45 research outputs found
Sources of Airborne Endotoxins in Ambient Air and Exposure of Nearby Communities—A Review
Endotoxin is a bioaerosol component that is known to cause respiratory effects in exposed populations. To date, most research focused on occupational exposure, whilst much less is known about the impact of emissions from industrial operations on downwind endotoxin concentrations. A review of the literature was undertaken, identifying studies that reported endotoxin concentrations in both ambient environments and around sources with high endotoxin emissions. Ambient endotoxin concentrations in both rural and urban areas are generally below 10 endotoxin units (EU) m−3; however, around significant sources such as compost facilities, farms, and wastewater treatment plants, endotoxin concentrations regularly exceeded 100 EU m−3. However, this is affected by a range of factors including sampling approach, equipment, and duration. Reported downwind measurements of endotoxin demonstrate that endotoxin concentrations can remain above upwind concentrations. The evaluation of reported data is complicated due to a wide range of different parameters including sampling approaches, temperature, and site activity, demonstrating the need for a standardised methodology and improved guidance. Thorough characterisation of ambient endotoxin levels and modelling of endotoxin from pollution sources is needed to help inform future policy and support a robust health-based risk assessment process
Managing power dissipation in closed-loop reverse electrodialysis to maximise energy recovery during thermal-to-electric conversion
Whilst the efficiency of reverse electrodialysis (RED) for thermal-to-electrical conversion has been theoretically demonstrated for low-grade waste heat, the specific configuration and salinity required to manage power generation has been less well described. This study demonstrates that operating RED by recycling feed solutions provides the most suitable configuration for energy recovery from a fixed solution volume, providing a minimum unitary cost for energy production. For a fixed membrane area, recycling feeds achieves energy efficiency seven times higher than single pass (conventional operation), and with an improved power density. However, ionic transport, water flux and concentration polarisation introduce complex temporal effects when concentrated brines are recirculated, that are not ordinarily encountered in single pass systems. Regeneration of the concentration gradient at around 80% energy dissipation was deemed most economically pragmatic, due to the increased resistance to mass transport beyond this threshold. However, this leads to significant exergy destruction that could be improved by interventions to better control ionic build up in the dilute feed. Further improvements to energy efficiency were fostered through optimising current density for each brine concentration independently. Whilst energy efficiency was greatest at lower brine concentrations, the work produced from a fixed volume of feed solution was greatest at higher saline concentrations. Since the thermal-to-electrical conversion proposed is governed by volumetric heat utilisation (distillation to reset the concentration gradient), higher brine concentrations are therefore recommended to improve total system efficiency. Importantly, this study provides new evidence for the configuration and boundary conditions required to realise RED as a practical solution for application to sources of low-grade waste heat in industr
Pyogenic spondylitis
Pyogenic spondylitis is a neurological and life threatening condition. It encompasses a broad range of clinical entities, including pyogenic spondylodiscitis, septic discitis, vertebral osteomyelitis, and epidural abscess. The incidence though low appears to be on the rise. The diagnosis is based on clinical, radiological, blood and tissue cultures and histopathological findings. Most of the cases can be treated non-operatively. Surgical treatment is required in 10–20% of patients. Anterior decompression, debridement and fusion are generally recommended and instrumentation is acceptable after good surgical debridement with postoperative antibiotic cover
Assuring the microbiological quality of water used to irrigate salad crops: an assessment of the options available
- Headline. Although no evidence to link the irrigation of salads to disease
outbreaks in the UK has been found, the industry should be seen to be taking the
issue of irrigation water quality seriously. The strategy should be to take
proactive measures to pre-empt the adoption of unnecessarily cautious standards
within grower protocols.
- Background and expected deliverables. Concerns have been expressed by some of
the major supermarkets that salad vegetables may become contaminated with
pathogens as a result of crop irrigation using poor quality water sources. As
salads are likely to be eaten raw and will have received a minimal level of
processing there are fears that consumers may be put at risk if irrigation water
quality is not controlled. To assure product quality and to protect consumer
confidence, some supermarkets may set stringent irrigation water quality
standards in future grower protocols. Product quality is of paramount importance
to growers, processors, retailers and consumers alike. However, the salad
growing industry advocates a proportionate, science-based approach to the
development of grower protocols rather than the adoption of an excessively
precautionary principle. The aim of this project was to generate the baseline
information needed by the industry to respond in a positive way to the concerns
of retailers. The findings should help to inform the decisions and actions
necessary to demonstrate and assure the quality of these products. The work
should also support and contribute to the broader commercial objectives of the
HDC regarding the efficient use of water.
- Summary of the project and main conclusions. The following research tasks
were undertaken in pursuit of the project’s aim. 1 A review of literature
relating to the microbiological quality of irrigation water and of salad crops.
2 A survey of current UK irrigated salad production to assess current usage and
underlying trends. 3 An evaluation of the technological and economic feasibility
of on-farm water treatment options. 4 An analysis and discussion of the data
collected and development of recommendations for the industry. The main
conclusions of this work are: Irrigation water is one of many potential sources
of contamination of salads. No published direct evidence has been found to link
the irrigation of salads to disease outbreaks in the UK. However, there is a
clear potential for this to occur. Published laboratory trials have shown that
pathogens associated with poor quality irrigation water may survive on lettuce
until harvest. Epidemiological investigations (not from UK) have indicated a
link between disease and poor quality irrigation water. On occasions, some UK
salad crops are probably irrigated with water of a lower microbiological
standard than that recommended for comparable uses (e.g. reuse of wastewater for
irrigation and bathing). The actual extent to which this occurs should be
quantified and reviewed. The lack of guidance on irrigation water quality is a
deterrent to proper water quality monitoring as most growers are unsure how they
should respond to the data that is generated. This situation should be corrected
as a matter of priority. It is reported that some of the multiple retailers in
the UK favour a standard for irrigation water close to that which would meet the
requirements for drinking water (i.e. absence or infrequent presence of E. coli
in 100 ml water). Our review of standards suggests that this may be an
unnecessarily cautious and expensive option. A grower faced with doubts about
water quality appears to have four options: Demonstrate existing water is of
adequate quality; Treat existing water; Change water source; Relocate crop. Â A
site specific water resources study should be undertaken before assuming that
treatment is necessary. Where water quality cannot be assured by management or
sourcing strategies, treatment technologies may be considered. Of the many
options, three technologies are likely to be suitable: ultra-violet (U/V)
treatment, thermal treatment, and sand filters. U/V is considered to be
attractive when taking all of the factors into account. Thermal treatment is the
most rigorous and reliable. With heat recovery, such treatment could be viable
in some cases. Sand filters offer the most farmer-friendly solution but these
systems offer less assurance of water quality.
 - Financial benefits. There are no direct financial benefits to be gained by
growers from this work. It may be prudent for growers to take proactive measures
to improve monitoring procedures to pre-empt the adoption of unnecessarily
cautious (and costly) standards in future grower protocols.
- Action points for growers. There is likely to be increasing scrutiny of the
microbiological quality of irrigation water. It is advised that growers review
their monitoring strategy as a matter of priority. Regular sampling of water
sources, at least monthly during the irrigation season, for faecal indicator
bacteria would be a good start. The development of such a dataset would aid
future decisions regarding the acceptability of particular sources
Morphological classification of bioaerosols from composting using scanning electron microscopy
This research classifies the physical morphology (form and structure) of bioaerosols emitted from open windrow composting. Aggregation state, shape and size of the particles captured are reported alongside the implications for bioaerosol dispersal after release. Bioaerosol sampling took place at a composting facility using personal air filter samplers. Samples were analysed using scanning electron microscopy. Particles were released mainly as small (1 μm) single cells, with aggregates occurring in smaller proportions. Most aggregates consisted of clusters of 2-3 particles as opposed to chains, and were <10 μm in size. No cells were attached to soil debris or wood particles. These small single cells or small aggregates are more likely to disperse further downwind from source, and cell viability may be reduced due to increased exposure to environmental factors
Progress towards a best practice method for modelling dispersion of bioaerosols from composting facilities
The promotion of composting in the UK as a sustainable waste management option has led to concerns regarding exposure of the public to potentially harmful emissions of airborne micro-organisms or bioaerosols. In response to public concerns, the Environment Agency in England and Wales requires a risk assessment for any licensed composting facility that has a sensitive receptor within 250m of the site boundary. An ongoing programme of studies in association with the Environment Agency has begun to explore methods to improve exposure assessments for bioaerosols. Our results have shown that is is possible to use air dispersion models for estimating downwind concentrations of bioaerosols, and the more advanced modelling options, such as the use of intermittent emission rates, result in lower downwind concentrations. Current risk assessments may be over-estimating the exposure of receptors to bioaerosols from composting, however further studies are needed to validate the results presented here. 1. INTRODUCTION The promotion of composting in the UK as a more sustainable waste management option has led to concerns regarding exposure of the public to potentially harmful emissions of airborne microorganisms or bioaerosols. The composting process is reliant on various micro-organisms, such as bacteria and fungi, to break down the organic matter. However, if as a result of composting operations these micro-organisms become airborne, may be breathed in, and due to their small size, can penetrate deep into the human respiratory system. Conditions such as farmer's lung disease and aspergillosis (Latgé, 1999) have been linked to high concentrations of bioaerosols, although dose-response relationships are not well defined. In response to public concerns, the Environment Agency in England and Wales requires a risk assessment for any licensed composting facility that has a sensitive receptor within 250m of th