Urban Institute Ireland Research Collection

The effect of using coarse grain in the upper layer of a gravel-based reed bed is investigated. The aim for testing the “anti-sized” arrangement of gravel media is to seek a solution for the practical problem of medium clogging in reed beds that frequently takes place during the treatment of high strength wastewaters. Results from parallel operations of an anti-sized and a conventional “mono-sized” reed bed reveal that the former has the advantage of greater pollutant removal efficiencies. A specific clogging tendency rate is defined to quantitatively describe the clogging behaviour. Calculation of the clogging tendency rate reveals that the anti-sized reed bed has a clear advantage over the mono-sized bed because of improved ability to counteract clogging. Greater pore space in the upper layer of the anti-sized bed allows the suspended solids to be filtered and penetrate farther into the bed matrix, thereby allowing the solid-storage capacity of the matrix to be used more effectively and prolonging the operational life time of the bed. As such, the anti-sized arrangement of reed bed media may provide a viable solution for the problem of clogging.

The concept, design and performance analysis of a four-stage novel constructed wetland system (CWs) capable of enhanced and simultaneous removal of phosphorus (P) and organic matter (OM) from wastewaters is described. Alum sludge, a largely available by-product of drinking water facilities using aluminium salts as coagulant was used as the media. Under a hydraulic loading rate of 1.27 m3/m2.d and a range of organic loading rate of 279.4–774.7 g-BOD5/m2.d and 361.1–1028.7 g-COD/m2.d, average removal efficiencies (mean ±SD) of 90.6 ±7.5% for BOD5 and 71.8 ±10.2% for COD were achieved, respectively. P removal was exceptional with average removal efficiency of 97.6 ±1.9% achieved for soluble reactive P at a mean influent concentration of 21.0 ±2.9 mg/l. Overall, the system holds great promise as a novel CWs for simultaneous removal of P and OM, and at the same time, it transforms alum sludge from a waste into a useful material.

This paper is a snapshot in time of the personal backgrounds, educational training, professional ranking, and productivity levels of those individuals with respect to Compendex-listed journal paper. Important questions are raised not only as to issues of age, gender, and nationality, but as to where the professoriate in geotechnical engineering is coming from, what level of experience they are bringing to their positions, and their professional standing. The results of this paper raise several, possibly unexpected observations including the apparent role that small, private, undergraduate programs have in grooming future faculty members; the fact that most female faculty members come from only a handful of doctoral programs; the increasing productivity of junior faculty members; and the aging of the community with respect to succession planning. This document is intended to be a discussion document for succession planning for the wider community.

A major landslide event occurred at Pollatomish, County Mayo, Ireland in September 2003, during a period of intense rainfall. It comprised about 30 significant individual longitudinal planar type slides of peat and weathered rock. Relatively simple limit state stability analyses, using the method of slices and an infinite slope analysis, were used to model the slide and it was found that the features observed on site could easily be reproduced. These included confirmation that thin layers of peat could be stable on steep slopes but the margin of safety reduces rapidly under elevated pore pressure conditions. As was observed in the field, the analyses suggested the most vulnerable zone was the upper layer of weathered rock but that slides could occur in the peat if its thickness was appreciable. Careful site characterization is vital in such studies. Here efforts have been made to understand the effect of fibres on the peat strength and some sensitivity analyes have been performed to assess the critical engineering parameters of the peat.

Two separate sets of reed bed systems were operated in parallel for the purpose to study a comparative behaviour of high strength animal wastewater treatment. Each system consisted of five-stage gravel-based reed beds. The only difference between the two systems lies in the gravel arrangement within the beds. One system employed single sized gravel as bed medium (termed as mono-sized bed) while the other used two layers of gravel with coarse grain as the upper layer (termed as anti-sized bed). It was demonstrated that both the systems have the strong capacity for animal wastewater treatment but no significant difference with regard to pollutants‟ removal efficiency. However, anti-sized system showed a clear advantage in its ability to retard the clogging phenomenon exhibited during the system operation and avoid the impairment of its long-term functioning and sustainability. Clogging development was monitored via daily record of evolution of water level after the reed bed fill-up step in tidal flow operation strategy. According to present study, anti-sized reed bed experienced more than 2-fold operating period without clogging as compared with mono-sized reed bed in their parallel operation. In addition, a conceptual model to predict the clogging time was attempted and its utility was demonstrated via the data of this study.

A comprehensive review of the current water pollution status in China has indicated that the urban lakes in Chinese cities have suffered from serious pollution and in high risk of eutrophication although the pollution sources have been largely controlled. The objective of this study lies in exploring a long term restoration of the aquatic ecosystem in Chinese city lakes using treatment wetland, an environmentally friendly and cost-effective technology. Trials from a subsurface horizontal flow constructed wetland (CW) have demonstrated that the treatment wetland can be used for such kind of purpose of lake water quality control. Average removal of 84.2% for COD, 53.8% for NH3-N, 47.9% for TN, 73.3% for TP and 86.6% for SS can be achieved. Relatively, low removal of nitrogen lies in the lack of nitrification and denitrification process. Accordingly, improved configuration of the treatment wetland system has been proposed and discussed. Finally, the importance of the integrated constructed wetland especially for the application of urban lake water treatment is highlighted.

The determination of characteristic bridge load effect is a complex problem. Usually, statistical extrapolation of simulated static load effects is used to derive a lifetime characteristic static load effect. However, when a vehicle crosses a bridge, dynamic interaction occurs which often causes a greater total load effect. This total load effect is related to the static load effect through a dynamic amplification factor (DAF). Specifications often recommend a conservative level for DAF, based on bridge length, number of lanes, and type of load effect only. Therefore significant improvements in the accuracy of this calculation are possible if a DAF, specific to the considered bridge, is applied. In this paper, the authors develop a novel method that considers site-specific bridge and traffic load conditions and allows for the reduced probability of both high static loading and high dynamic interaction occurring simultaneously. This approach utilises multivariate extreme value theory, in conjunction with static simulations and finite element vehicle-bridge dynamic interaction models. It is found that the dynamic allowance for the sample bridge and traffic considered, is significantly less than recommended by bridge codes. This finding can have significant implications for the assessment of existing bridge stock.

A Discrete Particle Scheme (DPS) consisting of interacting circular particles is utilised to examine the Multichannel Analysis of Surface Waves (MASW) technique. Synthetic earth models of various complexity are generated using the DPS and analysed by the MASW dispersion and inversion techniques. For normally dispersive cases, dominated by the fundamental mode, the MASW profiles closely match the true synthetic shear wave velocity (Vs) profiles. When tested on a model that contains a low velocity layer, the accuracy is reduced. MASW field tests at a highly uniform site in Norway (Onsøy) and a site with distinctive layer boundaries in Ireland (Ballinasloe) result in highly repeatable profiles of Vs. Resolution of dispersion curves at low frequencies (<10Hz) is a problem at the Ballinasloe test site, which limits the depth of penetration of the technique. MASW inversion results compare excellently with downhole seismic cone tests at the Onsøy test site and reasonably with a seismic refraction survey at the Ballinasloe site.

This paper describes the results of static compression and tension load tests performed on three-instrumented large diameter Continuous Flight Auger piles installed in Dublin boulder clay. The piles developed very high shaft resistance and, in contrast to piles driven into boulder clay which exhibit friction fatigue, the shaft distribution was uniform along the pile shaft. This resulted in the normalised average shear resistance being mobilised by a bored pile exceeding that of a pile driven in similar ground conditions. In contrast the base resistance of the test piles were significantly lower than a pile driven in similar ground conditions.

It is a common perception that biodiversity exists mainly in rural locations and this perception may be supported by the predominance of designated sites (e.g. Special Areas of Conservation, Special Protection Areas and Natural Heritage Areas) in rural areas. Given that approximately 40 per cent of the Irish population lives in rural areas the designated sites are indeed very important and their designation allows them particular protection. However, as Ireland’s population becomes increasingly urbanised, the role and management of urban biodiversity is becoming more important not only due to the encroachment of urban areas into previously undeveloped lands (i.e. urban sprawl) but also the recent trend towards increasing residential densities. These have heightened the role for proper recognition, protection and management of biodiversity in urban areas.

Increasingly, industrial operations adjoin residential communities. As the demand for natural resources increases, this problem is only more likely to exacerbate in coming decades. Thus, it is imperative to fully understand all potential damage mechanisms that may imperil nearby structures. This paper presents a case history that introduces a potential new mechanism, namely the unintentional triggering of liquefaction due to industrial blasting. The site in question is an early twentieth century town in the southeastern United States located adjacent to a granite quarry. Despite diligent control of blasting levels, there is a clear pattern of repeated damage radiating from the quarry area. This paper presents evidence collected to date that the damage mechanism is blasting-induced partial, repetitive liquefaction.

Building reuse is a linchpin to managing solid waste. Despite the various benefits beyond contributing to sustainability that can be realized through building reuse, including direct and indirect cost savings, truncated construction schedules, and reduced site disruptions, little formal consideration has been given to this topic, which places professional engineers at a disadvantage, when considering this as a design option. As each building project has its own specific requirements, reuse is not always the most economical solution, however, in cases where reuse is in part motivated by other factors such as heritage protection, substantial economic and environmental savings can be realized in tandem. Based on nearly two decades of professional experience, a generalized assessment method for reuse is proposed to facilitate benefit maximization. Applying this 10 step method, the costs related to building replacement and sustainable reuse are compared using two case histories and a theoretical building resulting. A clear correlation is shown as to the potential for savings as a function of project size.

Laboratory testing for foundation design offers advantages over field-testing, especially, where existing installations preclude easy accessibility. Advantages include a homogeneous soil, ability to place instrumentation throughout the soil mass, and capacity to bring the system to failure, as well as control over the failure mechanism. Repeatability is also achievable. Laboratory work, however, has its own challenges. For model-scale work, a main impediment is scaling: strength, dimensions, and boundary conditions hinder accurate modeling of the soil and brings a difficulty in representing scaled foundations. This paper describes the construction-oriented solutions pioneered for meeting the geometric requirements of ⅛th scaled laboratory testing of composite deep foundations for existing foundation enhancement, including drilled shafts, helical piers, and grouting. Results of the testing program are included as verification of the usefulness of the techniques.

A database of research quality CPTU and shear wave velocity information for Norwegian marine clays has been assembled so as to study the small strain stiffness relationships for these materials and to examine the potential use of CPTU and Vs data in combination for the purposes of characterising these soils. Data for sites where high quality block sampling was carried out have mostly been used. Improvements have been suggested to existing correlations between Gmax or Vs and index properties for these soils. Recent research has shown that CPTU qt and especially u2 and Vs can be measured reliably and repeatably and are not operator or equipment dependant. Therefore a new soil classification chart involving Qt and normalised shear wave velocity (Vs1) or Vs1 and Δu/σv0' is presented. Using this chart it is possible to clearly distinguish between clays of different OCR.

The adsorption characteristics of phosphate adsorption on the dewatered alum sludge were identified as a function of pH and ion strengths in solution. In addition, adsorption mechanisms were investigated by conducting batch tests on both the hydrolysis and P-adsorption process of the alum sludge, and making a comparative analysis to gain newer insights into understanding the adsorption process. Results show that the adsorption capacity decreased from 3.5 to 0.7 mg-P/g-sludge when the solution pH was increased from 4.3 to 9.0, indicating that adsorption capacity is largely dependent upon the pH of the system. The results of the competitive adsorption between phosphate and typical anions found in wastewater, such as SO42- and Cl-, onto alum sludge reveal that alum sludge can selectively adsorb phosphate ions. The insignificant effect of SO42- and Cl- on P-adsorption capacity indicates that phosphate adsorption is through a kind of inner-sphere complex reaction. During the adsorption process, the decrease of phosphate concentration in solution accompanied with an increase in pH values and concentrations of SO42-, Cl- and TOC (total organic carbon) suggests that phosphate replaced the functional groups from the surface of alum sludge which infers that ligand exchange is the dominating mechanism for phosphate removal. At the same time, the simultaneous decreases in PO43- and total aluminium concentration in solution indicate that chemical reaction and precipitation are other mechanisms of phosphate removal.

Aluminium-based water treatment residual (Al-WTR) is the most widely generated residual from water treatment facilities worldwide. It is regarded as a by-product of no reuse potential and landfilled. This study assessed Al-WTR as a potential phosphate-removing substrate in engineered wetlands for wastewater treatment. Results indicate the specific surface area ranged from 28.0 m2 g-1 to 41.4 m2 g-1 and this increased with increasing particle size. X-ray Diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and energy-dispersive X-ray spectroscopy all indicate that the Al-WTR is mainly composed of amorphous aluminium which influences its phosphorus (P) adsorption capacity. The pH and electrical conductivity ranged from 5.9 - 6.0 and 0.104 dS m-1 - 0.140 dS m-1 respectively, and both showed that it should suitably support plant growth. Batch tests showed a maximum P adsorption capacity of 31.9 mg-P g-1 and significant P removal was achieved in column tests. Overall, results showed that Al-WTR can be a low-cost, easily and locally available substrate for enhanced P removal in engineered wetlands and it carries the benefits of reuse of a by-product that promotes sustainability.

In this study, alum sludge was introduced into co-conditioning and dewatering with an anaerobic digested activated sludge to examine the role of the alum sludge in improving the dewaterbility of the mixed sludge and also in immobilizing phosphorus in the reject water. Experiments have demonstrated that the optimal mix ratio for the two sludges is 2:1 (anaerobic digested sludge: alum sludge; volume basis), and this can bring about 99% phosphorus reduction in the reject water through the adsorption of phosphorus by Al in the sludge. The phosphorus loading in wastewater treatment plants is itself derived from the recycling of reject water during the wastewater treatment process. Consequently, this co-conditioning and dewatering strategy can achieve a significant reduction in phosphorus loading in wastewater treatment plants. In addition, the use of the alum sludge can beneficially enhance the dewaterbility of the resultant mixed sludge by decreasing both the SRF and the CST, due to the alum sludge acting as a skeleton builder. Experiments have also demonstrated that the optimal polymer (Superfloc C2260) dose for the anaerobic digested sludge was 120 mg/l while the optimal dose for the mixed sludge (mix ratio 2:1) was 15 mg/l, highlighting a huge saving in polymer addition. Therefore, from the technical perspective, the co-conditioning and dewatering strategy can be viewed as a “win-win” situation. However, for its full-scale application, integrated cost-effective analysis of process capabilities, sludge transport, increased cake disposal, additional administration, polymer saving etc. should be factored in.

A comparative study of the NGI Direct Simple Shear Test (DSST) and the Mikasa Direct Shear Test (DST) is reported. Samples from Norwegian Drammen clay and Japanese Ariake clay were subjected to both types of test. An evaluation of these test results and a theoretical consideration on the different shearing mechanisms has shown that although the DST give generally higher stiffness and strength than the DSST, these differences can mainly be accounted for by the different shearing mechanisms and shearing rates. Sample disturbance due to transportation and handling may also be the reason for some of the difference. Tests on undisturbed and remoulded Drammen clay consolidated to stresses much higher than the in situ effective overburden stress give almost identical results. Thus the effects of sample disturbance and in situ structure in the clay were eradicated.

Due to increasing time, cost and transportation difficulties, Irish contractors are seeking an alternative to conventional static pile load tests. As a result several firms have adopted dynamic testing techniques to supplement and in some cases to replace conventional static tests. In order to assess the reliability of the systems and to address the concerns of owners and consulting engineers, a database comprising 43 pairs of static and dynamic tests on piles from 24 sites around Ireland has been assembled. The database was limited to medium to large diameter continuous flight auger (CFA) piles, typically 450 mm to 600 mm in diameter. Comparisons between actual measured settlement in static tests and predicted settlement for dynamic tests showed a clear pattern of underestimation of settlement by the dynamic tests, with the ratio between the two values typically varying between 0.4 and 1.2, with an average of about 0.8. This is due to the limited energy being imparted to the pile in the dynamic test. The results were best for piles in rock and worst for piles in clay. Scatter in the results increased with increasing pile load. However as all of the measured settlements were modest, the absolute numerical difference between the actual and predicted values was typically less than 3 mm, which may not be significant in many practical cases. For piles supporting non - sensitive structures, in areas where the ground conditions are well know, and provided the ratio the drop weight to the pile weight and to the pile SWL is at least 50% and 1.5% respectively, it seems possible that static tests can be replaced by dynamic ones. However for structures sensitive to settlement or for those in areas where ground conditions are uncertain, then it is suggested that the dynamic test should be calibrated by at least one static test.

Questions about the economic and environmental sustainability of current waste management scenarios in Europe for various organic wastes, the policy drive at the EU, and the subsequent adoption of EU policy at national levels, has given momentum for diversion of organic wastes away from landfills and ultimately on to the land. The land has always been the receptor of choice for animal manures, but it is now becoming a popular management route for other organic wastes. Currently in Ireland, land is examined by specific sectors and regarded as a resource available uniquely to each sector. In contrast, it is reasoned in this paper that treating the diverse organic wastes potentially suited for land application as a unit waste stream and developing a detailed accounting of waste quantities and characteristics would serve as a gateway towards a consistent and holistic strategy from which a comprehensive land application strategy at national level or regional level could be developed. The methodology used is a desk-based inventory that relied on existing secondary data in published reports. A literature based survey and quantification of organic wastes potentially suited for land application, in Ireland, was completed. The survey included a broad range of organic wastes from agricultural and non-agricultural activities - with animal manure, spent mushroom compost, biodegradable municipal waste, biosolids, sludge from onsite treatment plants, organic wastes from industrial sources the major ones. Reports from the Central Statistical Office of Ireland, study reports at the Environmental Protection Agency, Regional Waste Management Plans, Sludge Management Plans, County Waste Registries and European sources were consulted in association with codes and guidelines to determine the quantity and composition of organic wastes potentially suited for land application. Major and minor plant nutrients were used as a basis to describe the composition of the organic wastes. Finally a GIS-based database of the organic wastes potentially suited for land application was developed and a distributional analysis was performed at different spatial scales. Results of our analysis confirm that animal waste remains the largest source of organic waste in Ireland - as in most other European countries - and the major concern for management through land application due to the sheer volume of the waste. Between the small percentage of organic wastes of non-animal origin biosolids, sludge from industrial sources, biodegradable municipal wastes and spent mushroom compost constitute the major share. There is a spatial distribution of the organic wastes in terms of both the total quantity of organic waste and type of the organic wastes. While the volume of the non-agricultural wastes appears to be insignificant – compared to organic waste of animal origin – at a National level it constitutes a high local problem at lesser spatial scales, i.e. counties and regions. The research suggests that there is a need to a leap from the present, sector-specific approach used in managing the land application of waste to a comprehensive land application strategy that considers the total quantity and quality of waste relative to the land base suitable for receiving them.