PhD, EngD and MSc by research theses (SWEE)

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Browsing PhD, EngD and MSc by research theses (SWEE) by Subject "Activated carbon"

Now showing 1 - 4 of 4
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    ItemOpen Access
    Approaches to maximise the utilisation of residues from thermal conversion of oil palm waste.
    (Cranfield University, 2020-12) Ukanwa, Kalu Samuel; Patchigolla, Kumar; Sakrabani, Ruben
    Palm oil processing generates enormous volume of waste, which can be used as a feedstock in thermal processing. Subsequently, these can be valuable in the production of activated carbon (AC) and soil amelioration. The production of AC often results in secondary contamination through activating agents. This prompts the necessity for a non-toxic activating agent for high quality production of high adsorptive AC. Therefore this research aims to assess and determine the optimum route for efficient utilisation of biowaste from thermal conversion process of palm oil residues in producing activated carbon and soil amelioration by evaluating the impact of the selected utilisation techniques. In the production process, energy demand and process duration have influence on the efficiency of AC; therefore, an appropriate design configurations and parameter selection are required to achieve an anticipated yield. AC was produced by microwave and conventional techniques through pyrolysis. The feedstock was also used in combustion and the thermal residues were applied in agricultural soil and crop yield relative to application rate was assessed on Habanero chili pepper. Therefore, the requisite to quantify the processes, which include appropriate assessment of the technology and economic performance. The accomplishment of the project overall aim was dependent on the design of a microwave system for efficient biomass pyrolysis. The process also evaluated the microwave interaction with reactors implemented to produce AC from mixed oil palm waste, using Trona ore as an activating agent. The AC was analysed to determine the effectiveness of Trona ore for activation using Fourier infrared spectrometry, Brunauer-Emmett-Teller (BET) analyser and scanning electron microscope. The oil palm waste ash was applied to the soil. The optimum outcome of the microwave assisted technique for combine palm waste (CPW) was obtained at 600 W, BET surface area (SBET) is 980 m²/g compared to 920 m²/g from a conventional technique; total volume (Vtotal) 0.865 cm³/g; mean pore diameter 2.2 nm and AC yield is 42%. Therefore, this study additionally identifies the need for an even distribution of electromagnetic waves within the reactor during activation to ensure uniformity of AC. It also proposes that the design of a composite reactor for an industrial production of AC is necessary to enable heterogeneous waste stream of the process. For ash application, the physiological development and crop yield were measured. The combine maximum yield for both sites were 49 t/ha/first season and 71.8 t/ha/second season, occurred at 8 t/ha treatment plot against the control plot with 1.3 t/ha/first season and 0.7 t/ha/second season. The interaction between oil palm waste ash and soil, improved agronomic efficiency of Habanero chilli pepper by 66-69% and Scoville value by 3.52%. These utilisation routes (AC production and ash to soil) were further integrated for economic and technological benefits using Aspen plus Economy. The processes have 16-17% return on investment for the 8-9 year payback period. This study therefore concluded that thermal residues of oil palm waste are useful in the production of high quality AC and also has rich effect on agricultural soil.
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    ItemOpen Access
    Evolution of hybrid systems for treatment of effluents from the pesticide production industry.
    (2017-05) Goodwin, Lindsey Marie; Soares, Ana; Carra ruiz, Irene
    The pesticide production industry generates a high strength wastewater containing a range of toxic pollutants (2,4-dichlorphenoxy acetic acid: 2,4-D; 4-(2,4-dichlorphenox) propionic acid: 2,4-DP; 4-(2,4-dichlorophenox) butyric acid: 2,4-DB; 2,4-dichlorophenol: 2,4-DCP; 2,4,6-trichlorophenol: 2,4,6-TCP; 4-chlororthocresol: PCOC; 4-chloro-2-methyl phenoxyacetic acid: MCPA, 4-(4-chloro-2-methylphenoxy) butyric acid: MCPB and 2-(4-chloro-2-methylphenoxy) propionic acid: MCPP). These pesticides can enter the natural environment and water sources if not removed in a wastewater treatment plant. Treated effluents are regulated by legislation such as the Water Framework Directive (WFD). The organic matter and pesticides concentrations in the wastewater were highly variable across the 12 sampling campaign carried out. These results were expected, as the pesticide production facility manufactures different formulations at different intervals of time. The biochemical oxygen demand (BOD) and chemical oxygen demand (COD) concentrations ranged from 5101-18000 mg/L and 18675-47763 mg/L, respectively. The pesticides average concentrations for 2,4-DCP were high at 58.96 mg/L, followed by MCPA at 32.45 mg/L, PCOC with 21.91 mg/L, 2,4-D at 13,94 mg/L and MCPP at 7.58 mg/L. On the other side the average concentrations for 2,4-DB and 2,4,6-TCP were >5 mg/L and the average concentrations for 2,4-DP and MCPB were <1 mg/L. When evaluating different treatment options to design a hybrid system to treat the pesticide production industry wastewater it was clear that a biological treatment process should be considered due to the high BOD and COD. Anaerobic treatability tests indicated that the wastewater was toxic to organism present in anaerobic digested sludge, as no methane production was observed at dilutions >1%. Aerobic respirometry tests showed this wastewater was toxic to activated sludge microorganisms at dilutions >25%. Nevertheless, when testing the wastewater diluted to 25%, it was observed that the addition of nutrients (1.7 g/L NH4 and 0.23 g/L PO4) and alkalinity (and 0.1 g/L) enhanced the biological degradation, with pesticide removals of 63% for phenoxy acids (MCPB, MCPA, PCOC, MCPP), 34% for 2,4,6-TCP and 17% for dichloro acids (2,4-D, 2,4-DP, 2,4-DB, 2,4DCP).. Acclimatisation studies were inconclusive. The physical/chemical characterization of the key pollutants present in the pesticide production wastewater indicates their likelihood to be adsorbed (molecular weight >170 mg/L and Log Kₒw >2.5). Tests completed with granular activated carbon (GAC) indicated high adsorption capacity for these pollutants as 1 g/L GAC removed 100% of the phenoxy acids, 2,4,6-TCP and dichloro acids within 24h. Lab-scale column tests were completed with pesticides breaking through between 599-1374 bed volumes (BV) when using 3-30 minutes EBCT. Advanced oxidation processes (AOPs) showed no removal of pesticides when treating the wastewater with Fenton process even at high doses of H₂O₂ (12500 mg/L) and Fe²⁺(20 mg/L) Other tests were completed with UV/H₂O₂ using a dose of 1250 mg/L H₂O₂ and a UV intensity of 3 mW/cm² but low 30% total pesticides removal was also observed. On the other side, UV photolysis was a shown to be efficient at removing the pesticides without the presence of H₂O₂. The GAC-biological hybrid system showed that after GAC treatment the pesticide production wastewater was not toxic to the aerobic microorganisms at 75% wastewater dilution. After 552 BV GAC and biological treatment, removal efficiencies were significant with overall pesticide removals of 86% (phenoxy acids), 98% (dichloro acids) and 83% (2,4,6-TCP). Nevertheless, the effluent quality produced by this process would not bet high enough to achieve the limits described in the WFD and the GAC would need frequent regeneration, leading to high operational costs. A number of hybrid systems (granular activated carbon, membrane bioreactor and ultraviolet photolysis) were also investigated. The MBR-GAC pilot-plant showed very effective especially after dosing with additional nutrients and alkalinity. After diluting the wastewater to 25%, to prevent toxicity to the MBR process, and GAC, the removals reached 88% for COD, 72% for BOD and 86-99% for pesticides. Photolysis with UV showed promising results to replace the GAC, as the MBR-UV system achieved a total pesticides removal of 99-100%. The MBR-UV hybrid system generated an effluent with 5 μg/L MCPA, 1 μg/L MCPB, 7 μg/L MCPP, 22 μg/L PCOC, 39 μg/L 2,4-D, 0.75 μg/L 2,4-DP, 0.37 μg/L 2,4-DB, 5 μg/L 2,4-DCP and 5 μg/L 2,4,6-TCP. Nevertheless, even with high effectiveness of the MBR and UV system the effluent did not reach the discharge limits to meet WFD annual average environmental quality standards (EQS) for 2,4-D (0.3 μg/L) and MCPA (2 μg/L), just the EQS for 2,4-DCP (20μg/L) and MCPP (18 μg/L) would be met. The EQS are set for environmental water quality and could be met if the treated wastewater is discharged to a water body that ensures 1:150 dilution, assuming that no 2,4-D is present in receiving water body.
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    ItemOpen Access
    Pesticide removal from farm run-off using in-field treatment systems.
    (Cranfield University, 2018-12) Cosgrove, Stephanie Leanne; Jarvis, Peter; Jefferson, Bruce
    The use of pesticides in modern agriculture is necessary in order to maintain high crop yields, however this use of pesticides can risk contamination of potable water sources. In order to prevent potable water contamination, the movement of pesticides out from agricultural environments must be prevented. In this work, adsorption media has been considered as a means to do this as it can be used without external energy requirements and so can be used in remote locations such as farmland catchments. To understand the issue of pesticides in drinking water in the UK, a study on pesticide water quality compliance was conducted using data available from the Drinking Water Inspectorate water quality regulator. From this, a number of pesticides were identified to be of particular concern. The physico-chemical properties of these pesticides were then established and adsorption media suitable for their removal from water was identified. A field study was conducted to understand the specific conditions under which pesticide run-off occurs using a new sampling methodology that was proportional to the local rainfall. The work then researched in-field adsorption solutions for pesticide removal. This was investigated by using different activated carbon media and determining their speed and efficiency at removing three identified pesticides: metaldehyde, metazachlor and propyzamide. The practical applicability of each medium was then considered by understanding the headlosses that might be observed at a range of realistic flow rates as observed in the field study. This resulted in the selection of an activated carbon fabric for pilot testing in flowing water as a result of its superior kinetic uptake and its effective performance in a complex matrix (raw water) when compared with the other media tested. In addition, the ability to orientate the fabric into a range of practical and flexible configurations will enable reduced headlosses in agricultural environments. The results showed that the activated carbon medium had great potential, achieving approximately 46% removal of the pesticide metaldehyde during flume experiments.
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    Removal of Siloxanes from Biogas
    (Cranfield University, 2014-10) Hepburn, Caroline Amy; McAdam, Ewan; Simms, Nigel J.
    Economic utilisation of biogas arising from sewage sludge is hampered by the need to remove siloxanes, which damage gas engines upon combustion. This thesis applies on-line Fourier transform infrared spectroscopy to measure siloxanes in biogas upstream and downstream of the activated carbon vessels designed to adsorb siloxanes. On-line analysis provides accurate measurement of siloxane concentrations with a detection limit below the siloxane limits set by engine manufacturers, high data intensity and timely identification of breakthrough. Cost savings of up to £0.007 kWh- 1 may be realised compared to existing grab sampling. Using on-line analysis, the performance of full-scale and bench-scale carbon vessels were measured. Full-scale carbon contactors are typically operated at Reynold’s numbers close to the boundary between the laminar and transitional regimes (Re = 40 - 55). This thesis demonstrates, at full- and bench-scale, that increasing the Reynold’s number to site the adsorption process in the transitional regime increases media capacity, by 36% in dry gas and by 400% at 80% humidity. It is postulated that the change in gas velocity profile which occurs as Reynold’s number increases reduces the resistance to siloxane transport caused by gas and water films around the carbon particles, and therefore increases the rate of the overall adsorption process. In the laminar regime (Re = 31) increasing humidity from zero to 80% led to the classical stepwise reduction in adsorption capacity observed by other researchers, caused by the increasing thickness of the water film, but in the transitional regime (Re = 73) increasing humidity had no effect as no significant water film develops. It is therefore recommended that siloxane adsorption vessels should be designed to operate at Reynold’s numbers above 55. By choosing a high aspect ratio (tall and thin) both Reynold’s number and contact time can be optimised.