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Limiting infection transmission is central to the safety of all in dentistry, particularly during the current SARS-CoV-2 pandemic. Aerosol-generating procedures (AGPs) are crucial to the practise of dentistry; it is imperative to understand the inherent risks of viral dispersion associated with AGPs and the efficacy of available mitigation strategies.In a dental surgery setting, crown preparation and root canal access procedures were performed with an air turbine or electric speed-controlled hand-piece, with mitigation via rubber dam or high-volume aspiration and a no mitigation control. A phantom head was used with a 1.5 mL flow of artificial saliva infected with Φ6 bacteriophage (a surrogate virus for SARS-CoV-2) at ∼108plaque forming units mL-1, reflecting the upper limits of reported salivary SARS-CoV-2 levels. Bioaerosol dispersal was measured using agar settle plates lawned with the bacteriophage’s host,Pseudomonas syringae. Viral air concentrations were assessed using MicroBio MB2 air sampling, and particle quantities using Kanomax 3889 GEOα particle counters.Compared to an air turbine, the electric hand-piece reduced settled bioaerosols by 99.72%, 100.00% and 100.00% for no mitigation, aspiration and rubber dam, respectively. Bacteriophage concentrations in the air were reduced by 99.98%, 100.00% and 100.00%, with the same mitigation strategies. Use of the electric hand-piece with high-volume aspiration, resulted in no detectable bacteriophage, both on settle plates and in air samples taken 6-10-minutes post-procedure.To our knowledge, this study is the first to report the aerosolization of active virus as a marker for risk determination in the dental setting. Whilst this model represents a worst-case scenario for possible SARS-CoV-2 dispersal, these data showed that the use of electric hand-pieces can vastly reduce the risk of viral aerosolization, and therefore remove the need for clinic fallow time. Furthermore, our findings indicate that the use of particle analysis alone cannot provide sufficient insight to understand bioaerosol infection risk.

Hospital-acquired infections (HAIs) are a global challenge incurring mortalities and high treatment costs. The environment plays an important role in transmission due to contaminated air and surfaces. This includes microorganisms' deposition from the air onto surfaces. Quantifying the deposition rate of microorganisms enables understanding surface contamination and can inform strategies to mitigate the infection risk. We developed and validated a novel Automated Multiplate Passive Air Sampling (AMPAS) device. This enables sequences of passive deposition samples to be collected over a controlled time period without human intervention. AMPAS was used with air sampling to measure the effect of ventilation rate and spatial location on the deposition rate of aerosolized Staphylococcus aureus in a 32 m

The bioaerosol exposure data from the study by Akpeimeh, Fletcher, and Evans (2019) was used to compute the risk of infection from the exposure of dumpsite workers to Aspergillus fumigatus and Escherichia coli O157:H7. A stochastic (Markov Chain) model was used to model the transport of the inhaled dose though the human respiratory system and then integrated into the beta-Poisson dose-response model to estimate workers risks of respiratory and gastrointestinal (GI) infection. The infection risk was computed based on workers exposure to E. coli O157:H7 at 10-50% pathogen ingestion rate and pathogen-indicator ratio (P:I) of 1:103 and 1:104 , while exposure to A. fumigatus was based solely on the average initial exposure dose. The results showed that after 11 hours of exposure, workers engaged in scavenging, waste sorting, and site monitoring were at risk of respiratory and GI infection in the magnitude of 10-1 . However, the risk estimates associated with specific areas of the dumpsite showed that, the risk of GI infection at the active area ranged between 3.23 × 10-3 -1.56 × 10-2 and 3.25 × 10-4 -1.62 × 10-3 ; dormant area 2.06 × 10-3 -1.01 × 10-2 and 2.09 × 10-4 -1.04 × 10-3 ; entrance 1.85 × 10-3 -9.09 × 10-3 and 1.87 × 10-4 -9.27 × 10-4 ; boundary 1.82 × 10-3 -8.82 × 10-3 and 2.09 × 10-4 -8.94 × 10-4 for P:I = 1:103 and 1:104 respectively, while the risk of respiratory infection risks were in the magnitude of 10-1 for all four locations. The estimated risk of workers developing respiratory and gastrointestinal infections were high for all activities assessed at the dumpsite.

Many infectious diseases, including COVID-19, are transmitted by airborne pathogens. There is a need for effective environmental control measures which, ideally, are not reliant on human behaviour. One potential solution is Far-UVC which can efficiently inactivate pathogens, such as coronaviruses and influenza, in air. When appropriately filtered, and because of its limited penetration, there is evidence that Far-UVC does not induce acute reactions in the skin or eyes, nor delayed effects such as skin cancer. While there is laboratory evidence for far-UVC efficacy, there is limited evidence in full-sized rooms. In the first study of its type, we show that Far-UVC deployed in a room-sized chamber effectively inactivates aerosolised Staphylococcus aureus. At a room ventilation rate of 3 air changes per hour (ACH), with 5 filtered sources the steady-state pathogen load was reduced by 92.1% providing an additional 35 equivalent air changes (eACH). This reduction was achieved using Far-UVC intensities consistent with current regulatory limits. Far-UVC is likely to be more effective against common airborne viruses, including SARS-CoV-2, and should thus be an effective and “hands-off” technology to reduce airborne disease transmission. The findings provide room-scale data to support the design and development of safe and effective Far-UVC systems.

Activities associated with the open dumping of municipal solid waste has the potential for greater impact on the environment and public health compared to other forms of waste-to-land treatment of such wastes. However, there is a lack of quantitative data on the exposure to bioaerosols from open dumpsites, hence impeding the development of effective interventions that would reduce the risk of respiratory symptoms among scavengers and waste workers at such dumpsites. This study investigated exposure to bioaerosols at Olusosun open dumpsite, Lagos Nigeria using three methodologies; (1) Conducting a cross-sectional survey on the respiratory health of the population on the dumpsite, (2) Measuring bioaerosol concentrations in the ambient air by measuring four bioaerosols indicator groups (total bacteria, gram-negative bacteria, Aspergillus fumigatus and total fungi) using a Anderson six stage impactor sampler, (3) Measuring activity related exposures to bioaerosols using an SKC button personal sampler. After a cross sectional health survey of 149 participants (waste workers, scavengers, middlemen, food vendors and business owners), smokers reported higher symptoms of chronic cough (21%) and chronic phlegm (15%) compared to non-smokers (chronic cough 15%, chronic phlegm 13%). Years of work > 5 years showed no statistically significant association with chronic phlegm (OR 1.2, 95% CI 0.4–3.4; p > 0.05) or asthma (OR 1.8, 95% CI 0.6–5.2; p > 0.05). At the 95th percentile, the concentration of total bacteria was the highest (2189 CFU/m3), then gram negative bacteria (2188 CFU/m3), total fungi (843 CFU/m3) and Aspergillus fumigatus (441 CFU/m3) after ambient air sampling. A comparison of the data showed that the activity-based sampling (undertaken using body worn personal sampler) had higher bioaerosols concentrations (104 –106 CFU/m3), i.e. 2–3 logs higher than those recorded from static ambient air sampling. Bioaerosol exposure was highest during scavenging activities compared to waste sorting and site supervision. Particle size distributions showed that 41%, 46%, 76% and 63% of total bacteria, gram-negative bacteria, Aspergillus fumigatus and total fungi respectively were of respirable sizes and would therefore be capable of penetrating deep into the respiratory system, posing a greater human health risk. This study has shown that exposure to bioaerosols can be associated with activities undertaken at open dumpsites and may contribute to the high prevalence of the chronic respiratory symptoms among the workers in such environments.

Irrigation with treated wastewater could produce excessive accumulations within the plant and soil, negatively affecting the yield and production quality. In addition, the presence of biological and chemical contaminants could harm the agricultural environment, as well as the health of farmers and consumers. During this work, the suitability of secondary and tertiary treated wastewater for use in young grapevines was evaluated by studying the effect of the wastewater irrigation on the soil-plant system, crop yield, fruit quality and the presence of inorganic chemical contamination (salts, elements and heavy metals), organic chemical contamination (polycyclic aromatic hydrocarbons) and microbial contamination (E. coli, total coliforms). The results show that tertiary treated wastewater had positive impact on plant growth and yield while secondary treated wastewater had negative impact on fruit safety in comparison with tap water. Sodium levels in soils irrigated with treated wastewater increased at the end of the irrigation period while decreased during the wet season. The total polycyclic aromatic hydrocarbon concentrations in the soils ranged from 363 μg/kg to 374 μg/kg at the end of the experiment for all irrigation treatments applied. The use of tertiary treated wastewater was recommended for the irrigation of young grapevines as an alternative water source secured protection of environment, plant health and fruit quality.

Airborne microorganisms in hospitals have been associated with several hospital-acquired infections (HAIs), and various measures of indoor air quality (IAQ) parameters such as temperature, relative humidity, carbon dioxide (CO2 ), particle mass concentration, and particle size have been linked to pathogen survival or mitigation of pathogen spread. To investigate whether there are quantitative relationships between the concentration of airborne microorganisms and the IAQ in the hospital environment. Web of Science, Scopus and PubMed databases were searched for studies reporting airborne microbial levels and any IAQ parameter(s) in hospital environments, from database inception to October 2020. Pooled effect estimates were determined via random-effects models. Seventeen of 654 studies were eligible for the meta-analysis. The concentration of airborne microbial measured as aerobic colony count (ACC) was significantly correlated with temperature (r = 0.25 [95% CI = 0.06-0.42], p = 0.01), CO2 concentration (r = 0.53 [95% CI = 0.40-0.64], p ˂ 0.001), particle mass concentration (≤5 µg/m3 ; r = 0.40 [95% CI = 0.04-0.66], p = 0.03), and particle size (≤5 and ˃5 µm), (r = 0.51 [95% CI = 0.12-0.77], p = 0.01 and r = 0.55 [95% CI = 0.20-0.78], p = 0.003), respectively, while not being significantly correlated with relative humidity or particulate matter of size >5 µm. Conversely, airborne total fungi (TF) were not significantly correlated with temperature, relative humidity, or CO2 level. However, there was a significant weak correlation between ACC and TF (r = 0.31 [95% CI = 0.07-0.52], p = 0.013). Although significant correlations exist between ACC and IAQ parameters, the relationship is not definitive; the IAQ parameters may affect the microorganisms but are not responsible for the presence of airborne microorganisms. Environmental parameters could be related to the generating source, survival, dispersion, and deposition rate of microorganisms. Future studies should record IAQ parameters and factors such as healthcare worker presence and the activities carried out such as cleaning, sanitizing, and disinfection protocols. Foot traffic would influence both the generation of microorganisms and their deposition rate onto surfaces in the hospital environment. These data would inform models to improve the understanding of the likely concentration of airborne microorganisms and provide an alternative approach for real-time monitoring of the healthcare environment.

Graphical abstract, Highlights • Low-temperature biochars doubled biomethane production rate and enhanced yields. • Seaweed biochars and hydrochars from various feedstocks reduced biomethane yields. • Biochars with high levels of oxygen surface groups favoured biomethane augmentation., The augmentation of biochar produced at 450 and 600–650 °C and hydrochar produced at 250 °C has been investigated using biochemical methane potential experiments of cellulose. The feedstocks used for the char production included the lignocellulosic (oak wood), macroalgae (Fucus serratus) and aquatic plant (water hyacinth). Biomethane production was improved with the addition of lower-temperature biochars from oak wood (285 mL CH4/g VS) and water hyacinth (294 mL CH4/g VS), corresponding to 7 and 11% more than the control. The addition of these two biochars increased the methane production rate of 2.4 and 2.3 times the control, respectively. Higher temperature biochars showed no difference. Conversely, all hydrochars and macroalgae biochars augmentation reduced methane generation by 57–86 %. The chemical and structural composition of each of the chars differed significantly. Surface oxygen functionality appears to be the most important property of the biochars that improved digestion performance.

Self-contamination during doffing of personal protective equipment (PPE) is a concern for healthcare workers (HCW) following SARS-CoV-2 positive patient care. Staff may subconsciously become contaminated through improper glove removal, so quantifying this risk is critical for safe working procedures. HCW surface contact sequences on a respiratory ward were modelled using a discrete-time Markov chin for: IV-drip care, blood pressure monitoring and doctors’ rounds. Accretion of viral RNA on gloves during care was modelled using a stochastic recurrence relation. The HCW then doffed PPE and contaminated themselves in a fraction of cases based on increasing case load. The risk of infection from this exposure was quantified using a dose-response methodology. A parametric study was conducted to analyse the effect of: 1a) increasing patient numbers on the ward, 1b) the proportion of COVID-19 cases, 2) the length of a shift and 3) the probability of touching contaminated PPE. The driving factors for infection risk were surface contamination and number of surface contacts. HCWs on a 100% COVID-19 ward were less than 2-fold more at risk than on a 50% COVID ward (1.6% vs 1%), whilst on a 5% COVID-19 ward, the risk dropped to 0.1% per shift (sd=0.6%). IV-drip care resulted in higher risk than blood pressure monitoring (1.1% vs 1% pImportanceInfection risk from self-contamination during doffing PPE is an important concern in healthcare settings, especially on a COVID-19 ward. Fatigue during high workload shifts may result in increased frequency of mistakes and hence risk of exposure. Length of staff shift and number of COVID-19 patients on a ward correlate positively with the risk to staff through self-contamination after doffing. Cleaning of far-patient surfaces is equally important as cleaning traditional “high-touch surfaces”, given that there is an additional risk from bioaerosol deposition outside the patient zone(1).

In the context of increasingly airtight homes, there is currently little known about the type and diversity of microorganisms in the home, or factors that could affect their abundance, diversity and nature. In this study, we examined the type and prevalence of cultivable microorganisms at eight different sites in 100 homes of older adults located in Glasgow, Scotland. The microbiological sampling was undertaken alongside a household survey that collated information on household demographics, occupant behaviour, building characteristics, antibiotic use and general health information. Each of the sampled sites revealed its own distinct microbiological character, in both species and number of cultivable microbes. While some potential human pathogens were identified, none were found to be multidrug resistant. We examined whether the variability in bacterial communities could be attributed to differences in building characteristics, occupant behaviour or household factors. Sampled sites furnished specific microbiological characteristics which reflected room function and touch frequency. We found that homes that reported opening windows more often were strongly associated with lower numbers of Gram-negative organisms at indoor sites (p

Highlights • Biochar addition improved biomethane yield particularly at less favourable ISR 0.5–0.9. • Biochar provided a buffering effect at lower ISR and C/N ratio. • Factorial regression model provided optimal anaerobic co-digestion conditions. • Biochar effect is highly dependent on the digestion conditions., The anaerobic co-digestion (AcoD) of microalgae is a prospective option for generating biomethane from renewable sources. This study investigates the effects of inoculum-to-substrate ratio (ISR), C/N ratio and biochar (BC) load on the AcoD of Chlorella vulgaris and cellulose. An initial augmentation of BC at ISR 0.5–0.9 and C/N ratio 10–30 offered a pH buffering effect and resulted in biomethane yields of 233–241 mL CH4/g VS, corresponding to 1.8–4.6 times the controls. BC addition ameliorated significantly AcoD, supporting the digestate stability at less favourable conditions. The effect of the process variables was further studied with a 23 factorial design and response optimisation. Under the design conditions, the variables had less influence over methane production. Higher ISRs and C/N ratios favoured AcoD, whereas increasing amounts of BC reduced biomethane yield but enhanced production rate. The factorial design highlighted the importance of BC-load on AcoD, establishing an optimum of 0.58 % (w/v).

Microalgae have been presented as microorganisms with great potential to recover nutrient from wastewater. Mixotrophic cultivation of microalgae in nutrient rich wastewater can help eliminating the deficiencies of both phototrophic and heterotrophic growth by allowing the independent optimisation of respiration and photosynthesis processes. Nutrient control and uptake by mixotrophic microalgae can be achieved either in a single or two-stage process using sequential reactors in a continuous flow system. Therefore, this work aims at studying mixotrophic microalgae growth in a two-stage biological process under continuous flow conditions with biomass recycle to recover nutrients from wastewater, considering the effects of different operational conditions (hydraulic retention time (HRT), cell retention time (CRT) and different nitrogen sources). The optimum operational conditions for algal nutrient uptake were identified to be 48 h HRT and 14 d CRT, using a mix of nitrogen sources (Ammonium-N to Nitrate-N ratio of 1:1) with 40.0% and 93.2% of phosphorus of nitrogen recovery in algal biomass, respectively.

We report measurements of hydroxyl (OH) and hydroperoxy (HO2) radicals made by laser-induced fluorescence spectroscopy in a computer classroom (i) in the absence of indoor activities (ii) during desk cleaning with a limonene-containing cleaner (iii) during operation of a commercially available ‘air cleaning’ device. In the unmanipulated environment, the one-minute averaged OH concentration remained close to or below the limit of detection (6.5 x 105 molecule cm−3), whilst that of HO2 was 1.3 x 107 molecule cm−3. These concentrations increased to ~ 4 x 106 and 4 x 108 molecule cm−3, respectively during desk cleaning. During operation of the air-cleaning device, OH and HO2 concentrations reached ~ 2 x 107 and ~ 6 x 108 molecule cm−3 respectively. The potential of these OH concentrations to initiate chemical processing is explored using a detailed chemical model for indoor air (the INDCM). The model can reproduce the measured OH and HO2 concentrations to within 50% and often within a few % and demonstrates that the resulting secondary chemistry varies with the cleaning activity. Whilst terpene reactions products dominate the product composition following surface cleaning, those from aromatics and other VOCs are much more important during the use of the air cleaning device. This article is protected by copyright. All rights reserved.

Bacterial transmission from contaminated surfaces via hand contact plays a critical role in disease spread. However, the fomite‐to‐finger transfer efficiency of microorganisms during multiple sequential surface contacts with and without gloves has not been formerly investigated. We measured the quantity of Escherichia coli on fingertips of participants after 1‐8 sequential contacts with inoculated plastic coupons with and without nitrile gloves. A Bayesian approach was used to develop a mechanistic model of pathogen accretion to examine finger loading as a function of the difference between E coli on surfaces and fingers. We used the model to determine the coefficient of transfer efficiency (λ ), and influence of swabbing efficiency and finger area. Results showed that λ for bare skin was higher (49%, 95% CI = 32%‐72%) than for gloved hands (30%, CI = 17%‐49%). Microbial load tended toward a dynamic equilibrium after four and six contacts for gloved hands and bare skin, respectively. Individual differences between volunteers’ hands had a negligible effect compared with use of gloves (P < .01). Gloves reduced loading by 4.7% (CI = −12%‐21%) over bare skin contacts, while 20% of participants accrued more microorganisms on gloved hands. This was due to poor fitting, which created a larger finger surface area than bare hands.

Irrigation with raw, partially and treated wastewater is a widespread practice in many arid and semi-arid zones. The importance of wastewater for agriculture has increasingly been recognised not only as a valuable water resource but also for its nutrient value. However, inappropriate management of irrigation with wastewater can pose substantial risks to public health and the surrounding environment as a result of its microbial and toxic components. In this review, we summarise recent research and provide a broad overview of the potential risks associated with the chemicals in wastewater used for irrigation including their environmental, and health impacts, factors that may affect the fate of these chemicals, and available mitigation methods and management options to reduce their impacts. A primary aim of this review is to construct a generalised ranking of the risks from the chemical constituents of wastewater used for irrigation in arid and semi-arid zones.

The preparation of low-cost carbonaceous adsorbents for nitrogen recovery is of interest from agricultural and waste management perspectives. In this study, the gaseous ammonia (NH3) and aqueous ammonium (NH4+) sorption capacities have been measured for different types of carbonaceous chars produced under different conditions. The study includes a comparison of an oak-based hydrochar produced from hydrothermal carbonisation (HTC) at 250 &deg, C with two biochars produced from slow pyrolysis at 450 &deg, C and 650 &deg, C, respectively. The chars were also chemically modified with H2SO4, H3PO4, H2O2, and KOH to investigate the potential for sorption enhancement. The highest sorption capacities for NH3 were observed for the hydrochars with typical uptake capacities ranging from 18&ndash, 28 mg g&minus, 1 NH3. Sorption capacity for oak biochars is significantly lower and ranges from 4&ndash, 8 mg g&minus, 1 for biochars produced at 450 &deg, C, respectively. Hydrochar showed a substantially higher sorption capacity for NH3 despite its lower surface area. The CaCl2 extractable NH4+ following ammonia adsorption is incomplete. Typically, only 30&ndash, 40% of the N is released upon washing with CaCl2 in form of NH4+. Post chemical modification of the chars resulted in only limited enhancement of char NH3 and NH4+ sorption. H3PO4 treatment showed the greatest potential for increasing NH3/NH4+ sorption in biochars, while KOH and H2O2 treatment increased NH3 sorption in the hydrochar. As only marginal increases to char surface area were observed following char treatment, these findings suggest that char surface functionality is more influential than surface area in terms of char NH3/NH4+ sorption.

This study investigated the performance of four pilot-scale biofilters for the removal of bioaerosols from waste airstreams in a materials recovery facility (MRF) based in Leeds, UK. A six-stage Andersen sampler was used to measure the concentrations of four groups of bioaerosols (Aspergillus fumigatus, total fungi, total mesophilic bacteria and Gram negative bacteria) in the airstream before and after passing through the biofilters over a period of 11 months. The biofilters achieved average removal efficiency (RE) of 70% (35 to 97%) for A. fumigatus, 71% (35 to 94%) for total fungi, 68% (47 to 86%) for total mesophilic bacteria and 50% (-4 to 85%) for Gram negative bacteria, provided that the inlet concentration was high (103–105 cfu m−3), which is the case for most waste treatment facilities. The performance was highly variable at low inlet concentration with some cases showing an increase in outlet concentrations, suggesting that biofilters had the potential to be net emitters of bioaerosols. The gas phase residence time did not appear to have any statistically significant impact on bioaerosol removal efficiency. Particle size distribution varied between the inlet and outlet air, with the outlet having a greater proportion of smaller sized particles that represent a greater human health risk as they can penetrate deep into the respiratory system where gaseous exchange occurs. However, the outlet concentrations were low and would further be diluted by wind in full scale applications. In conclusion, this study shows that biofilters designed and operated for odour degradation can also achieve significant bioaerosol control in waste gas.

Irrigation of olive trees with treated wastewaters in arid and semi-arid regions is becoming a necessary alternative to addressing issues of water shortages. The irrigation requires a careful monitoring of soil and plants for a range of parameters including salts, nutrients, micro-elements, heavy metals, toxic pollutants, and pathogens. A 3-years monitoring of the above parameters in soil and leaves of olive trees in Crete, Greece was conducted using trees that were irrigated with three types of water: secondary treated wastewater (STW), tertiary treated wastewater (TTW), and tap water (TW). Plant growth was similar for all irrigation sources as indicated by measured trunk diameter, plant height, and photosynthetic activity. In addition, no significant differences in mineral leaf content were observed. Accumulation of nutrients (mainly P and K) and salts (Na) in soils 2 years after the application of both types of treated wastewater were observed in comparison to tap water. Magnesium, calcium, and boron concentrations in treated wastewaters were higher than TW. However no effects on soil concentrations were reported. Concentration of polycyclic aromatic hydrocarbons in soil ranged from 349.0 μg kg−1 to 395.4 μg kg−1 values not significantly different between the examined water sources. Finally, E. coli mean content in STW was 3580 ± 800 MPN 100 mL−1; however, the absence of microbial contamination was detected in leaves and fruits of olive trees. The results of this study suggest that STW and TTW can be applied successfully for the safe irrigation of the olive groves.

M. abscessus survives aerosolisation suggesting airborne transmission between people with CF may occur http://ow.ly/K2x6302JpAW

MOTIVATION: Proper management of fecal sludge has significant positive health and environmental externalities. Most research on managing onsite sanitation so far either simulates the costs of, or the welfare effects from, managing sludge in situ in pit latrines. Thus, designing management strategies for onsite rural sanitation is challenging, because the actual costs of transporting sludge for treatment, and sources for financing these transport costs, are not well understood. METHODS: In this paper we calculate the actual cost of sludge management from onsite latrines, and identify the contributions that latrine owners are willing to make to finance the costs. A spreadsheet-based model is used to identify a cost-effective transport option, and to calculate the cost per household. Then a double-bound contingent valuation method is used to elicit from pit-latrine owners their willingness-to-pay to have sludge transported away. This methodology is employed for the case of a rural subdistrict in Bangladesh called Bhaluka, a unit of administration at which sludge management services are being piloted by the Government of Bangladesh. RESULTS: The typical sludge accumulation rate in Bhaluka is calculated at 0.11 liters/person/day and a typical latrine will need to be emptied approximately once every 3 to 4 years. The costs of emptying and transport are high; approximately USD 13 per emptying event (circa 14% of average monthly income); household contributions could cover around 47% of this cost. However, if costs were spread over time, the service would cost USD 4 per year per household, or USD 0.31 per month per household-comparable to current expenditures of rural households on telecommunications. CONCLUSION: This is one of few research papers that brings the costs of waste management together with financing of that cost, to provide evidence for an implementable solution. This framework can be used to identify cost effective sludge management options and private contributions towards that cost in other (context-specific) administrative areas where onsite sanitation is widespread.

This study investigates the influence of pH on extraction of nitrogen and phosphorus from swine manure following hydrothermal treatment. Conditions include thermal hydrolysis (TH) at 120°C and 170°C, and hydrothermal carbonisation (HTC) at 200°C and 250°C in either water alone or in the presence of 0.1M NaOH, H2SO4, CH3COOH or HCOOH. Phosphorus extraction is pH and temperature dependent and is enhanced under acidic conditions. The highest level of phosphorus is extracted using H2SO4 reaching 94% at 170°C. The phosphorus is largely retained in the residue for all other conditions. The extraction of nitrogen is not as significantly influenced by pH, although the maximum N extraction is achieved using H2SO4. A significant level of organic-N is extracted into the process waters following hydrothermal treatment. The results indicate that operating hydrothermal treatment in the presence of acidic additives has benefits in terms of improving the extraction of phosphorus and nitrogen.

The use of biochar for the recovery of phosphate has potential for environmental and socio-economic benefits but it is often characterised by relatively low nutrient adsorption capacity. The aim of this study was to investigate the potential for improving biochar phosphate adsorption capacities following chemical modification with metal salts, acids and alkali. Modified biochars were produced from oak wood and paprika waste (greenhouse waste) following either chemical treatment of biomass (in-situ modification) or biochar (post modification). Other chemical treatments investigated included chemical oxidation, activation and salt treatment. Phosphate adsorption uptake capacities were determined by laboratory batch sorption tests, and results indicated that phosphate adsorption could be enhanced from relatively low levels (2.1% - 3.6%) to relatively high levels (66.4% - 70.3%) by impregnation with magnesium. These findings suggest that biochar mineral composition is a key property influencing biochar phosphate adsorption uptake capacity while surface area has less influence on sorption.

Computational Fluid Dynamics (CFD) is an increasingly popular tool for studying the impact of design interventions on the transport of infectious microorganisms. While much of the focus is on respiratory infections, there is substantial evidence that certain pathogens, such as those which colonise the skin, can be released into, and transported through the air through routine activities. In these situations the bacteria is released over a volume of space, with different intensities and locations varying in time rather than being released at a single point. This paper considers the application of CFD modelling to the evaluation of risk from this type of bioaerosol generation. An experimental validation study provides a direct comparison between CFD simulations and bioaerosol distribution, showing that passive scalar and particle tracking approaches are both appropriate for small particle bioaerosols. The study introduces a zonal source, which aims to represent the time averaged release of bacteria from an activity within a zone around the entire location the release takes place. This approach is shown to perform well when validated numerically though comparison with the time averaged dispersion patterns from a transient source. However, the ability of a point source to represent such dispersion is dependent on airflow regime. The applicability of the model is demonstrated using a simulation of an isolation room representing the release of bacteria from bedmaking., Highlights ► CFD simulation of room airflow for an empty chamber, and hospital isolation room. ► Methods demonstrated to simulate pathogen transport generated from nursing activity. ► Simulation of airborne bioaerosol transport validated using controlled bioaerosol tests. ► Total bioaerosol deposition fraction compared well to CFD simulations when using DRW.

The study looked at the performance of a three-level composting tower, each level of which could take around 200 t of shredded mixed municipal solid waste. The composting material moved sequentially down through the three floors, taking 8–10 days to complete the cycle, targeting an Animal By-Products Regulations (ABPR) compliance regime of 70°C for 1 h. Using a 16 mm trommel screen, the yield of compost-like output (CLO) was typically 25–30% of the input by weight. The post-composting separation plant was found to be very effective in giving a range of other products for recycling. An energy usage estimate for the tower alone (not including shredding or post-compost separation) showed consumption between 25 and 31 kWh per tonne of input. Detailed temperature measurements using 40 dataloggers in a batch of 200 t of material showed that the towers were not achieving ABPR compliance standards. Modifications to the towers, which included recirculating warm air from the top of the composting mass and auxiliary heating, are now producing ABPR-compliant CLO.

Air ionizers have seen increasing use as devices for improving indoor air quality, including applications designed to reduce the transmission of infection in healthcare environments. However, little attention has been given to understanding and quantifying the physical behavior of ions in indoor air. This study presents experimental data and a theoretical model to examine the factors that influence the concentration of ions in a ventilated room. The results demonstrate how, with an ionizer in operation, the ion concentration is governed by ion—ion interactions and electrical deposition at the walls, with the ventilation rate having a minimal influence. The results also demonstrate that an ion concentration > 1010 ions · m ×3 is necessary for these electrical effects to be significant, which has implications for the suitability of an ionizer for a particular location.

The potential for biochar and hydrochar to adsorb phosphate and ammonium is important for understanding the influence of these materials when added to soils, compost or other high nutrient containing environments. The influence of physicochemical properties such as mineral content, surface functionality, pH and cation exchange capacity has been investigated for a range of biochars and hydrochars produced from waste-derived biomass feedstocks. Hydrochars produced from hydrothermal carbonisation at 250 °C have been compared to low and high temperature pyrolysis chars produced at 400-450 °C and 600-650 °C respectively for oak wood, presscake from anaerobic digestate (AD), treated municipal waste and greenhouse waste. In spite of differences in char physicochemical properties and processing conditions, PO4-P and NH4-N sorption capacities ranged from about 0 to 30 mg g(-1) and 105.8-146.4 mg g(-1) respectively. Chars with high surface areas did not possess better ammonium adsorption capacities than low surface area chars, which suggests that surface area is not the most important factor influencing char ammonium adsorption capacity, while char calcium and magnesium contents may influence phosphate adsorption. Desorption experiments only released a small fraction of adsorbed ammonium or phosphate (

The installation of upper-room ultraviolet germicidal irradiation (UVGI) devices in ventilated rooms has the potential to reduce transmission of infections by an airborne route. However, the performance of such devices is dependant on several factors including the location of the lamp and the ventilation airflow in the room. This study uses a CFD model to evaluate the performance of UVGI devices by considering the cumulative UV-C dose received by the bulk room air in a ventilated room. By evaluating the UV dose rather than the resulting micro-organism inactivation the methodology can be used to optimise UVGI systems at the design stage, particularly when the source location of bioaerosol contaminants is not known. The study investigates the relationships between the lamp location, lamp power, ventilation system and room heating in a small, ventilated room. The results show that with ventilation air supplied at low level and extracted at high level the UVGI system performs better than with the air supplied at high level and extracted close to the floor. In addition the results show the presence of a heater in the room is unlikely to have a detrimental effect on performance and may promote mixing to increase the extent of disinfection.

Whilst a number of researchers have demonstrated the disinfection effectiveness of upper-room UV irradiation devices against a range of airborne microorganisms, it is technically difficult to determine the performance of such systems because the biological and physical processes involved can be complex. In particular, most of the quantitative data on the susceptibility of airborne microorganisms to UV irradiation is obtained from single-pass experiments which are not representative of the fragmented UV exposure experienced by airborne microorganisms in real rooms. This paper presents complete and partial mixing models for predicting an effective UV susceptibility constant, Z eff , that is appropriate for quantifying the behaviour of airborne microorganisms when irradiated using an upper-room system. The use of both decay and continuous contamination experimental techniques are discussed and related to the models presented. Experimental results are presented which indicate that Z eff for Serratia marcescens is up to an order of magnitude lower than the susceptibility constants derived from single-pass experiments, suggesting that using these data to design upper-room UV systems may lead to a lower than expected performance.

Although much hospital acquired infection is associated with person-to-person contact, there is increasing evidence that some nosocomial infections may be transmitted via the airborne route. However, the knowledge base concerning airborne microflora in hospitals is poor. In particular, there is a need for good quality data relating bioaerosol production to clinical activity in hospital wards. A short aerobiological survey was therefore undertaken by the authors on a respiratory ward at St James’s University Hospital in Leeds in order to gain an understanding of the relationship between activity and bioaerosol production. This survey involved regular microbiological and particulate (0.3–5 m) sampling of the ward air, together with an observational study of ward activity. Two identical four-bed ward bays were surveyed, one containing high dependency patients who regularly used noninvasive ventilators (NIVs), and the other containing patients who did not require mechanical ventilation. The survey found a correlation between activity and aerosol production.

The effectiveness of any ultraviolet germicidal irradiation (UVGI) system is governed by the passage of airborne microorganisms through the UV field. This paper describes a new method for evaluating the performance of UVGI devices using computational fluid dynamic (CFD) simulations. A microorganism inactivation equation is combined with a scalar transport equation to describe the concentration of airborne microorganisms in the presence of a UV field. The solution of this equation, in conjunction with the momentum and turbulent energy equations, allows the effect of both the airflow and the UV field on the microorganism distribution to be examined. Solutions are shown for the airflow and microorganism concentration through a bench scale flow apparatus, at five different UV intensities. The results from the CFD model are validated against the experimental data, obtained from the flow apparatus, for aerosolised Pseudomonas aeruginosa microorganisms. Good comparisons are seen, giving confidence in the application of the technique to other situations.

Conventionally treated sewage sludge may contain high concentrations of potentially pathogenic microorganisms and additional treatment is required to minimise the risks to health if it is to be recycled to agricultural land. Mesophilic anaerobic digestion (MAD) is the most widely used process in the UK for stabilising sludge prior to agricultural recycling, but little is known about the fate of a number of enteric pathogens as the sludge passes through the treatment processes. The aim of this study was to determine the efficiency of MAD in removing the bacterial enteric pathogens, Salmonella senftenberg, Listeria monocytogenes and Campylobacter jejuni which were added as a spike to the digester feedstock, together with the die-off of indigenous Escherichia coli already present in the sludge. The primary sludge digestion stage of MAD was found to achieve a log removal of 1.66 for E. coli, 2.23 for L. monocytogenes and 2.23 for S. senftenberg. However, the extent of die-off was a function of the numbers of pathogens in the feed and as these increased the log removal also increased. The numbers of C. jejuni were not affected by primary sludge digestion. Additional die-off was provided by secondary sludge digestion with log removals of 1.70 for E. coli, 2.10 for S. senftenberg and 0.36 for C. jejuni.

Pseudomonas aeruginosa is a common and important pathogen in people with cystic fibrosis (CF). Recently epidemic strains of P. aeruginosa associated with increased morbidity, have been identified. The method of transmission is not clear, but there is evidence of a potential airborne route. The aim of this study was to determine whether different strains of P. aeruginosa isolated from people with CF were able to survive within artificially generated aerosols in an aerobiological chamber.Viable P. aeruginosa could still be detected up to 45min after halting generation of the aerosols. All of the strains of P. aeruginosa expressing a non-mucoid phenotype isolated from people with CF had a reduced ability to survive within aerosols compared to an environmental strain. Expression of a mucoid phenotype by the strains of P. aeruginosa isolated from people with CF promoted survival in the aerosol model compared to strains expressing a non-mucoid phenotype.

Background Cystic fibrosis (CF) is an inherited multi-system disorder characterised by chronic airway infection with pathogens such as Pseudomonas aeruginosa. Acquisition of P. aeruginosa by patients with CF is usually from the environment, but recent studies have demonstrated patient to patient transmission of certain epidemic strains, possibly via an airborne route. This study was designed to examine the survival of P. aeruginosa within artificially generated aerosols. Results Survival was effected by the solution used for aerosol generation. Within the aerosols it was adversely affected by an increase in air temperature. Both epidemic and non-epidemic strains of P. aeruginosa were able to survive within the aerosols, but strains expressing a mucoid phenotype had a survival advantage. Conclusion This would suggest that segregating individuals free of P. aeruginosa from those with chronic P. aeruginosa infection who are more likely to be infected with mucoid strains may help reduce the risk of cross-infection. Environmental factors also appear to influence bacterial survival. Warming and drying the air within clinical areas and avoidance of humidification devices may also be beneficial in reducing the risk of cross-infection.

Background In recent years there has been renewed interest in the use of air ionisers to control of the spread of airborne infection. One characteristic of air ions which has been widely reported is their apparent biocidal action. However, whilst the body of evidence suggests a biocidal effect in the presence of air ions the physical and biological mechanisms involved remain unclear. In particular, it is not clear which of several possible mechanisms of electrical origin (i.e. the action of the ions, the production of ozone, or the action of the electric field) are responsible for cell death. A study was therefore undertaken to clarify this issue and to determine the physical mechanisms associated with microbial cell death. Results In the study seven bacterial species (Staphylococcus aureus, Mycobacterium parafortuitum, Pseudomonas aeruginosa, Acinetobacter baumanii, Burkholderia cenocepacia, Bacillus subtilis and Serratia marcescens) were exposed to both positive and negative ions in the presence of air. In order to distinguish between effects arising from: (i) the action of the air ions; (ii) the action of the electric field, and (iii) the action of ozone, two interventions were made. The first intervention involved placing a thin mica sheet between the ionisation source and the bacteria, directly over the agar plates. This intervention, while leaving the electric field unaltered, prevented the air ions from reaching the microbial samples. In addition, the mica plate prevented ozone produced from reaching the bacteria. The second intervention involved placing an earthed wire mesh directly above the agar plates. This prevented both the electric field and the air ions from impacting on the bacteria, while allowing any ozone present to reach the agar plate. With the exception of Mycobacterium parafortuitum, the principal cause of cell death amongst the bacteria studied was exposure to ozone, with electroporation playing a secondary role. However in the case of Mycobacterium parafortuitum, electroporation resulting from exposure to the electric field appears to have been the principal cause of cell inactivation. Conclusion The results of the study suggest that the bactericidal action attributed to negative air ions by previous researchers may have been overestimated.