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Item Open Access Toughening tetrafunctional epoxy resins with thermoplastics(Cranfield University, 1988-12) Gilbert, A. H.; Bucknall, CliveThe study described in this thesis examines how modification with different thermoplastics affects the structure and properties of a tetrafunctional epoxy re5ín_ Polyetherimide (PEI) is found to give the best improvement in fracture properties without loss in Youngs Modulus and the PEI/epoxy system is used as the basis for further study. The influences of PEI concentration, initial cure temperature, test temperature and the presence of a second thermoplastic additive, are investigated. The information provided gives insight into the likely mechanisms of toughening in tetrafunctional epoxy/thermoplastic blends. Flory-Huggins Lattice Theory is used to describe miscibility behaviour for a number of curing thermoplastic/epoxy blends and the predictions compared with the actual morphologies observed. Further, the sensitivity of the expected miscibility behaviour to fluctuations in Flory Huggins interaction parameter X12 and number-average molecular weight Mn of the thermoplastic, is considered. Dynamic mechanical analysis is used to monitor the changing viscoelastic properties of curing thermoplastic/epoxy blends, allowing investigation of the way different thermoplastics influence the state transformation profile of a curing epoxy resin.Item Open Access The role of environmental effects and Acinetobacter spp in enhanced biological phosphate removal(1996-02) Jones, M; Stephenson, TomOne aim of this work was to define the role of Ac/nefojbacfer spp. in enhanced biological phosphate removal (EBPR). A culture enrichment and selective medium technique was developed to isolate Acinetobacter spp. from both conventional and EBPR activated sludges. The methodology proved to be successful and Acinetobacter spp. thus isolated were investigated for their enhanced phosphate removing abilities alongside reference cultures. The cultures were studied in shake flask batch investigations and in sequencing batch reactors (SBRs). None of the Acinetobacter spp. isolates studied exhibited EBPR. A study of the effect of several environmental parameters; temperature, pH and influence of electron acceptors was the other aim of the work. Acclimatised EBPR sludges were used in these investigations which were studied in shake flask batch investigations and in SBRs. Temperature was shown to be an important variable; optimal wastewater temperature for anaerobic release and aerobic uptake of phosphate was found to be around 30°C. EBPR was still observed at extremes of 5 and 40°C and activation energies were also determined. pH levels also influenced EBPR. Batch studies showed different pH optima for anaerobic phosphate release and aerobic phosphate uptake. The presence of nitrates and nitrites in the anaerobic phase, thereby establishing anoxic as opposed to truly anaerobic conditions was evaluated. Under the operating conditions of the study, nitrate and nitrite concentrations up to 100 mgN I'1 still showed ~ 70 % phosphate removal. During comparison of nitrate, nitrite and air as electron acceptors, aeration removed over 90% phosphate, nitrate addition 51-64% and nitrite addition <10%. Acetate was shown to be the preferred carbon substrate as opposed to glucose and methanol. Nitrate had less inhibitory effect on EBPR at the higher substrate concentration of 400 mg I'1 (as COD).Item Open Access A crop choice framework for a more sustainable agriculture, the case of the Argolid Valley in Greece(1996-08) Blatsou, Condylenia; Lemon, MarkThis thesis integrates a number of disciplines from the natural and social sciences to develop a crop choice framework for a “more” sustainable agriculture. The biophysical, socio-political and technoeconomic influences upon farmer’s decisions form the central component of the framework with policy makers the intended target. The sustainability of agriculture generates a lot of debate among academic and policy communities. The literature concerning this debate is considered and it is argued that sustainability is site specific and can only be discussed in relative rather than absolute terms. The research is carried out in three phases each of which contributes to the final framework. The first phase produces a generic framework which is then applied to a particular area, the Argolid Valley in the Peloponnese, Greece. The modified framework is then used to evaluate a specific “crop” (greenhouse roses) and it is demonstrated that the crop will only be adopted by a minority of farmers with particular characteristics. However, it constitutes a useful example for the assessment of whether a crop is promoting sustainability in all its social, economic, ecological and agronomic dimensions. The thesis provides an overview of the disciplinary components that a crop choice framework should include and the techniques employed to support this. Similarly, by underlining the critical role of the farmer, it aims to produce a conceptual framework which is useful for policy formulation and decision-making.Item Open Access Minimising particulate passage during ripening of direct filters(1996-12) Colton, Jason; Fitzpatrick, C. S. B.A significant consideration in forward planning for water treatment works design and operation concerns the effectiveness of filtration plant in providing a barrier to particulates in the low micron size range, including Cryptosporidium oocysts. The filter ripening period has long been identified as a cause for concern with respect to particulate passage into the filtrate, this work has shown that up to 54% of all particles that pass into supply during a 48 hour run, do so in the first hour of operation The aim of this study was to investigate methods of reducing particulate passage into the filtrate during ripening and identify optimums. Thus strengthening the filtration barrier to Cryptosporidium oocysts. The work was carried out on a large direct filtration pilot plant treating an upland lake source. Variables investigated included, filter media type and size, backwash regimes and durations, start-up strategies such as slow-start, and filtration rate. The two filter media types and configurations that gave best removal were in beds of 0.5-1.0mm silica sand and 2m beds of 2.0-3.35mm quartz sand. A combined air/water backwash, at rates to achieve collapse-pulsing, reduced the numbers of particles in the filtrate during ripening and increased run lengths when compared to water only wash and air followed by water wash. Optimum backwash durations identified for the 0.5-1.0mm sarid and 2.0-3.35mm sand were 4 and 3 minutes respectively. The effect of start-up strategies on the numbers of particles in the filtrate during ripening was found to be variable. Slow start (both 1/2 hour and 1 hour) performed well under normal conditions experienced at the plant but performance was adversly affected by deteriorating raw water conditions. Delayed start was not as effective as slow start under normal conditions but was much more effective during periods of poorer raw water quality. Higher filtration rates (10 and 20m/h) resulted in much greater numbers of particles in the filtrate during ripening, thus fast-start was not a viable option. Cost benefit analysis of the technical options showed backwash optimisation and delayed start to be attractive retro-fit options in terms of cost effective reduction of particulate passage during filter ripening.Item Open Access Nitrogen mineralisation and leaching losses from farm-yard manure under simulated centre pivot irrigation(1997) Almadini, Addukrahman Mohammad; Leeds-Harrison, Peter B.Nitrogen (N) leaching losses resulting from agricultural activity are a major concern to researchers and land managers in different parts of the world, due to the adverse effects of dissolved nitrogen on the water environment and on farmers’ returns. In this study the effects of intermittent irrigation, such as that occurring under centre pivot irrigation, on leaching losses of nitrogen mineralised by micro-organisms from different application rates of farm-yard manure (from 0 to 80 t FYM ha¯¹) and N fertiliser (300 kg N ha¯¹) mixed with sand have been examined using pots and leaching columns. Different N species (Ammonium, NH₄ᶧ-N; nitrate, NO₃¯-N; and total soluble nitrogen, TSN) have been investigated in the effluent samples collected from the bottoms of the pots and columns. Initially, in the pot experiments the results showed that there were significant differences (P = 5%) between the amounts of nitrogen mineralised from the different FYM application rates under different wetting treatments. The moisture conditions had greater effects on nitrogen mineralisation than FYM application rates. However, the opposite was observed when the C:N ratio of the applied FYM was narrowed by the addition of urea as a N fertiliser. Nitrification did not occur in a mixture of FYM- sand (i.e., un-modified sand), which was attributed to the lack of nitrifying bacteria in the mixture. However, inoculating the mixture with a sandy loam field soil caused NO₃¯-N to be the major N species in the effluent samples. In the leaching columns,NO₃¯-N was the dominant nitrogen form found in the effluent. NO₃¯-N concentration was significantly affected by the irrigation practices. The highest concentration (95 mg NO₃¯-N ɭ¯¹) has been found for the treatment in which the top sections containing the applied FYM have been maintained at the field capacity moisture condition. A relationship between the frequency of water application and NO₃¯-N movement in the soil columns was found. The amount of NO₃¯-N leached from the soil columns wetted every four days > eight days > twelve days. This suggests that frequent irrigation practices leach NO₃¯-N further in the soil profile increasing the possibility of NO₃¯-N leaching beyond the root zone. In addition to water application practices, the start of NO₃¯-N breakthrough was related to the moisture conditions of the soil columns. For the soil columns maintained continuously at the field capacity, 812 ml cumulative effluent was needed before the NO₃¯-N breakthrough, compared to 610, 464, and 381 ml which were needed for the soil columns intermittently wetted for 4, 8, and 12 days, respectively. This indicates that more water is needed before NO₃¯-N breakthrough under wet conditions than under dry conditions. The amounts of N leached from the soil columns were correlated with the ratio of effluent to water applied, suggesting that irrigation and drainage practices have an impact on NO₃¯-N leaching losses. This study has demonstrated that there are relationships between the frequency of irrigation and N mineralisation and leaching losses from the applied FYM, which lead to the conclusion that minimum NO₃¯-N leaching losses are likely to be obtained under irrigated, fields when adequate adjustments for the nitrogen mineralised from the applied FYM are made and proper irrigation scheduling is practiced. The best management of nitrogen, which aims to maximise crop yields and minimise environmental impact, is proposed for centre pivot irrigation in the Kingdom of Saudi Arabia.Item Open Access A comparison of floating and sunken media biological aerated filters (BAF)(1997-03) Mann, Allan; Stephenson, TomThe aim of this experimental work was to directly compare the performance of two types of media support in pilot scale biological aerated filter (BAF) reactors. The two media types were identical in shape and size except one was sunken with a relative density of 1.05 and the other floating with a relative density of 0.92 and made of polypropylene. Empty bed tracer studies were initially undertaken to ascertain the hydraulic characteristics of the media types under different process conditions. Almost ideal plug-flow was seen without aeration but with aeration some mixing and by-passing was seen which increased with higher aeration rates. Aerator design and positioning had little effect on the flow and that the sunken media would perform best in downflow and the floating media in upflow during biological treatment. Two methods of start-up were employed during unsteady state analysis, activated sludge seeding and the use of the process liquid (settled domestic sewage) at the operational flowrate. Both methods showed a similar total start-up time of 28 d. At steady state the floating media removed 78% suspended solids (SS) and 75% soluble chemical oxygen demand (sCOD) compared to 66% and 68% respectively in the sunken media. At high flowrates and during shock loadings of up to 1.5 times the nominal flowrate the floating media again showed a better performance than the sunken media. With increasing shock loadings the recovery time increased with a corresponding decrease in solids and soluble COD removal rates. At the maximum SS loading of 1.397 kg m'3 d'1 ( 1.403 kg m"3 d'1 sCOD) only 35% (30% sCOD) removal was seen in the sunken media compared to 60% (40% sCOD) in the floating media. The steady state results were used to produce an empirical model relating effluent soluble COD to influent COD and reactor height. Assuming plug flow the profiles showed a first order rate of reaction. A first order empirical model was then established based on that used for trickling filters, which produced constants dependent on the media type. During tertiary treatment low ammonia loadings of 0.2 kg m'3 d"1 restricted autotrophic growth and led to preferential growth of heterotrophic bacteria. At ammonia loadings of up to 1.16 kg m'3 d"1 nitrification was rapid. Below 5 °C nitrification was minimal but almost full nitrification was achieved at approximately 10 °C. Though backwashing was carried out only on a weekly basis, overwashing appeared to have caused a gradual reduction in treatment efficiency. During nitrification the sunken media was more efficient at ammonia removal than the floating media, indicating that the autotrophic bacteria prefer the more open structure of the sunken media. Reactor profiles indicated a zero to half order reaction.Item Open Access Fouling characteristics of membrane filtration applied to wastewater(1998) Thomas, M HThe use of microfiltration and ultrafiltration in waste water treatment is attracting increasing interest. The problem of membrane fouling and the high costs associated with the process has limited large scale applications. This study forms part of a project to optimise the design of a membrane bioreactor. A pilot plant has been used to assess the performance of three tubular membrane modules. The wastewater used has been taken from an existing biological reactor to simulate the conditions found in a membrane bioreactor. Commercially available membrane modules of different specification have been tested. The study has centred around the fouling characteristics of the membranes under varying operating conditions. The flux produced after 24 hours continuous operation has been used to assess the degree of fouling present. The hydrodynamic conditions have been varied, and an optimal cross flow velocity range has been identified. The feed wastewater has been varied, and the specific flux at different MLSS concentrations recorded. The specific flux shows a decline with increasing MLSS concentration. The magnitude and rate of this decline is membrane dependant. The permeate product water shows a reduction of more than 99% for SS, BOD, and COD over the feed stream under all conditions used. The DOC also shows a reduction of up to 72%, indicating that the membranes reject a portion of the high molecular weight molecules present in the feed stream. The energy consumption has been estimated from the final permeate flux produced under each set of conditions. The lowest value has been found to be 1.75 kWhm-3, which was achieved at the lowest cross flow velocity used during the trials. This illustrates the influence of pressure drop through the system, which is proportional to the flow velocity squared.Item Open Access Mycoflora of wheat straw : effects of environmental factors on spoilage and straw quality(1998-02) Willcock, Joanne; Magan, NareshThe effect on the mycoflora, succession and deterioration of straw quality over a range of environmental conditions, including 0.75 to 0.98 water activity (aw), 10- 30°C and pH 4.4-6.4 were investigated. Isolation and colonisation of natural mycoflora and individual fungal species were significantly influenced by temperature x aw x pH interactions (P <0.05). Generally, the least growth occurring at 0.75 aw and 10°C, and the maximum at 0.98 aw and 30°C. Small scale respiratory apparatus was modified to measure respiration of the natural mycoflora and five individual species (Alternaria alternata, Cladosporium cladosporioides, Eurotium amstelodami, Fusariwn culmorum and Pénicillium aurantiogriseum) on wheat straw for the first time. Respiratory activity significantly increased with increasing temperature and aw (P <0.05). At the highest temperature (30°C) there was almost a linear increase, whereas at the lowest temperature (10°C), a lag time occurred prior to increased respiratory activity. Maximum dry matter losses (DML) were found to be 3.40 % at 30°C and 0.98 aw. Dry matter losses were found to change with storage period, and temperature x aw interactions. Significant loss of the carbohydrate components (P <0.05), assuming no loss of true lignin, was observed at 20°C when the apparent lignin content rose with increasing aw and, once 0.90 aw had been reached, remained at 140 % of the starting value. Of three biocides (Adesol 20, Busan 881 and Lastil 40), Lastil 40 was found to be most effective in vitro and on straw of significantly reducing fungal populations. Field trials with biocides and Nutri-Shield® at different storage moisture contents demonstrated that wads of straw on the surface of the top bales of the stack at 15 and 23 % moisture content provided the most effective storage treatment and significantly conserved the straw quality (P <0.05). All of the treatments, except wads of straw in nets, had increased apparent lignin contents, which showed that degradation had occurred.Item Open Access Soil incorporation of bio-solids into arable cropping(Cranfield University, 1999) Moseley, Peter; Earl, R."The application of bio-solids to established arable crops, using shallow injection techniques developed during this study, is feasible in environmental, economic,agronomic and engineering terms." Novel approaches to bio-solids disposal and recycling are required to compensate for expected increases in production, and to alleviate the extemal pressures exerted on the water company through legislation and increased public awareness of environmental issues. A review of previous work has identied bio-solids application to arable cropping as a promising benecial outlet for increased volumes of waste. From this doctoral study, in collaboration with a parallel fast track project, a improved, shallow injection system has been developed, based on soil mechanics theory and extensive laboratory and field testing. Environmental pollution, in terms of odour and ammonia emissions, may be signicantly reduced through the use of this system, when compared to other shallow injection or surface application methods. Nitrate leaching was found to be unaffected by the increased retention of valuable nutrients under field conditions prevailing during the study period, and no detrimental effect on agronomic performance has been identied following application to crops up to three months prior to harvest. Economically, a market exists for this technology, through the enhanced nutrient value of the bio-solids product. However, product quality, consistency and other enviromnental issues require solutions before the full economic benefits and market acceptance can be realised. Theoretically, the increased application "window of opportunity" has the potential to increase producers operating profits substantially (1.7%/yr, Anglian Water Services Region) through reduced inventory, storage and distribution costs. Maximisation of enviromnental benefits has been addressed in terms of implement control, by maintaining constant tine attitude to the soil, through a parallel linkage system. A analysis of the force system associated with the parallel lirkage system, in conjunction with the development of a model to predict tine depth, was used to examine ways of optimising the dynamic performance of the system. This work demonstrated that geometric changes to the parallel linkage are unlikely to affect dynamic performance. However, the use of frictionless linkage joints in conjunction with depth control skids was shown to improve dynamic performance signicantly and a novel multiple curve fitting technique was developed to improve the accuracy of the depth prediction model.Item Open Access Silvoarable agroforestry(The Royal Scottish Forestry Society, 1999-01-01) Beaton, A.; Incoll, L. D.; Burgess, Paul J.Introduction: A silvoarable system of land management implies the cultivation of trees and arable crops on the same area of land, a system practised quite commonly in southern Europe and in the tropics. The system comprises two components: tree rows, generally one tree wide, and arable alleys, alternating across the field. The first major development of silvoarable practice in the UK took place during the 1960s and 1970s when Bryant & May established extensive poplar plantations on lowland farmland in southern England to supply their own market for match veneer timber (Beaton, 1987). Since the demise of the Bryant Sr May market for match timber in 1978, interest in the potential for silvoarable systems lay dormant until the advent of food crop surpluses in the 1980s.Item Open Access Upflow and downflow biological aerated filters (BAFs) for wastewater treatment(1999-03) Mendoza-Espinosa, Leopoldo Guillermo; Stephenson, TomInvestigations on two small pilot-scale biological aerated filters operating in upflow and downflow mode using identical media were undertaken in order to compare their performance for the removal of carbonaceous matter and ammonia, calibration of empirical models for suspended solids, soluble and total COD and their resistance to organic and hydraulic shock loadings. The initial existence of a plenum chamber under the media bed caused severe reduction in active volume in the downflow reactor. Elimination of the plenum chamber by means of the addition of media solved the problem and both reactors presented plug-flow conditions. Their performance for carbonaceous matter and ammonia removal was compared. With the exception of ammonia, the removal efficiencies for the parameters studied in both types of reactor were very similar. The downflow reactor achieved a greater removal of ammonia than the upflow BAF. Autrotrophic activity was located at the bottom of the reactor in the downflow column and at the top in the upflow unit. Had the running conditions been set identically for both columns, the difference in performance between the two reactors may have been due to the impact of the backwashing on the biological population, effectively washing-out the autotrophs. The verification of a simple empirical model for soluble COD removal for a different type of media than the previously reported was conducted. The new values for the media constant and the overall process constant of the system suggested that overall, the performance of the system was dictated by its media type/liquid flow characteristics. The constants from 4 empirical models were used to predict the removal of SS, sCOD and tCOD in a small BAF (0.07 m3 empty bed volume) and a large BAF (0.69 m3 empty bed volume). The model for soluble COD that included parameters such as gas and liquid velocity provided values closer to the actual observed values. The model for suspended solids and tCOD removal (based on a rapid gravity filters model) was efficient in predicting the overall removal rates of SS and tCOD in both reactors. When the models were used for scaling-up results, only the simplest model that did not include parameters such as gas and liquid velocity was effective. It was demonstrated that a small pilot-scale BAF was not capable of absorbing high peak organic shock loads when the organic loads were increased from a normal load of 1.2-1.4 kg sCOD m-3 d-1 to shock loads between 5.1- 7.3 kg sCOD m-3 d-1, based on empty bed volumes. Nevertheless, the effect on the biomass was limited as normal performance resumed very quickly. Increases in the hydraulic velocity from 0.7-1.0 m h' 1 to 1.5-2.9 m h" 1 had little affect on BAF performance in terms of soluble COD removal. Soluble COD effluent concentrations of <40 mg I-1 (-16 mg 1-1 BOD5) were detected thus, meeting most discharge consents in UK sewage works. The recovery of the reactor in both cases was fast, resuming normal performance within 60 min after the application of the shock load.Item Open Access A naturally ventilated crop protection structure for tropical conditions.(Cranfield University, 1999-06) Kamaruddin, Rezuwan; Douglass, M. P.; Bailey, B. J.This study presents the theoretical and experimental results of natural ventilation rates induced by stack, wind and the combination of both stack and wind effects for a typical crop protection structure suitable for the tropics. The structure consists of simple structural frame, transparent roofing and insect screen side walls. It was found the relative importance of the stack and wind effects is dependent on the ratio between wind speed and the square root of the inside-outside temperature difference (u/AT°.5). In this study, the wind effect dominates over the stack effect when the ratio u/AT" becomes greater than 0.5. Ventilation rate induced by the stack effect was found to increase with increasing temperature difference between inside and outside of the crop protection structure according to a power law, with an index of 0.5. The wind effect ventilation rate was found to increase linearly with increasing outside wind speed measured at eaves level. In addition, the combination of the stack and wind effects could be represented as the vectorial sum of two the independent effects (40sw = [43)k2 + (1)„,nd21 0.5). However, the result of the wind effect in the combined effects was insignificant when the ratio of ventilator opening to the total wall area is higher than 20 %. Different methods have been used to determine the natural ventilation rates. The dynamic tracer gas was used as the control; direct airspeed measurement, energy balance and neutral plane methods were used to quantify ventilation induced by the stack effect. Pressure field measurements were used to quantify ventilation by wind effect. In addition, the dynamic tracer gas, energy balance, and stack and wind methods were used to quantify ventilation induced by the combined effects. However, these methods have their constraints and limitations because of statistically significant differences in the comparison between the methods. The tracer gas method was found very difficult to use in the highly porous structure. In addition, the ventilation rate measured by this method was 30-40 % less than the other methods. The energy balance method has the advantage that it estimates many important climatic and crop parameters, however, the errors were found to be the highest. The neutral plane method was suitable for measuring ventilation induced by stack effect, the simplest method, requiring only the measurement of the inside and outside temperatures. The direct airspeed measurement method was much easier to handle and the result was comparable to other methods suitable for determining the ventilation induced by the wind effect. The physical properties of the covering materials, namely light transmission, coefficient of discharge and airflow characteristics were also determined in this study. It was found that the light transmissions of transparent polythene film and insect screens were close to each other. The coefficient of discharge and light transmission were dominant parameters in the ventilation rate calculation. It was found that when air flows through a screen, the pressure drop increases linearly with the square of approach airspeed. Airflow distributions inside the crop protection structure induced by the stack and wind effects are also presented in this study. Finally, this study presents information on natural ventilation for tropical greenhouses that was not previously available.Item Open Access Development of a novel medium to improve the performance of Biological Aerated Filters (BAFs)(1999-10) Moore, Rebecca Ellen; Stephenson, Tom; Quarmby, Joanne; Millier, P.A foamed clay, StarLight C, was selected as a potential BAF medium after qualifying as a filter medium according to the BEWA standard tests, and showing the propensity to collect a biofilm. At loading rates > 10 kg COD/ m3 working volume/ d, two pilot- scale downflow BAFs running in parallel and containing either StarLight C or medium A (a standard expanded clay) achieved a mean of 87% suspended solids removal and 75% soluble COD removal. Both reactors were backwashed daily for ten minutes at a liquid flow rate corresponding to 40% of the minimum fluidisation velocity (Vmf) of the media. The approximate experimental Vmf of StarLight C was 120 m/h compared to 215 m/h for medium A. Therefore, the BAF using StarLight C exhibited between 11 and 19 % increased productivity at liquid velocities from 1.4 to 2.4 m/h. Lowering the Vmf of a BAF medium should also reduce the operating and capital costs of the process. According to representatives of the wastewater treatment companies, high operating costs are the major disadvantage of the BAF process. Increasing the feed bentonite concentration from 35 g/1 to 56 g/1 produced a StarLight C variant with improved crush resistance and a lower attrition rate. Meanwhile, a larger extruder nozzle was used to increase the particle size of the medium. Pilot-scale trials showed that the maximum run times were extended by between 8 and 31 hours when using the larger variant (2.5-4.5 mm diameter) compared to the smaller (1.5-3.5 mm diameter). Observing logarithmic head loss development and the cessation of suspended solids removal in the lower region of the reactor, suggested that the smaller StarLight C was an inefficient filter medium. Using an environmental scanning electron microscope, hydrated biofilms were observed growing on StarLight C’s surface. The highly variable biofilm distribution and structure is not accounted for by current biofilm and mechanistic process models. A first-order empirical model described the removal of soluble COD in the top section of the reactors containing medium A, small StarLight C and large StarLight C. The first-order constants were dependant on the liquid velocity and at 1.4 m/h were 61 d"1, 45 d'1 and 33 d"1 respectively.Item Open Access Low-cost membranes for submerged membrane bioreactors(2000-04) Gander, Michelle; Judd, Simon J.The present work aims to assess the feasibility of using an ostensibly low-cost polypropylene (PP) material for processing municipal wastewater from the University sewage works. Two different types of hydrophilic membranes were employed, both being macroscopically homogenous (i.e. isotropic) in their physical nature. These were: • An extruded polymeric membrane (EPP) containing microscopic glass beads as a fibrulating agent (0.5 jam pore size), and • A non-woven felt of microscopic fibres (NWPP) of 1.5, 3 and 5 jam pore size. The membrane materials were mounted on plate and frame modules and used in a submerged membrane bioreactor (MBR) run at 0.06 bar, fed continuously with primary effluent. Membrane performance was assessed in terms of specific flux and rejection, the latter with respect to indicator bacteria. Overall bioreactor performance was measured in terms of BOD5 and COD removal and the extent of nitrification. An initial economic analysis was also undertaken to identify major costs in treating municipal wastewater with the two configurations of MBR. Analysis of these two areas concluded that: • flux decline is most significant in the first few hours of filtration, • bacterial rejection increases with the formation of the dynamic membrane, • organics removal is high even when mixed liquor suspended solids are low, • sludge production is reduced due to long solids retention times and substrate inhibited microorganisms, and • economics point to submerged MBRs being more cost efficient than side-stream MBRs due to their lower operating costs. Only one NWPP membrane (5 jum pore size) could be concluded to be suitable for use to treat municipal wastewater, and only if disinfection was not required. The other NWPP membranes where highly susceptible to fouling, therefore producing a permeate flux unacceptable for commercial treatment processes. The PS membrane showed the most suitable characteristics for treatment of municipal wastewater in submerged MBRs.Item Open Access Assessing the potential of full-scale phosphorus recovery by struvite precipitation(2000-09) Jaffer, Yasmin; Parsons, SimonFormation of struvite (MgNH4P04.6H20) at sewage treatment works can cause major operational problems and decrease efficiency. Struvite has a commercial value and the controlled formation of it, in a specified location, would be beneficial. A mass balance was conducted at full-scale across a whole sewage treatment plant, to identify a stream to conduct bench-scale struvite crystallisation studies on. The most suitable stream was identified as the centrifuge liquors. The average flow of the liquor stream was 393 m3 d'1 and the composition was as follows: 167 mg L'1 phosphorus, 44 mg L'1 magnesium, 615 mg L 1 ammonium, 56 mg L 1 calcium and 2580mg L'1 of alkalinity. The pH averaged at 7.6 and the stream had a predicted struvite precipitation potential of 140 mg L'1. Struvite crystallisation occurred quickly during the trials, by raising the pH of the centrifuge liquors to 9.0 and dosing with magnesium. Up to 97% phosphorus removal, as struvite was achieved. Struvite formation occurred when the molar ratio of magnesium : phosphorus was at least 1.05 : 1. Below this ratio phosphorus removals of 72% were observed, but not exclusively as struvite. Annual yields of struvite were calculated to be 42-100 tonnes a year, depending on the dose regime. Revenue from the sale of produced struvite could be £8,400-20,000 a year.Item Open Access Responses of composite tea plants to drought and irrigation in the Southern Highlands of Tanzania.(2002-01) Mizambwa, Firmin Cyprian; Stephens, WilliamThe responses of composite tea plants to drought and irrigation were studied in a line-source experiment in the Southern Highlands of Tanzania. Two scion clones (SI5/10 and K35) were grafted onto each of three rootstock clones (6/8, SFS150 and PC81). The scions were also grafted onto each other (i.e. SI5/10 on K35 and vice versa), and cuttings of ungrafted clones SI5/10 and K35 were prepared at the same times as the controls. In February 1996, the plants were field planted at a spacing of 1.2 x 0.8 m. Six differential irrigation treatments ranging from rainfed conditions (no irrigation) to full irrigation were imposed during the dry seasons, though from planting up to the end of August 1998, the experiment was uniformly irrigated to ensure successful crop establishment. The experiment was irrigated whenever the potential soil water deficit in the fully irrigated plots reached 40 - 50 mm. Between December 1996 and May 1997 shoots above 0.5 m in length were removed or “tipped” to produce a level plucking surface. Routine harvesting started on 16 June 1997, and continued at intervals of 13 to 17 days during the warm season (September to May) and 22 to 29 days in the cool season (June to August). The choice of the scion influenced both the response to water stress and the yield response to drought of the composite plants. Similarly, the soil water availability appeared to modify the effects of rootstock on the yield of the scion. Although not reaching statistical significance, the use of composite plants led to an overall mean annual yield increase of 9% (range between combinations 4 to 21%) in the unirrigated plots, but less than 1% (range -6 to 6%) in the well watered plots when clone S I5/10 was used as a scion. By contrast, using clone K35 as a scion, the overall mean annual yield increase whether irrigated or unirrigated was less than 3% (range -12 to 11%). In the driest plots, rootstocks 6/8 and SFS150 consistently increased the yields of scion clones S I5/10 (by 21%) and K35 (by 11%) respectively. During the dry season, some composite plants survived the drought better than the ungrafted plants. Assessing the effect of rootstocks on the composition of harvested shoots (i.e. shoots of different sizes/stages and the proportion of the total weight that were composed of coarse and broken leaf) revealed that none of the rootstocks had a significant effect on the composition of harvested shoots. Likewise, the rootstocks did not affect the bush morphology as assessed by ground cover development, shoot population density, stem diameter and number of branches. The use of composite plants in tea production by both smallholders and commercial companies is technically feasible, but the benefits to be realised depend on the rootstock/scion combinations used. The extra cost of producing plants by grafting when large-scale tea growers opt to use composites rather than the conventional plants was estimated to be only US $ 100 ha⁻¹. Due to low labour costs, the corresponding cost for the smallholders was US $ 47 ha⁻¹. The payback period when composite plants were used in tea production was the same as that of the conventional plants, but this period was shorter for smallholders than the commercial companies. The payback period was in year 1 (i.e. the first season of harvesting) for the small-scale growers compared with year 2 or 3 (depending on the prices of made tea) for the commercial companies. Assessing the probability of getting a yield increase necessary to make the use of composites worthwhile revealed that for some combinations, there were higher chances of getting such yield increase. For example, the probability of getting a yield increase of 200 kg of made tea ha⁻¹ in one year was 81% when scion clone SI5/10 was grafted onto rootstock 6/8. The corresponding probability was 74% when clone K35 was grafted onto rootstock SFS150. These results and their implications for the tea industry are discussed. The way forward commercially as well as the future research to increase our knowledge for efficient use of composite plants in tea production is proposed.Item Open Access Improving the adoption levels of manufacturing strategy formulation processes(Cranfield University, 2002-03) Ellson, Tom; Baines, Paul R.This thesis investigates the adoption rate of manufacturing strategy formulation processes and provides insights into why current formulation process workbooks are not widely adopted. A paradigm is developed to enhance the adoption of process workbooks in the manufacturing environment and attempts to bridge the gap between tried and tested processes and their practical application in manufacturing industry. Manufacturing strategy formulation processes have been developed to assist manufacturing companies in the development of manufacturing strategies. There is evidence that the adoption of these processes and the development of strategies within manufacturing industry are beneficial. However, some literature provides anecdotal evidence suggesting that adoption levels of these formulation processes are low. The research programme investigates if, and why, the adoption of manufacturing strategy formulation processes has been low. lndustrially based interviews have been used that confirm the low level of adoption of these processes. A variety of reasons have been identified. These mainly focus on the presentation and format of process workbooks. Several proposals are made to enhance the adoption of manufacturing strategy formulation processes. I particular, the research identifies four key areas that should be considered in the future presentation of manufacturing strategy formulation process. These key areas can be summarised as validity, attention, simplicity, and holistic perspective forming the basis of a paradigm to increase the use of workbooks and the adoption of strategy formulation processes by manufacturing managers. The findings of this research and the development of a paradigm offer practical assistance to bridge the gap between research activities and practitioner requirements. The paradigm has been evaluated by further interviews with industry practitioners and makes a useful contribution to the formulation and application of strategy in manufacturing industry.Item Open Access Using particle monitors to minimise Cryptosporidium risk(2002-07) Hamilton, Paul; Parsons, SimonOver the last two decades, there bas been much interest in whether particle counters hold any significant benefit over conventional nephelometric turbidimeters in monitoring potable water treatment processes. Southern Water, which supplies drinking water to two million customers living in Kent, Sussex, Hampshire and the Isle of Wight first used particle counters at one of its works in 1992. This study presents the key results of a three-year study, conducted in conjunction with Cranfield University to find the most beneficial use of these monitors, so that a sensible investment can be made. This study comprised a series of monitoring trials, conducted at different ground and surface water treatment works. In many instances,. there was a strong similarity between turbidity and particle count trends, effectively making one of monitors redundant However, particle counters were shown to be beneficial in three ways: (a) they could be more sensitive to changes in water quality at low turbidities (below 0.1 NTU), (b) they could be more sensitive to changes associated with larger particle sizes and ( c) they could also provide useful information on particle size distribution. This issue of monitor sensitivity bas been analysed using a regression model built from experimental data For a given water sample, this model predicts how many more times sensitive particle counters will be, in detecting changes in water quality, compared to nephelometric turbidimeters. This indicated that whereas turbidimeters typically 'flat-line' at low values, particle counters are frequently more sensitive and so can be used as a fine-tuning optimisation tool below 0.1 NTU. However, this sensitivity is also proportional to the particle size distribution of the sample; particle counters are more suited to samples containing a high proportion of large particles (> 1 0µm). This explains why particle counters are not always 'more sensitive' below 0.1 NTU. Although no links could be found between particle counts (and turbidity) and Cryptosporidium oocysts, it appears that if oocysts are present in the raw water then inferior particle removal across a treatment process can lead to increased risk. Cryptosporidium oocysts were found even in very low turbidity (<0.1 NTU) treated water samples. This shows the need for fine-tuning treatment processes below 0.1 NTU and highlights a potential optimisation role for particle counters. The study concludes, however, that particle counters are best used as an optional process research/optimisation tool only: turbidimeters remain the preferred monitor for process control Indeed, the study finds no overwhelming evidence to justify the permanent installation of particle counters at treatment works. However, an increased use of portable particle counters in optimisation work is recommended. Consideration is given to other practical concerns such as where and how to use particle counters and what parameters to measure. The value of particle counters' sizing ability has also been assessed. In addition to sensitivity modelling, particle size distribution data revealed a large difference in the volume of particles passed by two sludge treatment plants. The study concludes that, where particle counters are used, there may be some value in monitoring particle size distribution using a particle size ratio or a similar statistic.Item Open Access Intelligent imaging systems for automotive applications(SPIE, 2003-03-31) Thompson, Chris; Huang, Yingping; Fu, ShanIn common with many other application areas, visual signals are becoming an increasingly important information source for many automotive applications. For several years CCD cameras have been used as research tools for a range of automotive applications. Infrared cameras, RADAR and LIDAR are other types of imaging sensors that have also been widely investigated for use in cars. This paper will describe work in this field performed in C2VIP over the last decade - starting with Night Vision Systems and looking at various other Advanced Driver Assistance Systems. Emerging from this experience, we make the following observations which are crucial for "intelligent" imaging systems: 1. Careful arrangement of sensor array. 2. Dynamic-Self-Calibration. 3. Networking and processing. 4. Fusion with other imaging sensors, both at the image level and the feature level, provides much more flexibility and reliability in complex situations. We will discuss how these problems can be addressed and what are the outstanding issues.Item Open Access Report of Committee III.2: fatigue and fracture(Elsevier, 2003-12-31) Brennan, Feargal P.COMMITTEE MANDATE Concern for crack initiation and growth under cyclic loading as well as unstable crack propagation and tearing in ship and offshore structures. Due attention shall be paid to practical application and statistical description of fracture control methods in design, fabrication and service. Consideration is to be given to the suitability and uncertainty of physical models. The work shall be coordinated with that of Committee V.2.