1,721,067 research outputs found
A pcr-based method for SARS-COV-2 variant detection in wastewater.
Get PDFMcAdam, Ewan - Associate SupervisorThe COVID-19 outbreak, caused by the SARS-CoV-2 virus, rapidly evolved into a worldwide
pandemic, as declared by World Health Organization on 11th March 2020. The continued spread
since early 2020 has resulted in many variants of this virus. Most mutations found along its genome
are known as single nucleotide polymorphisms (SNPs) where only one base pair is mutated. Current
real-time qualitative polymerase chain reaction (RT-qPCR) protocols, so called gold-standard
method, are used to confirm if a person is positive or negative for the virus. There is a lack of available
technology for rapid identification of variants. In order to identify the presence of a viral variant it is
necessary to perform sequencing. Sequencing is expensive and may take hours to days to complete.
Due to its cost, sequencing is widely unavailable in most countries. Even in countries where
sequencing is available, like the UK, the number of samples sequenced are less than 10% of total
cases due to extremely high cost.
Wastewater-based epidemiology (WBE) is a novel approach that would help monitor and
possibly revert the current health crisis. It has been reported the presence of SARS-CoV-2 RNA in
faeces of infected individuals. This makes it possible to detect and monitor SARS-CoV-2 in
wastewater samples, providing a health status report of the population within the catchment. To this
context, WBE also enables to monitor the dissemination of variants for early warning of the outbreak
within the defined population.
In this project, a RT-qPCR method was developed targeting unique SNPs of SARS-CoV-2.
This assay uses two probes, both targeting the same sequence, one with the SNP and the other non-
SNP. These mutations are found in the N-gene of SARS-CoV-2 viral RNA, a conserved region that
contains unique SNPs specific to each variant for differentiation. By using two probes, binding
competition occurs, and the differentiation is done by observing an earlier detection with the SNP
probe (~6 cycles). In addition to this, this method can be coupled with a melt curve analysis for further
confirmation.
Currently, there is a lack of available technology for rapid identification of variants of concern
within the community. This assay can be implemented for routine WBE. By developing a SNP-PCR
assay to detect specific variants of concern using WBE, it would be possible to accurately detect
variants. This information provides a comprehensive health report on the population that could
possibly help revert the current health crisis.MSc by Research in Wate
Ammonia inhibition and toxicity in anaerobic digestion: A critical review
Get PDFAs a waste management technology which offers environmental benefit and renewable energy production, anaerobic digestion (AD) has become the preferred technology for the treatment of organic waste. However, in such waste streams nitrogen contents are likely to be high. There is prevailing literature evidence suggests that high ammonia concentration especially its free molecular form (NH3), derived from nitrogen content in substrates is the cause of inhibition and sudden failure of the AD process. This paper comprehensively reviews previous knowledge from digestion studies using high nitrogen waste streams as feedstocks and critically analysed the considerable variations in the inhibition/toxicity levels reported for ammonia. Literature evidences suggest methanogens, particularly acetoclastic methanogens are most susceptible to ammonia toxicity, and therefore this review has a particular focus on the mechanism of the ‘selective’ inhibition to methanogens and the impact of ammonia toxicity to the overall methanogen population in an AD digester. This population change explains in many reported cases that sufficient acclimatisation can significantly alleviate the phenomenon of inhibition and specific requirement of certain trace nutrients. Currently available mitigation strategies for high nitrogen content feedstock digestion are reviewed and discussed in relation to the population change and trace nutrient requirements.</p
SCALE up of hollow fibre membrane contactors for biogas upgrading.
Get PDFHollow fibre membrane contactors (HFMC) are a gas-liquid contacting technology
suggested as a successor to existing gas-liquid absorption columns for the selective
separation of carbon dioxide (CO₂) from biogas i.e. biogas upgrading, which in the United
Kingdom (UK) is a rapidly expanding sector for renewable heat production. Current
incentivisation schemes also encourage process innovation to reduce cost, and those
that enable the revaluation of waste. In response to these drivers, this thesis firstly
describes the implementability of HFMC as a successor technology to packed columns
for biogas upgrading, due to its capability for process intensification, and subsequently
introduces how to employ environmentally sourced ammonia to drive chemical
absorption in HFMC, thereby extending process intensification, whilst also reducing
aeration costs and through a unique contribution of the membrane, enables the
crystallisation of ammonium bicarbonate which can increase value as a new product.
This thesis has introduced an assessment of mass transfer in multi-module
configurations to further intensify the process and demonstrated that when producing a
high purity methane product, a simplified mass transfer model, based on the overall mass
transfer coefficient, can be used to determine gas product quality, process scale and
membrane configuration. Mass transfer behaviour in commercially favoured transverse
flow HFMC modules was compared to parallel flow HFMC modules, typically used in
laboratory investigation which are known to suffer from maldistribution, to enable the
reconciliation of maldistribution with a description of parallel flow and the translation of
the overall mass transfer coefficient across module scale. The resilience of HFMC to
industrial conditions, including gas-phase contaminants such as particulates, was
assessed at a WWTW, demonstrating the primary mechanism of fouling to arise from
the absorbent, in particular biological adsorption and clogging of the shell-side, which is
readily reversible through chemical cleaning. Integration of an NH₃ chemically reactive
absorbent for the co-production of a high purity methane product and recovery of
ammonium bicarbonate demonstrates that the reduction in specific nucleation rate and
preferential crystal growth in HFMC protects the system from blocking by the reaction
product, in contrast the high specific nucleation rate and subsequent agglomeration of
the reaction product induces process blocking during column operation.STREAM EngD programm
Operation and configuration of reverse electrodialysis for thermal to electric conversion applications.
No full textReverse electrodialysis (RED) is a membrane-based technology which enables the sustainable
production of electricity through harnessing the Gibbs free energy of mixing solutions with a
salinity gradient. Whilst RED research has largely focussed on power production from sea water
and river water, efforts to decarbonise the energy sector have led to interest in ‘closed-loop’
RED, which utilises synthetic saline solutions for applications in energy storage and thermal to
electric conversion. To realise the potential of RED for these applications, research is required
to determine the operating conditions and configurations which enable high power output and
energy efficiency and reduce the levelised cost of electricity. In this work, the use of sodium
chloride solutions with an increased concentration gradient in a recycle configuration is
demonstrated to maximise the work produced from a fixed volume when current density is
optimised, minimising the unitary cost of electricity produced by RED. However, these
conditions exacerbate phenomena such as osmosis, ionic transport, and concentration
polarisation, introducing complex temporal effects which must be managed. Features of
electrodialysis modules such as an increased intermembrane distance and the low water
permeability of membranes have been demonstrated to improve energy efficiency obtained
using these feeds at low current densities, however, compromises power density at higher
current densities. Membranes with low water permeability and low resistance are required to
maximise power and energy efficiency using these feeds. Whilst the use of larger stack size has
been shown to be associated with greater exergy losses due to water transport, increasing the
cell pair number has been identified as an effective strategy to increase the process scale,
enabling improvements to both power and efficiency.PhD in Water, including Desig
Using design theory to bridge Design and Science: understanding innovation and the role of Design when developing novel technologies.
Get PDFThe value of design is nowadays largely recognised, especially in its manifestations of
design thinking, product and service design, business organisation as well as disruptive
innovation. Design in the context of the present study is examined from a different
perspective, the one of modern design theory. It is treated as a human activity of
generating innovative concepts, regardless of fields of disciplines, in an attempt to
identify which are the techniques that enable invention to occur. The study aims at
providing a better understanding of design and its cognitive processes, relying on formal
design theory and using a real-world design challenge as a case study.
The case study corresponds to a global, high-profile project funded by the Bill & Melinda
Gates Foundation. Contemporary western-style toilets require a large quantity of clean
water and an integrated sewage system to operate, but 2.3 billion people remain without
access to improved sanitation. For this part of the globe’s population, a waterless and
energy-neutral toilet would constitute a solution with high potential. An important piece
of this toilet is a technology which dewaters and dries human faeces so that it can be
further processed by the system. At the moment, such a technology with low requirements
in terms of size, energy and power demands does not exist. In the context of this research,
a novel, patented drying technology was designed and developed.
The novel dryer designed and developed in the context of the aforementioned project is
represented by using modern design theory. The case study is also used to demonstrate
the way that innovative concepts are generated and to identify the design techniques that
are crucial to invention process, irrelevant to the field or discipline within which it takes
place.PhD in Water, including Desig
Phosphorus removal in passive treatment technologies for tertiary wastewater treatment
Get PDFThe treatment of phosphorus at small sewage works requires alternative approaches
to the traditional chemical precipitation and biological removal pathways, as such
approaches do not align well to the requirements at such a scale in relation to the use
of chemicals, increased energy demands and/or increased sludge production. At small
sewage works, constructed wetlands are often used as a tertiary treatment for solid
removal and some associated biological degradation. The current work aims to assess
the potential to upgrade such systems for phosphorus removal by replacing the
traditional media with a reactive alternative. This was accomplished through a series
of laboratory and pilot trials to establish the most appropriate media and understand
the underlying mechanisms. Determination of key properties, such as retention
capacity, mechanical strength and regeneration potential, identified steel slag and
phosfate™ as media that were suitable for in depth investigation. Both were shown to
be effective at phosphorus removal if sufficient contact time was provided such that 1
mg L-
1
effluent concentrations was achieved when an empty bed contact time of 48
hours was used. A detailed investigation of the media revealed that steel slag worked
through a two-step process where initially calcium was dissolved into the water from
the surface of the media and then precipitated with the phosphorus to form calcium
phosphate.
The presence of alkalinity in steel slag bed inhibited the precipitation of phosphorus
through calcium, as carbonates were precipitated instead. There was also a risk
associated with the leachability of aluminum and flushing of retained phosphorus
during the treatment of wastewater with very low phosphorus concentrations from
the bed.
In the case of Phosfate™ , the binding agent resulted in very high effluent pH and the
formation of colloidal phosphates that needed to be filtered out to enable low effluent
phosphorus concentrations to be achieved.
The results indicated that both media have the potential to remove phosphorus from
tertiary effluents, but the issues of leachability of aluminum from steel slag bed and the release of retained phosphorus should be investigated further before full scale
trials. The colloidal phosphorus observed escaping effluent from phosfate™ bed and
that the elevated effluent pH should be solved before full scale trials
The nano membrane toilet: separation processes.
Get PDFIt is estimated that 61 % and 29 % of the global population lack safely managed
sanitation and clean water services respectively. The water Sustainable Development
Goals (SDG 6) actioned by the UN, aim to provide global access to sanitation and clean
water by 2030. However, in low income countries (LICs) conventional centralised
wastewater treatment plants are economically unfeasible and for affordable
decentralised alternatives, only 22 % of the waste is safely managed, leading to
contamination of water resources. The Reinvent the Toilet Challenge (RTTC) initiated
by the Bill & Melinda Gates Foundation (BGMF) proposes to innovate off-grid, self-
sustaining systems, which are able to safely manage human waste and provide
opportunity for resource recovery, at ≤US$0.05 user⁻¹ d⁻¹. In response, the Nano
Membrane Toilet (NMT) developed at Cranfield University propositions a household
scale sanitation system which combusts human faeces and provides an off-grid
opportunity for advanced treatment technologies to treat the liquid fraction, comprising
faecally contaminated urine (FCU). This thesis investigated a series of potential
separation processes which integrate with the combustor, for FCU treatment.
It was demonstrated that solids liquid separation can be facilitated post flush
with a screw auger, which allowed for effective faecal solids recovery for the
combustor. Thermally driven membrane processes, which operate from heat energy,
evidenced that high water quality where reuse standards could be achieved (with
operational optimisation) in a single stage. In addition, they proved robust to faecal
contamination and manipulated odour profiles to change negative perception. The most
adaptable process, membrane distillation (MD), provided a salinity gradient consisting
of a concentrated retentate and deionised permeate where salinity gradient energy was
converted to electrical energy through reverse electrodialysis (RED), sufficient to power
an auxiliary low voltage fluidic device (0.25 W) for 4.9 hours. Importantly, the
integrated separation processes within this thesis, evidenced high quality water and
energy recovery, which are the foundations of an SDG 6 solution.PhD in Water, including Desig
Ammonia recovery and utilisation for biogas upgrading in membrane contactors.
Get PDFPidou, Marc - Associate SupervisorThis thesis has developed an innovative system for biogas upgrading using
hollow fibre membrane contactors (HFMC) whilst recovering ammonia from
wastewater as a reactive solvent to intensify CO₂ absorption. An expanded two-
phase region for ammonia-water separation was identified and exploited to foster
selective, low energy recovery of concentrated gas-phase ammonia from
wastewater by vacuum thermal stripping. Selective stripping was translated to a
gas-liquid contacting column which demonstrated mass transfer rates analogous
to commercially established stripping processes. Investment in selective
ammonia recovery from anaerobic digester centrate represents a cost saving
over a 20-year economic lifetime relative to biological nitrogen removal. During
physical CO₂ absorption in HFMC, solvent chilling and gas pressurisation were
observed to increase flux and selectivity, thereby reducing membrane area and
path length for biogas upgrading. Chilled conditions will promote wetting
resilience to favour the application of microporous membranes, which are low-
cost and technologically mature. Translation to recovered ammonia solvents will
further intensify CO₂ absorption, but can result in gas-side reactions within the
ternary CO₂-NH₃-H₂O system which reduce process stability. In a positive
synergy, chilled, pressurised conditions could limit ammonia ‘slip’ and maintain
the system below a critical threshold to prevent gas-side reactions and improve
process resilience. Pressurised, reactive crystallisation in HFMC during CO₂
absorption by ammonia solvents was demonstrated for the first time, and
observed to occur at a consistent supersaturation level. Consequently,
ammonium bicarbonate crystals exhibited consistent characteristics independent
of pressure which supports simplified online control and solids recovery for scale-
up. The integrated system proposed in this thesis presents a cost effective,
circular economy solution for ammonia recovery and biogas upgrading which is
closely aligned to net zero ambitions within the water sector and wider society.STREAM EngD Programm
Biogas enhancement with membranes
Get PDFBiogas 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
Anaerobic membrane bioreactors in upflow anaerobic sludge blanket configuration for energy neutral sewage treatment.
Get PDFAnaerobic 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.PhD in Wate
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