the sludge that is generated as by-product from the process for its suitability for land application. Taking into consideration optimum doses to minimize pollutants (turbidity, chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN), and E. coli), optimum mixing times and cost, FeCl 3 was the best performing coagulant. Generated sludges had higher nutrient content and fewer E. coli than raw DSW, and did not display any evidence of phytotoxicity to the growth of Lolium perenne L. using germination tests. The study discussed the results in a sustainable farm management context, and suggested that the effluent (supernatant) from the treatments may be recycled to wash farm yards, saving water. In parallel, the sludge portion can be applied to amend soil properties with no adverse impacts on the grass growth, providing an agronomic value as an organic fertilizer, and reducing the risk of nutrient losses. This management approach could minimize the overall net cost compared to land application of raw DSW. • Chemical coagulants showed significant removal of turbidity, COD, TP, TN, and E. coli. • Full removal and inactivation of Escherichia coli was achieved by ferric chloride. • No evidence of phytotoxicity to the growth of Lolium perenne L. caused by sludges. • Effluent from the coagulant treatment could be recycled for yard wash-down. • This management approach could minimize the cost compared to land application of DSW. [ABSTRACT FROM AUTHOR]

Phosphorus (P) loss from intensive dairy farms is a pressure on water quality in agricultural catchments. At farm scale, P sources can enter in-field drains and open ditches, resulting in transfer along ditch networks and delivery into nearby streams. Open ditches could be a potential location for P mitigation if the right location was identified, depending on P sources entering the ditch and the source-sink dynamics at the sediment-water interface. The objective of this study was to identify the right location along a ditch to mitigate P losses on an intensive dairy farm. High spatial resolution grab samples for water quality, along with sediment and bankside samples, were collected along an open ditch network to characterise the P dynamics within the ditch. Phosphorus inputs to the ditch adversely affected water quality, and a step change in P concentrations (increase in mean dissolved reactive phosphorus (DRP) from 0.054 to 0.228 mg L−1) midway along the section of the ditch sampled, signalled the influence of a point source entering the ditch. Phosphorus inputs altered sediment P sorption properties as P accumulated along the length of the ditch. Accumulation of bankside and sediment labile extractable P, Mehlich 3 P (M3P) (from 13 to 97 mg kg−1) resulted in a decrease in P binding energies (k) to < 1 L mg−1 at downstream points and raised the equilibrium P concentrations (EPC 0) from 0.07 to 4.61 mg L−1 along the ditch. The increase in EPC 0 was in line with increasing dissolved and total P in water, demonstrating the role of sediment downstream in this ditch as a secondary source of P to water. Implementation of intervention measures are needed to both mitigate P loss and remediate sediment to restore the sink properties. In-ditch measures need to account for a physicochemical lag time before improvements in water quality will be observed. Image 1 • P inputs to ditch altered sorptive properties and accumulated in sediment. • Low P binding and high equilibrium P in sediment acting as secondary P source. • Measures needed to remediate ditch water and restore sediment P attenuation. • Physico-chemical lag time expected for water quality measures. [ABSTRACT FROM AUTHOR]

Cattle and cow slurry storage is a significant source of agricultural greenhouse gas (GHG) and ammonia (NH3) emissions. While acidification has been demonstrated to significantly reduce these emissions, a knowledge gap exists to identify a range of chemical amendments that are safe, suitable and cost effective to mitigate both GHG and NH 3 gases simultaneously. The current study showed that ferric chloride, sulphuric acid, alum and acetic acid were extremely effective at abating emissions, with NH 3 reduced by 96%, 85%, 82% and 73%, respectively. In terms of methane (CH 4), ferric chloride, alum, sulphuric acid and acetic acid reduced emissions by 98%, 96%, 95% and 94%, respectively. Previous studies have found that the reduction of >pH 6 can inhibit the release of these gases; however, the effectiveness can vary depending on each amendment's composition. The cost benefit analysis, assessed the amendments in terms of both gaseous emissions reduction and net cost. Sulphuric acid, acetic acid, ferric chloride and alum ranked best, respectively. Currently, the cost of implementing these amendments is, at best, cost neutral. Therefore, incentivising chemical amendments for the abatement of GHG and NH 3 gases from slurry storage is needed. This incubation experiment is an effective means of pre-screening amendments before they are explored at pilot or full scale with subsequent field application. Future research should consider the assessment of cheaper on- and off-farm alternative waste streams as slurry amendment. Image 1 • Acidification of cattle and dairy slurry was investigated. • Target pH of 5.5 resulted in a 96% reduction in NH 3 and 98% reduction in CH 4. • Ferric chloride reductions were independent of pH value. • Cost analysis revealed financial incentives are needed for scaled implementation. [ABSTRACT FROM AUTHOR]

Organic soils have low sorption capacities for phosphorus (P), and may pose a risk of P loss to water if P applications to these soils coincide with runoff events. Little is known about the magnitude of exports of P in overland flow following application of P fertiliser onto these soils, or on the influence of the frequency on P losses and persistence. The number of P fertiliser applications was surveyed across 39 commercial farms to assess current practice and inform the design of a rainfall runoff experiment to evaluate the effect of frequency of P applications on losses and persistence across time. Superphosphate (16% P) was applied in single (equivalent to 30 and 55 kg P ha−1 applied at day 0) and split (equivalent to 15 and 27.5 kg P ha−1 applied in two doses at days 0 and 55) applications to an organic soil inclined at a slope of 6% in a rainfall simulator experiment. The surface runoff of dissolved reactive phosphorus (DRP) was measured in controlled 30-min rainfall simulations conducted intermittently over an 85-day period. The DRP losses in surface runoff after the first rainfall event were 44.6 and 97.8 mg L−1 for single applications of 30 and 55 kg ha−1, respectively, and 13.3 and 21.8 mg L−1 for the same rates split in two doses, indicating that single P applications had disproportionately bigger impacts on losses than split applications. This supports the idea that frequent, but smaller, P applications can minimise the impact of fertilisation on waters. Dissolved reactive P concentrations remained significantly higher than those from the control samples until the end the experiment for almost all the P treatments, highlighting the long-lasting effects of added P and the elevated risk of P losses on organic soils. For climates with frequent rainfall events, which are likely to coincide with fertiliser applications, smaller but more frequent P applications can reduce the risk of P transfer as opposed to one single application. • A farm survey indicated that 40% of organic soils receive one fertiliser application. • The survey showed that mineral soils receive high numbers of fertiliser applications. • Mineral fertiliser was the predominant form of fertiliser used on farms. • Rainfall simulators examined impact of fertiliser applications on P in runoff. • Frequent, small applications of fertiliser minimise the possibility of P loss. [ABSTRACT FROM AUTHOR]

An understanding of the seasonal variation in the standing stock of metals and nutrients in emergent vegetation of constructed wetlands (CWs), as well as the amounts present in aboveground (AG) and belowground (BG) biomass, is crucial to their design and management. Given that biomass harvesting is a labour and time consuming operation, a paucity of information currently exists on accumulation and standing stocks in biomass in CWs, in particular in North Western European countries. To address this knowledge gap, this paper examined the seasonal variations of metals and nutrients in Phragmites australis (Cav.) Trin. ex Steudel in a CW treating municipal wastewater, with a view to identifying an optimal time for biomass harvesting of the AG vegetation. Although the AG biomass was greatest in August (1636 ± 507 g m −2 ), the maximum concentrations and accumulations of metals and nutrients occurred at different times throughout the duration of the study (April to November). Furthermore, with the exception of zinc and nitrogen, metals and nutrients measured in BG biomass ranged from 66% (phosphorus) to greater than 80% (nickel and chromium) of the AG biomass. This indicates that analysis of only the emergent shoots may significantly underestimate the metal and nutrient uptake and capacity of the plant. In order to effectively target the bulk of metals and nutrients, an AG harvest in late August or September is suggested. [ABSTRACT FROM AUTHOR]

Given the current decline of natural wetlands worldwide and the consequent negative impacts on amphibians, wetlands constructed for the treatment of wastewaters have the potential to play a role in the protection of these animals. However, there is a paucity of information regarding the value of constructed wetlands (CWs) to amphibians, particularly relating to the terrestrial phase of their life-cycle. This study compares the terrestrial habitats of natural wetlands (NWs) and CWs as refuges for the smooth newt ( Lissotriton vulgaris , [L., 1758]) with the aim of developing recommendations for CWs (both new and existing) to enhance their usefulness as newt-friendly habitats. Terrestrial habitats surrounding NWs and CWs were mapped using ArcGIS. Potential barriers to newt movement in addition to the presence of features such as wood or stone which could act as potential newt refuges were also mapped. Natural wetlands had significantly more terrestrial habitat types than CWs and while woodlands at both wetland types were most likely to contain features of benefit to newts, terrestrial habitats of NWs contained more features compared to those of CWs. The application of a Habitat Suitability Index, which assesses the likelihood of the presence of newts, resulted in seven of eight NWs compared to only two of eight CWs receiving “good” scores, the lower scores for CWs being due primarily to the presence of a barrier to newt movement. Recommendations for enhancing the design and management of CWs for smooth newts include less intensive ground maintenance, reduction of barriers to newt movement, judicious planting of suitable trees or shrubs and the provision of additional refuges such as wood or stone. [ABSTRACT FROM AUTHOR]

Landfill leachate is the result of water percolating through waste deposits that have undergone aerobic and anaerobic microbial decomposition. In recent years, increasingly stringent wastewater discharge requirements have raised questions regarding the efficacy of co-treatment of leachate in municipal wastewater treatment plants (WWTPs). This study aimed to (1) examine the co-treatment of leachate with a 5-day biochemical oxygen demand (BOD 5 ): chemical oxygen demand (COD) ratio less than or slightly greater than 0.26 (intermediate age leachate) in municipal WWTPs (2) quantify the maximum hydraulic and mass (expressed as mass nitrogen or COD) loading of landfill leachate (as a percentage of the total influent loading rate) above which the performance of a WWTP may be inhibited, and (3) quantify the impact of a range of hydraulic loading rates (HLRs) of young and intermediate age leachate, loaded on a volumetric basis at 0 (study control), 2, 4 and 10% (volume landfill leachate influent as a percentage of influent municipal wastewater), on the effluent ammonium concentrations. The leachate loading regimes examined were found to be appropriate for effective treatment of intermediate age landfill leachate in the WWTPs examined, but co-treatment may not be suitable in WWTPs with low ammonium-nitrogen (NH 4 -N) and total nitrogen (TN) emission limit values (ELVs). In addition, intermediate leachate, loaded at volumetric rates of up to 4% or 50% of total WWTP NH 4 -N loading, did not significantly inhibit the nitrification processes, while young leachate, loaded at volumetric rates greater of than 2% (equivalent to 90% of total WWTP NH 4 -N loading), resulted in a significant decrease in nitrification. The results show that current hydraulic loading-based acceptance criteria recommendations should be considered in the context of leachate NH 4 -N composition. The results also indicate that co-treatment of old leachate in municipal WWTPs may represent the most sustainable solution for ongoing leachate treatment in the cases examined. [ABSTRACT FROM AUTHOR]

The true efficacy of a programme of agricultural mitigation measures within a catchment to improve water quality can be determined only after a certain hydrologic time lag period (subsequent to implementation) has elapsed. As the biophysical response to policy is not synchronous, accurate estimates of total time lag (unsaturated and saturated) become critical to manage the expectations of policy makers. The estimation of the vertical unsaturated zone component of time lag is vital as it indicates early trends (initial breakthrough), bulk (centre of mass) and total (Exit) travel times. Typically, estimation of time lag through the unsaturated zone is poor, due to the lack of site specific soil physical data, or by assuming saturated conditions. Numerical models (e.g. Hydrus 1D) enable estimates of time lag with varied levels of input data. The current study examines the consequences of varied soil hydraulic and meteorological complexity on unsaturated zone time lag estimates using simulated and actual soil profiles. Results indicated that: greater temporal resolution (from daily to hourly) of meteorological data was more critical as the saturated hydraulic conductivity of the soil decreased; high clay content soils failed to converge reflecting prevalence of lateral component as a contaminant pathway; elucidation of soil hydraulic properties was influenced by the complexity of soil physical data employed (textural menu, ROSETTA, full and partial soil water characteristic curves), which consequently affected time lag ranges; as the importance of the unsaturated zone increases with respect to total travel times the requirements for high complexity/resolution input data become greater. The methodology presented herein demonstrates that decisions made regarding input data and landscape position will have consequences for the estimated range of vertical travel times. Insufficiencies or inaccuracies regarding such input data can therefore mislead policy makers regarding the achievability of water quality targets. [ABSTRACT FROM AUTHOR]

Management changes such as drainage, fertilisation, afforestation and harvesting (clearfelling) of forested peatlands influence watertable (WT) position and groundwater concentrations of nutrients. This study investigated the impact of clearfelling of a peatland forest on WT and nutrient concentrations. Three areas were examined: (1) a regenerated riparian peatland buffer (RB) clearfelled four years prior to the present study (2) a recently clearfelled coniferous forest (CF) and (3) a standing, mature coniferous forest (SF), on which no harvesting took place. The WT remained consistently below 0.3 m during the pre-clearfelling period. Results showed there was an almost immediate rise in the WT after clearfelling and a rise to 0.15 m below ground level (bgl) within 10 months of clearfelling. Clearfelling of the forest increased dissolved reactive phosphorus concentrations (from an average of 28–230 μg L−1) in the shallow groundwater, likely caused by leaching from degrading brash mats. [Copyright &y& Elsevier]

Highlights: [•] Two forest catchments were studied to assess efficacy of best management practices. [•] Concentrations of nitrogen and phosphorus were examined before and after harvesting. [•] Harvesting impacted phosphorus and nitrogen concentrations. [•] Forest operations should use best management practices where possible. [•] Concentrations of nutrients in stream were below threshold limits within 15 months. [ABSTRACT FROM AUTHOR]

The dairy industry produces vast quantities of dairy processing sludge (DPS), which can be processed further to develop second generation products such as struvite, biochars and ashes (collectively known as STRUBIAS). These bio-based fertilizers have heterogeneous nutrient and metal contents, resulting in a range of possible application rates. To avoid nutrient losses to water or bioaccumulation of metals in soil or crops, it is important that rates applied to land are safe and adhere to the maximum legal application rates similar to inorganic fertilizers. This study collected and analysed nutrient and metal content of all major DPS (n = 84) and DPS-derived STRUBIAS products (n = 10), and created an application calculator in MS Excel™ to provide guidance on maximum legal application rates for ryegrass and spring wheat across plant available phosphorus (P) deficient soil to P-excess soil. The sample analysis showed that raw DPS and DPS-derived STRUBIAS have high P contents ranging from 10.1 to 122 g kg−1. Nitrogen (N) in DPS was high, whereas N concentrations decreased in thermo-chemical STRUBIAS products (chars and ash) due to the high temperatures used in their formation. The heavy metal content of DPS and DPS-derived STRUBIAS was significantly lower than the EU imposed limits. Using the calculator, application rates of DPS and DPS-derived STRUBIAS materials (dry weight) ranged from 0 to 4.0 tonnes ha−1 y−1 for ryegrass and 0–4.5 tonnes ha−1 y−1 for spring wheat. The estimated heavy metal ingestion to soil annually by the application of the DPS and DPS-derived STRUBIAS products was lower than the EU guideline on soil metal accumulation. The calculator is adaptable for any bio-based fertilizer, soil and crop type, and future work should continue to characterise and incorporate new DPS and DPS-derived STRUBIAS products into the database presented in this paper. In addition, safe application rates pertaining to other regulated pollutants or emerging contaminants that may be identified in these products should be included. The fertilizer replacement value of these products, taken from long-term field studies, should be factored into application rates. [Display omitted] • No tool exists for safe land application of dairy processing sludge and STRUBIAS. • These products are highly variable in terms of their nutrient-metal profiles. • A tool was developed for maximum legal application rates for bio-based products. • Application rates calculated based on soil P and nutrient and metal loading rates. [ABSTRACT FROM AUTHOR]

Abstract: Losses of phosphorus (P) when pig slurry applications to land are followed by a rainfall event or losses from soils with high P contents can contribute to eutrophication of receiving waters. The addition of amendments to pig slurry spread on high P Index soils may reduce P and suspended sediment (SS) losses. This hypothesis was tested at laboratory-scale using runoff boxes under simulated rainfall conditions. Intact grassed soil samples, 100 cm-long, 22.5 cm-wide and 5 cm-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]. The grassed soil was then subjected to three rainfall events (10.3 ± 0.15 mm h−1) at time intervals of 48, 72, and 96 h following slurry application. Each sod received rainfall on 3 occasions. Results across three rainfall events showed that for the control treatment, the average flow weighted mean concentration (FWMC) of TP was 0.61 mg L−1, of which 31% was particulate phosphorus (PP), and the average FWMC of SS was 38.1 mg L−1. For the slurry treatment, there was an average FWMC of 2.2 mg TP L−1, 47% of which was PP, and the average FWMC of SS was 71.5 mg L−1. Ranked in order of effectiveness from best to worst, PAC reduced the average FWMC of TP to 0.64 mg L−1 (42% PP), FeCl3 reduced TP to 0.91 mg L−1 (52% PP) and alum reduced TP to 1.08 mg L−1 (56% PP). The amendments were in the same order when ranked for effectiveness at reducing SS: PAC (74%), FeCl3 (66%) and alum (39%). Total phosphorus levels in runoff plots receiving amended slurry remained above those from soil only, indicating that, although incidental losses could be mitigated by chemical amendment, chronic losses from the high P index soil in the current study could not be reduced. [Copyright &y& Elsevier]

Abstract: Forestry on peatland throughout the world is now focused on minimising destructive effects to the surrounding environment, especially during harvesting. These effects may be mitigated through the use of well-developed riparian buffers zones (RBZs). However, much of the commercial forestry planted in Ireland and the UK in the mid-20th century was planted without adequate RBZs. The creation of new RBZs prior to clearfelling may be a possible mitigation measure in these circumstances. The aim of this paper was to assess the nutrient content and phosphorus (P) adsorption capacity of the soil, and survival of planted saplings in a RBZ, positioned downslope from a standing forest and partly covered with brash mats, five years after its establishment. Dissolved reactive phosphorus (DRP) concentrations were significantly higher under the brash mats in the RBZ when compared to all other areas. The standing forest had the highest concentrations of ammonium nitrogen (NH4-N), while total oxidised nitrogen (TON) was similar for all areas. Water extractable phosphorus and desorption–adsorption testing also confirmed the high concentrations of P under the brash mats, but P did not leach through the peat to the stream. The overall survival rate of the saplings was relatively high, with over half of Quercus robur (oak) (57%), Sorbus aucuparia (rowan) (57%) and Betula pendula (birch) (51%) surviving. Salix cinerea (willow) (22%), Alnus glutinosa (alder) (25%) and Ilex aquifolium (holly) (44%) did not survive as successfully. The RBZ was capable of providing nutrients for the survival of planted saplings, fertilizing the peat with degrading brash material and preventing elevated levels of nutrients entering the adjacent aquatic ecosystem. [Copyright &y& Elsevier]

Abstract: Dairy soiled water (DSW) is a dilute, low nutrient effluent produced on Irish dairy farms through the regular washing down of milking parlours and holding areas. In Ireland, there is no closed period for the land application of DSW except where heavy rain is forecast within 48h. Chemical amendments have the potential to decrease phosphorus (P) and suspended sediment (SS) loss from DSW applied to land. This study examined the impact of three time intervals (12, 24 and 48h) between DSW application and rainfall and five treatments (control, unamended DSW, and DSW amended with lime, alum or ferric chloride (FeCl2)) on P and sediment losses from an intact grassland soil in runoff boxes. Rainfall was simulated at 10.5±1mmh−1. Phosphorus concentrations (1–1.6mgL−1) in runoff from DSW application, while not quantitative measures of P loss to surface waters in the field, indicated the importance of incidental P losses and that the current 48h restriction in Ireland is prudent. Unamended DSW application increased P loss by, on average, 71%, largely due to an increase in particulate phosphorus (PP) loss. All three amendments were effective in decreasing P and SS losses in runoff and, apart from the SS results for lime, were significantly different (p<0.05) to the control at at least one time point. Lime (a 64% reduction in total phosphorus (TP) in comparison with DSW only) was less effective than alum or FeCl2, likely due to the lower solubility of CaCO3 in water. Chemical amendment showed potential to decrease P losses from land application of DSW, but the efficacy of such amendments would need to be assessed in field trials and a cost–benefit analysis conducted to further examine whether they could be practically implemented on farms. [Copyright &y& Elsevier]

Abstract: Emerging remediation technologies such as chemical amendment of dairy cattle slurry have the potential to reduce phosphorus (P) solubility and consequently reduce P losses arising from land application of dairy cattle slurry. The aim of this study was to determine the effectiveness of chemical amendment of slurry to reduce incidental losses of P and suspended sediment (SS) from grassland following application of dairy cattle slurry and to examine the effect of amendments on metal concentrations in runoff water. Intact grassed-soil samples were placed in two laboratory runoff boxes, each 200-cm-long by 22.5-cm-wide by 5-cm-deep, before being amended with dairy cattle slurry (the study control) and slurry amended with either: (i) alum, comprising 8% aluminium oxide (Al2O3) (1.11:1 aluminium (Al):total phosphorus (TP) of slurry) (ii) poly-aluminium chloride hydroxide (PAC) comprising 10% Al2O3 (0.93:1 Al:TP) (iii) analytical grade ferric chloride (FeCl2) (2:1 Fe:TP), (iv) and lime (Ca(OH)2) (10:1 Ca:TP). When compared with the study control, PAC was the most effective amendment, reducing dissolved reactive phosphorus (DRP) by up to 86% while alum was most effective in reducing SS (88%), TP (94%), particulate phosphorus (PP) (95%), total dissolved phosphorus (TDP) (81%), and dissolved unreactive phosphorus (DUP) (86%). Chemical amendment of slurry did not appear to significantly increase losses of Al and Fe compared to the study control, while all amendments increased Ca loss compared to control and grass-only treatment. While chemical amendments were effective, the reductions in incidental P losses observed in this study were similar to those observed in other studies where the time from slurry application to the first rainfall event was increased. Timing of slurry application may therefore be a much more feasible way to reduce incidental P losses. Future work must examine the long-term effects of amendments on P loss to runoff and not only incidental losses. [Copyright &y& Elsevier]

Groundwater contamination was characterised using a methodology which combines shallow groundwater geochemistry data from 17 piezometers over a 2yr period in a statistical framework and hydrogeological techniques. Nitrate–N (NO3-N) contaminant mass flux was calculated across three control planes (rows of piezometers) in six isolated plots. Results showed natural attenuation occurs on site although the method does not directly differentiate between dilution and denitrification. It was further investigated whether NO3-N concentration in shallow groundwater (<5m below ground level) generated from an agricultural point source on a 4.2ha site on a beef farm in SE Ireland could be predicted from saturated hydraulic conductivity (Ksat ) measurements, ground elevation (m Above Ordnance Datum), elevation of groundwater sampling (screen opening interval) (m AOD) and distance from a dirty water point pollution source. Tobit regression, using a background concentration threshold of 2.6mg NO3-NL−1 showed, when assessed individually in a step wise procedure, Ksat was significantly related to groundwater NO3-N concentration. Distance of the point dirty water pollution source becomes significant when included with Ksat in the model. The model relationships show areas with higher Ksat values have less time for denitrification to occur, whereas lower Ksat values allow denitrification to occur. Areas with higher permeability transport greater NO3-N fluxes to ground and surface waters. When the distribution of Cl− was examined by the model, Ksat and ground elevation had the most explanatory power but Ksat was not significant pointing to dilution having an effect. Areas with low NO3 concentration and unaffected Cl− concentration points to denitrification, low NO3 concentration and low Cl− chloride concentration points to dilution and combining these findings allows areas of denitrification and dilution to be inferred. The effect of denitrification is further supported as mean groundwater NO3-N was significantly (P <0.05) related to groundwater N2/Ar ratio, redox potential (Eh), dissolved O2 and N2 and was close to being significant with N2O (P =0.08). Calculating contaminant mass flux across more than one control plane is a useful tool to monitor natural attenuation. This tool allows the identification of hot spot areas where intervention other than natural attenuation may be needed to protect receptors. [Copyright &y& Elsevier]

The use of filter media to adsorb phosphorus (P) from nutrient-rich waters is an effective, simple and low-cost method to recover and reuse P as an inorganic fertiliser replacement. Although it is assumed that the saturated filter media can be applied to cropland as a safe fertiliser replacement, there is presently a lack of information on the fertiliser replacement value (FRV) of such products and their negative effects on plants and soil. Therefore, the aims of this paper were to evaluate the (1) P removal capacity and plant response to soil application of waste media from three sectors (industry, agriculture, and construction and demolition), and natural and synthetic materials (2) potentially confounding risks arising from the reuse of media as a fertiliser replacement, and (3) factors affecting their fertilising efficiency once applied to soil. The predominant factors affecting the FRV of P-saturated media were their adsorption capacity and chemical composition, soil pH, and composition of water used for saturation. Some measures to overcome the negative impacts of the land application of P-saturated media include selecting the most appropriate soil-filter material combinations, the use of P solubilising microorganisms, and mixing with manure before land application. Despite confounding factors and a lack of information on the performance of some media under comparable study conditions, this study found that there is a significant potential for P-saturated filter media to partially replace the use of P mineral fertilisers and aid in the attainment of a "circular economy" in agriculture. Image 1 • Fertiliser success lies in the correct combination of filter medium, soil and water. • C&D, agriculture, industry, and natural/synthetic waste are potential fertilisers. • Adsorption capacity, composition, soil pH affect the fertiliser replacement value. • Significant potential for P-loaded filter media to replace P mineral fertilisers. [ABSTRACT FROM AUTHOR]

• Effective P removal has been achieved using a model-based design approach • Nitrogen limitation can influence P removal negatively in an EBPR-PAS system • Controlling NH 4 and HCO 3 is critical to balancing PAOs and microalgae populations • The performance of the EBPR-PAS system was robust at different light intensities Photo-activated sludge (PAS) systems are an emerging wastewater treatment technology where microalgae provide oxygen to bacteria without the need for external aeration. There is limited knowledge on the optimal conditions for enhanced biological phosphorus removal (EBPR) in systems containing a mixture of polyphosphate accumulating organisms (PAOs) and microalgae. This research aimed to study the effects of substrate composition and light intensity on the performance of a laboratory-scale EBPR-PAS system. Initially, a model-based design was developed to study the effect of organic carbon (COD), inorganic carbon (HCO 3) and ammonium-nitrogen (NH 4 -N) in nitrification deprived conditions on phosphorus (P) removal. Based on the mathematical model, two different synthetic wastewater compositions (COD:HCO 3 :NH 4 -N: 10:20:1 and 10:10:4) were examined at a light intensity of 350 µmol m−2 sec−1. Add to this, the performance of the system was also investigated at light intensities: 87.5, 175, and 262.5 µmol m−2 sec−1 for short terms. Results showed that wastewater having a high level of HCO 3 and low level of NH 4 -N (ratio of 10:20:1) favored only microalgal growth, and had poor P removal due to a shortage of NH 4 -N for PAOs growth. However, lowering the HCO 3 level and increasing the NH 4 -N level (ratio of 10:10:4) balanced PAOs and microalgae symbiosis, and had a positive influence on P removal. Under this mode of operation, the system was able to operate without external aeration and achieved a net P removal of 10.33 ±1.45 mg L−1 at an influent COD of 100 mg L−1. No significant variation was observed in the reactor performance for different light intensities, indicating the EBPR-PAS system can be operated at low light intensities with a positive influence on P removal. Image, graphical abstract [ABSTRACT FROM AUTHOR]