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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2006.11.027 Byline: M. Rodgers, D. de Paor, E. Clifford Keywords: Horizontal flow biofilm reactor; Step-feed; Organic carbon and nitrogen removal; Dairy washings; Agricultural wastewater Abstract: In Ireland, dairy farmyard washwater commonly comprises farmyard run-off and dairy parlour washings. Land-spreading is the most widely used method for treating this wastewater. However, this method can be labour intensive and can cause, in some cases, the degradation of surface and ground waters, mainly due to nitrogen contamination. In this study, a horizontal flow biofilm reactor (HFBR) with step-feed was constructed and tested in the laboratory, to remove organic carbon and nitrogen from a agricultural strength synthetic washwater (SWW). The HFBR had an average top plan surface area (TPSA) of 0.1002m.sup.2 and consisted of a stack of 45 polystyrene horizontal sheets -- -15 sheets embedded with 25mm deep frustums above 30 sheets with 10mm deep frustums. The frustums acted as miniature reservoirs. The sheets were alternately offset to allow the wastewater to flow horizontally along each sheet and vertically from sheet to sheet down through the reactor. Biofilms developed on the sheets and treated the wastewater. During the 212-d study, the total hydraulic loading rate based on the TPSA of the sheets was 35lm.sup.-2 d.sup.-1. SWW was pumped for 10min each hour, in a step feed arrangement at a rate of 23.33lm.sup.-2 d.sup.-1 on to the top sheet during Phases 1 and 2, and 11.67lm.sup.-2 d.sup.-1 onto Sheet 16 during Phase 1 (days 1-92) and onto Sheet 30 during Phase 2 (days 93-212). The substrate loading rate during Phases 1 and 2 was 94.8g total chemical oxygen demand (COD)m.sup.-2 d.sup.-1 and 10.5g total nitrogen (TN)m.sup.-2 d.sup.-1, based on the TPSA. At steady state in Phase 2, the unit achieved excellent carbon removal of 99.7% 5-day biochemical oxygen demand (BOD.sub.5) and 96.7% total COD, equivalent to TPSA removal rates of 67.5g BOD.sub.5 m.sup.-2 d.sup.-1 and 91.7g CODm.sup.-2 d.sup.-1. The nitrogen removal percentages were 98.3% total ammonium-nitrogen (NH.sub.4-N.sub.t) and 72.8% TN, which equated to TPSA removal rates of 4.8g NH.sub.4-N.sub.t m.sup.-2 d.sup.-1 and 7.6g TNm.sup.-2 d.sup.-1. No sloughing of solids or clogging of media occurred during the study. The unit was simple to construct and operate, with little maintenance. Author Affiliation: Department of Civil Engineering, National University of Ireland, Galway, Ireland Article History: Received 7 February 2006; Revised 16 November 2006; Accepted 26 November 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2006.03.005 Byline: M.G. Healy, M. Rodgers, J. Mulqueen Keywords: Recirculating sand filters; Dairy parlor wastewaters; Forward flow; Organic loading rate Abstract: 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.sup.-2 d.sup.-1; a higher system hydraulic loading rate (of 13.4Lm.sup.-2 d.sup.-1) caused surface ponding. The system hydraulic loading rate of 10Lm.sup.-2 d.sup.-1 gave a filter chemical oxygen demand (COD), TSS, and total kjeldahl nitrogen (TKN) loading rate of 14, 3.7, and 2.1gm.sup.-2 d.sup.-1, respectively, and produced consistent COD and TSS removals of greater than 99%, and an effluent NO.sub.3-N concentration of 42mgL.sup.-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. Author Affiliation: Department of Civil Engineering, National University of Ireland, Galway, Ireland Article History: Received 23 June 2005; Revised 21 January 2006; Accepted 15 March 2006

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jenvman.2005.07.003 Byline: M. Rodgers, M.G. Healy, J. Prendergast 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 (NH.sub.4.sup.+-N) loading rates, ranging from 0.17[+ or -]0.01 (0.71[+ or -]0.06gm.sup.-2 d.sup.-1) to 0.70[+ or -]0.02kgm.sup.-3 d.sup.-1 (2.9[+ or -]0.1gm.sup.-2 d.sup.-1). The biofilm plastic module was moved vertically in and out of the wastewater in continuous cycles. The maximum NH.sub.4.sup.+-N removal rate was reached during the maximum loading phase, when a NH.sub.4.sup.+-N loading rate of 0.70[+ or -]0.02kgm.sup.-3 d.sup.-1 (2.9[+ or -]0.1gm.sup.-2 d.sup.-1) was applied to the system. During this loading period, the average NH.sub.4.sup.+-N removal rate was 0.30[+ or -]0.10kgm.sup.-3 d.sup.-1 (1.30[+ or -]0.40gm.sup.-2 d.sup.-1). Author Affiliation: Department of Civil Engineering, National University of Ireland, Galway, Ireland Article History: Received 23 December 2004; Revised 7 June 2005; Accepted 26 July 2005

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: 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: 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]

Abstract: Recirculation of fully nitrified effluent from a laboratory horizontal-flow biofilm reactor (HFBR) to a mixed pre-denitrification reactor (DR) was used to remove organic carbon and nitrogen from synthetic dairy wastewater. Three recirculation ratios of 2, 4, and 6 were examined in this study and the average filtered chemical oxygen demand (CODf) and total nitrogen (TN) removals were up to 97.4% and 85.5%, respectively, at 11°C. In the DR, the nitrate nitrogen removal efficiencies and rates were 86–96% and 22–34gN/m3 d. In the HFBR, the ammonium nitrogen removal rates were 293–337mgN/m2 d. [Copyright &y& Elsevier]

Abstract: The field-saturated hydraulic conductivity (K fs) finds use in many agricultural, environmental and geotechnical investigations and designs. It is commonly derived from falling-head tests in a well, but its derivation is sometimes based on assumptions that may not always hold. The aim of this study was to develop graphs for falling head percolation tests for 340 and 60mm diameter wells—centred in two separate cylindrical soil tanks—for use in deriving K fs of a fine sand placed in the tanks. The graphs were obtained from results from the finite element program SEEP/W that was used to model percolation from the tank wells into sand, fine sand and silt of known K fs; the soils were all initially field-saturated, and the tests were carried out under (i) field-saturated (by spray irrigation) and (ii) draining conditions. For the modelled field-saturated tests on the three soils, the graphs of fall of head in the well, ΔH w, against the parameter K fs ×Δt, where Δt is the time taken for the particular fall ΔH w to occur, were coincident. This indicated that for a given measured fall, ΔH w, for a particular head of water, H w, in a well, K fs could be calculated by dividing the parameter K fs ×Δt, by the observed time, Δt, for the fall, ΔH w, to occur. For the modelled tests on the three draining soils, there was another inverse relationship between ΔH w and the parameter K fs ×Δt for small falls in well heads after start-up. There was good agreement between the K fs value of a fine sand measured in a cylindrical constant-head laboratory permeameter and that obtained using the graphs and the experimental results from both the field-saturated fine sand, and the same fine sand in draining mode at small falls of head in the well. This suggests that falling head tests on non-irrigated soils—initially field-saturated—could be used to determine K fs from early time falls in well heads. Since the time parameter greatly increases with increasing well size and decreasing pressure heads in the percolation well, it is quicker to carry out falling-head percolation tests in smaller test wells and at higher heads in the well. The procedure employed for obtaining K fs for the soils within the K fs range examined could be extended to the field. [Copyright &y& Elsevier]

Abstract: The design and operation of wastewater treatment systems for single houses, farms, hotels, leisure centres, small communities and small businesses are a challenge to wastewater engineers. In this paper, a pilot-scale system comprising a vertically moving biofilm reactor (VMBR) followed by a stratified sand filter was constructed and its performance was evaluated. The vertically moving biofilm reactor was operated as a sequencing batch biofilm reactor (VMSBBR). The results show that the VMSBBR unit efficiently removed 94.8% of the filtered chemical oxygen demand (CODf) from a synthetic wastewater with the influent CODf of 1096±425mg/l, leaving 45±16mg/l CODf in the effluent, at an organic loading rate of 0.9kg COD/m3 day. After the system had been operated for 133 days, the removal efficiency of orthophosphate (PO4-P) reached 90%. A sand filter polished the effluent from the VMSBBR unit and reduced suspended solids (SS) to 4.4mg/l and total bacterial by 3log10 units. The advantages of the treatment system studied for small wastewater flows include: (1) simple operation and maintenance—sludge was only disposed of once on Day 206 during the 7.5-month study period; clogging, which often happens in other attached-growth biofilm systems, did not take place; (2) efficient removal of COD and phosphorus; and (3) low-energy consumption—the electricity consumption was 4.6kWh/population equivalent (p.e.) year, or 0.6kWh/m3 wastewater treated or 0.6kWh/kg COD removed. [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]

The release of phosphate ions (PO4–P) from soils to surface waters and overland flow was examined in this study. Sand and undisturbed soil cores were ponded in beakers and the surface waters were subjected to a gentle swirling action by a paddle agitator. Slabs of soil were also placed in a flume, saturated and subjected to overland flow. A comparison of the mass of PO4–P released to surface waters in the agitator test with that released to surface runoff in the flume tests and in the literature on field losses at the plot and sub-catchment scales was made. Leighton Buzzard silica sand was washed free of all phosphate ions and a constant weight of this sand was placed in 1 l beakers; each sand preparation was saturated with a constant volume of water of differing concentration of P as KH2PO4. The sands were then carefully ponded with deionised water, that was gently swirled by the agitator rotating at 20 rpm. Samples of the ponded water were taken at increasing times, up to 12 h. Layers of the sand were then carefully recovered in 5 mm depth increments and the porewater extracted using vacuum filtration and analysed for PO4–P ions to determine the depth of release of P from the porewater. A Fickian diffusion model was used to model the transfer of PO4–P to the surface water. Cores of undisturbed soil in grassland for the agitator test, soil samples from the soil surrounding the cores for analysis for P extracted by Morgan’s reagent and slabs of soil from adjoining ground for placement in a flume for surface runoff tests were taken from sites of known low, medium and high Morgan’s P-values. Additional cores were taken at a high Morgan’s P site to evaluate the release of P from soil at several depths in the agitator. Sub-layers were employed to determine the depth distribution of Morgan’s P and if a relationship existed between Morgan’s P at the several depths and the concentration of P released to the surface water. The agitator sand tests showed that the depth to which P was released from the sand porewater (the depth of interaction) was about 20 mm below the sand surface in agreement with previous studies. After an initial short period of convective transfer, release of P from the sand porewater to the surface water proceeded in accordance with Fickian diffusion law. Model output and measured data were in good agreement. Morgan’s P on 0–20 mm deep grassland soil samples gave good correlation with mass of P released to the surface water but values from 0 to 100 mm deep samples did not. Morgan’s P in the grassland soil samples showed an exponential decline with depth. Agitator test P from many soil cores behaved in accordance with Fickian diffusion law but others exhibited fluctuating concentrations of P with time, suggestive of sorption–desorption during the tests. The masses of P released from grassland soils in the agitator tests were comparable with those released in the flume tests and with those measured in surface runoff from small plots and small sub-catchments as reported in the literature, suggesting that, with further development, the agitator test might be a suitable environmental test for P release to surface runoff. The results are discussed in relation to environmental tests for soil P and the potential for control of P loss to surface waters. [Copyright &y& Elsevier]

Most of the scientific studies of forest impacts on stream flows have been conducted in North America. Many were primarily concerned with felling effects. These have generally found forests to be associated with reducing both peak and low flows. Their results, however, may not necessarily be directly applicable to European forests due to differences in tree species, forest management, catchment physiography and climate. Forests are a major land cover in Europe, and there are plans to promote and further expand the area of European forests. The recent droughts and floods in different parts of Europe have heightened interest in the role of forests on river flow regimes, particularly flood peak and dry weather baseflows. This paper presents the hydrological results from 28 basins across Europe sampling a wide range of forest types, climate conditions and ground conditions. The aim was to determine if forestry can have significant impacts on stream flows and to identify particularly critical situations. The findings highlighted coniferous plantations on poorly drained soils in NW Europe and eucalyptus in Southern Europe as the situations where the most marked changes to flows are likely to occur. In contrast, other forest types, and changes in forest cover at a regional scale will be likely to have a relatively small effect on peak and low flows. [Copyright &y& Elsevier]

The pilot plant study comprised the construction and monitoring of a new vertically moving biofilm system (VMBS) for treating municipal wastewater. The system operated on site for 11 months. The biofilm module in this system, consisting of high surface area plastic media, was vertically and repeatedly moved in cycles up into the air and down into the wastewater. The vertical movement of the biofilm module supplied sufficient oxygen for the removal of the organic carbon in the wastewater. The overall physical oxygen transfer coefficient (Kla) measured at the cycle speed of six cycles per minute was 2.53 per hour. During the pilot study, dissolved oxygen (DO) concentrations in the bulk fluid were in the range of 1.5–5 mg/l. It was found that the areal removal rate of filtered chemical oxygen demand (COD) was up to 35 g COD/(m2 day) and the bulk fluid volumetric filtered COD removal rate was 2.62 kg COD/(m3 day). The field experiment showed that clogging commonly found in other biofilm systems did not occur in this system. The power consumption was in the range of 0.09–0.25 kWh/m3 wastewater flow, 0.40–2.19 kWh/kg COD removal and 1.24–1.74 kWh/kg BOD removal. The new biofilm system offers potential for reduced reactor volumes, energy saving, simple construction and easy operation. [Copyright &y& Elsevier]

A model study on the spacing of mole drains and their influence on pore-water pressure heads was carried out using the finite element package SEEP/W for both transient-state and steady-state conditions. The aims were: to optimise mole drain spacing by modelling two drain spacings and to contribute to the understanding of mole drain performance; to compare pore-water pressure heads generated over a 12-day rainfall period by the model with those measured by a multipoint tensiometer in the field; to compare watertables for the two spacings under a range of steady-state rainfalls and hydraulic conductivity of the several soil layers. The drained field soil was three-layered, with a 150 mm thick permeable clay topsoil overlying a quasi-triangular wedge of permeable loosened clay soil over the mole drains that were drawn in a virgin clay subsoil of very low hydraulic conductivity. Mole drains of 0.075 m diameter were installed in the field at a depth of 0.45 m and tensiometer data were available for a spacing of 1.07 m; two spacings of 1.075 and 2.0 m were used in the modelling. There was good agreement between the pore-water pressures generated by the model and those measured by a multipoint tensiometer in the field for the 12-day sequential rainfall period. In the steady-state analysis, steady rainfalls of 5, 12 and 30 mm per day were imposed on a range of hydraulic conductivities of the soil layers for the two drain spacings. The close spacing of 1.075 m was shown by the model to give good control of the watertable while the more distant spacing of 2.0 m failed to control the saturation of the topsoil under a steady-state rainfall of 5 mm per day. For Irish soil and rainfall conditions, a mole drain spacing of 1 m or less is required to provide satisfactory control of the watertable in contrast with 2–3 m spacing commonly employed in the low-rainfall east of UK. [Copyright &y& Elsevier]

Abstract: Age differences in navigation strategies have been demonstrated in animals, with aged animals more likely to prefer an egocentric (route) strategy and younger animals more likely to prefer an allocentric (place) strategy. Using a novel virtual Y-maze strategy assessment (vYSA), the present study demonstrated substantial age differences in strategy preference in humans. Older adults overwhelmingly preferred an egocentric strategy, while younger adults were equally distributed between egocentric and allocentric preference. A preference for allocentric strategy on the Y-maze strategy assessment was found to benefit performance on an independent assessment (virtual Morris water task) only in younger adults. These results establish baseline age differences in spatial strategies and suggest this may impact performance on other spatial navigation assessments. The results are interpreted within the framework of age differences in hippocampal structure and function. [Copyright &y& Elsevier]

This work presents the results of a Pareto analysis of critical challenges for emerging manufacturing technologies in c-Si photovoltaics. By soliciting input from members of the PV R&D community, these challenges have been prioritized for six different sub-categories, the first three associated with Processing Challenges and the following three in the area of Metrology Challenges: (1) Feedstock, Crystallization and Wafering; (2) Cell Materials and Processing; (3) Module Integration; (4) Materials and Device Characterization; (5) Reliability and Durability (Measurements); and (6) Modeling and Simulation. Some sub-categories feature a large differential in scoring from the top challenge(s) to lower scored challenges (e.g. Module Integration, Modeling and Simulation), indicating topics of high interest. Other sub-categories feature a more evenly distributed level of prioritization (e.g. Cell Materials and Processing), indicating many high priority challenges within the same area. In total, 14 top critical challenges were identified for the six sub-categories, and a brief review for each of these is provided. As industry and academia seek R&D topics to help push for higher efficiencies and lower cost c-Si modules, this Pareto analysis can hopefully provide some objective insight into areas of high interest for the general PV community. [ABSTRACT FROM AUTHOR]

Abstract: A horizontal flow biofilm reactor (HFBR) designed for the treatment of synthetic wastewater (SWW) was studied to examine the spatial distribution and dynamics of nitrogen transformation processes. Detailed analyses of bulk water and biomass samples, giving substrate and proportions of ammonia oxidising bacteria (AOB) and nitrite oxidising bacteria (NOB) gradients in the HFBR, were carried out using chemical analyses, sensor rate measurements and molecular techniques. Based on these results, proposals for the design of HFBR systems are presented. The HFBR comprised a stack of 60 polystyrene sheets with 10-mm deep frustums. SWW was intermittently dosed at two points, Sheets 1 and 38, in a 2 to 1 volume ratio respectively. Removals of 85.7% COD, 97.4% 5-day biochemical oxygen demand (BOD5) and 61.7% TN were recorded during the study. In the nitrification zones of the HFBR, which were separated by a step-feed zone, little variation in nitrification activity was found, despite decreasing in situ ammonia concentrations. The results further indicate significant simultaneous nitrification and denitrification (SND) activity in the nitrifying zones of the HFBR. Sensor measurements showed a linear increase in potential nitrification rates at temperatures between 7 and 16°C, and similar rates of nitrification were measured at concentrations between 1 and 20mg NH4-N/l. These results can be used to optimise HFBR reactor design. The HFBR technology could provide an alternative, low maintenance, economically efficient system for carbon and nitrogen removal for low flow wastewater discharges. [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]