Browsing by Author "McAdam, Ewan"
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Item Open Access Anaerobic membrane bioreactors in upflow anaerobic sludge blanket configuration for energy neutral sewage treatment.(2018-03) Wang, Kanming; McAdam, Ewan; Soares, AnaAnaerobic membrane bioreactors (AnMBRs) are emerging as a promising technology to offer the prospect to achieve energy neutral sewage treatment. The key challenges limiting full-scale application of AnMBR for municipal wastewater treatment are high operational cost of energy demand for fouling control and high capital cost of membrane investments. This thesis explores a novel pseudo dead-end gas sparging regime for membrane fouling control, enabling a high sustainable flux (15 L m ¯² h¯¹) with low energy demand (0.14 kWh m⁻³ ) in upflow anaerobic sludge blanket (UASB) configured AnMBR, sufficient to achieve energy neutral sewage treatment. However, this strategy is only possible within low solids environment, emphasising the importance of solids management in the UASB reactor. Solids accumulated in the sludge blanket enhances UASB treatment efficiency during the steady-state operation, indicating to control the sludge blanket at a threshold between the sludge blanket development and steady-state period. The granular inoculum has good stability which exerts a positive influence on reactor stability and sustained permeability, whilst the flocculent inoculum enables to deliver similar sustained membrane operation provided the sludge blanket is controlled. Low temperatures (average temperature of 10 °C) cause the instability of UASB reactor especially for the one with flocculent inoculum biomass. It is therefore proposed to keep relatively high upflow velocity (Vup) of 0.8-0.9 m h⁻¹ in the UASB reactor for granular AnMBR to promote the stratification of particular and granular material, whilst reducing Vup to 0.4 m h⁻¹ for flocculent AnMBR to minimise solids washout and sustain membrane operation at low temperatures. The potential for permeability recovery following peak flow (diurnal peaks and storm water flows) has been investigated and evidenced, suggesting that membrane surface area for AnMBR can be specified based on average flow, providing a considerable (67 %) capital cost reduction compared with the design based on peak flows (three times of average flow). Importantly, this thesis promotes UASB configured AnMBR as a highly reliable and more economically viable technology, facilitating to achieve the energy neutral sewage treatment at ambient temperature.Item Open Access Biogas enhancement with membranes(Cranfield University, 2014-04) McLeod, Andrew J.; McAdam, Ewan; Jefferson, BruceBiogas is generated during anaerobic digestion (AD) of sewage sludge at wastewater treatment works (WWTW) and consists of approximately 50-70 % methane (CH4) balanced primarily by carbon dioxide (CO2). It is commonly used directly as a fuel gas for the renewable generation of electricity on-site by combined heat and power (CHP) engines. However, as a result of governmental incentivisation, biogas possesses a greater value when applied to the national gas grid as a natural gas substitute. However, this requires enhancement of the CH4 content to that comparable to natural gas by selective removal of CO2; a process known as biogas upgrading. This thesis explores the potential of hydrophobic micro-porous hollow fibre membrane contactors (HFMCs) to biogas upgrading. HFMCs allow non-dispersive contact between the biogas and a liquid solvent for the preferential absorption of CO2, which is conventionally facilitated by packed-column gas scrubbing technology. However, recent gas absorption literature has demonstrated many practical and operational advantages of HFMCs, which suggests they may be effective for biogas upgrading at WWTW. In this thesis, HFMCs were used to explore the mechanism and controllability of the undesirable co-absorption of CH4, known as methane slip. This was found to be attributable to the phase limiting mass transfer, with liquid-limited physical absorption in water exhibited 5.2 % slip whereas gas-limited chemical absorption displayed just 0.1 %. Ammonia-rich wastewaters were investigated as sustainable chemical absorbents using HFMCs and exhibited comparable chemically enhanced absorption to analogue synthetic ammonia solutions. The recovery of the subsequent reaction product (ammonium bicarbonate) by crystallisation facilitated by the membrane was also examined. The potential of this approach was summarised within two hypothetical wastewater flowsheets, where upgrading using a return liquor absorbent acts as a return liquor treatment and where ion exchange allows 100 % application of wastewater derived ammonia to biogas upgrading. These both offered potential economic advantages versus conventional flowsheets with 100 % biogas application to CHP.Item Open Access Comparable membrane permeability can be achieved in granular and flocculent anaerobic membrane bioreactor for sewage treatment through better sludge blanket control(Elsevier, 2019-02-05) Wang, Kanming; Soares, Ana; Jefferson, Bruce; McAdam, EwanMBR, to establish the impact of biomass selection on sustaining membrane permeability for sewage treatment. When operated as an UASB (10 °C), similarly poor organics removal was observed for both inocula, which was overcome by membrane integration, producing solids-free permeate and consistently low CODt (34–39 mg L−1) and BOD5 (10–13 mg L−1), sufficient to meet discharge standards. At an average sewage temperature of 22 °C, membrane permeabilities in granular (G-AnMBR) and flocculent (F-AnMBR) systems were comparable. However, at lower temperature (10 °C), significant fouling was observed in F-AnMBR at a flux of 7.5 L m−2 h−1. The permeability decline was ascribed to a decreased particle settling velocity which induced washout of smaller particles into the membrane tank, subsequently increasing the colloidal concentration due to the floc erosion induced by gas sparging. This was confirmed by halving UASB upflow velocity in the F-AnMBR, which reduced pCOD and colloidal load by 31–36% onto the membrane, permitting comparable permeability to G-AnMBR. The UASB configured AnMBR promoted low solids loading onto the membrane, enabling pseudo dead-end gas sparging to be used which reduced specific energy demand. Analysis of the dead-end filtration cycle attributed the primary resistance (85–88%) to the development of a concentrated but less compact cake. Importantly, this study evidences comparable permeabilities in G-AnMBR and F-AnMBR through controlling solids retention, and specifying filtration cycle length to minimise solids deposition, such that low energy membrane operation can be achieved (<0.122 kW h m−3).Item Open Access Comparison of fouling between aerobic and anaerobic MBR treating municipal wastewater(IWA Publishing, 2018-11-26) Wang, K. M.; Martin Garcia, N.; Soares, Ana; Jefferson, Bruce; McAdam, EwanThe key driver for anaerobic membrane bioreactors (AnMBR) for municipal wastewater treatment is enabling the transition to energy neutral wastewater treatment. However, municipal wastewater delivers a comparatively constrained methane yield, which means energy conservation must be prioritised to achieve the proposed energy neutral ambition. A critical focus on membrane fouling is therefore warranted, as membrane operation represents the primary energy demand in MBRs. This review seeks to quantify the characteristics of the prevailing AnMBR biological suspension and to ascertain whether knowledge transfer exists between fouling characteristics in aerobic and anaerobic MBRs for municipal applications. Analysis of literature data revealed that the level of extractable extracellular polymeric substrate is slightly higher in aerobic MBRs than in anaerobic MBRs. However, AnMBR comprises considerably higher soluble microbial product concentrations, which have been widely reported to increase fouling propensity in aerobic systems. More distinct is the difference in the colloidal and fine solids fraction (between 1 and 10–15 μm), which is likely to dominate fouling in anaerobic systems and limit knowledge transfer from aerobic MBRs. Literature data on energy production was compared to that employed for membrane operation, and evidences that despite the challenging character of the particle matrix, energy neutral operation is achievable for AnMBR applied to municipal wastewater treatment.Item Open Access The cost of a small membrane bioreactor(IWA Publishing, 2015-07-23) Lo, C. H.; McAdam, Ewan; Judd, Simon J.The individual cost contributions to the mechanical components of a small membrane bioreactor (MBR) (100–2,500 m3/d flow capacity) are itemised and collated to generate overall capital and operating costs (CAPEX and OPEX) as a function of size. The outcomes are compared to those from previously published detailed cost studies provided for both very small containerised plants (<40 m3/day capacity) and larger municipal plants (2,200–19,000 m3/d). Cost curves, as a function of flow capacity, determined for OPEX, CAPEX and net present value (NPV) based on the heuristic data used indicate a logarithmic function for OPEX and a power-based one for the CAPEX. OPEX correlations were in good quantitative agreement with those reported in the literature. Disparities in the calculated CAPEX trend compared with reported data were attributed to differences in assumptions concerning cost contributions. More reasonable agreement was obtained with the reported membrane separation component CAPEX data from published studies. The heuristic approach taken appears appropriate for small-scale MBRs with minimal costs associated with installation. An overall relationship of net present value = (a tb)Q(−c lnt+d) was determined for the net present value where a = 1.265, b = 0.44, c = 0.00385 and d = 0.868 according to the dataset employed for the analysis.Item Open Access Data in support of "The role of mixing on the kinetics of nucleation and crystal growth in membrane distillation crystallisation"(Cranfield University, 2024-06-27) McAdam, EwanItem Open Access Data related to "Examining disruptive gas-phase reactions during CO2 capture in membrane contactors: CO2-NH3-H2O as a model ternary system"(Cranfield University, 2024-05-23 17:10) Luqmani, Ben; Pidou, Marc; McAdam, EwanData related to figures for "Examining disruptive gas-phase reactions during CO2 capture in membrane contactors: CO2-NH3-H2O as a model ternary system"Item Open Access Data related to "Membrane-assisted reactive crystallisation for the recovery of dissolved phosphorus in vivianite form from liquid effluents"(Cranfield University, 2023-08-31 14:38) McAdam, Ewan; Chen, Lo-I; Le Corre Pidou, KristellData supporting article titled "Membrane-assisted reactive crystallisation for the recovery of dissolved phosphorus in vivianite form from liquid effluents"Item Open Access Data related to "Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems"(Cranfield University, 2021-10-11 17:11) Bajón fernández, Yadira; Mercer, Edwina; USHER, SHANE; McAdam, Ewan; R. Stoner, BrianData related to "Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems"Item Open Access Data related to "The role of solvent temperature and gas pressure on CO2 mass transfer during biogas upgrading within porous and dense-skin hollow fibre membrane contactors"(Cranfield University, 2023-04-14 14:37) Luqmani, Ben; McAdam, Ewan; Pidou, MarcSource data for published works: 'The role of solvent temperature and gas pressure on CO2 mass transfer during biogas upgrading within porous and dense-skin hollow fibre membrane contactors'.Item Open Access Data related to figures from "Transitioning through the vapour-liquid equilibrium for low energy thermal stripping of ammonia from wastewater..."(Cranfield University, 2023-04-21 14:29) Luqmani, Ben; Pidou, Marc; McAdam, EwanSupporting dataset related to figures in the following work : "Transitioning through the vapour-liquid equilibrium for low energy thermal stripping of ammonia from wastewater...".Item Open Access Data supporting "Modifying supersaturation rate with membrane area can minimise scaling and improve control over crystal growth in membrane distillation crystallisation"(Cranfield University, 2023-06-30 11:09) Ouda, Alaa; McAdam, Ewan; Bajón fernández, YadiraThis Excel file consists of the data used to generate the figures in this paper. Each figure is placed in a separate Excel sheet while the formatting of the figures was consistent with a Word file.Item Open Access Data supporting the publication "Transforming wastewater ammonia to carbon free energy: Integrating fuel cell technology with ammonia stripping for direct power production"(Cranfield University, 2022-03-08 09:18) Davey, Chris; Luqmani, Ben; Thomas, Navya; McAdam, EwanData File supporting article titled "Transforming ammonia to carbon free energy: Integrating fuel cell technology with ammonia stripping for direct power production"Item Open Access Data supporting: 'CO2 absorption into aqueous ammonia using membrane contactors: Role of solvent chemistry and pore size on solids formation for low energy solvent regeneration'(Cranfield University, 2022-10-13 16:42) Bavarella, Salvatore; Luqmani, Ben; Thomas, Navya; Brookes, Adam; Moore, Andrew; Vale, Peter; Pidou, Marc; McAdam, EwanSolids formation can substantially reduce the energy penalty for ammonia solvent regeneration in carbon capture and storage (CCS), but has been demonstrated in the literature to be difficult to control. This study examines the use of hollow fibre membrane contactors, as this indirect contact mediated between liquid and gas phases in this geometry could improve the regulation of solids formation. Adoption of a narrower pore size membrane was shown to dissipate wetting after crystallisation in the solvent, illustrating membrane contactors as a stable platform for the sustained separation of CO2 coupled with its simultaneous transformation into a solid. Through resolving previous challenges experienced with solids formation in multiple reactor configurations, the cost benefit of using ammonia as a solvent can be realised, which is critical to enabling economically viable CCS for the transition to net zero, and can be exploited within hollow fibre membrane contactors, eliciting considerable process intensification over existing reactor designs for CCS.Item Open Access Data supporting: 'Downscaling reverse osmosis for single-household wastewater reuse: towards low-cost decentralised sanitation through a batch open-loop configuration'(Cranfield University, 2022-10-31 09:16) Thomas, Navya; McAdam, Ewan; Davey, ChrisThere is a significant demand for water recycling in low-income countries. However, wastewater infrastructure is primarily decentralised, necessitating the development of affordable household-scale reclamation technology. In this study, a batch open-loop reverse osmosis (RO) system is therefore investigated as a low-cost clean water reclamation route from highly saline concentrated blackwaterItem Open Access Data: Hydrodynamics (Reynolds number) determine scaling, nucleation and crystal growth kinetics in membrane distillation crystallisation(Cranfield University, 2023-09-05 16:18) McAdam, Ewan; Jikazana, Aphiwe; Campo Moreno, PabloDataset for journal article "Hydrodynamics (Reynolds number) determine scaling, nucleation and crystal growth kinetics in membrane distillation crystallisation"Item Open Access Design and commissioning of a multi-mode prototype for thermochemical conversion of human faeces(Elsevier, 2018-03-23) Jurado Pontes, Nelia; Somorin, Tosin; Kolios, Athanasios J.; Wagland, Stuart; Patchigolla, Kumar; Fidalgo, Beatriz; Parker, Alison; McAdam, Ewan; Williams, Leon; Tyrrel, SeanThis article describes the design and commissioning of a micro-combustor for energy recovery from human faeces, which can operate both in updraft and downdraft modes. Energy recovery from faecal matter via thermochemical conversion has recently been identified as a feasible solution for sanitation problems in low income countries and locations of high income countries where access to sewage infrastructures is difficult or not possible. This technology can be applied to waterless toilets with the additional outcome of generating heat and power that can be used to pre-treat the faeces before their combustion and to ensure that the entire system is self-sustaining. The work presented here is framed within the Nano Membrane Toilet (NMT) project that is being carried out at Cranfield University, as part of the Reinvent the Toilet Challenge of the Bill and Melinda Gates Foundation. For this study, preliminary trials using simulant faeces pellets were first carried out to find out the optimum values for the main operating variables at the scale required by the process, i.e. a fuel flowrate between 0.4 and 1.2 g/min of dry faeces. Parameters such as ignition temperature, residence time, and maximum temperature reached, were determined and used for the final design of the bench-scale combustor prototype. The prototype was successfully commissioned and the first experimental results, using real human faeces, are discussed in the paper.Item Open Access Development of a staged anaerobic pond for methane recovery from domestic wastewater(Elsevier, 2018-08-08) Cruddas, Peter; McAdam, Ewan; Asproulis, Nikolaos; Antoniadis, Antonis F.; Ansari, Irfan; Best, D.; Jefferson, Bruce; Cartmell, Elise; Collins, G.; Porca, E.; Peña-Varón, M. R.Since their inception in larger pond systems, the focus of anaerobic ponds has shifted from solids removal to optimising biogas production and reducing physical footprint to minimise land requirements. In this study, a horizontally baffled (HBAP) and vertically baffled (VBAP) anaerobic pond were compared. Distinct differences in the removal efficiency of COD fractions were observed, with particulate COD removal of 78% and 32%, and soluble COD removal of −26% and 19% in the HBAP and VBAP, respectively. A staged pond (SAP) was constructed through an HBAP placed upstream of a VBAP, with an additional HBAP used as a control (CAP). The SAP demonstrated superior biogas recovery potential over the control: methane production by the conclusion of the study was 6.09 and 9.04 LCH4 m−3 wastewater treated for the CAP and SAP, respectively. Methanogenic activity in the ponds was higher closer to the outlet, and hydrogenotrophic methanogenesis dominated over acetoclastic pathways.Item Open Access Downscaling reverse osmosis for single-household wastewater reuse: towards low-cost decentralised sanitation through a batch open-loop configuration(IWA Publishing, 2022-04-15) Davey, C. J.; Thomas, Navya; McAdam, EwanThere is a significant demand for water recycling in low-income countries. However, wastewater infrastructure is primarily decentralised, necessitating the development of affordable household-scale reclamation technology. In this study, a batch open-loop reverse osmosis (RO) system is therefore investigated as a low-cost clean water reclamation route from highly saline concentrated blackwater. In a single-stage configuration, increasing feed pressure from 10 to 30 bars improved selective separation at water recovery exceeding 85%, whereas lower cross-flow velocity improved product recovery, reducing specific permeate energy demand from 21 to 4.8 kWh m−3. Rejection achieved for total phosphorous (99%), chemical oxygen demand (COD, 96%), and final pH (8.7) of the RO permeate was compliant with the ISO30500 reuse standard for discharge. However, the rejection of total nitrogen in the RO permeate was non-compliant with the reuse standard due to the transmission of low-molecular weight (MW) uncharged organic compounds. It is suggested that rejection may be improved by increasing feed pressure to rebalance selectivity but may also be controlled by reducing fluid residence time (storage) to constrain the hydrolysis of urea. The economic analysis identified that a high-pressure 1812 element cost of ∼US$30 meets the sanitation affordability index of US$0.05 capita−1 day−1. However, the unit cost of a high-pressure feed pump must be reduced to ∼US$500 to obtain an affordable system cost. These unit costs can be achieved by manufacturing 1812 elements at economies of scale, and by adopting pumping solutions that have been developed for other applications requiring high pressures and low flows. Overall, our findings suggest that RO in the batch open-loop configuration has the potential to deliver affordable and safe water production from blackwater in a decentralised (single-household) context.Item Open Access Enhancing the removal of a diverse range of hazardous chemicals from wastewaters(Cranfield University, 2014-01) Petrie, Bruce; Cartmell, Elise; McAdam, Ewan; Lester, John N.Due to increasingly stringent legislation covering the discharge of hazardous chemicals into the environment, existing wastewater treatment processes need to be upgraded for their removal. This thesis explores the removal of a diverse range of hazardous chemicals during secondary wastewater treatment with the overall aim of enhancing their removal simultaneously by activated sludge. Previous research in this field has made the broad comparison of full-scale activated sludge plants (ASPs) which receive varying influent sewage compositions and flow. Consequently, assessing the direct impact of process operation to hazardous chemical removal has been difficult. In this study, the independent impact of the process variables solids retention time (SRT) and hydraulic retention time (HRT) were examined using a pilot-scale ASP. To measure ASP resilience for the removal of a wide range of hazardous chemicals of varied chemistry and preferred removal pathways steroid estrogens, nonylphenolic surfactants and metals were monitored. Cont/d.
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