Urban Institute Ireland

Design and development of a low-cost thermal response rig

Wed, 01 Aug 2012 00:00:00 GMT

Design and development of a low-cost thermal response rig Hemmingway, Phil; Long, Michael (Michael M.) A thermal response test (TRT) is a controlled insitu test during which a known quantity of heat energy is injected into a closed loop heat-exchanger pipe while the heat dissipation rate into the surrounding ground is monitored. Results from a test can be interpreted to determine a number of ground thermal parameters with are vital design requirements for any medium to large scale ground source energy system. This paper describes the design and construction of a low cost TRT rig and compares the results obtained from a test using the constructed rig and a commercially built rig in order to evaluate the accuracy of the constructed equipment. The TRT rig is designed in accordance with the following principles: keep construction costs low, improve the cost-efficiency of TRT testing by incorporating remote data transmission capability and ensure attainment of sufficient accuracy to satisfy the design requirements of ground source energy systems. Analysis of data collected by the TRT rigs result in a calculated thermal conductivity of 1.9 W/mK in both cases. This value falls within the range expected for the tested geological formation and confirms the accuracy of both test rigs.

Geothermal energy : settlement and water chemistry in Cork, Ireland

Fri, 01 Jul 2011 00:00:00 GMT

Geothermal energy : settlement and water chemistry in Cork, Ireland Hemmingway, Phil; Long, Michael (Michael M.) Detailed analysis of potential water chemistry and settlement issues associated with the installation of open-loop geothermal systems is infrequently carried out. This has led to the failure of several previously installed systems. Chemical analysis of water extracted from beneath the Cork docklands, Ireland has been performed by the authors in order to assess the suitability of the area for the exploitation of open-loop geothermal energy. The possibility of settlement induced by pumping of groundwater for open-loop systems has also been examined. Current market penetration of ground source heat pumps in Ireland is discussed to illustrate the infancy of the technology in Ireland relative to other European countries and to highlight the necessity of approaching the possible installation of such systems with the care required. Water extracted from beneath the docklands shows that significant water chemistry issues exist. Laboratory and field tests confirm that optimal concentration levels of several water chemistry characteristics are significantly exceeded; leading to the conclusion that open-loop exploitation in the area may not be suitable. In addition, settlement induced by pumping of water could potentially lead to a consolidation settlement in excess of 30 mm due primarily to the existence of highly compressible alluvium.

Geothermal energy in small countries - laying the foundations for innovative development

Sun, 04 Sep 2011 00:00:00 GMT

Geothermal energy in small countries - laying the foundations for innovative development Hemmingway, Phil; Long, Michael (Michael M.) Creation of an environment in which shallow geothermal energy can thrive will require a coherent approach and a high level of collaboration with professionals from countries that have developed technical expertise in the area. Implementation of regulations, standards and guidelines adapted from best practice in countries such as Switzerland, Germany and Sweden, in addition to understanding the mistakes and successes made by these countries, with respect to the development of their geothermal industries, will help small countries such as Ireland to develop a well-regulated market for the technology. This paper outlines and addresses some of the technical, regulatory and certification issues faced particularly by small countries in their efforts to develop a shallow geothermal energy industry, provides examples of best practice with regard to development in countries with established geothermal energy industries and presents proposed solutions to these issues / barriers using the existing situation in Ireland by way of example. Fourth World Engineers Convention: Engineers Power the World – Facing the Global Energy Challenge, Geneva, Switzerland, 4-9 September 2011

Developing Geothermal Energy Research Capabilities at University College Dublin

Sat, 01 Jan 2011 00:00:00 GMT

Developing Geothermal Energy Research Capabilities at University College Dublin Hemmingway, Phil; Long, Michael (Michael M.) Ireland has one of the highest energy dependencies in Europe and as such must adapt quickly to increase renewable energy exploitation levels in order to secure its energy future. A mix of renewable energy technology types (wind, solar, biomass, wave, tidal, geothermal) will be required in order to achieve Ireland’s national renewable energy generation targets. Geothermal (or ground source) energy can have a part to play in this mix. Over the last number of years the School of Civil, Structural & Environmental Engineering in University College Dublin has begun to develop shallow geothermal energy research capabilities in several areas of interest. Early studies involved the investigation of water chemistry and settlement issues at several sites on the Cork docklands. It was concluded that the chemical characteristics of the water contained in the aquifer could hinder the development of open loop geothermal systems in the area, and that settlement may be a potential concern in cases where open loop systems are installed due to the presence of highly compressible alluvium deposits. Subsequent work has involved the development, construction & performance validation of a thermal response testing rig for site thermal characterisation, installation of both domestic and commercial sized energy piles for research purposes and investigation of soil, rock and grout thermal properties using both steady-state and non-steady-state laboratory testing techniques. This paper gives a brief overview of the completed and ongoing work in the School of Civil, Structural & Environmental Engineering. Geothermal Energy - Progress and Developments in Ireland and Internationally, May 2011, Kilkenny, Ireland

Energy Foundations - Potential for Ireland

Tue, 01 Mar 2011 00:00:00 GMT

Energy Foundations - Potential for Ireland Hemmingway, Phil; Long, Michael (Michael M.) With one of the highest energy dependencies in the European Union, Ireland must adapt quickly to renewable energy technologies or risk paying the penalty in the form of high energy prices in years to come. Escalating energy costs have led to a renewed interest in alternative energy technologies and ground source energy is one such resource which is being increasingly considered. This paper presents some of the practical considerations of energy foundations, evidenced from the installation of a number of test energy piles. In addition, a preliminary feasibility study of an energy foundation system for a planned university administrative building and an overview of the current status of ground source energy technology in Ireland are presented. Building heating and cooling loads are estimated based on high building energy standards which the university hopes to implement in all building projects going forward. The proposed energy foundation system is shown to have the capacity to provide the heating and cooling base loads for the building Geo-Frontiers 2011, Dallas, Texas, March 13-16, 2011

Co-conditioning of the anaerobic digested sludge of a municipal wastewater treatment plant with alum sludge : benefit of phosphorus reduction in reject water

Sat, 01 Dec 2007 00:00:00 GMT

Co-conditioning of the anaerobic digested sludge of a municipal wastewater treatment plant with alum sludge : benefit of phosphorus reduction in reject water Yang, Y.; Zhao, Y.Q.; Babatunde, A.O.; Kearney, P. 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.

On the role of gypsum (CaSO_4.2H_2O) in conditioning and dewatering of a waterworks sludge

Thu, 01 Jan 2004 00:00:00 GMT

On the role of gypsum (CaSO_4.2H_2O) in conditioning and dewatering of a waterworks sludge Zhao, Y.Q.; Allen, Stephen; Sun, Guangzhi Problems concerning the management and utilization of sludge derived from water treatment processes are still not fully solved. A common approach is direct discharge to a landfill site. This study provides experimental data to demonstrate the effectiveness of a combination of gypsum (CaSO4x2H2O) and an organic polymer in alum sludge conditioning and dewatering. Experimental results demonstrated that the filterability of dually conditioned alum sludge was significantly improved by the addition of gypsum at a 1:1 ratio (WT/WT) to original sludge solids. Dewatering tests showed that a further decrease of almost seven percentage of sludge cake equilibrium moisture content was achieved by the involvement of gypsum compared to the situation of single polymer conditioning. The importance of this study lies in the possible application of dewatered alum sludge to land use or as a filter medium in constructed wetland for wastewater treatment, providing a positive solution to the problem of alum sludge disposal.

Optimising the performance of a lab-scale tidal flow reed bed system treating agricultural wastewater

Thu, 01 Jan 2004 00:00:00 GMT

Optimising the performance of a lab-scale tidal flow reed bed system treating agricultural wastewater Zhao, Y.Q.; Sun, Guangzhi; Lafferty, C.; Allen, Stephen A gravel-based tidal flow reed bed system was operated with three different strategies in order to investigate its optimal performance for the treatment of high strength agricultural wastewaters. According to the three strategies, individual reed beds of the system were saturated and unsaturated with the wastewaters for different periods while steady hydraulic and organic loadings were maintained. Experiment results demonstrated that the system produced highest pollutant removal efficiencies with relatively short saturated period and long unsaturated period, highlighting the importance of O2 transfer into reed bed matrices during the treatment of high strength wastewaters. Significant removals of some major organic and inorganic pollutants were achieved with all the three operation strategies. Nitrification was not the major route of NH4-N removal when the system was under high organic loading. Due to the filtration of suspended solids and accumulation of biomass, gradual clogging of the reed bed matrices took place. The clogging caused concerns over the long-term efficiency of the current tidal flow reed bed system.

From "fills" to filter : insights into the reuse of dewatered alum sludge as a filter media in a constructed wetland

Sun, 01 Jul 2007 00:00:00 GMT

From "fills" to filter : insights into the reuse of dewatered alum sludge as a filter media in a constructed wetland Babatunde, A.O.; Zhao, Y.Q.; Yang, Y.; Kearney, P. Dewatered alum sludge, a by-product of drinking water treatment plants, hitherto consigned to landfills was used to develop a novel bio-filter in form of a constructed wetland. Performance results have demonstrated the benefits of the alum sludge cakes in a lab-scale system in enhancing phosphorus (P) removal from an animal farm wastewater. Although P and organic matter were concurrently removed in the system, there was a probable “one off” release of organics from the system, and this coincided with an increase in inlet P concentration from 39.2 mg-P/l to 163.0 mg-P/l. A conceptual model was then proposed to explain and discuss this.

Dewatered alum sludge : a potential adsorbent for phosphorus removal

Thu, 01 Jun 2006 00:00:00 GMT

Dewatered alum sludge : a potential adsorbent for phosphorus removal Yang, Y.; Tomlinson, D.; Kennedy, S.; Zhao, Y.Q. Alum sludge refers to the by-product from the processing of drinking water in Water Treatment Works. In this study, groups of batch experiments were designed to identify the characteristics of dewatered alum sludge for phosphorus adsorption. Air-dried alum sludge (moisture content 10.2%), which was collected from a Water Treatment Works in Dublin, was subjected for artificial P-rich wastewater adsorption tests using KH2PO4 as a model P source. Adsorption behaviours were investigated as a function of amount and particle size of alum sludge; pH of solution; and adsorption time. The results have shown that pH plays a major role not only in the adsorption process but also in the adsorption capacity. With regard to adsorption capacity, this study reveals the Langmuir adsorption isotherm being the best fit with experimental data (R2=0.98-0.99). The maximum adsorption capacities range from 0.7 to 3.5mg-P/g when the pH of the synthetic P solution was varied from 9.0 to 4.3, accordingly. The outcome of this study indicated that alum sludge is suitable for use as an adsorbent for removal of phosphate from wastewater.

Phosphorus removal in laboratory-scale unvegetated vertical subsurface flow constructed wetland systems using alum sludge as main substrate

Wed, 01 Jul 2009 00:00:00 GMT

Phosphorus removal in laboratory-scale unvegetated vertical subsurface flow constructed wetland systems using alum sludge as main substrate Babatunde, A.O.; Zhao, Y.Q. This research has two eventual goals: (1) To optimize performance of subsurface constructed wetlands for removal of phosphorus (P) (2) To demonstrate that dewatered alum sludge (a by-product), can be reused as a constructed wetland substrate. To achieve these, alum sludge from a water treatment plant was characterized and used as main substrate in four experimental vertical sub-surface flow constructed wetland systems treating dairy farm wastewater. Results show that the alum sludge has suitable hydraulic characteristics (uniformity coefficient = 3.6) for use as a substrate, and in the batch studies, up to 48.6mg-P was removed by 1g of the alum sludge at a P concentration of 360mg-P/l and a dosage of 5g/l. Results from the experimental systems highlight the significant P removal ability of the alum sludge. However, the inclusion of pea gravel at the infiltrative surface of some of the systems had a negative effect on the P removal performance. Sequential P-fractionation results show that there was no significant increase in the easily extractable P, but for total P, there was significant increase, although this was found to decrease with depth. This study shows that the novel use of dewatered alum sludge can bring about high P removal in vertical subsurface flow constructed wetland systems.

On the necessity of sludge conditioning with non-organic polymer : AOP approach

Wed, 01 Jul 2009 00:00:00 GMT

On the necessity of sludge conditioning with non-organic polymer : AOP approach Zhao, Y.Q.; Keogh, C.; Tony, Maha A. Organic polymers have long been used as sludge conditioners to improve its dewaterability in sludge management practice. Although polymers can bring about a great dewatering performance of the sludge, their potential health related risk remains unknown regarding their residual in dewatered sludge cakes in the environment when the sludge is finally disposed as landfill especially in long term point of view. For this regard, as an initiative action, Fenton (Fe2+/H2O2) and its related reagents were tested in this study as potential alternative an alum sludge conditioners for the purpose of eliminating the perceived long term risk associated with polymer residual in the environment.

Some experience in measuring pore water suction in Dublin glacial till

Wed, 01 Sep 2004 00:00:00 GMT

Some experience in measuring pore water suction in Dublin glacial till Long, Michael (Michael M.); Menkiti, Christopher O.; Follet, Ben Several recent articles and discussions in GIN, by Penman (2002), Thomann et al. (2003), Ridley (2003) and Sellers et al. (2003) highlight the importance of pore water pressure and suctions and in particular the difficulties associated with measuring suction. This article outlines some recent experience in measuring suctions, which were developed in cut slopes in a very stiff glacial till during the Dublin Port Tunnel (DPT) project in Ireland. A particular feature of the project was the execution of a fully instrumented 12m deep trial excavation (Menkiti et al., 2004). Initially some background to the project and to the problem will be given. Then some details of the specification, installation technique and some examples of the measurements obtained will be outlined. Finally some conclusions will be made on the lessons learned and recommendations will be made for future similar applications.

An investigation of two peat slope failures in the Wicklow mountains

Wed, 01 Dec 2010 00:00:00 GMT

An investigation of two peat slope failures in the Wicklow mountains Boylan, Noel; Long, Michael (Michael M.) Although peat slope failures have occurred in Ireland for many thousands of years their causal factors and the triggering mechanisms involved are poorly understood. A particular barrier to quantitative assessment of the risk of failures is the lack of knowledge of the geotechnical properties of peat and its role in failures. In order to advance the understanding of these issues case history data is invaluable. This paper describes a case study from the Wicklow mountains where a desk and remote sensing based study was used to identify peat slope failures. Subsequently detailed field studies were carried out at two failure locations. It was found that although the full causal factors at the time of failure are unknown, a common factor was that the failure took place in a zone of highly decomposed and relatively low fibre content peat. A revision of the standard test method for fibre content for use in peat soils is proposed.

Two strategies for phosphorus removal from reject water of municipal wastewater treatment plant using alum sludge

Tue, 01 Dec 2009 00:00:00 GMT

Two strategies for phosphorus removal from reject water of municipal wastewater treatment plant using alum sludge Yang, Y.; Zhao, Y.Q.; Babatunde, A.O.; Kearney, P. In view of the well recognized need of reject water treatment in MWWTP (municipal wastewater treatment plant), this paper outlines two strategies for P removal from reject water using alum sludge, which is produced as by-product in drinking water treatment plant when aluminium sulphate is used for flocculating raw waters. One strategy is the use of the alum sludge in liquid form for co-conditioning and dewatering with the anaerobically digested activated sludge in MWWTP. The other strategy involves the use of the dewatered alum sludge cakes in a fixed bed for P immobilization from the reject water that refers to the mixture of the supernatant of the sludge thickening process and the supernatant of the anaerobically digested sludge. Experimental trials have demonstrated that the alum sludge can efficiently reduce P level in reject water. The co-conditioning strategy could reduce P from 597-675 mg P/L to 0.14-3.20 mg P/L in the supernatant of the sewage sludge while the organic polymer dosage for the conditioning of the mixed sludges would also be significantly reduced. The second strategy of reject water filtration with alum sludge bed has shown a good performance of P reduction. The alum sludge has P-adsorption capacity of 31 mg-P/g-sludge, which was tested under filtration velocity of 1.0 m/h. The two strategies highlight the beneficial utilization of alum sludge in wastewater treatment process in MWWTP, thus converting the alum sludge as a useful material, rather than a waste for landfill.

A comparative study between the NGI direct simple shear apparatus and the Mikasa direct shear apparatus

Thu, 01 Feb 2007 00:00:00 GMT

A comparative study between the NGI direct simple shear apparatus and the Mikasa direct shear apparatus Hanzawa, Hideo; Nutt, Nigel; Lunne, Tom; Tang, Y.X.; Long, Michael (Michael M.) 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.

A novel alum-sludge based constructed wetland system to reduce pollution effects of agricultural runoff : first results

Mon, 01 Jan 2007 00:00:00 GMT

A novel alum-sludge based constructed wetland system to reduce pollution effects of agricultural runoff : first results Babatunde, A.O.; Zhao, Y.Q. This paper is a research brief highlighting the development of a novel alum sludge based constructed wetland system, aimed at reducing the pollution effects of agricultural run-offs. Alum sludge is a by-product of drinking water treatment plants where aluminium sulphate is used as coagulant. The alum sludge cakes were used as the main support matrix in the constructed wetland system, having been shown to have a greater capacity to retain contaminants, especially phosphorus, through sorption phenomena, ionic exchange and other physico-chemical processes. The dewatered alum sludge cakes proved beneficial in enhancing and sustaining phosphorus removal in the system, while the removal of organics is thought to be enhanced by the tidal flow mechanism employed. Overall removal of 82.3 + 3.5% (BOD5) and 85.5 + 2.1 % (COD) were achieved in the system

Assessment of an MASW technique incorporating discrete particle modelling

Sun, 01 Jun 2008 00:00:00 GMT

Assessment of an MASW technique incorporating discrete particle modelling Donohue, Shane; Long, Michael (Michael M.) 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.

Constructive approaches towards water treatment works sludge management : an international review of beneficial re-uses

Thu, 01 Mar 2007 00:00:00 GMT

Constructive approaches towards water treatment works sludge management : an international review of beneficial re-uses Babatunde, A.O.; Zhao, Y.Q. Till date, virtually all known drinking water processing systems generate an enormous amount of residual sludge, and what else to do with this rapidly increasing 'waste' stream in an economic and environmentally sustainable manner remains a significant environmental issue. Perhaps, the realization of this fact has led to series of concerted efforts aimed at beneficial re-uses in an effort to close the loop between efficient water treatment and sustainable sludge management. This paper therefore presents a comprehensive review of available literature on attempts at beneficial reuses of water treatment plant sludge, in an effort to provide a compendium of recent and past developments, and update our current state of knowledge. Four broad categories of uses, which included over eleven possible ways in which waterworks sludges can be reused were identified and examined. Obvious advantages of such reuse options were highlighted and knowledge gaps identified. Future issues that will assist in the development of sustainable waterworks sludge management options with a multi-prong approach were equally discussed.

Fluoride removal from drinking water by adsorption using bone char as a biosorbent

Tue, 01 Apr 2008 00:00:00 GMT

Fluoride removal from drinking water by adsorption using bone char as a biosorbent Ma, W.; Ya, F.; Wang, R.; Zhao, Y.Q. As a biomass material, bone char was investigated for the feasibility to be used as a cost-effective biosorbent for fluoride removal from drinking water in groundwater environment. Based on the batch tests with natural tourmalin and active alumina being the reference adsorbents, BF (referring to bone char) has demonstrated a higher fluoride adsorption capacity. This capacity was found being increased with the increase of fluoride concentration. Furthermore, BF based column adsorption experiments indicated that the fluoride removal could be significantly affected by flow rate and bed height. A mass transfer model developed in this study can be used to optimize the bed configuration and operation parameters. Experimental results and predicted data by the model have shown a good consistent. A full-scale BF fixed-bed to treat fluoride-containing groundwater in Northeast China has been successfully operated since 2002.

A hierarchy for land application of organic wastes : influence of urban stakeholders

Wed, 01 Sep 2010 00:00:00 GMT

A hierarchy for land application of organic wastes : influence of urban stakeholders Taffese Tanto, Mebrate; Magette, W. L. Paper presented at RAMIRAN 2010 14th Ramiran international conference : Treatment and Use of Organic Residues in Agriculture - Challenges and Opportunities towards Sustainable Management, Lisbon, 12-15 September 2010

A promising approach of reject water treatment using a tidal flow constructed wetland system employing alum sludge as main substrate

Wed, 01 Jun 2011 00:00:00 GMT

A promising approach of reject water treatment using a tidal flow constructed wetland system employing alum sludge as main substrate Yang, Y.; Zhao, Y.Q.; Wang, S.P.; Guo, X.C.; Ren, Y.X.; Wang, L.; Wang, X.C. This study examined a novel reuse of the alum sludge, an inescapable by-product of the production of drinking water when aluminium salt is added as a coagulant, as the main medium in a laboratory-scale multi-stage constructed wetland (CW) system for reject water treatment. Such reject water is a main concern in municipal wastewater treatment plant (MWWTP) for increasing the organic and nutrient loading. A “tidal flow” strategy was employed to enhance the wetland aeration to stimulate organic pollutants and N oxidation while the “step feed” operation was adopted to supply the necessary amount of carbon source for denitrification. The results reveal that alum sludge acted as P adsorbent can secure the P removal. Meanwhile, high removals of ammoniacal-nitrogen and organic matters can also be obtained due to the active bacteria attached growth on the alum sludge surface. The results show that average removal efficiencies of 65.4 ± 12.3% for COD, 67.8 ± 9.2% for BOD5, 33.6 ± 17.0% for N and 99.5 ± 0.49% for P can be achieved over a period of 190 days. This indicates that novel reuse of alum sludge as medium in CW system can provide a promising approach for reject water treatment. Therefore, it will significantly reduce the amount of pollutants feedback through reject water recycling in a MWWTP.

Purification capacity of a highly loaded laboratory scale tidal flow reed bed system with effluent recirculation

Wed, 01 Sep 2004 00:00:00 GMT

Purification capacity of a highly loaded laboratory scale tidal flow reed bed system with effluent recirculation Zhao, Y.Q.; Sun, Guangzhi; Allen, Stephen The purification capacity of a laboratory scale tidal flow reed bed system with final effluent recirculation at a ratio of 1:1 was investigated in this study. In particular, the four-stage reed bed system was heavily loaded with strong agricultural wastewater. Under the hydraulic and organic loading rates of 0.43 m3/m2.d and 1055 gCOD/m2.d, respectively, the average removal efficiencies obtained for COD, BOD5, SS, NH4-N and P were 77%, 78%, 66%, 62% and 38%, respectively. Even with the high loading rates, about 30% of NH4-N was converted into NO2-N and NO3-N from the mid-stage of the system where nitrification took place. The results suggest that the multi-stage reed bed system could be employed to treat strong wastewater under high loading, especially for the substantive mass removal of solids, organic matter and ammoniacal-nitrogen. Tidal flow combined with effluent recirculation is a favourable operation strategy to achieve this objective.

Removal of ammoniacal-nitrogen from an artificial landfill leachate in downflow reed beds

Fri, 29 Oct 2004 00:00:00 GMT

Removal of ammoniacal-nitrogen from an artificial landfill leachate in downflow reed beds Connolly, Roseanne; Zhao, Y.Q.; Sun, Guangzhi; Allen, Stephen The fate of ammoniacal-nitrogen (NH4-N) was studied in a lab-scale downflow reed bed system treating an artificial landfill leachate. Individual reed beds were submerged by the leachate, then drained and rinsed by tap water. It was discovered that NH4-N was removed by a two-staged process, adsorption onto the reed bed media followed by nitrification into nitrite-nitrogen (NO2-N) and nitrate-nitrogen (NO3-N). A drop of NH4-N level of the leachate was observed when the reed beds were submerged. By rinsing of the beds, part of the NH4-N adsorbed inside the bed matrices was re-released into the rinse water. The presence of NO2-N and NO3-N in the rinse water demonstrated that nitrification process took place while the NH4-N was being retained inside the bed matrices. For artificial leachates with NH4-N levels of 150±5 mg/l, an average removal rate of 43.8% in a three-hour treatment was achieved; mass balance analysis indicated that processes of adsorption, and transformation into NO2-N and NO3-N accounted for 63.7%, 4.3% and 24.4% of the NH4-N removal, respectively. This study also demonstrated that in general greater recirculation rate of effluent around the downflow reed beds gives higher NH4-N removal.

Kinetics of aqueous photocatalytic oxidation of fulvic acids in a photocatalysis-ultrafiltration reactor (PUR)

Thu, 01 Jun 2006 00:00:00 GMT

Kinetics of aqueous photocatalytic oxidation of fulvic acids in a photocatalysis-ultrafiltration reactor (PUR) Fu, J.F.; Ji, Min; Zhao, Y.Q.; Wang, Lizhang The photocatalysis of natural organic matter, fulvic acid (FA), by P25 TiO2 in terms of UV254 and TOC concentrations was investigated in this study. The experiments were conducted in a lab-scale photocatalysis-ultrafiltration reactor (PUR) with TiO2 suspension. Groups of experiments were designed to examine the effects of pH of bulk solution, TiO2 concentration and additives strength as well as light intensity on the degradation of FA. Results from this study revealed that the degradable behaviour of FA can be reasonably described by first-order kinetics. In addition, it was demonstrated that low pH value, increased additives concentration and relative high light intensity were all beneficial parameters for TOC removal. By inspecting the relationship between rate constant (k) and influencing factors, an overall FA oxidation rate kinetic model was established. The utility of the model was demonstrated by the agreement of predictive and experimental results.

Settling behaviour of polymer flocculated water-treatment sludge I : analyses of settling curves

Sun, 01 Feb 2004 00:00:00 GMT

Settling behaviour of polymer flocculated water-treatment sludge I : analyses of settling curves Zhao, Y.Q. Settling behaviour of polymer conditioned water-treatment sludge was investigated in this study for the purpose of a better understanding of a so-called “CML30 method”, which was developed in previous study to evaluate the optimum polymer dosage in sludge conditioning. The “CML30 method” is on the basis of a 30 min settling test in 100 ml measuring cylinders. In this study, the series of settling tests in 100, 500 and 1000 ml measuring cylinders were respectively performed and the settling curves (interfacial height to dose and time) were the main focuses for presentation and analyses in great detail in this paper. According to the experimental data presented in this study, settling behaviour may be controlled by both the growth of large sized floc and progressively decreased viscosity. The “speed-up” phenomenon in small polymer dose range obviously enhances the settlement and plays a critical role for the settling set in a 100 ml measuring cylinder at a special dose and at the settling time interval 5-30 min. It is such special observation that leads to the success of so-called ad hoc “CML30 method”. However, sludge settling behaviour could be controlled by the formation of networked structure which is involved in excess polymer during the large range (say over 10 mg/l for the case tested) of polymer doses. The higher liquid viscosity values derived from excess polymer will increase the drag force for the resistance of the settlement. In addition, wall effects are likely to interplay with the internal networked structure in large dosed region.

Settling behaviour of polymer flocculated water-treatment sludge II : effects of floc structure and floc packing

Mon, 01 Mar 2004 00:00:00 GMT

Settling behaviour of polymer flocculated water-treatment sludge II : effects of floc structure and floc packing Zhao, Y.Q. On the basis of experiments carried out using an image analysis system and static zone settlement, the alum sludge floc structure and the floc packing status with varied polymer dosages were examined in greater detail to reveal the link with the settling behaviour manifested in the “CML30 method”. The results of image analysis lead to the findings of the floc size with a pattern in initially great increase with low polymer dose and finally a plateau being reached at higher amount of polymer addition. Meanwhile, a polymer dosage in the range of 2.0 – 20.0 mg/l (for sludge SS = 4,595 mg/l) can result in the increase of the floc fractal dimension (DF) up to an average value of 1.72 (raw sludge DF being 1.06), indicating greater compactness of the floc solids. These floc features control the settling behaviour of the “CML30 method”, especially in small polymer dosages. However, in large polymer doses, the controlling factor is derived from the floc 'packing' status (referring to the inter – floc contact manner). This 'packing' status may associate with viscosity of settling medium (supernatant) and the excess polymer in bulk solution. All these affect the sludge floc networked structure in overdosing range.

An alternative arrangement of gravel media in tidal flow reed beds treating pig farm wastewater

Mon, 01 Jan 2007 00:00:00 GMT

An alternative arrangement of gravel media in tidal flow reed beds treating pig farm wastewater Sun, Guangzhi; Zhao, Y.Q.; Allen, Stephen 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.

Effectiveness of a drinking-water treatment sludge in removing different phosphorus species from aqueous solution

Sun, 01 Jul 2007 00:00:00 GMT

Effectiveness of a drinking-water treatment sludge in removing different phosphorus species from aqueous solution Razali, Melanie; Zhao, Y.Q.; Bruen, Michael Drinking-water treatment sludge (DWTS) produced at water treatment plants is an inescapable by-product and has long been treated as a waste for landfill. In this study, a series of batch adsorption tests were conducted using a wide range of phosphorus (P) species to determine the adsorption capacities of freshly dewatered aluminium salt based DWTS. The adsorption process is highly dependant on the pH of the suspension and is good at low pHs with adsorption capacities in the order of orthophosphate>polyphosphate>organic phosphate when these three P species were simulated according to their level in typical municipal wastewater. At pH 4.0, the adsorption capacity for orthophosphate was 10.2 mg-PO43-/g DWTS, polyphosphate was 7.4 mg-PO43-/g DWTS and organic phosphate was 4.8 mg-PO43-/g DWTS. Subsequently, a continuous flow column test with dewatered Al-based DWTS as filter medium was conducted at a hydraulic loading of 2.79 m3/m2.d and an extremely high P loading of 210.5 PO43-/m2.d. The sludge bed remained stable and removed over 80% P in a 30 day period and the bed did not reach saturation point for over 60 days. This proves the potential of the sludge as a filter material in various forms of P immobilization, thus converting it from a waste to a useful material in pollutant control.

Characteristics and mechanisms of phosphate adsorption on dewatered alum sludge

Fri, 01 Sep 2006 00:00:00 GMT

Characteristics and mechanisms of phosphate adsorption on dewatered alum sludge Yang, Y.; Zhao, Y.Q.; Babatunde, A.O.; Wang, L.; Ren, Y.X.; Han, Y. 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.

Reuse of aluminium-based water treatment sludge to immobilize a wide range of phosphorus contamination : equilibrium study with different isotherm models

Mon, 01 Oct 2007 00:00:00 GMT

Reuse of aluminium-based water treatment sludge to immobilize a wide range of phosphorus contamination : equilibrium study with different isotherm models Zhao, Y.Q.; Razali, Melanie; Babatunde, A.O.; Yang, Y.; Bruen, Michael The adsorption equilibrium of a wide range of phosphorus species by an aluminium-based water treatment sludge (Al-WTS) was examined in this study. Four kinds of adsorption-isotherm models, namely Langmuir, Freundlich, Temkin and Dubinin-Radushkevich, were used to fit the adsorption equilibrium data. In order to optimise the adsorption-isotherm model, correlation coefficient (R2) and four error functions were employed to facilitate the evaluation of fitting accuracy. Experiments have demonstrated that the Al-WTS may be an excellent raw material to adsorb P in polluted aqueous environment with adsorption ability in the order of KH2PO4 (ortho-P) > Na(PO3)6 (poly-P) > C10H14N5O7P·H2O (organic-P). More importantly, this study provides an entire comparison of the four isotherms in describing the P adsorption behaviour. By considering both the standard least-square based R2 and the results of four error functions analysis, this study reveals that the Freundlich isotherm appears to be the best model to fit the experimental equilibrium data. Langmuir and Temkin isotherms are also good models in current experimental conditions while Dubinin-Radushkevich isotherm poorly described the adsorption behaviour. The error analysis in this study provides vital evidence to reflect its role in facilitating the optimisation in adsorption isotherm study. Obviously, R2 seems inadequate in optimising multi-isotherm models due to its inherent bias resulting from the least-squares linearisation.

Optimising photoelectrocatalytic oxidation of fulvic acid using response surface methodology

Fri, 01 Jun 2007 00:00:00 GMT

Optimising photoelectrocatalytic oxidation of fulvic acid using response surface methodology Fu, J.F.; Zhao, Y.Q.; Wu, Qiuli In this paper, statistics-based experimental design with response surface methodology (RSM) was employed to investigate the effect of operation conditions on photoelectrocatalytic oxidation of fulvic acid (FA) using a Ti/TiO2 electrode in a photoreactor. Initially, the Box-Behnken design was employed including the three key variables (initial pH, potassium peroxodisulphate (K2S2O8) and bias potential). Thereafter, the mutual interaction and effects between these parameters and optimum conditions were obtained in greater detail by means of SAS and Matlab software. The results of this investigation reveal that: (1) the regression analysis with R2 value of 0.9754 shows a close fit between the experimental results and the model predictions; (2) three-dimension response surface plot can provide a good manner for visualizing the parameter interactions; and (3) the optimum pH, K2S2O8 and bias potential is found to be 3.8, 88.40mg/L, 0.88V respectively and the highest FA removal efficiency of 57.1% can be achieved.

Involvement of gypsum (CaSO4.2H2O) in water treatment sludge dewatering : a potential benefit in disposal and reuse

Sun, 01 Jan 2006 00:00:00 GMT

Involvement of gypsum (CaSO4.2H2O) in water treatment sludge dewatering : a potential benefit in disposal and reuse Zhao, Y.Q. This research assessed the use of gypsum (CaSO4.2H2O) as a skeleton builder for sludge dewatering since polymer conditioning of sludge affected only the rate of water release, not the extent of dewatering. The use of gypsum as a physical conditioner, in association with a polymer, could improve sludge filterability. More significantly, gypsum serves as a skeleton builder, forming a permeable and rigid lattice structure that can remain porous under high positive pressure during the compression step after the cake growth of the filtration, thereby maintaining the size of the micro-passages through which water is expressed. Experiments using a high pressure cell apparatus showed that a further decrease of two to seven percent of the equilibrium moisture content of the sludge cake was achieved, for sludge thicknesses for dewatering of 1 to 10 cm, by the addition of gypsum with 60% of the original sludge solids when compared to the single polymer conditioning. The importance of the addition of gypsum in alum sludge dewatering is not only the improvement in the extent of dewatering, but also the potential application of transforming dewatered alum sludge from ‘waste’ for landfill to useful ‘fertilizer’ or to be used as filter medium/adsorbent for wastewater treatment engineering.

Anti-sized reed bed system for animal wastewater treatment : a comparative study

Thu, 01 Jul 2004 00:00:00 GMT

Anti-sized reed bed system for animal wastewater treatment : a comparative study Zhao, Y.Q.; Sun, Guangzhi; Allen, Stephen 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.

Enhanced removal of organic matter and ammoniacal-nitrogen in a column experiment of tidal flow constructed wetland system

Wed, 26 Jan 2005 00:00:00 GMT

Enhanced removal of organic matter and ammoniacal-nitrogen in a column experiment of tidal flow constructed wetland system Sun, Guangzhi; Zhao, Y.Q.; Allen, Stephen This study investigated the efficiency of a four-stage tidal flow constructed wetland system for the removal of organic matter and ammoniacal-nitrogen from diluted piggery wastewater. The results demonstrated that the operation of tidal flow enhanced the transfer of oxygen into wetland matrices. The overall oxygen consumption rate in the tidal flow system (357 gO2/m2∙d) was considerably higher than the rate obtainable in conventional wetlands. Most oxygen consumption (99%) was due to the decomposition of organic matter. The total supply of oxygen into the wetlands (473 gO2/m2∙d) exceeded the demand for the treatment. The percentage removal of BOD5 and NH4-N was improved by effluent recirculation at a ratio of 1:1. Immobilization by microbial cells and adsorption were found to be the main routes for the removal of ammoniacal-nitrogen. Significant nitrification could not take place under the treatment condition of the experiment.

A study of dual polymer conditioning of aluminum-based drinking water treatment residual

Mon, 01 Jan 2007 00:00:00 GMT

A study of dual polymer conditioning of aluminum-based drinking water treatment residual Ma, W.; Zhao, Y.Q.; Kearney, P. Conditioning of an alum-based water treatment sludge by single and dual polymers was investigated in this study. Capillary suction time (CST), specific resistance to filtration (SRF) and settling rate of conditioned sludge were used to evaluate the sludge dewatering characteristics. Sludge dewaterability resulting from single and dual polymer conditioning were compared for the purpose of exploring the validity and effectiveness of dual polymer conditioning strategy. Unlike activated sludge derived from wastewater treatment, results from this study have demonstrated that conditioning of the alum sludge by the combined use of an cationic polymer (FO-4140) followed by an anionic polymer (LT-25) does not exhibit considerable advantage in further improvement of sludge dewaterability with comparison of single polymer conditioning. This study supports the view that for alum-based water treatment sludge, inter particle bridging seems to be the dominative mechanism and the charge neutralization plays a less important role in the conditioning process. In addition, an intrinsic relationship between CST and SRF was deducted and tested via the experimental data obtained from the study.

Alum sludge-based constructed wetland system for enhanced removal of P and OM from wastewater : concept, design and performance analysis

Sun, 01 Aug 2010 00:00:00 GMT

Alum sludge-based constructed wetland system for enhanced removal of P and OM from wastewater : concept, design and performance analysis Babatunde, A.O.; Zhao, Y.Q.; Zhao, X.H. 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.

Use of dewatered alum sludge as a substrate in reed bed treatment systems for wastewater treatment

Tue, 01 Jan 2008 00:00:00 GMT

Use of dewatered alum sludge as a substrate in reed bed treatment systems for wastewater treatment Zhao, Y.Q.; Babatunde, A.O.; Razali, Melanie; Harty, F. In this paper, two laboratory scale simulated reed beds were investigated for the purpose of assessing the feasibility and effectiveness of using dewatered alum sludge as a possible substrate for wastewater treatment reed bed systems. One horizontal subsurface flow set-up and one vertical flow set-up were used. The horizontal flow system was planted with Phragmites australis while the vertical flow system was left unplanted. Thus, the latter was more akin to a sand filter system, but was examined with the potential use as a planted vertical reed bed system. The influent source used was farmyard wastewater. It is expected that the present study will provide the basis for long-term and large-scale trials in realising the concept of integrating “waste” into treatment processes. Results obtained so far have shown that the dewatered alum sludge holds great promise as a low-cost resource media for use in reed bed treatment systems. Appreciable and stable performance was obtained during the continuous operation at high hydraulic, organic and phosphorus loadings. In particular, both wetlands achieved over 90% phosphorus removal, reflecting the significant advantage of this novel approach over conventional reed bed treatment systems. However, extensive research into possible surface clogging and possible release of some substances from the sludge to the treated effluent is necessary to ensure reliability of the system. This will help make the alum sludge based reed bed environmentally and economically justifiable.

Re-use of dewatered aluminium-coagulated water treatment residual to immobilize phosphorus : batch and column trials using a condensed phosphate

Sat, 01 Mar 2008 00:00:00 GMT

Re-use of dewatered aluminium-coagulated water treatment residual to immobilize phosphorus : batch and column trials using a condensed phosphate Babatunde, A.O.; Zhao, Y.Q.; Yang, Y.; Kearney, P. The aluminium content in dewatered aluminium-coagulated water treatment residual (DAC-WTR) can lead to a high phosphorus (P) removal capacity. Therefore, DAC-WTR has been used as adsorbent/soil amendment to remove P in several studies, focusing mostly on orthophosphates (ortho-P). This study is concerned with extending such reuse of DAC-WTR to remove P using a condensed phosphate as the model P source. Using a 48-hr equilibration time and a 1.18mm (mean particle size); (1) P removal was found to increase with increasing DAC-WTR dosage, but specific uptake of P per mass of DAC-WTR was decreased (2) A maximum adsorption capacity of 4.52mg-P/g of DAC-WTR was obtained at a pH of 4.0. In the continuous flow test, P removal efficiency decreased from 90 to 30% when loading was increased from 3.9 to 16.5g-P/m2.d. An average 45% removal efficiency was obtained after an intentional P loading surge. At the end of the continuous flow test, an operating removal capacity of 2.66 mg-P/g of DAC-WTR was determined which was 83.3% of the adsorption maxima obtained in the batch tests. There was no excessive loss of solids during the continuous flow test and aluminium content in the effluent remained below 0.1mg-Al3+/l. These results have demonstrated that dewatered DAC-WTR can further be used as a low-cost adsorbent media for condensed phosphate removal.

Constructed wetlands for environmental pollution control : a review of developments, research and practice in Ireland

Tue, 01 Jan 2008 00:00:00 GMT

Constructed wetlands for environmental pollution control : a review of developments, research and practice in Ireland Babatunde, A.O.; Zhao, Y.Q.; O'Neill, M.; O'Sullivan, B. For the purpose of synthesizing a compendium of efforts aimed at environmental pollution control through the use of constructed wetlands systems (CWs) in Ireland, a detailed review of CWs was undertaken. Emphasis was placed on the diverse range of development, practice and researches on CWs technology, placing them in the overall context of the need for low-cost and sustainable wastewater treatment systems. The potential use of CWs in protecting estuarine quality within the current legislative framework is considered, as well as the emerging concept of integrated constructed wetlands (ICWs). In addition, an assessment of the efficiency of CWs in operation in Ireland towards abating environmental pollution was done, and compared with CWs operating in other European countries. The need for sufficient and appropriate data to assist in further development of CWs and modelling studies, and instilling confidence in the public is also highlighted.

Geotechnical properties of Dublin boulder clay

Sat, 01 Sep 2007 00:00:00 GMT

Geotechnical properties of Dublin boulder clay Long, Michael (Michael M.); Menkiti, Christopher O. Geotechnical characteristics of Dublin Boulder Clay (DBC) based on detailed site investigation and site experience from some recent large projects in Dublin are presented. This paper attempts to synthesise available information in parallel with recent work by Skipper et al (2005), who provide an updated understanding of the geology of the DBC. Having assessed the effects of sampling disturbance, the paper characterises the various formations and sub-units of the DBC. The interpreted material behaviour is related to observed engineering performance. It was found from the behaviour of earth retained structures that intact, clayey, DBC formations are 2 to 3 times stiffer than assessed from high quality laboratory tests on block samples. DBC is shown to be significantly stiffer than other well-characterised tills. Relatively inexpensive Multi Channel Surface Wave techniques (MASW) can give very reliable estimates of in situ small strain stiffness. High undrained triaxial compression strengths were measured and it appears that simple UU tests on high quality specimens give good results. Significant strength anisotropy was suggested by undrained triaxial extension strengths that were only 30% to 50% of the triaxial compression strengths. Field horizontal permeability values of the intact clayey till units have a representative mean of about 10-9 m/s and when compared to laboratory values suggest that the material may exhibit some degree of anisotropy of permeability. Overall, the measured engineering parameters for the DBC are favourable for many construction projects. Further work is required in order to understand the in situ horizontal stress profile and the stiffness anisotropy of the till. KEYWORDS: Glacial soils, In situ testing, laboratory tests, site investigation, strength, stiffness.

Conditioning of aluminium-based water treatment sludge with Fenton’s reagent : effectiveness and optimising study to improve dewaterability

Sun, 01 Jun 2008 00:00:00 GMT

Conditioning of aluminium-based water treatment sludge with Fenton’s reagent : effectiveness and optimising study to improve dewaterability Tony, Maha A.; Zhao, Y.Q.; Fu, J.F.; Tayeb, Aghareed M. Alternative conditioning of aluminium-based drinking water treatment sludge using Fenton reagent (Fe2+/H2O2) was examined in this study. Focuses were placed on effectiveness and factors to affect such novel application of Fenton process. Experiments have demonstrated that considerable improvement of alum sludge dewaterability evaluated by capillary suction time (CST) can be obtained at the relative low concentrations of Fenton reagent. A Box-Behnken experimental design based on the response surface methodology was applied to evaluate the optimum of the influencing variables, i.e. iron concentration, hydrogen peroxide concentration and pH. The optimal values for Fe2+, H2O2, and pH are 21 mg g-1 DS-1(dry solids), 105 mg g-1 DS-1 and 6, respectively, at which the CST reduction efficiency of 48±3 % can be achieved, this agreed with that predicted by an established polynomial model in this study.

Response surface optimization of phosphorus species adsorption onto powdered alum sludge

Sun, 01 Jun 2008 00:00:00 GMT

Response surface optimization of phosphorus species adsorption onto powdered alum sludge Fu, J.F.; Zhao, Y.Q.; Razali, Melanie; Bruen, Michael The purpose of this study is to optimize adsorption conditions of powdered alum sludge (PAS) as low-cost adsorbent for the removal of three P-species (ortho-P, poly-P and organic-P) from wastewater using the response surface methodology (RSM). Initially, RSM in the basis of a three-variable Box-Behnken design was used to determine the effect of pH (from 4 to 7), PAS mass (from 0.1 to 0.5 g) and PAS particle size (from 125 to 420 μm) on the response levels (removal efficiencies of the three P-species). Three response surface quadratic models in terms of three factors were then obtained from an analysis of the experimental data using a SAS computer package. Thereafter, the effect of each of the parameters on P removal for each of the three species was examined using the three-dimensional response surface. All three parameters (pH, PAS mass and PAS particle size) had a significant effect on the removal of each of the P species. Finally, optimal conditions for P species removal were determined at which the P-removals of 99.8 % (for ortho-P), 94.9 % (for poly-P) and 94.8 % (for organic-P) were achieved, respectively. The results derived from the verification experiments agreed with that predicted by the models, confirming the suitability of the established models and the success of RSM in optimizing the PAS adsorption conditions.

Influence of ageing on the structure and phosphate adsorption capacity of dewatered alum sludge

Mon, 15 Dec 2008 00:00:00 GMT

Influence of ageing on the structure and phosphate adsorption capacity of dewatered alum sludge Yang, Y.; Zhao, Y.Q.; Kearney, P. In line with the increasing studies on the beneficial reuse of alum sludge from a “waste” into useful raw material, this paper reports an in-depth investigation of the effects of ageing time on the structure and the phosphate adsorption capacity of a dewatered alum sludge obtained from a local drinking water treatment plant in Ireland. During the ageing period from 0 day to up to 18 months, the adsorption capacity of the sludge varied from 21.4 to 23.9 mg-P g-1-sludge at pH 4.3, 14.3 to 14.9 mg-P g-1-sludge at pH 7.0 and 0.9 to 1.1 mg-P g-1-sludge at pH 9.0, respectively, indicating marginal effect of ageing time on such sludge's ability to adsorb phosphate. This result seems conflict with other studies reported in the literature. To reveal such, series of investigations including physicochemical characterization, morphological structure, BET surface area and porous structure of the aged sludge were carried out. All the results conclusively show that ageing time has insignificant effect on the structure and properties of the dewatered alum sludge and thus the phosphate adsorption capacity of the alum sludge remains insignificant change during the ageing.

Use of dewatered alum sludge as main substrate in treatment reed bed receiving agricultural wastewater : long-term trial

Thu, 01 Jan 2009 00:00:00 GMT

Use of dewatered alum sludge as main substrate in treatment reed bed receiving agricultural wastewater : long-term trial Zhao, Y.Q.; Zhao, X.H.; Babatunde, A.O. This study aims to explore a novel application of dewatered alum sludge cakes (DASC) as the main medium in a single model reed bed to treat phosphorus-rich animal farm wastewater under "tidal flow" operation on a long term basis. It is expected that the cakes act as the carrier for developing biofilm and also serve as adsorbent to enhance phosphorus (P) immobilization. Results have demonstrated that average removal efficiencies of 73.3±15.9% for COD, 82.9±12.3% for BOD5, 86.4±6.0% for RP (reactive P), 88.6±7.2% for SRP (soluble reactive P) and 77.6±17.5% for SS can be achieved during the two year's operation. More significantly, the "P-adsorption proportion" by DASC in the reed bed is 42% of the overall P removal. The remaining removal of P may be contributed by the trapping and filtration process of DASC. Therefore, the lifetime of the DASC in reed bed is reasonably longer than that determined from the batch isotherm test.

Photo-catalytic degradation of an oil-water emulsion using the photo-Fenton treatment process : effects and statistical optimization

Thu, 01 Jan 2009 00:00:00 GMT

Photo-catalytic degradation of an oil-water emulsion using the photo-Fenton treatment process : effects and statistical optimization Tony, Maha A.; Purcell, Patrick J.; Zhao, Y.Q.; Tayeb, Aghareed M.; El-Sherbiny, M.F. The application of advanced oxidation processes (AOPs) to the treatment of an effluent contaminated with hydrocarbon oils was investigated. The AOPs conducted were Fe2+/H2O2 (Fenton’s reagent), Fe2+/H2O2/UV (Photo-Fenton’s reagent) and UV-photolysis. These technologies utilize the very strong oxidizing power of hydroxyl radicals to oxidize organic compounds to harmless end products such as CO2 and H2O. A synthetic wastewater generated by emulsifying diesel oil and water was used. This wastewater might simulate, for example, a waste resulting from a hydrocarbon oil spill, onto which detergent was sprayed. The experiments utilising the Photo-Fenton treatment method with an artificial UV source, coupled with Fenton’s reagent, suggest that the hydrocarbon oil is readily degradable, but that the emulsifying agent is much more resistant to degradation. The results showed that the COD (chemical oxygen demand) removal rate was affected by the Photo-Fenton parameters (Fe2+, H2O2 concentrations and the initial pH) of the aqueous solution. In addition, the applicability of the treatment method to a ‘real’ wastewater contaminated with hydrocarbon oil is demonstrated. The ‘real’ wastewater was sourced at a nearby car-wash facility located at a petroleum filling station and the experimental results demonstrate the effectiveness of the treatment method in this case. A statistical analysis of the experimental data using the Statistical Analysis System (SAS) and the response surface methodology (RSM) based on the experimental design was applied to optimize the Photo-Fenton parameters (concentrations of Fe2+, H2O2 and initial pH) and to maximize the COD removal rate (more than 70%).

Exploitation of Fenton and Fenton-like reagents as alternative conditioners for alum sludge conditioning

Thu, 01 Jan 2009 00:00:00 GMT

Exploitation of Fenton and Fenton-like reagents as alternative conditioners for alum sludge conditioning Tony, Maha A.; Zhao, Y.Q.; Tayeb, Aghareed M. The use of Fenton’s reagent (Fe2+/H2O2) and Fenton-like reagents containing transition metals of Cu(II), Zn(II), Co(II) and Mn(II) for an alum sludge conditioning to improve its dewaterability was investigated in this study. The results obtained were compared with those obtained from conditioning the same alum sludge using cationic and anionic polymers. Experimental results show that Fenton’s reagent was the best among the Fenton and Fenton-like reagents for the alum sludge conditioning. A considerable effectiveness of capillary suction time (CST) reduction efficiency of 47% can be achieved under test conditions of Fe2+/H2O2 = 20/125 mg/gDS (Dry Solids) and pH = 6.0. The observation of floc-like particles after Fenton’s reagent conditioning of alum sludge suggests that the mechanism of Fenton’s reagent conditioning was different with that of polymer conditioning. In spite of the less efficiency in CST reduction of Fenton’s reagent in alum sludge conditioning compared with that of polymer conditioning, is less than that of polymer conditioning. This study provided an example of proactive treatment engineering which is aimed at seeking a safe alternative to the use of polymers in sludge conditioning towards achieving a more sustainable sludge management strategy.

Investigation of phosphorus desorption from P-saturated alum sludge used as a substrate in constructed wetland

Tue, 07 Apr 2009 00:00:00 GMT

Investigation of phosphorus desorption from P-saturated alum sludge used as a substrate in constructed wetland Zhao, X.H.; Zhao, Y.Q. Phosphorus (P) desorption from P-saturated alum sludge, which was used as main substrate in a novel constructed wetland for wastewater treatment, was studied. Groups of batch experiments were designed and conducted to explore the efficiencies of P extraction using different acids (HCl, HNO3, H2SO4) and bases (NaOH, KOH). The results showed that either acid or base is efficient for P-extraction and the efficiency relied mainly on the concentrations of H+/OH-, not the type of acid or base. Considering the efficiency, price and safety of the acids and bases tested, H2SO4 was chosen as most suitable reagent for P-extraction. A Box-Behnken experimental design based on the response surface methodology (RSM) was applied to evaluate the optimum of H2SO4 extraction. The optimal condition for the mass of sludge, H2SO4 concentration and volume was 0.8 g, 0.063 M and 142 ml, respectively. At such optimal condition, the maximum P-extraction efficiency of 98.2 % was achieved. Additionally, most of the main components of the saturated sludge, such as metals (Al, Ca, Mg, Fe), TOC (total organic carbon) and nitrogen can also be extracted. Overall, the results supported that H2SO4 seems to be an efficient and cost-effective reagent among all the reagents tested for P-saturated alum sludge treatment.

Evaluating the photo-catalytic application of Fenton’s reagent augmented with TiO2 and ZnO for the mineralization of an oil-water emulsion

Sun, 01 Feb 2009 00:00:00 GMT

Evaluating the photo-catalytic application of Fenton’s reagent augmented with TiO2 and ZnO for the mineralization of an oil-water emulsion Tony, Maha A.; Zhao, Y.Q.; Purcell, Patrick J.; El-Sherbiny, M.F. In the present work, homogenous (photo-Fenton) and heterogeneous photo-assisted systems (Fenton/TiO2/UV, Fenton/ZnO/UV and Fenton/TiO2/UV/Air) were investigated for the treatment of a diesel-oil wastewater emulsion. The augmentation of the photo-Fenton process by heterogeneous TiO2 increased the reaction rate, in terms of COD reduction efficiency from 61% to 71%. Furthermore, the COD removal efficiency was increased to 84% when air was bubbled through the reactants. However, if the Fenton/TiO2/UV/Air process is to be utilized as a treatment for this wastewater, the separation of the TiO2 from the treated effluent would need further consideration.

Multivariate-parameter optimization of acid blue-7 wastewater treatment by Ti/TiO2 photoelectrocatalysis via Box-Behnken design

Wed, 01 Jul 2009 00:00:00 GMT

Multivariate-parameter optimization of acid blue-7 wastewater treatment by Ti/TiO2 photoelectrocatalysis via Box-Behnken design Fu, J.F.; Zhao, Y.Q.; Xue, X.D.; Li, W.C.; Babatunde, A.O. The aim of this study is to obtain optimal decolourization conditions for Acid blue-7 (AB7) wastewater treatment by Ti/TiO2 photoelectrocatalysis using response surface methodology (RSM). On the basis of a three-variable Box-Behnken design (BBD), RSM was used to determine the effect of pH values (ranged from 3.2 to 6), light intensity (ranged from 10 to 20 ×102μW/cm2) and bias potential (ranged from 0.1 to 1.1V) on the levels of response, i.e. decolourization efficiency. By applying the quadratic regression analysis, the equations describing the behaviors of the response as simultaneous functions of the selected independent variables were developed. Accordingly, the optimal conditions were determined as pH of 3.41, light intensity of 16.02×102μW/cm2 and bias potential of 0.68V. Decolourization efficiency of 90.13%, obtained experimentally under such optimal conditions was highly agreed with that of 90.44%, estimated by the equations.