Now showing 1 - 8 of 8
  • 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.
    Scopus© Citations 153  1906
  • Publication
    Effects of livestock wastewater variety and disinfectants on the performance of constructed wetlands in organic matters and nitrogen removal
    Background, aim and scope: Treatment performance of constructed wetlands (CWs) is largely dependent on the characteristics of the wastewater. Although livestock wastewater is readily biodegradable in general, its variety in biodegradability can still be significant in practice. In addition, it is a common practice to periodically use disinfectants in livestock activities for health concerns. Obviously, the residual of the disinfectants in livestock wastewater may have serious inhibitory effect on the microbial activities during wastewater treatment. Thus, the main objective of this study was to examine the variety of livestock wastewater in biodegradability and its effect on the performance of a pilot scale tidal flow CWs (TFCWs) in organic matter and nitrogen removal. Furthermore, investigation of the potential inhibition of the chosen disinfectants on organic matter biodegradation and nitrification was another aim of this study. Materials and methods: The TFCWs system consisted of four-stage downflow reed beds with a hydraulic loading rate of 0.29 m3/m2·per day. Long-term stored livestock wastewater and fresh livestock wastewater were used, respectively, as feed to the system in different periods. Meanwhile, batch aeration tests were carried out to investigate the difference in biodegradation of the two types of wastewaters. Inhibitions of two types of disinfectants, namely UNIPRED and HYPROCLOR ED, on microbial activities were investigated in laboratory batch tests, with dosage of from 0.05% to 0.5%. Results: With fresh livestock wastewater, removal efficiencies of up to 93% and 94% could be achieved with average of 73% and 64% for chemical oxygen demand (COD) and TN, respectively. The performance deteriorated when the system was fed with long-term stored wastewater. In the batch tests, the long-time stored wastewater was characterized as non-biodegradable or at least very slowly biodegradable, while the fresh wastewater was readily biodegradable. UNIPRED showed very strong inhibition on both heterotrophic organisms and nitrifiers. Tested inhibition started from content of 0.05%, which is 1/10 of the recommended usage rate. Inhibitory effect of HYPROCLOR ED on COD degradation started from 0.1% and complete inhibition occurred from content of 0.3%, while significant inhibition on nitrification started from 0.1%. Conclusions: Livestock wastewater could vary significantly in biodegradability and it may turn to be non-biodegradable after a long-term storage. The variety of the livestock wastewater has a decisive influence on the performance of the CWs system, especially in TN elimination. In addition, the application of disinfectants UNIPRED and HYPROCLOR ED may cause serious inhibition on microbial activities and subsequent system failure.
    Scopus© Citations 12  655
  • Publication
    High rate nitrogen removal in an alum sludge-based intermittent aeration constructed wetland
    A new development on treatment wetland technology for the purpose of achieving high rate nitrogen removal from high strength wastewater has been made in this study. The laboratory scale alum sludge-based intermittent aeration constructed wetland (AlS-IACW) was integrated with predenitrification, intermittent aeration, and step-feeding strategies. Results obtained from 280 days of operation have demonstrated extraordinary nitrogen removal performance with mean total nitrogen (TN) removal efficiency of 90% under high N loading rate (NLR) of 46.7 g N m–2 d–1. This performance was a substantial improvement compared to the reported TN removal performance in literature. Most significantly, partial nitrification and simultaneous nitrification denitrification (SND) via nitrite was found to be the main nitrogen conversion pathways in the AlS-IACW system under high dissolved oxygen concentrations (3–6 mg L–1) without specific control. SND under high dissolved oxygen (DO) brings high nitrogen conversion rates. Partial nitrification and SND via nitrite can significantly reduce the demand for organic carbon compared with full nitrification and denitrification via nitrate (up to 40%). Overall, these mechanisms allow the system to maintaining efficient and high rate TN removal even under carbon limiting conditions.
      1169Scopus© Citations 178
  • Publication
    On the fit of statistical and k-C* models to projecting treatment performance in a constructed wetland system
    The objective of this study was to assess the suitability of statistical and the k-C* models to projecting treatment performance of constructed wetlands by applying the models to predict the final effluent concentrations of a pilot field-scale constructed wetlands system (CWs) treating animal farm wastewater. The CWs achieved removal rates (in g/m2.d) ranging from 7.1-149.8 for BOD5, 49.8-253.8 for COD and 7.1-47.0 for NH4-N. Generally, it was found that the statistical models developed from multiple regression analyses (MRA) were stronger in predicting final effluent concentrations than the k-C* model. However, both models were inadequate in predicting the final effluent concentrations of NO3-N. The first-order area-based removal rate constants (k, m/yr) determined from the experimental data were 200.5 for BOD5, 80.1 for TP and 173.8 for NH4-N and these indicate a high rate of pollutant removal within the CWs.
      686Scopus© Citations 16
  • Publication
    Removal of glyphosate from aqueous environment by adsorption using water industrial residual
    (Elsevier, 2011-04) ; ;
    This study investigated the glyphosate adsorption by water treatment residual (termed as alum sludge) in dewatered form (DAS) and liquid form (LAS). Batch adsorption tests were carried out with DAS at different pH, particle size and DAS mass. Standard jar tests were conducted with LAS at two different concentrations (3 g/l and 5 g/l) for glyphosate adsorption. Thereafter, the glyphosate-enriched LAS (after adsorption tests) was subjected to sludge conditioning procedure with polymer LT25 as conditioner to explore any possible further glyphosate reduction. The results indicate that alum sludge has the high adsorption capacity of 85.9 mg/g for DAS and 113.6 mg/g for LAS. This demonstrated the potential of the alum sludge to be an efficient and cost-effective adsorbent for glyphosate removal in comparison with other adsorbents, such as soils, humic substances, clay minerals, and layered double hydroxides (LDH). The polymer conditioning of the glyphosate-enriched LAS cannot bring about the further glyphosate reduction in the supernatant of the dewatered LAS. Overall, this study promotes the beneficial reuse of alum sludge in wide range of pollutant control in environmental engineering.
      3777Scopus© Citations 131
  • Publication
    Comprehensive analysis of step-feeding strategy to enhance biological nitrogen removal in alum sludge-based tidal flow constructed wetlands
    Step-feeding strategies have been extensively studied and comprehensively analyzed in this study for a four-stage alum sludge-based tidal flow constructed wetlands (AlS-TFCWs) system. Enhanced total nitrogen removal of 83% is achieved under high nitrogen loading rate of 19.1 g N/m2 d. The key issues towards the success of a significant nitrogen removal in step-feeding TFCWs are the bed resting time (which provides better aeration for nitrification) and up flow stage/delayed input of side stream(s) (which ensure favorable environment for better denitrification). Simultaneous nitrification and denitrification (SND) was found effective in the 1st stage of the system and SND via nitrite is the main nitrogen conversion mechanism. The optimal influent distribution fraction for step-feeding purpose can be estimated from a theoretical basis, which is a function of the influent BCOD/TKN ratio. Therefore the influent distribution fraction should be adjusted according to the variety of influent characteristics, rather than a fixed value.
    Scopus© Citations 72  1232
  • Publication
    A two-prong approach of beneficial reuse of alum sludge in engineered wetland : first experience from Ireland
    Effective management of the industrial waste requires a sustainable approach that maximizes its value of reuse/recycle for other industrial demands and the environment needs. This paper aims in exploring the potential of the intended purposes in the newly developed dewatered aluminum-water treatment sludge (Al-WTS) based engineered wetland (EW) for wastewater treatment. Due to the low energy requirement and aesthetical appearance EW is seen as a ‘green’ wastewater treatment technique worldwide for a wide variety of wastewater treatment. The Al-WTS based EW developed at University College Dublin, Ireland, represents the latest initiative at using engineering ingenuity to further improve EWs performance. This paper summarizes the background of development and the results derived from different phases of the development of Al-WTS based EW.
      815Scopus© Citations 17
  • 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.
    Scopus© Citations 48  1121