Now showing 1 - 10 of 75
  • Publication
    From "fills" to filter : insights into the reuse of dewatered alum sludge as a filter media in a constructed wetland
    (DesTech Publications, 2007-07) ; ; ;
    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.
  • Publication
    On the necessity of sludge conditioning with non-organic polymer : AOP approach
    (DEStech Publications, 2009-07) ; ;
    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.
  • Publication
    Process-based modelling of phosphorus removal in a novel constructed wetland system using dewatered alum-sludge as substrate
    A process-based model that can evaluate the transport and the fate of phosphorus (P) in agricultural wastewater was developed for a novel 4-stage dewatered alum sludge cakes (DASC) based constructed wetlands (CWs) system using STELLA software (version 9.1.4). The model considered adsorption, plant and microbial uptakes as the major forms of P involved in the transformation chains. The results were obtained by experimental procedure through laboratory measurement, from literature and/or calibration. The observed effluent P concentration in the CWs ranged from 3.62 to 8.50 mg/L (stage 1), 2.00 to 4.45 mg/L (stage 2), 1.39 to 3.76 mg/L (stage 3) and 0.52 to 2.36 mg/L (stage 4), whereas the simulated values ranged from 2.12 to 10.99 mg/L (stage 1), 1.32 to 5.65 mg/L (stage 2), 0.84 to 3.64 mg/L (stage 3) and 0.53 to 2.25 mg/L (stage 4), respectively. The simulated and observed values of P removal in the CWs system were in good agreement. A mass balance analysis was performed for all the major processes which resulted in a major pathway of P removal through adsorption (64–75%, 58–66%, 57–63% and 49–58%) followed by plant uptake (7–11%, 8–14%, 14–17% and 9–19%) and microbial uptake (3–7%, 3–5%, 9–12% and 7–12%) for stage 1, stage 2, stage 3 and stage 4, respectively. Thus the mathematical model developed in this study could be used to explain the removal processes and simulate the fate of P in the DASC-based CWs system.
      346Scopus© Citations 8
  • Publication
    Fate of water treatment residual : an entire profile of Ireland regarding beneficial reuse
    (Taylor & Francis, 2011-04) ; ;
    Ireland's water treatment residual (WTR) production rate and reuse situation was investigated to complement the novel research on WTR reuse development in University College Dublin, Ireland. The resulting GIS maps reveal the state of WTR production, disposal and beneficial reuse throughout the country. The total WTR production in Ireland is 15,679 tonnes of dry solids per annum with over 90% of WTR being aluminium-salt-coagulated WTR. Only 8% of WTR is recycled or reused via composting, landspreading, cement manufacturing, constructed wetlands and quarry remediation. The authors recommend that there be further attempts to use WTR in constructed wetlands and cement manufacturing in Ireland.
      2065Scopus© Citations 12
  • Publication
    Pilot field-scale demonstration of a novel alum sludge-based constructed wetland system for enhanced wastewater treatment
    In this study, beneficial reuse of the alum-contained drinking water treatment sludge is extended into developing a novel constructed wetland system (CWs) using the alum sludge as main substrate. The study reports on the first pilot field-scale alum sludge-based CWs operated in the tidal flow mode with enhanced capacity for phosphorus and organic matter removal from animal farm wastewater. The concept of the development is presented and this is followed by the performance analysis of the first CWs of its kind. The CWs consists of four identical compartments in series operated using a tidal flow strategy with a hydraulic loading rate of 0.29 m3/m2.d. First year analysis of the system’s performance shows that it is a unique and promising low-cost wastewater treatment system. The mean monthly removal efficiencies obtained was determined to range from 57%-84%, 36%-84%, 11%-78%, 49%-93%, 75%-94%, 73%-97% and 46%-83% for BOD5, COD, TN, NH4-N, TP, P (inorganic phosphorus) and SS. The system showed a distinct phosphorus removal and also, the system was effective in reducing levels of organics and ammonium-nitrogen. More importantly, the system showcases a novel reuse alternative for the alum sludge as opposed to its landfilling, demonstrating a win-win technique with a great potential for larger-scale application.
      1764Scopus© Citations 139
  • Publication
    Fenton and Fenton-like AOPs for alum sludge conditioning : effectiveness comparison with different Fe2+ and Fe3+ salts
    (Taylor & Francis, 2010-11) ; ;
    Currently, organic polymers are adopted in alum sludge (aluminium-coagulated drinking water treatment sludge) conditioning. However, there are important concerns regarding the use of these polymers because of the unknown and long-term effects of the potential release of excess polymer to the surrounding environment when the sludge is landfilled. Therefore, as an initiative action, this study aimed at investigating alternative chemical conditioning methods and focused mainly on exploiting Fenton (Fe2+/H2O2) and Fenton-like (Fe3+/H2O2) reagents as the conditioner. Experiments have been conducted to test the effectiveness of Fenton’s reagent (containing the ferrous salts of chloride, sulphate or oxalate), Fenton-like reagent (containing ferric salts of chloride and sulphate) and the coagulation method using FeCl3 for an alum sludge conditioning at a constant hydrogen peroxide and iron salt concentrations of 125 and 20 mg/g DS (dry solids), respectively. The effectiveness on dewaterability of the alum sludge demonstrated that the maximum reduction (%) of SRF (specific resistance to filtration) and CST (capillary suction time) of 74 % and 47 %, respectively, can be obtained when Fenton’s reagent was adopted for sludge conditioning. Such reduction of 64% for SRF and 38% for CST can be achieved when Fenton-like reagents were applied.
      999Scopus© Citations 26
  • Publication
    Preliminary investigation of constructed wetland incorporating microbial fuel cell: Batch and continuous flow trials
    This study has served as more encouraging signs that constructed wetlands (CWs) can incorporate microbial fuel cells (MFCs) into their design to produce electrical energy while treating wastewater. Two 3.7 L CW-MFCs have been constructed to treat swine wastewater with one (System 1) operated in batch mode while the other (System 2) was operated in continuous, upward flow mode and incorporated air diffusion heads to aerate the cathode. System 1 removed, on average, 71.5% of COD (with initial concentration of 3190–7080 mg/L) and produced a peak power density of 12.83 μW/m2. The aeration of the cathode significantly enhanced the performance of the CW-MFC, with System 2 demonstrating an average of 76.5% COD removal (average influent COD concentration of 1058.45 ± 420.89 mg/L) with a peak power density of 9.4 mW/m2.
      1848Scopus© Citations 202
  • Publication
    Forms, patterns and extractability of phosphorus retained in alum sludge used as substrate in laboratory-scale constructed wetland systems
    (Elsevier, 2009-10-01) ;
    This study examined the form, pattern and extractability of phosphorus (P) retained in alum sludge (an aluminium-containing drinking water treatment residual in dewatered cake form), which was used as substrate in laboratory scale constructed wetland systems for P-rich wastewater treatment. Used alum sludge samples from successive depth ranges in the laboratory scale vertical flow constructed wetland systems were examined for KCl extractable P. The samples were also sequentially fractionated into two main categories consisting of readily available P and P forms that are not easily decomposed. The extracted fractions included labile P, microbial P, (Fe + Al) P, humic P, (Ca + Mg) P and residual P. A major proportion of P retained in the used alum sludge was in forms that are not easily decomposed. Of the P forms that are not easily decomposed, the P associated with Ca and Mg accounted for a higher proportion of the inorganic fraction as compared to the P associated with the Fe and Al. The results also show that in most cases, the concentration of the P forms decreased with increasing depth from the topmost surface of the alum sludge in the systems.
      523Scopus© Citations 27
  • Publication
    Performance evaluation and prediction for a pilot two-stage on-site constructed wetland system employing dewatered alum sludge as main substrate
    Dewatered alum sludge, a widely generated by-product of drinking water treatment plants using aluminium salts as coagulants was used as main substrate in a pilot on-site constructed wetland system treating agricultural wastewater for 11 months. Treatment performance was evaluated and spreadsheet analysis was used to establish correlations between water quality variables. Results showed that removal rates (in g/m2.d) of 4.6-249.2 for 5 day biochemical oxygen demand (BOD5), 35.6-502.0 for chemical oxygen demand (COD), 2.5-14.3 for total phosphorus (TP) and 2.7-14.6 for phosphate (PO4-P) were achieved. Multiple regression analysis showed that effluent BOD5 and COD can be predicted to a reasonable accuracy (R2=0.665 and 0.588, respectively) by using input variables which can be easily monitored in real time as sole predictor variables. This could provide a rapid and cheap alternative to such laborious and time consuming analyses and also serve as management tools for day-to-day process control.
      995Scopus© Citations 44
  • Publication
    Constructed wetlands for environmental pollution control : a review of developments, research and practice in Ireland
    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.
      10918Scopus© Citations 158